TEXTILE TESTING
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About This Presentation
TEXTILE TESTING AND QUALITY CONTROL
Slide Content
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 1
1.0 QUALITY EVALUATION OF TEXTILES :
1.1 INTRODUCTION
Testing of textiles provides valuable aid to those engaged in the production,
distribution & consumption of textiles provided instruments & techniques are
used effectively but testing instrument can not make decisions & at the end
some person has to interpret & analyze the data available. The type of textile
testing instruments available is large. Many of them are simple in principle and
have been used by the textile industry for a long time. Some important
instruments are relatively new, as also are commercial models of equipment
developed in research laboratories. The choice of instruments and the testing
techniques employed will be governed largely by the information required as well
as how accurate and detailed that information has to be.
The subject of textile testing can be covered by answering few ‘W’ questions.
Why do we test? What do we test? When do we test? Who should do the test?
1.2 WHY DO WE TEST?
1.2.1Selection of Raw Materials :
Raw material cost is the highest amongst all component of cost. This
accounts for 60-70% in cotton & synthetics. Therefore selection of raw
material becomes extremely important & any lapse in this part may lead
the organization to run into trouble. Ensuring optimum quality of raw
material not only reduces the product cost at desired level but also ensure
good working conditions inside the mills.
Page 1 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 1
1.0 QUALITY EVALUATION OF TEXTILES :
1.1 INTRODUCTION
Testing of textiles provides valuable aid to those engaged in the production,
distribution & consumption of textiles provided instruments & techniques are
used effectively but testing instrument can not make decisions & at the end
some person has to interpret & analyze the data available. The type of textile
testing instruments available is large. Many of them are simple in principle and
have been used by the textile industry for a long time. Some important
instruments are relatively new, as also are commercial models of equipment
developed in research laboratories. The choice of instruments and the testing
techniques employed will be governed largely by the information required as well
as how accurate and detailed that information has to be.
The subject of textile testing can be covered by answering few ‘W’ questions.
Why do we test? What do we test? When do we test? Who should do the test?
1.2 WHY DO WE TEST?
1.2.1Selection of Raw Materials :
Raw material cost is the highest amongst all component of cost. This
accounts for 60-70% in cotton & synthetics. Therefore selection of raw
material becomes extremely important & any lapse in this part may lead
the organization to run into trouble. Ensuring optimum quality of raw
material not only reduces the product cost at desired level but also ensure
good working conditions inside the mills.
Page 1 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Raw material differs from manufacturer to manufacture. For some, it may
be fibre, for some it may be yarn & for processor it may be grey fabric.
1.2.2Process Control :
Testing of intermediate products i.e. lap, sliver, roving & some of wastes
like comber noil extends lot of help in process control. In the spinning
mill, most common testing for process control is testing count (Hank) at
various stages. For reliable corrective action, one can use ‘Quality
Control Charts’ for control of the count.
1.3 RESEARCH
Testing helps in determining direction in research work. Often research worker
finds himself at cross roads & the result of testing will help the scientist to decide
which path to follow next.
1.4 PROCESS DEVELOPMENT
Process development can be taken as applied form of research. The objective
of process development is to investigate simpler, cheaper, quicker or energy
efficient methods of doing the same work, improving the quality of product
without changing inputs i.e. blending of different fibres at different stages. Here
one should be clear about which properties are to be listed in order to avoid
unnecessary wastage of time.
1.5 TESTING OF FINISHED PRODUCT
Even if we have selected raw material of right quality & it seems that our process
is fairly controlled, we cannot assure product of specified quality because of lack
of knowledge about lot of variables in the process. Therefore it is a standard
Page 2 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Raw material differs from manufacturer to manufacture. For some, it may
be fibre, for some it may be yarn & for processor it may be grey fabric.
1.2.2Process Control :
Testing of intermediate products i.e. lap, sliver, roving & some of wastes
like comber noil extends lot of help in process control. In the spinning
mill, most common testing for process control is testing count (Hank) at
various stages. For reliable corrective action, one can use ‘Quality
Control Charts’ for control of the count.
1.3 RESEARCH
Testing helps in determining direction in research work. Often research worker
finds himself at cross roads & the result of testing will help the scientist to decide
which path to follow next.
1.4 PROCESS DEVELOPMENT
Process development can be taken as applied form of research. The objective
of process development is to investigate simpler, cheaper, quicker or energy
efficient methods of doing the same work, improving the quality of product
without changing inputs i.e. blending of different fibres at different stages. Here
one should be clear about which properties are to be listed in order to avoid
unnecessary wastage of time.
1.5 TESTING OF FINISHED PRODUCT
Even if we have selected raw material of right quality & it seems that our process
is fairly controlled, we cannot assure product of specified quality because of lack
of knowledge about lot of variables in the process. Therefore it is a standard
Page 2 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
practice to test finished product against specifications and the products which
are falling beyond tolerances are being rejected. Some times a forecast of the
probable performance in a subsequent process is required. Now from fibre
properties we can predict that what is going to be C.S.P. of cotton or from yarn
properties we can have some idea about performance of yarn in Winding as well
as in weaving.
1.6 CHECKING SPECIFICATIONS
To ensure the goods purchased are as per given specification or purchased
machines are capable of producing goods of the quality as desired by
manufacturers, testing is a must.
Sometimes samples are being sent with a tag to produce identical product, here
again suitable analysis techniques and testing are required to produce sample of
same specification.
Page 3 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
practice to test finished product against specifications and the products which
are falling beyond tolerances are being rejected. Some times a forecast of the
probable performance in a subsequent process is required. Now from fibre
properties we can predict that what is going to be C.S.P. of cotton or from yarn
properties we can have some idea about performance of yarn in Winding as well
as in weaving.
1.6 CHECKING SPECIFICATIONS
To ensure the goods purchased are as per given specification or purchased
machines are capable of producing goods of the quality as desired by
manufacturers, testing is a must.
Sometimes samples are being sent with a tag to produce identical product, here
again suitable analysis techniques and testing are required to produce sample of
same specification.
Page 3 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
2.0 SELECTION OF SAMPLE
In textile most of the tests are destructive in nature therefore testing is conducted
on a very very small part of the population i.e. referred as “sample”
2.1 RANDOM SAMPLE
In case of random sampling every individual in the population has got an equal
chance of being included in the sample without any bias. Normally it is desired
that a sample should be random & representative of the lot.
2.2 BIASED SAMPLE
Some time unknowingly bias occurs during sample collection due to location or
any other reason . Some specimen have more chance of being included in the
sample.
For different tests , different type of sampling techniques are adopted ( in case
of fibre , yarn and fabric ) to get correct test results .
2.3 PLANNED SAMPLE
Some time it might be useful to draw test sample in a planned manner,
particularly when we want to cover entire process or deliveries of machines in a
given time frame i.e. checking of uster & imperfections in case of ring frame.
Page 4 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
2.0 SELECTION OF SAMPLE
In textile most of the tests are destructive in nature therefore testing is conducted
on a very very small part of the population i.e. referred as “sample”
2.1 RANDOM SAMPLE
In case of random sampling every individual in the population has got an equal
chance of being included in the sample without any bias. Normally it is desired
that a sample should be random & representative of the lot.
2.2 BIASED SAMPLE
Some time unknowingly bias occurs during sample collection due to location or
any other reason . Some specimen have more chance of being included in the
sample.
For different tests , different type of sampling techniques are adopted ( in case
of fibre , yarn and fabric ) to get correct test results .
2.3 PLANNED SAMPLE
Some time it might be useful to draw test sample in a planned manner,
particularly when we want to cover entire process or deliveries of machines in a
given time frame i.e. checking of uster & imperfections in case of ring frame.
Page 4 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
3.0 FIBRE TESTING
Testing of fibres is required for determining their quality. Unless quality of raw
material is not controlled it will not be possible to get a quality finished product.
We can broadly divide fibre testing in two categories –
1) Testing of Cotton Fibre
2) Testing of Man-made Fibres
3.1Testing of Cotton Fibre
Following are the main properties of cotton fibre –
i) Fibre length
ii)Fibre fineness
iii)Fibre strength
iv)Maturity of cotton
v) Colour
vi)Trash%
vii)Neps
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
3.0 FIBRE TESTING
Testing of fibres is required for determining their quality. Unless quality of raw
material is not controlled it will not be possible to get a quality finished product.
We can broadly divide fibre testing in two categories –
1) Testing of Cotton Fibre
2) Testing of Man-made Fibres
3.1Testing of Cotton Fibre
Following are the main properties of cotton fibre –
i) Fibre length
ii)Fibre fineness
iii)Fibre strength
iv)Maturity of cotton
v) Colour
vi)Trash%
vii)Neps
Page 5 of 85
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 2
SAMPLING PROCEDURE FOR FIBRE TESTING
The quality of a cotton sample is mainly dependent on the various physical
properties of the fibres in the sample. The most important physical
characteristics are length, fineness, maturity and strength of the fibres. There are
large variations in these characteristics not only between fibres of different
samples but also between the fibres constituting the same sample.
Investigations have shown that the variations in length observed between fibres
in a bulk sample are of the same order as those observed between fibres on a
single seed of that variety. The characters of any random sample picked out
from a bulk cannot be expected to be representative of the bulk in view of this
large variation. Hence, before carrying out any tests for fibre characteristics, it is
preferable to prepare a test sample which is, as far as possible, truly
representative of the constituents of the bulk. The details of the procedures
employed for proper sampling and the methods adopted for determining the
various physical quality factors of cotton fibres are described in the following
sections.
Sampling Techniques For The Determination of Fiber Properties
The sampling method used to select a fiber for testing depends upon the form in
which the fiber is available. Therefore fibers in bales, in sliver, card web, yarn etc
will require different techniques The test result of sample may not be the same
as obtained by testing bulk sample. Two source of error may be present.
Random error & error due to bias.
Sampling from Bales
In order to obtain a representative sample from a lot of bales it is necessary to
distribute the sample to be selected over the bales in the lot and different layers
in the bale. The number of bales to be selected at random from a lot shall be in
accordance with Table-1.
Page 6 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 2
SAMPLING PROCEDURE FOR FIBRE TESTING
The quality of a cotton sample is mainly dependent on the various physical
properties of the fibres in the sample. The most important physical
characteristics are length, fineness, maturity and strength of the fibres. There are
large variations in these characteristics not only between fibres of different
samples but also between the fibres constituting the same sample.
Investigations have shown that the variations in length observed between fibres
in a bulk sample are of the same order as those observed between fibres on a
single seed of that variety. The characters of any random sample picked out
from a bulk cannot be expected to be representative of the bulk in view of this
large variation. Hence, before carrying out any tests for fibre characteristics, it is
preferable to prepare a test sample which is, as far as possible, truly
representative of the constituents of the bulk. The details of the procedures
employed for proper sampling and the methods adopted for determining the
various physical quality factors of cotton fibres are described in the following
sections.
Sampling Techniques For The Determination of Fiber Properties
The sampling method used to select a fiber for testing depends upon the form in
which the fiber is available. Therefore fibers in bales, in sliver, card web, yarn etc
will require different techniques The test result of sample may not be the same
as obtained by testing bulk sample. Two source of error may be present.
Random error & error due to bias.
Sampling from Bales
In order to obtain a representative sample from a lot of bales it is necessary to
distribute the sample to be selected over the bales in the lot and different layers
in the bale. The number of bales to be selected at random from a lot shall be in
accordance with Table-1.
Page 6 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Table-1 : Number of Bales to be selected from a lot
No. of Bales
In the Lot
No. of Bales to be
Selected
Up to 50
51 to 100
101 to 150
151 to 300
301 to 500
501 to 1000
1001 & Above
2
4
7
13
20
32
40
In view of the variation observed in most of the fibre properties, both within and
between the layers of cotton in a bale, it is desirable to open the bale and draw
tufts from different positions in at least 10 equally-spaced layers. In practice the
selection of the layers from a bale may be done as given below:
The bale is kept lengthwise on the ground and the hoops are broken. A thin
layer of cotton is removed from the top and the tufts are drawn from various
positions on the exposed surface. Then a thick slab (about one-tenth the height
of the bale) is removed and the tufts are drawn from the newly exposed surface.
The procedure is repeated till the tufts are drawn from at least 10 layers. While
drawing the tufts from various layers, care shall be taken to avoid any bias in
selecting the positions for drawing the tufts. The material so drawn from the bale
shall not be less than 2 kg.
In case it is not economical to open the bale completely, the gross sample may
be obtained by breaking one or more of the hoops round the bale and then
taking out a lump of at least 1 kg of material from each of the two exposed sides
of the bale. The material so taken shall include portions from the hard, soft and
middle parts of the bale.
The material so obtained from all the bales selected from the lot shall be
thoroughly mixed to get a gross sample.
Page 7 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Table-1 : Number of Bales to be selected from a lot
No. of Bales
In the Lot
No. of Bales to be
Selected
Up to 50
51 to 100
101 to 150
151 to 300
301 to 500
501 to 1000
1001 & Above
2
4
7
13
20
32
40
In view of the variation observed in most of the fibre properties, both within and
between the layers of cotton in a bale, it is desirable to open the bale and draw
tufts from different positions in at least 10 equally-spaced layers. In practice the
selection of the layers from a bale may be done as given below:
The bale is kept lengthwise on the ground and the hoops are broken. A thin
layer of cotton is removed from the top and the tufts are drawn from various
positions on the exposed surface. Then a thick slab (about one-tenth the height
of the bale) is removed and the tufts are drawn from the newly exposed surface.
The procedure is repeated till the tufts are drawn from at least 10 layers. While
drawing the tufts from various layers, care shall be taken to avoid any bias in
selecting the positions for drawing the tufts. The material so drawn from the bale
shall not be less than 2 kg.
In case it is not economical to open the bale completely, the gross sample may
be obtained by breaking one or more of the hoops round the bale and then
taking out a lump of at least 1 kg of material from each of the two exposed sides
of the bale. The material so taken shall include portions from the hard, soft and
middle parts of the bale.
The material so obtained from all the bales selected from the lot shall be
thoroughly mixed to get a gross sample.
Page 7 of 85
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Reduction of Gross Sample
The gross sample shall be spread out evenly on a level ground in the form of
either a square with each side slightly greater than 1 m, or in the case of a larger
sample, a rectangle with the shorter side slightly greater than 1 m, and the larger
side slightly greater than 2 m. A suitable framework of size 1 x 1 m with 25 sub-
squares or 1 x 2 m with 50 sub-squares, one or more tufts of fibres shall be
pulled out at random, taking care not to exercise and bias in favour of or against
any particular place within a sub-square, and that tufts drawn from each sub-
square weigh about 4 g in the former case and about 2 g in the latter case. The
quantity of cotton thus drawn shall constitute the reduced sample.
The reduced sample shall be well mixed and divided into 25 or 50 approximately
equal parts. From each of these parts, one or more tufts of fibres shall be
extracted at random, taking care that the fibres drawn are nearly equal in weight,
and the total weight of fibres thus drawn is not less than the quantity required for
relevant tests. The material so taken out shall constitute the test sample.
CTRL Method of Sampling and Preparation of Drawbox Sliver
The reduced sample is divided into 32 approximately equal parts by successive
dichotomy. From each portion a small tuft of fibres is extracted in a
random manner. Approximately the same quantity of fibres is taken from
each group so that the total weight of the final test sample is between 200
mg and 500 mg.
For most fibre tests like length by Balls and Baer sorters, maturity by Caustic
soda method, and bundle strength by Pressley Strength Tester and Stelometer,
it is convenient to prepare a representative sliver out of the test sample, by
cleaning it free of leaf bits and other extraneous matter, mixing various portions
thoroughly and then parallelising the fibres. For this purpose, the test sample,
after cleaning by hand and mixing is passed through a drawbox repeatedly 5 to
Page 8 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Reduction of Gross Sample
The gross sample shall be spread out evenly on a level ground in the form of
either a square with each side slightly greater than 1 m, or in the case of a larger
sample, a rectangle with the shorter side slightly greater than 1 m, and the larger
side slightly greater than 2 m. A suitable framework of size 1 x 1 m with 25 sub-
squares or 1 x 2 m with 50 sub-squares, one or more tufts of fibres shall be
pulled out at random, taking care not to exercise and bias in favour of or against
any particular place within a sub-square, and that tufts drawn from each sub-
square weigh about 4 g in the former case and about 2 g in the latter case. The
quantity of cotton thus drawn shall constitute the reduced sample.
The reduced sample shall be well mixed and divided into 25 or 50 approximately
equal parts. From each of these parts, one or more tufts of fibres shall be
extracted at random, taking care that the fibres drawn are nearly equal in weight,
and the total weight of fibres thus drawn is not less than the quantity required for
relevant tests. The material so taken out shall constitute the test sample.
CTRL Method of Sampling and Preparation of Drawbox Sliver
The reduced sample is divided into 32 approximately equal parts by successive
dichotomy. From each portion a small tuft of fibres is extracted in a
random manner. Approximately the same quantity of fibres is taken from
each group so that the total weight of the final test sample is between 200
mg and 500 mg.
For most fibre tests like length by Balls and Baer sorters, maturity by Caustic
soda method, and bundle strength by Pressley Strength Tester and Stelometer,
it is convenient to prepare a representative sliver out of the test sample, by
cleaning it free of leaf bits and other extraneous matter, mixing various portions
thoroughly and then parallelising the fibres. For this purpose, the test sample,
after cleaning by hand and mixing is passed through a drawbox repeatedly 5 to
Page 8 of 85
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
10 times. The sliver so prepared can be taken to be completely representative of
the bulk sample.
B.S. Zoning Method
This method gives a numerical sample, obtained by repeatedly halving the
representative samples. The total number of fibres required(n) in the sample is
estimated and tuft of fibres from various parts (m) of the bulk is taken. The
portion so taken is divided into two taking care to avoid fibre breakage, and
rejecting one-half, the choice of which half to be rejected being half is rejected at
random. This process for each tuft is continued until a number of fibres equal to
about n/m of the total required in each group is obtained. The required sample
consists of all the fibres remaining in each group. If two samples are required the
m halves remaining after the last division may be used for the second sample,
provided any further reduction of sample size which is required is carried out in a
manner similar to that just given.
Sampling for Other Tests
For tests on the Fibrograph, the test specimen is directly prepared from the
reduced sample. For tests on the Nickerson-Hunter Cotton Colorimeter, a larger
reduced sample, of about ½ kg is prepared, which is divided into three or four
tests on the Micronaire instrument sufficient quantity from the laboratory sample
is well-opened, cleaned and thoroughly mixed to get about 8 gms, of sample.
Textiles and moisture
Introduction
The properties of textile fibres are in many cases strongly affected by the atmospheric
moisture content. Many fibres, particularly the natural ones, are hygroscopic in that they
are able to absorb water vapour from a moist atmosphere and to give up water to a dry
atmosphere. If sufficient time is allowed, equilibrium will be reached. The amount of
moisture that such fibres contain strongly affects many of their most important physical
Page 9 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
10 times. The sliver so prepared can be taken to be completely representative of
the bulk sample.
B.S. Zoning Method
This method gives a numerical sample, obtained by repeatedly halving the
representative samples. The total number of fibres required(n) in the sample is
estimated and tuft of fibres from various parts (m) of the bulk is taken. The
portion so taken is divided into two taking care to avoid fibre breakage, and
rejecting one-half, the choice of which half to be rejected being half is rejected at
random. This process for each tuft is continued until a number of fibres equal to
about n/m of the total required in each group is obtained. The required sample
consists of all the fibres remaining in each group. If two samples are required the
m halves remaining after the last division may be used for the second sample,
provided any further reduction of sample size which is required is carried out in a
manner similar to that just given.
Sampling for Other Tests
For tests on the Fibrograph, the test specimen is directly prepared from the
reduced sample. For tests on the Nickerson-Hunter Cotton Colorimeter, a larger
reduced sample, of about ½ kg is prepared, which is divided into three or four
tests on the Micronaire instrument sufficient quantity from the laboratory sample
is well-opened, cleaned and thoroughly mixed to get about 8 gms, of sample.
Textiles and moisture
Introduction
The properties of textile fibres are in many cases strongly affected by the atmospheric
moisture content. Many fibres, particularly the natural ones, are hygroscopic in that they
are able to absorb water vapour from a moist atmosphere and to give up water to a dry
atmosphere. If sufficient time is allowed, equilibrium will be reached. The amount of
moisture that such fibres contain strongly affects many of their most important physical
Page 9 of 85
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
properties. The consequence of this is that the moisture content of all textile products has
to be taken into account when these properties are being measured. Furthermore because
the percentage of moisture that can be retained by fibres is quite high (up to 40% with
some fibres), the moisture content can have a significant effect on the mass of the
material. This factor has a commercial importance in cases where material such as yarns
and fibres is bought and sold by weight.
Effect of moisture on physical properties
The physical properties of fibres can be affected by their moisture content. In general the
fibres that absorb the greatest amount of moisture are the ones whose properties change
the most. Three main types of properties are affected.
i)Dimensional
The mass of the fibres is simply the sum of the mass of the dry fibre plus the mass of the
water. The absorption of moisture by fibres causes them to swell, because of the
insertion of water molecules between the previously tightly packed fibre molecules.
Because the fibre molecules are long and narrow most of the available intermolecular
spaces are along the length of the molecules rather than at the ends, so that the swelling
takes place mainly in the fibre width. Nylon is a notable exception to this,
The change in volume of a fibre is linked to the changes in its length and cross-
sectional area by simple geometry. The change in volume is also linked to the
amount of water that has been absorbed. The swelling of fibres is a continuous
process which takes place in step with their increasing moisture content.
Fabrics made from fibres that absorb large amounts of water are affected by the
swelling. When such a fabric is soaked in water the increase in width of the
fibres leads to an increase in diameter of the constituent yarns. Depending on
the closeness of spacing of the yarns this can lead to a change in dimensions of
the fabric. However, on subsequent drying out the structure does not necessarily
revert to its original state. This behaviour is responsible for the dimensional
stability problems of certain fabrics. Advantage is taken of fibre swelling in the
construction of some types of water proof fabrics whose structures are designed
to close up when wetted, so making them more impermeable to water.
2. Mechanical
Some fibres, such as wool and viscose, lose strength when they absorb water and some,
such as cotton, flax, hemp and jute, increase in strength Furthermore the extensibility,
that is the extension at a given load, can increase for some fibres when they are wet.
These changes in strength and extension have consequences for many other textile
properties besides tensile strength. Some properties such as fabric tearing strength are
ones that are obviously likely to be affected by fibre strength, but for other ones such as
crease resistance or abrasion resistance the connection between them and changes in
Page 10 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
properties. The consequence of this is that the moisture content of all textile products has
to be taken into account when these properties are being measured. Furthermore because
the percentage of moisture that can be retained by fibres is quite high (up to 40% with
some fibres), the moisture content can have a significant effect on the mass of the
material. This factor has a commercial importance in cases where material such as yarns
and fibres is bought and sold by weight.
Effect of moisture on physical properties
The physical properties of fibres can be affected by their moisture content. In general the
fibres that absorb the greatest amount of moisture are the ones whose properties change
the most. Three main types of properties are affected.
i)Dimensional
The mass of the fibres is simply the sum of the mass of the dry fibre plus the mass of the
water. The absorption of moisture by fibres causes them to swell, because of the
insertion of water molecules between the previously tightly packed fibre molecules.
Because the fibre molecules are long and narrow most of the available intermolecular
spaces are along the length of the molecules rather than at the ends, so that the swelling
takes place mainly in the fibre width. Nylon is a notable exception to this,
The change in volume of a fibre is linked to the changes in its length and cross-
sectional area by simple geometry. The change in volume is also linked to the
amount of water that has been absorbed. The swelling of fibres is a continuous
process which takes place in step with their increasing moisture content.
Fabrics made from fibres that absorb large amounts of water are affected by the
swelling. When such a fabric is soaked in water the increase in width of the
fibres leads to an increase in diameter of the constituent yarns. Depending on
the closeness of spacing of the yarns this can lead to a change in dimensions of
the fabric. However, on subsequent drying out the structure does not necessarily
revert to its original state. This behaviour is responsible for the dimensional
stability problems of certain fabrics. Advantage is taken of fibre swelling in the
construction of some types of water proof fabrics whose structures are designed
to close up when wetted, so making them more impermeable to water.
2. Mechanical
Some fibres, such as wool and viscose, lose strength when they absorb water and some,
such as cotton, flax, hemp and jute, increase in strength Furthermore the extensibility,
that is the extension at a given load, can increase for some fibres when they are wet.
These changes in strength and extension have consequences for many other textile
properties besides tensile strength. Some properties such as fabric tearing strength are
ones that are obviously likely to be affected by fibre strength, but for other ones such as
crease resistance or abrasion resistance the connection between them and changes in
Page 10 of 85
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
fibre tensile properties is less apparent. It is because of these changes in properties that
textile tests should be carried out in a controlled atmosphere.
3) Electrical
The moisture content of fibres also has an important effect on their electrical properties.
The main change is to their electrical resistance. The resistance decreases with increasing
moisture content. For fibres that absorb water the following approximate relation
between the electrical resistance and the moisture content holds for relative humidities
between 30% and 90%.
RM
n
= k
Where R = resistance,
M = moisture content (%)
and n and k are constants
The changes in resistance are large : there is approximately a tenfold decrease
in resistance for every 13% increase in the relative humidity. This fall in
resistance with increasing moisture content means that static electrical charges
are more readily dissipated when the atmospheric relative humidity is high.
Atmospheric moisture
The moisture content of textile materials when they are in equilibrium with their
surroundings is determined by the amount of moisture in the air. Therefore the
moisture content of those materials that absorb water can vary from day to day
or from room to room. The atmospheric moisture level is normally expressed in
terms of relative humidity and not absolute water content.
Relative humidity
The amount of moisture that the atmosphere can hold increases with its temperature so
that warmer air can hold more water than cold air.
When considering the effects of atmospheric moisture on textile materials the
important quantity is not how much moisture the air already holds, but how much
more it is capable of holding. This factor governs whether fibres will lose
moisture to or gain moisture from the atmosphere. The capacity of the
atmosphere to hold further moisture is calculated by taking the maximum
possible atmospheric moisture content at a particular temperature and working
out what percentage of it has already been taken up. This quantity is known as
the relative humidity (RH) of the atmosphere and it can be defined in two ways .
In terms of the mass of water vapour in the atmosphere:
Mass of water vapour in given volume of air
RH = ----------------------------------------------------------- x 100 %
Mass of water vapour required to saturate
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
fibre tensile properties is less apparent. It is because of these changes in properties that
textile tests should be carried out in a controlled atmosphere.
3) Electrical
The moisture content of fibres also has an important effect on their electrical properties.
The main change is to their electrical resistance. The resistance decreases with increasing
moisture content. For fibres that absorb water the following approximate relation
between the electrical resistance and the moisture content holds for relative humidities
between 30% and 90%.
RM
n
= k
Where R = resistance,
M = moisture content (%)
and n and k are constants
The changes in resistance are large : there is approximately a tenfold decrease
in resistance for every 13% increase in the relative humidity. This fall in
resistance with increasing moisture content means that static electrical charges
are more readily dissipated when the atmospheric relative humidity is high.
Atmospheric moisture
The moisture content of textile materials when they are in equilibrium with their
surroundings is determined by the amount of moisture in the air. Therefore the
moisture content of those materials that absorb water can vary from day to day
or from room to room. The atmospheric moisture level is normally expressed in
terms of relative humidity and not absolute water content.
Relative humidity
The amount of moisture that the atmosphere can hold increases with its temperature so
that warmer air can hold more water than cold air.
When considering the effects of atmospheric moisture on textile materials the
important quantity is not how much moisture the air already holds, but how much
more it is capable of holding. This factor governs whether fibres will lose
moisture to or gain moisture from the atmosphere. The capacity of the
atmosphere to hold further moisture is calculated by taking the maximum
possible atmospheric moisture content at a particular temperature and working
out what percentage of it has already been taken up. This quantity is known as
the relative humidity (RH) of the atmosphere and it can be defined in two ways .
In terms of the mass of water vapour in the atmosphere:
Mass of water vapour in given volume of air
RH = ----------------------------------------------------------- x 100 %
Mass of water vapour required to saturate
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this volume at the same temperature
Alternatively it can also be defined as the ratio of the actual vapour pressure to
the saturated vapour pressure at the same temperature expressed as a
percentage.
Actual vapour pressure x 100%
RH = -------------------------------------------
Saturated vapour pressure
The absolute humidity is defined as the weight of water present in unit volume of
moist air measured in grams per cubic metre.
It is important to note that the relative humidity of the atmosphere changes with
temperature even when the total quantity of water vapour contained in the air
remains the same.
The amount of moisture contained by fibres that are in equilibrium with the
atmosphere is dependent on the relative rather than the absolute humidity.
Standard atmosphere
Because of the important changes that occur in textile properties as the moisture
content changes, it is necessary to specify the atmospheric conditions in which
any testing is carried out. Therefore a standard atmosphere has been agreed for
testing purposes and is defined as a relative humidity of 65% and a temperature
of 20
o
C. For practical purposes certain tolerances in these values are allowed
so that the testing atmosphere is RH 65% + 2%.; In tropical regions a
temperature of 27 + 2o C may be used.
Regain and moisture content
The amount of moisture in a fibre sample can be expressed as either regain or moisture
content. Regain is the weight of water in a material expressed as a percentage of the oven
dry weight.
100 x W
Regain = ------------- %
D
where D is the dry weight and W is the weight of absorbed water.
Moisture content is the weight of water expressed as a percentage of the total
weight
100x W
Moisture content = -------------- %
D + W
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
this volume at the same temperature
Alternatively it can also be defined as the ratio of the actual vapour pressure to
the saturated vapour pressure at the same temperature expressed as a
percentage.
Actual vapour pressure x 100%
RH = -------------------------------------------
Saturated vapour pressure
The absolute humidity is defined as the weight of water present in unit volume of
moist air measured in grams per cubic metre.
It is important to note that the relative humidity of the atmosphere changes with
temperature even when the total quantity of water vapour contained in the air
remains the same.
The amount of moisture contained by fibres that are in equilibrium with the
atmosphere is dependent on the relative rather than the absolute humidity.
Standard atmosphere
Because of the important changes that occur in textile properties as the moisture
content changes, it is necessary to specify the atmospheric conditions in which
any testing is carried out. Therefore a standard atmosphere has been agreed for
testing purposes and is defined as a relative humidity of 65% and a temperature
of 20
o
C. For practical purposes certain tolerances in these values are allowed
so that the testing atmosphere is RH 65% + 2%.; In tropical regions a
temperature of 27 + 2o C may be used.
Regain and moisture content
The amount of moisture in a fibre sample can be expressed as either regain or moisture
content. Regain is the weight of water in a material expressed as a percentage of the oven
dry weight.
100 x W
Regain = ------------- %
D
where D is the dry weight and W is the weight of absorbed water.
Moisture content is the weight of water expressed as a percentage of the total
weight
100x W
Moisture content = -------------- %
D + W
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Regain is the quantity usually used in the textile industry
Factors affecting the regain
Different fibre types absorb different amounts of moisture depending on their affinity for
water.
For a given fibre type the moisture content is governed by a number of factors:
1.Relative humidity. The higher the relative humidity of the atmosphere,
the higher is the regain of textile material which is exposed to it.
2.Time. Material that is in equilibrium at a particular relative humidity which
is then moved to an atmosphere with a different relative humidity takes a
certain amount of time to reach a new equilibrium. The time taken
depends on the physical form of the material and how easily the moisture
can reach or escape from the individual fibres.
3.Temperature. Temperature will affect the regain of material. In testing
laboratory as temp. variation are small, for practical purposes the
temperature does not affect the regain of a sample.
4.Previous history. The moisture content of textile materials in equilibrium
with a particular relative humidity depends on the previous history of the
material.
The material will have a different moisture content depending on whether it was
previously wet or dry. Processing of the material can also change its regain value by
altering its ability to absorb moisture. The removal of oils, waxes and other impurities
can also change the regain by removing a barrier on the fibre surface to the flow of
moisture vapour. For example the standard regain value for scoured wool is 16% and that
for oil combed tops is 19%.
Method of measuring regain
To measure the regain of a sample of textile material it is necessary to weigh the
material, dry it and then weigh it again. The difference between the masses is then the
mass of water in the sample.
Mass of water x 100%
Regain = ------------------------------
Oven dry mass
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Regain is the quantity usually used in the textile industry
Factors affecting the regain
Different fibre types absorb different amounts of moisture depending on their affinity for
water.
For a given fibre type the moisture content is governed by a number of factors:
1.Relative humidity. The higher the relative humidity of the atmosphere,
the higher is the regain of textile material which is exposed to it.
2.Time. Material that is in equilibrium at a particular relative humidity which
is then moved to an atmosphere with a different relative humidity takes a
certain amount of time to reach a new equilibrium. The time taken
depends on the physical form of the material and how easily the moisture
can reach or escape from the individual fibres.
3.Temperature. Temperature will affect the regain of material. In testing
laboratory as temp. variation are small, for practical purposes the
temperature does not affect the regain of a sample.
4.Previous history. The moisture content of textile materials in equilibrium
with a particular relative humidity depends on the previous history of the
material.
The material will have a different moisture content depending on whether it was
previously wet or dry. Processing of the material can also change its regain value by
altering its ability to absorb moisture. The removal of oils, waxes and other impurities
can also change the regain by removing a barrier on the fibre surface to the flow of
moisture vapour. For example the standard regain value for scoured wool is 16% and that
for oil combed tops is 19%.
Method of measuring regain
To measure the regain of a sample of textile material it is necessary to weigh the
material, dry it and then weigh it again. The difference between the masses is then the
mass of water in the sample.
Mass of water x 100%
Regain = ------------------------------
Oven dry mass
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Regain is based on the oven dry mass, which for most fibres is the constant
mass obtained by drying at a temperature of 105 + 2
o
C. Constant mass is
achieved by drying and weighing repeatedly until successive weighing differ by
less than 0.5%.
This is also called oven dry weight.
Standard Regain Values
Fibre type Regain (%)
Man-made fibres
Acetate 6.5
Acrylic 1.5
Nylon 6, 6 and 6 4.5
Polyester 0.4
Polypropylene 0
Triacetate 3.5
Viscose 11-12
Natural fibres
Cotton – natural yarn 8.5
Linen fibre 12
Linen yarn 8.75
Silk 11
Wool 16-18.0
Shirley Moisture Meter
Electrical resistance of different textile materials varies considerably at different
regains. This principal is used in Shirley Moisture Meter. Initially instrument was
designed to measure moisture of Raw cotton & yarn however later its use was
extended to other textile materials & tables were prepared to give corrected
values.
The electrode consist of a central conductor insulated from an outer circular
sheath. When pressed into the cotton the fiber bridges the insulation &
resistance is measured. Two electrode one for raw cotton & one for yarn is used.
The difference being that for yarns spacing between conducting element is
increased.
This counteracts the increased conductivity of yarns due to more or less parallel
arrangement of the fibers compared with random arrangement of the fibers in
loose cotton. The indicating unit translate resistance value into regain values
On one of two dials.. One dial covers normal range from 7-11 percent & other
For Damp 9-15 & Dry from 5-9 percent range.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Regain is based on the oven dry mass, which for most fibres is the constant
mass obtained by drying at a temperature of 105 + 2
o
C. Constant mass is
achieved by drying and weighing repeatedly until successive weighing differ by
less than 0.5%.
This is also called oven dry weight.
Standard Regain Values
Fibre type Regain (%)
Man-made fibres
Acetate 6.5
Acrylic 1.5
Nylon 6, 6 and 6 4.5
Polyester 0.4
Polypropylene 0
Triacetate 3.5
Viscose 11-12
Natural fibres
Cotton – natural yarn 8.5
Linen fibre 12
Linen yarn 8.75
Silk 11
Wool 16-18.0
Shirley Moisture Meter
Electrical resistance of different textile materials varies considerably at different
regains. This principal is used in Shirley Moisture Meter. Initially instrument was
designed to measure moisture of Raw cotton & yarn however later its use was
extended to other textile materials & tables were prepared to give corrected
values.
The electrode consist of a central conductor insulated from an outer circular
sheath. When pressed into the cotton the fiber bridges the insulation &
resistance is measured. Two electrode one for raw cotton & one for yarn is used.
The difference being that for yarns spacing between conducting element is
increased.
This counteracts the increased conductivity of yarns due to more or less parallel
arrangement of the fibers compared with random arrangement of the fibers in
loose cotton. The indicating unit translate resistance value into regain values
On one of two dials.. One dial covers normal range from 7-11 percent & other
For Damp 9-15 & Dry from 5-9 percent range.
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CHAPTER – 4
FIBRE LENGTH
Among the various properties which determine the quality of cotton, fibre length
occupies a dominant position as it influences, to a large extent, the spinnability of
a cotton. Moreover fibre length can be easily estimated. Hence, this
characteristic of cotton has assumed great importance in commercial
transactions and the price of a cotton sample is largely based on this
characteristic.
Any sample of cotton will contain fibres varying in length from 2mm onwards, the
upper limit being decided by the variety of cotton under consideration and the
conditions under which it has been grown. This variation is found markedly even
when fibres removed from an individual cotton seed are considered. In view of
the above, what we generally aim at is to obtain a measure of fibre length which
can be considered as average for the whole sample or which is likely to influence
the spinning performance most.
DEFINITIONS OF FIBRE LENGTH PARAMETRES
Mean length:
The arithmetic mean of the length of all the fibres present in a small but
representative sample of cotton, based on weight-length distribution or relative
number-length distribution.
Upper Quartile Length:
The length for which 75 per cent of all the observed values are lower and 25 per
cent higher, by weight or by number
Modal Length:
The most frequently occurring length of fibres in the weight distribution of the
sample.
Page 15 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 4
FIBRE LENGTH
Among the various properties which determine the quality of cotton, fibre length
occupies a dominant position as it influences, to a large extent, the spinnability of
a cotton. Moreover fibre length can be easily estimated. Hence, this
characteristic of cotton has assumed great importance in commercial
transactions and the price of a cotton sample is largely based on this
characteristic.
Any sample of cotton will contain fibres varying in length from 2mm onwards, the
upper limit being decided by the variety of cotton under consideration and the
conditions under which it has been grown. This variation is found markedly even
when fibres removed from an individual cotton seed are considered. In view of
the above, what we generally aim at is to obtain a measure of fibre length which
can be considered as average for the whole sample or which is likely to influence
the spinning performance most.
DEFINITIONS OF FIBRE LENGTH PARAMETRES
Mean length:
The arithmetic mean of the length of all the fibres present in a small but
representative sample of cotton, based on weight-length distribution or relative
number-length distribution.
Upper Quartile Length:
The length for which 75 per cent of all the observed values are lower and 25 per
cent higher, by weight or by number
Modal Length:
The most frequently occurring length of fibres in the weight distribution of the
sample.
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Median:
The particular value of length above and below which exactly 50% of the fibres
lie. For moderately skewed distributions the median is related to the mean and
modal lengths in the following way:
Mode – mean = 3 (median – mean)
Effective Length:
It is difficult to give a clear scientific definition for effective length. It may be
defined as the upper quartile of the numerical length distribution from which
some of the shortest fibres are eliminated by an arbitrary construction. The fibres
eliminated are those shorter than half the effective length.
Percentage of Short Fibres:
The percentages of fibres less than half the effective length or less than any
specified length.
Coefficient of Variation:
The standard deviation of weight-length or relative number-length frequencies
expressed as a percentage of the mean length.
Span Length:
The distance spanned by a specified percentage of the fibres in the test beard.
2.5% span length is the distance from the clamp on a fibre beard to a point upto
which only 2.5% of the fibres extend. 50% span length is the distance of the
point to which 50% span length is the distance of the point to which 50% of the
fibres extend and 66.7% span length is the distance upto which 66.7% of the
fibres extend.
Uniformity Ratio:
The ratio of 50% span length to the 2.5% span length expressed as a
percentage.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Median:
The particular value of length above and below which exactly 50% of the fibres
lie. For moderately skewed distributions the median is related to the mean and
modal lengths in the following way:
Mode – mean = 3 (median – mean)
Effective Length:
It is difficult to give a clear scientific definition for effective length. It may be
defined as the upper quartile of the numerical length distribution from which
some of the shortest fibres are eliminated by an arbitrary construction. The fibres
eliminated are those shorter than half the effective length.
Percentage of Short Fibres:
The percentages of fibres less than half the effective length or less than any
specified length.
Coefficient of Variation:
The standard deviation of weight-length or relative number-length frequencies
expressed as a percentage of the mean length.
Span Length:
The distance spanned by a specified percentage of the fibres in the test beard.
2.5% span length is the distance from the clamp on a fibre beard to a point upto
which only 2.5% of the fibres extend. 50% span length is the distance of the
point to which 50% span length is the distance of the point to which 50% of the
fibres extend and 66.7% span length is the distance upto which 66.7% of the
fibres extend.
Uniformity Ratio:
The ratio of 50% span length to the 2.5% span length expressed as a
percentage.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Dispersion:
It represents the variation in the length of fibres. It is the interquartile range
expressed as a percentage of effective length.
MEASUREMENT OF FIBRE LENGTH
Single Fibre Measurement
It is possible, with patience, good lighting, a microscope slide over a scale, and
medicinal paraffin to control the fibres, to measure the length of individual cotton
fibre. Each fibre is taken and gently straightened over the slide with the tips of
the little fingers; the length is then recorded. This method is obviously tedious
and time consuming and not used in the mill laboratory. At least 400-500 fibers
are measured in case of cotton to arrive at mean length due to large variation in
the sample.
PRINCIPLE OF BAER SORTER
A numerical sample of fibres is arranged in the form of an array in the
descending order of length and form a tracing of this array of length, mean
length, percentage of short fibres and dispersion are calculated.
DESCRIPTION
The Baer Sorter consists of a abed of combs which control and enable the
sample of fibres to be fractionalized into length groups. The Baer Sorter has 12
bottom combs are hinged at one end and are supported by a rod, extending the
width of the frame at the other end. The rod can be moved from its position and
when it is drawn, the rod can be dropped one by one. The needle of the bottom
combs are pointing upwards and in between the bottom combs, three top combs
are placed. The space between the two bottom combs is ¼ inch except the first
Page 17 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Dispersion:
It represents the variation in the length of fibres. It is the interquartile range
expressed as a percentage of effective length.
MEASUREMENT OF FIBRE LENGTH
Single Fibre Measurement
It is possible, with patience, good lighting, a microscope slide over a scale, and
medicinal paraffin to control the fibres, to measure the length of individual cotton
fibre. Each fibre is taken and gently straightened over the slide with the tips of
the little fingers; the length is then recorded. This method is obviously tedious
and time consuming and not used in the mill laboratory. At least 400-500 fibers
are measured in case of cotton to arrive at mean length due to large variation in
the sample.
PRINCIPLE OF BAER SORTER
A numerical sample of fibres is arranged in the form of an array in the
descending order of length and form a tracing of this array of length, mean
length, percentage of short fibres and dispersion are calculated.
DESCRIPTION
The Baer Sorter consists of a abed of combs which control and enable the
sample of fibres to be fractionalized into length groups. The Baer Sorter has 12
bottom combs are hinged at one end and are supported by a rod, extending the
width of the frame at the other end. The rod can be moved from its position and
when it is drawn, the rod can be dropped one by one. The needle of the bottom
combs are pointing upwards and in between the bottom combs, three top combs
are placed. The space between the two bottom combs is ¼ inch except the first
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
two bottom combs which will be 3/16 inch apart. The top combs, when placed
between the two bottom combs, the distance between them will be 1/8 inch.
Manipulation of the fibres is done by a grip called tweezer, depressor and a blunt
needle.
PROCEDURE
The position of fibre unit in the instrument is shown in fig. A representative
sample of cotton is made into sliver by drawing and doubling several times with
the fibres strengthened and parallelised. The bundle of fibres must be as narrow
as possible through out the whole process. The method of sorting is a s follows:
1.The sorter is placed with the back facing the operator. The prepared sample
is slightly twisted and placed on the bottom combs at the right hand side
of the sorter, with a small tuft protruding.
2.From the protruding end, all the loose fibres are removed by means of the
tweezer until, the ends are aligned. The removed loose fibres are kept
separately and introduced in the original sample later.
3.A tuft of fibres all pulled out, combed and transferred to the left hand side of
the sorter so that the comb nearest to the operator forms the starting line
for the tuft, while at the other end the longest fibres protrude out. The tuft
is pressed into the combs by means of depressor.
4.The process is repeated till all fibres on the right side, all combings are
transferred to the let hand side.
5.The top combs are inserted in their position to grip and to control the slippage
of the fibres.
6.The sorter, is then turned round so that the front faces the operator.
7.The bottom combs are dropped one by one successively till the tips of the
longest fibres are seen.
8.The fibres are pulled by the tweezer, combed, straightened and laid
perpendicular to a base line on a black velvet pad. When these fibres are
Page 18 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
two bottom combs which will be 3/16 inch apart. The top combs, when placed
between the two bottom combs, the distance between them will be 1/8 inch.
Manipulation of the fibres is done by a grip called tweezer, depressor and a blunt
needle.
PROCEDURE
The position of fibre unit in the instrument is shown in fig. A representative
sample of cotton is made into sliver by drawing and doubling several times with
the fibres strengthened and parallelised. The bundle of fibres must be as narrow
as possible through out the whole process. The method of sorting is a s follows:
1.The sorter is placed with the back facing the operator. The prepared sample
is slightly twisted and placed on the bottom combs at the right hand side
of the sorter, with a small tuft protruding.
2.From the protruding end, all the loose fibres are removed by means of the
tweezer until, the ends are aligned. The removed loose fibres are kept
separately and introduced in the original sample later.
3.A tuft of fibres all pulled out, combed and transferred to the left hand side of
the sorter so that the comb nearest to the operator forms the starting line
for the tuft, while at the other end the longest fibres protrude out. The tuft
is pressed into the combs by means of depressor.
4.The process is repeated till all fibres on the right side, all combings are
transferred to the let hand side.
5.The top combs are inserted in their position to grip and to control the slippage
of the fibres.
6.The sorter, is then turned round so that the front faces the operator.
7.The bottom combs are dropped one by one successively till the tips of the
longest fibres are seen.
8.The fibres are pulled by the tweezer, combed, straightened and laid
perpendicular to a base line on a black velvet pad. When these fibres are
Page 18 of 85
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
exhausted. One comb is dropped and the fibres next in order of length
are similarly pulled out and laid on the pad all fibres being carefully
spread out to uniform density. The process is continued until the tuft is
exhausted and the fibre array is obtained.
After the pattern is built up, a transparent scale, with 1/8 inch lines is placed over
the pattern. Reading on the transparent scale, the values of the co-ordinates are
marked on a graph sheet and the pattern is drawn. The diagram is called
“SORTER DIAGRAM”. The diagram is analysed for the following fibre
particulars.
1. Effective Length
2. Mean length
3. Percentage of short fibres
4. Dispersion
Fibre Sorter Methods
As single fibre measurement takes time and hand stapling requires experience
(although even then this is a subjective test), alternative methods have been
developed. One of the most popular is the use of the fibre sorter, examples of
which are the Baer, the Shirley, and the Suter Webb. The fibre sorter is an
instrument which enables the sample to be fractionalised into length groups.
Basically, the operation involves four main steps:
1.The preparation of a fringe or tuft with all the fibres aligned at one end.
2.The separation or withdrawal of fibres in order of decreasing length.
3.The preparation of a sorter diagram by laying the fibres on a black velvet
pad in decreasing order of length, the fibre parallel and their lower ends
aligned along a horizontal base line.
4.The analysis of the diagram.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
exhausted. One comb is dropped and the fibres next in order of length
are similarly pulled out and laid on the pad all fibres being carefully
spread out to uniform density. The process is continued until the tuft is
exhausted and the fibre array is obtained.
After the pattern is built up, a transparent scale, with 1/8 inch lines is placed over
the pattern. Reading on the transparent scale, the values of the co-ordinates are
marked on a graph sheet and the pattern is drawn. The diagram is called
“SORTER DIAGRAM”. The diagram is analysed for the following fibre
particulars.
1. Effective Length
2. Mean length
3. Percentage of short fibres
4. Dispersion
Fibre Sorter Methods
As single fibre measurement takes time and hand stapling requires experience
(although even then this is a subjective test), alternative methods have been
developed. One of the most popular is the use of the fibre sorter, examples of
which are the Baer, the Shirley, and the Suter Webb. The fibre sorter is an
instrument which enables the sample to be fractionalised into length groups.
Basically, the operation involves four main steps:
1.The preparation of a fringe or tuft with all the fibres aligned at one end.
2.The separation or withdrawal of fibres in order of decreasing length.
3.The preparation of a sorter diagram by laying the fibres on a black velvet
pad in decreasing order of length, the fibre parallel and their lower ends
aligned along a horizontal base line.
4.The analysis of the diagram.
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Analysis of Sorter Diagram
By placing the tracing over graph paper ruled in sixteenths of an inch, the
diagram can be readily divided into 1/8 in. classes. Alternatively it can be read in
mm also by using paper of 1 mm square.
Average or Mean Length
The sum of the base line readings divided by the base line length gives the
mean length in units of 1/8 in. or mm, the class interval. Multiplying by 4
expresses the mean length in 1/32 in. units. This is the mean height of the curve
and is obtained by dividing the total area under the curve by the base length.
Maximum Length
This is read directly from the diagram.
Modal Length
The mode of a frequency distribution is the class value of the class with the
highest frequency; in other words, the most ‘fashionable’ value. Since distances
along the base line are assumed to be proportional to frequency, the modal
length will be given by the class which has the greatest base length.
Effective Length
This value has been defined as the length of the main bulk of the longer fibres. It
is obtained by a geometrical construction on the sorter diagram, a construction
which also produces several other useful quantities. Figure illustrates this
operation.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Analysis of Sorter Diagram
By placing the tracing over graph paper ruled in sixteenths of an inch, the
diagram can be readily divided into 1/8 in. classes. Alternatively it can be read in
mm also by using paper of 1 mm square.
Average or Mean Length
The sum of the base line readings divided by the base line length gives the
mean length in units of 1/8 in. or mm, the class interval. Multiplying by 4
expresses the mean length in 1/32 in. units. This is the mean height of the curve
and is obtained by dividing the total area under the curve by the base length.
Maximum Length
This is read directly from the diagram.
Modal Length
The mode of a frequency distribution is the class value of the class with the
highest frequency; in other words, the most ‘fashionable’ value. Since distances
along the base line are assumed to be proportional to frequency, the modal
length will be given by the class which has the greatest base length.
Effective Length
This value has been defined as the length of the main bulk of the longer fibres. It
is obtained by a geometrical construction on the sorter diagram, a construction
which also produces several other useful quantities. Figure illustrates this
operation.
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1.Q is the mid-point of OA, i.e. OQ = OA.
2.From Q draw QP’ parallel to OB to cut the curve at P’.
3.Drop the perpendicular P’P.
4.Mark off OK equal to ¼ OP and erect the perpendicular K’K. This is a firs
approximation to the effective length.
5.S is the mid point of K’K.
6.From S draw SR’ parallel to OB to cut the curve at R’.
7.Drop the perpendicular R’R.
8.Mark off OL equal to ¼ OR.
9.Erect the perpendicular L’L. This is the effective length.
There are one or two points to note about this construction. The short fibres are,
in the main, ignored; this action is justified since the classers deliberately reject
the short fibre when hand stapling. Further, the effect of the initial rapid change
in length from the maximum is reduced; therefore the effective length is a
characteristic of the bulk of the longer fibres. The term ‘effective’ is used
because it is to this length value that many machinery settings are related, in
particular the distance between the nips of successive pairs of drafting rollers.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
1.Q is the mid-point of OA, i.e. OQ = OA.
2.From Q draw QP’ parallel to OB to cut the curve at P’.
3.Drop the perpendicular P’P.
4.Mark off OK equal to ¼ OP and erect the perpendicular K’K. This is a firs
approximation to the effective length.
5.S is the mid point of K’K.
6.From S draw SR’ parallel to OB to cut the curve at R’.
7.Drop the perpendicular R’R.
8.Mark off OL equal to ¼ OR.
9.Erect the perpendicular L’L. This is the effective length.
There are one or two points to note about this construction. The short fibres are,
in the main, ignored; this action is justified since the classers deliberately reject
the short fibre when hand stapling. Further, the effect of the initial rapid change
in length from the maximum is reduced; therefore the effective length is a
characteristic of the bulk of the longer fibres. The term ‘effective’ is used
because it is to this length value that many machinery settings are related, in
particular the distance between the nips of successive pairs of drafting rollers.
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The Relation Between Effective Length and Staple and Staple Length
We have seen earlier that basis of judgement of staple differs between markets
and types of cotton. These differences can be accommodated by making certain
corrections to the effective length. Lord and Underwood report that, ‘For
American Upland cottons, from about ¾ in. to 11/4 in, staple and classed on the
basis of American Staple Length Standards, a simple conversion formula is;
American Staple = 0.91 x effective length
For Egyptian-type cottons no staple length standards are in universal use, but on
the average it is found that the staple length is equal to the effective length.
Percentage Short Fibre
This is the percentage of fibres less than half the effective length. In figure the
percentage short fibre is therefore given by (RB x100/OB) (per cent)
Dispersion
The uniformity, or perhaps more aptly the variability of the cotton, can be
expressed as the ‘inter-quartile range’. In Figure L’L is the upper quartile and
M’M is the lower quartile, the inter-quartile range. This measure of the dispersion
may now be expressed as a range. This measure of the dispersion may now be
expressed as a percentage of the effective length:
NL’
Dispersion = ------ x 100 (per cent)
LL’
The Fibrograph
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
The Relation Between Effective Length and Staple and Staple Length
We have seen earlier that basis of judgement of staple differs between markets
and types of cotton. These differences can be accommodated by making certain
corrections to the effective length. Lord and Underwood report that, ‘For
American Upland cottons, from about ¾ in. to 11/4 in, staple and classed on the
basis of American Staple Length Standards, a simple conversion formula is;
American Staple = 0.91 x effective length
For Egyptian-type cottons no staple length standards are in universal use, but on
the average it is found that the staple length is equal to the effective length.
Percentage Short Fibre
This is the percentage of fibres less than half the effective length. In figure the
percentage short fibre is therefore given by (RB x100/OB) (per cent)
Dispersion
The uniformity, or perhaps more aptly the variability of the cotton, can be
expressed as the ‘inter-quartile range’. In Figure L’L is the upper quartile and
M’M is the lower quartile, the inter-quartile range. This measure of the dispersion
may now be expressed as a range. This measure of the dispersion may now be
expressed as a percentage of the effective length:
NL’
Dispersion = ------ x 100 (per cent)
LL’
The Fibrograph
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A fringe of cotton is prepared by taking about ½ OZ of cotton and combing it by
means of two hand combs. The prepared sample is in a straightened condition
with the fibres divided between the tow combs; those longer than ¼ in. are
caught in the teeth in a random position along their length. The fibre fringes are
places on the measuring unit in such a way that they lie over a long narrow slot
behind which are mounted the photo-electric cells. A light source illuminates the
fringes and the amount of light penetrating through the fringes is measured
electronically. At the start of the measurement the fringes are scanned across
the densest region, i.e. near the comb teeth, and the light which penetrates will
be a minimum. As the sample is traversed towards the fibre ends, more and
more light will fall on to the photo-electric cells.
The new ‘Servo-Fibrograph’ automatically records the change in the amount of
light reaching the cells, not in terms of intensity of illumination but as a special
form of frequency distribution. This curve is traced out on a card which is then
removed from the instrument and analysed.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
A fringe of cotton is prepared by taking about ½ OZ of cotton and combing it by
means of two hand combs. The prepared sample is in a straightened condition
with the fibres divided between the tow combs; those longer than ¼ in. are
caught in the teeth in a random position along their length. The fibre fringes are
places on the measuring unit in such a way that they lie over a long narrow slot
behind which are mounted the photo-electric cells. A light source illuminates the
fringes and the amount of light penetrating through the fringes is measured
electronically. At the start of the measurement the fringes are scanned across
the densest region, i.e. near the comb teeth, and the light which penetrates will
be a minimum. As the sample is traversed towards the fibre ends, more and
more light will fall on to the photo-electric cells.
The new ‘Servo-Fibrograph’ automatically records the change in the amount of
light reaching the cells, not in terms of intensity of illumination but as a special
form of frequency distribution. This curve is traced out on a card which is then
removed from the instrument and analysed.
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Construct the tangent to the curve to cut the horizontal at N and the vertical axis
at A. OA is then the average length of fibres longer than ¼ in. Distance along ON
represent the frequency percentage of fibres longer than ¼ in.
From S, the 50 percent mark, construct the tangent ST to cut the vertical axis at
T. OT is then the upper half mean length of fibres longer than ¼ in., based on a
weight distribution. The ratio OA/OT x 100 percent gives the length uniformity
ratio of the fibres. The upper half mean length approximates to the staple length
obtained by the cotton classers.
The Digital Fibrograph
Principal
As its name implies, the Digital Fibrograph presents the test results in digital or
numeric form. Preferably, a special fibre sampler, a ‘Fibrosampler’, is used to
prepare the beards by a light source is similar to that used in the earlier
fibrograph but the signals from the measuring console are fed into a separate
transistorised unit. The signals are electronically processed and the results fed
back to the measuring unit which has two four-digit counters facing the operator.
One counter is for selecting % S.L. and the other counter gives ‘Length’. A
Servo-follower system connected to the photoelectric cells indicates on the
‘Amount’ counter the relative number of fibres in the sample beards at the point
where the light beam passes through them. A Servo-computer ‘remember’ the
total number of fibres in the sample at 0.15 in. distance from the center of the
comb teeth and computes the number of fibres corresponding to the different
Span Lengths. When a span length is selected, the comb carrier moves until the
number of fibres under the lighthouse is equal to the number of fibres
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Construct the tangent to the curve to cut the horizontal at N and the vertical axis
at A. OA is then the average length of fibres longer than ¼ in. Distance along ON
represent the frequency percentage of fibres longer than ¼ in.
From S, the 50 percent mark, construct the tangent ST to cut the vertical axis at
T. OT is then the upper half mean length of fibres longer than ¼ in., based on a
weight distribution. The ratio OA/OT x 100 percent gives the length uniformity
ratio of the fibres. The upper half mean length approximates to the staple length
obtained by the cotton classers.
The Digital Fibrograph
Principal
As its name implies, the Digital Fibrograph presents the test results in digital or
numeric form. Preferably, a special fibre sampler, a ‘Fibrosampler’, is used to
prepare the beards by a light source is similar to that used in the earlier
fibrograph but the signals from the measuring console are fed into a separate
transistorised unit. The signals are electronically processed and the results fed
back to the measuring unit which has two four-digit counters facing the operator.
One counter is for selecting % S.L. and the other counter gives ‘Length’. A
Servo-follower system connected to the photoelectric cells indicates on the
‘Amount’ counter the relative number of fibres in the sample beards at the point
where the light beam passes through them. A Servo-computer ‘remember’ the
total number of fibres in the sample at 0.15 in. distance from the center of the
comb teeth and computes the number of fibres corresponding to the different
Span Lengths. When a span length is selected, the comb carrier moves until the
number of fibres under the lighthouse is equal to the number of fibres
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corresponding to that span length. The span length is then indicated by the
‘Length’ counter, which indicates, in mm, the movement of the comb carrier. Now
there are two counters t set the amount and these two corresponding Length
counter to give two length i.e., 2.5% & 50% simultaneously.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
corresponding to that span length. The span length is then indicated by the
‘Length’ counter, which indicates, in mm, the movement of the comb carrier. Now
there are two counters t set the amount and these two corresponding Length
counter to give two length i.e., 2.5% & 50% simultaneously.
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Relationship Between Fibre Length (mm)
Measured by Different Instruments
BAER SORTER EFFECTIVE LENGTH (Y)
Digital Fibrograph Y = 1.013x + 4.39
2.5% Span Length (x)
Uster Apparatus Y = 0.933x + 9.04
Effective Length (x)
Uster Apparatus Y = 0.996x + 9.12
Upper half mean length (x)
BAER SORTER MEAN LENGTH (Y)
Digital Fibrograph Y = 1.242x + 9.78
50% Span Length (x)
Uster Apparatus Y = 0.941x + 9.45
Mean Length (x)
DIGITAL FIBROGRAPH 2.5% SPAN LENGTH (Y)
Uster apparatus – Upper half Y = 0.946x + 5.64
Mean length (x)
Uster Apparatus – Effective length (x)Y = 0.878x + 5.77
DIGITAL FIBROGRAPH 50% SPAN LENGTH (Y)
Uster Apparatus – Mean length (x)Y = 0.672x – 1.60
Note: If the 2.5% span length of a cotton as tested on Digital fibrograph is
30mm, then the Baer sorter effective length is estimated to be 34.8mm
(1.013 x 30 + 4.39).
The conversions for fibre length and strength are subject to appreciable error
and should be used only as approximate estimates.
Mean Length
Uniformity Ratio = x 100
Upper half mean length
Based on uniformity ratio, the cotton samples can be graded as per United
States Department of Agriculture (USDA). The rating is given as:
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Relationship Between Fibre Length (mm)
Measured by Different Instruments
BAER SORTER EFFECTIVE LENGTH (Y)
Digital Fibrograph Y = 1.013x + 4.39
2.5% Span Length (x)
Uster Apparatus Y = 0.933x + 9.04
Effective Length (x)
Uster Apparatus Y = 0.996x + 9.12
Upper half mean length (x)
BAER SORTER MEAN LENGTH (Y)
Digital Fibrograph Y = 1.242x + 9.78
50% Span Length (x)
Uster Apparatus Y = 0.941x + 9.45
Mean Length (x)
DIGITAL FIBROGRAPH 2.5% SPAN LENGTH (Y)
Uster apparatus – Upper half Y = 0.946x + 5.64
Mean length (x)
Uster Apparatus – Effective length (x)Y = 0.878x + 5.77
DIGITAL FIBROGRAPH 50% SPAN LENGTH (Y)
Uster Apparatus – Mean length (x)Y = 0.672x – 1.60
Note: If the 2.5% span length of a cotton as tested on Digital fibrograph is
30mm, then the Baer sorter effective length is estimated to be 34.8mm
(1.013 x 30 + 4.39).
The conversions for fibre length and strength are subject to appreciable error
and should be used only as approximate estimates.
Mean Length
Uniformity Ratio = x 100
Upper half mean length
Based on uniformity ratio, the cotton samples can be graded as per United
States Department of Agriculture (USDA). The rating is given as:
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Uniformity Ratio Rating
Above 80% Uniform
75 – 80% Average uniform
71 – 75% Slightly irregular
70 and below Irregular
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Uniformity Ratio Rating
Above 80% Uniform
75 – 80% Average uniform
71 – 75% Slightly irregular
70 and below Irregular
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CHAPTER – 5
FIBRE FINENESS
Fibre fineness is another very important parameter which plays significant role in
yarn spinning. Fibre fineness denotes the size of cross section of the fibre or in
other terms it can be expressed as linear density of the fibres in micrograms per
inch (10
-6
g/inch). The fineness is also expressed in millitex which is weight inn
milligrams of one kilometre length of fibre. This is identical to the unit of
10
-6
gm/cm. The fineness plays a prominent part in determining the spinning
performance. When irregularity is considered, the best yarn that con be
produced is one in which the fibres are distributed along the strand in a random
order. The irregularity in the strand is dependent upon the average number of
fibres in cross-section. With a greater number of fibres in the cross-section, the
basic irregularity is reduced. If the fibres are fine, the number of fibres in cross-
section is more and irregularity is less. The finer the fibre the greater the total
surface area available in inter-fibre contact and less twist is needed to provide
necessary cohesion. The resistance of fibre to twisting and bending are also
affected by the fineness.
SIGNIFICANCE
1.To spin finer yarn we require finer fibres as certain minimum number of
fibres is must to spin in yarn (70-80).
2.From finer fibres, apart from better spinnability, better evenness can also
be achieved for the same count.
3.Yarn strength is also affected by fibre fineness to some extent.
4.A finer fibre can be spun to finer counts than a coarse fibre.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 5
FIBRE FINENESS
Fibre fineness is another very important parameter which plays significant role in
yarn spinning. Fibre fineness denotes the size of cross section of the fibre or in
other terms it can be expressed as linear density of the fibres in micrograms per
inch (10
-6
g/inch). The fineness is also expressed in millitex which is weight inn
milligrams of one kilometre length of fibre. This is identical to the unit of
10
-6
gm/cm. The fineness plays a prominent part in determining the spinning
performance. When irregularity is considered, the best yarn that con be
produced is one in which the fibres are distributed along the strand in a random
order. The irregularity in the strand is dependent upon the average number of
fibres in cross-section. With a greater number of fibres in the cross-section, the
basic irregularity is reduced. If the fibres are fine, the number of fibres in cross-
section is more and irregularity is less. The finer the fibre the greater the total
surface area available in inter-fibre contact and less twist is needed to provide
necessary cohesion. The resistance of fibre to twisting and bending are also
affected by the fineness.
SIGNIFICANCE
1.To spin finer yarn we require finer fibres as certain minimum number of
fibres is must to spin in yarn (70-80).
2.From finer fibres, apart from better spinnability, better evenness can also
be achieved for the same count.
3.Yarn strength is also affected by fibre fineness to some extent.
4.A finer fibre can be spun to finer counts than a coarse fibre.
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MEASUREMENT OF FIBRE FINENESS
Fineness can be measured by measuring fibre cross section but as cross section
of fibres are not regular, direct determination of area is not possible. Some
dimensional features i.e. swollen hair diameter, ribbon width etc., can be used to
specify fibre fineness to some extent.
The fineness of cotton fibres can be determined by either direct method such as
gravimetric dimensional measurement or by indirect method i.e. Air flow method.
DIRECT METHOD
Gravimetric Method:
In this method two types of practices are prevalent:
(a)In ASTM procedure about 100 fibres are taken from each comb sorter
groups and weighted, from which weight per unit length is calculated. In
this case meanlength is used to calculate the weight per unit length.
(b)In another method known number of fibres are first cut into in 1cm length
and then they are weighed on a torsion balance or quartz micro-balance.
There are two objections in this method.
(i)Fibre of different length grade may have different fineness value.
(ii)In a single fibre, fineness may vary over the whole length.
INDIRECT METHOD
The direct methods are generally tedious and more time consuming therefore
indirect method of the measurement of fineness are more popular. These are
mainly based on measurement of resistance to the flow of air by fibre plugs, or
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
MEASUREMENT OF FIBRE FINENESS
Fineness can be measured by measuring fibre cross section but as cross section
of fibres are not regular, direct determination of area is not possible. Some
dimensional features i.e. swollen hair diameter, ribbon width etc., can be used to
specify fibre fineness to some extent.
The fineness of cotton fibres can be determined by either direct method such as
gravimetric dimensional measurement or by indirect method i.e. Air flow method.
DIRECT METHOD
Gravimetric Method:
In this method two types of practices are prevalent:
(a)In ASTM procedure about 100 fibres are taken from each comb sorter
groups and weighted, from which weight per unit length is calculated. In
this case meanlength is used to calculate the weight per unit length.
(b)In another method known number of fibres are first cut into in 1cm length
and then they are weighed on a torsion balance or quartz micro-balance.
There are two objections in this method.
(i)Fibre of different length grade may have different fineness value.
(ii)In a single fibre, fineness may vary over the whole length.
INDIRECT METHOD
The direct methods are generally tedious and more time consuming therefore
indirect method of the measurement of fineness are more popular. These are
mainly based on measurement of resistance to the flow of air by fibre plugs, or
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on the principle of vibrating strings in the case of single fibres, as described
below:
Air-flow Method
In this method a fibre of constant weight are filled-in a fixed area and air is
allowed to pass through. The flow of air is affected by the surface area of the
fibres. The variation in air-flow is directly translated into the values of linear
density.
Specific surface is defined as the ratio of surface area to volume,
Eg specific surface of a cylinder
Let the volume= ^ ( d/2) square X l where d is the diameter of cylinder
The surface area ignoring the end = ^ d l
Specific surface area S= ^ dl / ^ ( d/2) square X l = 4/d
This ratio also equals the ratio Perimeter of cross-section/ Area of cross-section
= ^ d / ^ ( d/2) square = 4/d
Thus S Is proportional to 1/ d
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
on the principle of vibrating strings in the case of single fibres, as described
below:
Air-flow Method
In this method a fibre of constant weight are filled-in a fixed area and air is
allowed to pass through. The flow of air is affected by the surface area of the
fibres. The variation in air-flow is directly translated into the values of linear
density.
Specific surface is defined as the ratio of surface area to volume,
Eg specific surface of a cylinder
Let the volume= ^ ( d/2) square X l where d is the diameter of cylinder
The surface area ignoring the end = ^ d l
Specific surface area S= ^ dl / ^ ( d/2) square X l = 4/d
This ratio also equals the ratio Perimeter of cross-section/ Area of cross-section
= ^ d / ^ ( d/2) square = 4/d
Thus S Is proportional to 1/ d
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VARIOUS INSTRUMENTS TO MEASURE FIBRE FINENESS
(Air-flow Method)
1)Sheffield Micronaire:
The Micronaire instrument works in conjunction with an air-compressor. The
latter, through the pressure regulation system supplies air to the Micronaire
instrument at the constant pressure of 0.33 kg/cm
2
(4.7 psi for the Sheffield
Micronaire). Initially, the instrument is calibrated with the master-plug. A test
specimen of 3.24g is weighed and well opened by hand. It is then placed into
the cylindrical chamber of the Micronaire instrument. The fibre compression
plunger is inserted into the cylinder and locked by turning. The air at definite
pressure is forced through the sample and the volume rate of airflow is
measured on the scale to the nearest 0.1 scale unit at the point level with the top
of rotometer type float. Usually two specimens are taken from each cotton and
duplicate tests are carried out on each specimen. The second test on each
specimen is carried out by removing the specimen from the chamber and
repacking it in the reverse direction. The sample for the Micronaire test should
be well opened, cleaned and thoroughly mixed.
The fineness scale in the Sheffield Micronaire is suitable only for very fine and
medium fine cottons. The coarse desi varieties of cotton give a high reading
beyond the range of the scale, necessitating the determination of fibre fineness
by direct gravimetric method which is time-consuming. Recently two techniques
(a) by using a plug of 60 grains (3.89g) sample weight and normal air pressure of
6 psi; and (b) by suing a plug of 50 grains (3.24 g) sample weight and reduced
air pressure of 4 psi, were tried at the Laboratory whereby the flowmeter reading
could be kept within the range of the Micronaire scale. Both the testing methods
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
VARIOUS INSTRUMENTS TO MEASURE FIBRE FINENESS
(Air-flow Method)
1)Sheffield Micronaire:
The Micronaire instrument works in conjunction with an air-compressor. The
latter, through the pressure regulation system supplies air to the Micronaire
instrument at the constant pressure of 0.33 kg/cm
2
(4.7 psi for the Sheffield
Micronaire). Initially, the instrument is calibrated with the master-plug. A test
specimen of 3.24g is weighed and well opened by hand. It is then placed into
the cylindrical chamber of the Micronaire instrument. The fibre compression
plunger is inserted into the cylinder and locked by turning. The air at definite
pressure is forced through the sample and the volume rate of airflow is
measured on the scale to the nearest 0.1 scale unit at the point level with the top
of rotometer type float. Usually two specimens are taken from each cotton and
duplicate tests are carried out on each specimen. The second test on each
specimen is carried out by removing the specimen from the chamber and
repacking it in the reverse direction. The sample for the Micronaire test should
be well opened, cleaned and thoroughly mixed.
The fineness scale in the Sheffield Micronaire is suitable only for very fine and
medium fine cottons. The coarse desi varieties of cotton give a high reading
beyond the range of the scale, necessitating the determination of fibre fineness
by direct gravimetric method which is time-consuming. Recently two techniques
(a) by using a plug of 60 grains (3.89g) sample weight and normal air pressure of
6 psi; and (b) by suing a plug of 50 grains (3.24 g) sample weight and reduced
air pressure of 4 psi, were tried at the Laboratory whereby the flowmeter reading
could be kept within the range of the Micronaire scale. Both the testing methods
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were found to be accurate for predicting fineness. The first method is
recommended for testing very coarse desi varieties of Indian cottons.
2)WIRA Cotton Fineness Meter:
A new version of WIRA Cotton Fineness Meter has been marketed by the
Shirley Developments Ltd. The scale of this instrument is graduated in
Micronaire units. It takes a 5g sample. The standard samples for the calibration
of instrument are provided by the Shirley Institute.
3)Arealometer:
The instrument is portable and it measures the parameters such as specific
surface area, fibre weight and immaturity ratio. A small sample of 152 mg is
used. The instrument is similar to the Wheatstone bridge in which the three of
the resistances consist of copper capillaries and the fourth is the fibre plug under
test.
4)Port-Ar:
The resistance a plug of cotton fibres offers to the flow of air is measured as an
approximate indication of the fineness of fibre. A predetermined mass of loose
cotton fibres is placed in the specimen holder and compressed to a fixed volume,
the resistance to air flow is measured and expressed as Micronaire reading.
Instruments available to measure resistance to air flow use compressed air or
vacuum and are constructed to measure air flow under constant pressure drop
across the plug, to measure pressure drop when a constant flow of air is
maintained.
The Micronaire reading of cotton fibres is a function of both fineness and
maturity and is related to mill processing performance and to the quality of the
end products. Factors correlated with Micronaire reading include cleaning
efficiency, neppiness, and the strength & uniformity of the yarn.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
were found to be accurate for predicting fineness. The first method is
recommended for testing very coarse desi varieties of Indian cottons.
2)WIRA Cotton Fineness Meter:
A new version of WIRA Cotton Fineness Meter has been marketed by the
Shirley Developments Ltd. The scale of this instrument is graduated in
Micronaire units. It takes a 5g sample. The standard samples for the calibration
of instrument are provided by the Shirley Institute.
3)Arealometer:
The instrument is portable and it measures the parameters such as specific
surface area, fibre weight and immaturity ratio. A small sample of 152 mg is
used. The instrument is similar to the Wheatstone bridge in which the three of
the resistances consist of copper capillaries and the fourth is the fibre plug under
test.
4)Port-Ar:
The resistance a plug of cotton fibres offers to the flow of air is measured as an
approximate indication of the fineness of fibre. A predetermined mass of loose
cotton fibres is placed in the specimen holder and compressed to a fixed volume,
the resistance to air flow is measured and expressed as Micronaire reading.
Instruments available to measure resistance to air flow use compressed air or
vacuum and are constructed to measure air flow under constant pressure drop
across the plug, to measure pressure drop when a constant flow of air is
maintained.
The Micronaire reading of cotton fibres is a function of both fineness and
maturity and is related to mill processing performance and to the quality of the
end products. Factors correlated with Micronaire reading include cleaning
efficiency, neppiness, and the strength & uniformity of the yarn.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
This portable instrument does not require compressed air or electric power for
operation. It determines the Micronaire value and equivalent fibre thickness (in
terms of specific surface area). The instrument is provided with Micronaire scale
ranging from 2.5 to 7. Port-Ar does not need a separate balance for weighing. It
tests a specimen of 8 g.
5)Speedar:
It measures specific surface area. This instrument does not require any fixed
weight of sample. Any weight between 5g to 10g can be used. Therefore, it is
speedier in testing the sample.
6)ATIRA Fineness Tester:
In this instrument, air pressure is built up by pumping air by hand into a small
tank containing a loosely fitting float. This arrangement maintains fairly constant
air pressure when the float descends in the tank. The escaping air flows through
an adjustable needle valve connected in series with the sample chamber. An
accurately weighted 5g quantity of the fluffed sample is taken in the sample
chamber and compressed into a plug of fixed dimensions by the perforated
piston. The junction of the needle valve and the sample chamber is connected to
a reservoir manometer, the calibrated portion of which is in an incli8ned position
to spread out the scale increase the sensitivity. When the air from the air tank
flows out under constant pressure through the regulated needle valve and the
cotton sample, the manometer indicates directly the fibre fineness in micrograms
per inch. This instrument is also provided with an MH scale, as this scale is
believed to agree better with the air-flow than the fibre weight sale.
Note:Nowadays most of fineness tester used are either Portar or Speedar type
as testing is quicker in such instruments. Instruments can give data
directly in the form of computer printout for vide variety of cotton.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
This portable instrument does not require compressed air or electric power for
operation. It determines the Micronaire value and equivalent fibre thickness (in
terms of specific surface area). The instrument is provided with Micronaire scale
ranging from 2.5 to 7. Port-Ar does not need a separate balance for weighing. It
tests a specimen of 8 g.
5)Speedar:
It measures specific surface area. This instrument does not require any fixed
weight of sample. Any weight between 5g to 10g can be used. Therefore, it is
speedier in testing the sample.
6)ATIRA Fineness Tester:
In this instrument, air pressure is built up by pumping air by hand into a small
tank containing a loosely fitting float. This arrangement maintains fairly constant
air pressure when the float descends in the tank. The escaping air flows through
an adjustable needle valve connected in series with the sample chamber. An
accurately weighted 5g quantity of the fluffed sample is taken in the sample
chamber and compressed into a plug of fixed dimensions by the perforated
piston. The junction of the needle valve and the sample chamber is connected to
a reservoir manometer, the calibrated portion of which is in an incli8ned position
to spread out the scale increase the sensitivity. When the air from the air tank
flows out under constant pressure through the regulated needle valve and the
cotton sample, the manometer indicates directly the fibre fineness in micrograms
per inch. This instrument is also provided with an MH scale, as this scale is
believed to agree better with the air-flow than the fibre weight sale.
Note:Nowadays most of fineness tester used are either Portar or Speedar type
as testing is quicker in such instruments. Instruments can give data
directly in the form of computer printout for vide variety of cotton.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 6
FIBRE STRENGTH
Fibre strength is generally considered to be next to fibre length and fineness in
the order of importance amongst fibre properties and for cottons beyond a
certain staple length this property assumes greater significance.
The different measures available for reporting fibre strength are ‘breaking
strength’, ‘tensile strength’ and ‘tenacity or intrinsic strength’. Breaking strength
denotes the maximum tension the fibre is able to sustain before it breaks. In the
case of cotton fibre, it depends upon various factors such as the inherent
strength of the material constituting it, the number and intensity of weak places
and the area of cross-section of the fibre. It is mainly due to the last factor that
coarse cottons generally record higher values for fibre breaking strength than
finer ones. Therefore, in order to compare strength of two cottons differing in
fineness, it is necessary to eliminate the effect of the difference in cross-
sectional area by calculating from the values the fibre strength per unit cross-
sectional area. However, the determination of the area of cross-section is
difficult in the case of cotton fibres due to irregular shape of the cross-sections.
Hence it is a common practice to divide the breaking load by the fibre weight per
unit length which can be taken as proportional to cross-sectional area, assuming
the density to be the same for all varieties of cotton. The value so obtained is
known as ‘intrinsic strength’ or ‘tenacity’. Intrinsic strength is found to be better
related to spinning quality than the breaking strength. The strength
characteristics can be determined either on individual fibres or on bundles of
fibres.
DIFFERENT TYPES OF INSTRUMENTS
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 6
FIBRE STRENGTH
Fibre strength is generally considered to be next to fibre length and fineness in
the order of importance amongst fibre properties and for cottons beyond a
certain staple length this property assumes greater significance.
The different measures available for reporting fibre strength are ‘breaking
strength’, ‘tensile strength’ and ‘tenacity or intrinsic strength’. Breaking strength
denotes the maximum tension the fibre is able to sustain before it breaks. In the
case of cotton fibre, it depends upon various factors such as the inherent
strength of the material constituting it, the number and intensity of weak places
and the area of cross-section of the fibre. It is mainly due to the last factor that
coarse cottons generally record higher values for fibre breaking strength than
finer ones. Therefore, in order to compare strength of two cottons differing in
fineness, it is necessary to eliminate the effect of the difference in cross-
sectional area by calculating from the values the fibre strength per unit cross-
sectional area. However, the determination of the area of cross-section is
difficult in the case of cotton fibres due to irregular shape of the cross-sections.
Hence it is a common practice to divide the breaking load by the fibre weight per
unit length which can be taken as proportional to cross-sectional area, assuming
the density to be the same for all varieties of cotton. The value so obtained is
known as ‘intrinsic strength’ or ‘tenacity’. Intrinsic strength is found to be better
related to spinning quality than the breaking strength. The strength
characteristics can be determined either on individual fibres or on bundles of
fibres.
DIFFERENT TYPES OF INSTRUMENTS
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The instruments generally used for determining the tensile strength or the ‘load-
extension’ diagram of textile materials can be classified into three groups, based
on the principle used for the application of load, namely, those of: (i) the rate of
traverse (CRT); (ii) the constant rate of specimen elongation (CRE); and (iii) the
constant rate of loading (CRL) types.
i)Constant Rate of Traverse:
In the instruments of the CRT type, the specimen is held between two
clamps, one of which (the lower clamp in a vertical arrangement) is
traversed at a constant speed to exert a load on the specimen. The other
clamp works against a spring or a pendulum suitable weighted. The load
on the specimen is measured by the extension of the spring or the swing
of the pendulum, as the case may be. In these instruments, the rate of
loading depends on the extensibility of the specimen and hence will vary
with the type of specimen under test. In the case of instruments using a
pendulum principle, the errors due to inertia are appreciable. As there is
a time lag before the pendulum is accelerated to the required speed, there
will be a lag in the rate of loading in the initial stages, while at the later
stages there is a likelihood of the pendulum overshooting beyond the
breaking load of the specimen.
ii)Constant Rate of Specimen Elongation:
In the instruments of the CRE type, the application of load is made in such
a way that the rate of elongation of the specimen is kept constant. This
can be accomplished by modifying the CRT instruments suitably so as to
render negligible movement of the upper clamp. For this purpose, the
upper clamp is fixed to a stiff support and the load on this support is
measured by suitable means such as a strain gauge as in the case of the
Instron Tester.
iii)Constant Rate of Loading:
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
The instruments generally used for determining the tensile strength or the ‘load-
extension’ diagram of textile materials can be classified into three groups, based
on the principle used for the application of load, namely, those of: (i) the rate of
traverse (CRT); (ii) the constant rate of specimen elongation (CRE); and (iii) the
constant rate of loading (CRL) types.
i)Constant Rate of Traverse:
In the instruments of the CRT type, the specimen is held between two
clamps, one of which (the lower clamp in a vertical arrangement) is
traversed at a constant speed to exert a load on the specimen. The other
clamp works against a spring or a pendulum suitable weighted. The load
on the specimen is measured by the extension of the spring or the swing
of the pendulum, as the case may be. In these instruments, the rate of
loading depends on the extensibility of the specimen and hence will vary
with the type of specimen under test. In the case of instruments using a
pendulum principle, the errors due to inertia are appreciable. As there is
a time lag before the pendulum is accelerated to the required speed, there
will be a lag in the rate of loading in the initial stages, while at the later
stages there is a likelihood of the pendulum overshooting beyond the
breaking load of the specimen.
ii)Constant Rate of Specimen Elongation:
In the instruments of the CRE type, the application of load is made in such
a way that the rate of elongation of the specimen is kept constant. This
can be accomplished by modifying the CRT instruments suitably so as to
render negligible movement of the upper clamp. For this purpose, the
upper clamp is fixed to a stiff support and the load on this support is
measured by suitable means such as a strain gauge as in the case of the
Instron Tester.
iii)Constant Rate of Loading:
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In the instruments of the CRL type, the mode of application of load is such
that the rate of loading is constant throughout the duration of the test.
This can be effected by the sliding of a weight down an inclined plane or
by the extension of a spring or flow of water at a constant rate etc. The
CRL type of instruments are usually preferred for accurate scientific work
in view of the case of interpretation of the results obtained with these
instruments.
In the CRE and the CRL types of instruments, it is easy to adjust the
‘time-to-break’ while this adjustment is not easy in the CRT type of
instruments. The test results with the CRE and the CRL instruments
show less variation than those obtained with the CRT type of instruments
as in the latter the rate of loading is dependent on the extensibility of the
specimen. Hence, where accurate interpretation of results is required the
CRT instruments are not recommended although these are widely used in
view of the ease of operation and rapidity of testing. Some instruments
like the Instron can be made to function both on the CRE and the CRL
principles.
FACTORS INFLUENCING STRENGTH TEST RESULTS
Tensile strength of cotton fibres is influenced by various factors such as the time
taken to rupture the specimen, the test length of the specimen and relative
humidity of the atmosphere in which the sample is conditioned and tested. For
comparing the results on different samples and to obtain reproducible results on
a given sample, it is necessary that tensile tests are carried out under specified
conditions.
The tensile strength recorded by a fibre depends on the time taken for the
progressive deformation and its eventual rupture. A lower ‘time to break’
invariably results in a higher breaking load. In most instruments used for tensile
strength test on fibres, the time to break can be varied by controlling the ‘rate of
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
In the instruments of the CRL type, the mode of application of load is such
that the rate of loading is constant throughout the duration of the test.
This can be effected by the sliding of a weight down an inclined plane or
by the extension of a spring or flow of water at a constant rate etc. The
CRL type of instruments are usually preferred for accurate scientific work
in view of the case of interpretation of the results obtained with these
instruments.
In the CRE and the CRL types of instruments, it is easy to adjust the
‘time-to-break’ while this adjustment is not easy in the CRT type of
instruments. The test results with the CRE and the CRL instruments
show less variation than those obtained with the CRT type of instruments
as in the latter the rate of loading is dependent on the extensibility of the
specimen. Hence, where accurate interpretation of results is required the
CRT instruments are not recommended although these are widely used in
view of the ease of operation and rapidity of testing. Some instruments
like the Instron can be made to function both on the CRE and the CRL
principles.
FACTORS INFLUENCING STRENGTH TEST RESULTS
Tensile strength of cotton fibres is influenced by various factors such as the time
taken to rupture the specimen, the test length of the specimen and relative
humidity of the atmosphere in which the sample is conditioned and tested. For
comparing the results on different samples and to obtain reproducible results on
a given sample, it is necessary that tensile tests are carried out under specified
conditions.
The tensile strength recorded by a fibre depends on the time taken for the
progressive deformation and its eventual rupture. A lower ‘time to break’
invariably results in a higher breaking load. In most instruments used for tensile
strength test on fibres, the time to break can be varied by controlling the ‘rate of
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loading’, ‘rate of traverse’ or ‘rate of extension’ depending on the nature of the
instrument.
Another factor influencing fibre strength values is the ‘gauge length’ used, the
strength obtained at a longer gauge length being generally lower. The
dependence of fibre strength on gauge length is due to the presence of weak
places in the fibre. Lord pointed out that the strength of a fibre is the strength of
the weakest place, no matter how much stronger the specimen is at other
places. Thus, if structural imperfections are distributed along the length of a
fibre, some short elements may contain one or more weak places and others
may be free of them such that the chance of a weak place appearing in a
specimen increases with the test length. The extent of change of strength with
gauge length when fibres are broken individually or in the form of a bundle was
studied by Morlier et.al. Strength tests on fibre bundles are generally carried out
at nominal zero gauge length. However, tests at zero gauge length do not give
all the information required about the strength of the fibres in a sample, as the
influence of weak spots would not come into play at this test length and,
therefore, it would be desirable to carryout the tests at finite gauge lengths.
Moreover, it has been well established that the bundle strength measured at 1/8
in. (3mm) gauge length has better correlation with yarn strength than the
strength values measured at other gauge lengths. Hence the use of 1/8 in.
(3mm) gauge length for bundle strength tests has now become very common.
The strength of cotton fibres is affected by the humidity of the atmosphere in
which it is conditioned and tested, the strength increasing with the rise in relative
humidity. On the basis of extensive studies on the variation of single fibre
strength with increase in relative humidity, it has been possible to arrive at
correction factors (Table) with the help of which one can calculate the single fibre
strength at the standard atmosphere of 65% RH from the strength obtained at
any ambient humidity.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
loading’, ‘rate of traverse’ or ‘rate of extension’ depending on the nature of the
instrument.
Another factor influencing fibre strength values is the ‘gauge length’ used, the
strength obtained at a longer gauge length being generally lower. The
dependence of fibre strength on gauge length is due to the presence of weak
places in the fibre. Lord pointed out that the strength of a fibre is the strength of
the weakest place, no matter how much stronger the specimen is at other
places. Thus, if structural imperfections are distributed along the length of a
fibre, some short elements may contain one or more weak places and others
may be free of them such that the chance of a weak place appearing in a
specimen increases with the test length. The extent of change of strength with
gauge length when fibres are broken individually or in the form of a bundle was
studied by Morlier et.al. Strength tests on fibre bundles are generally carried out
at nominal zero gauge length. However, tests at zero gauge length do not give
all the information required about the strength of the fibres in a sample, as the
influence of weak spots would not come into play at this test length and,
therefore, it would be desirable to carryout the tests at finite gauge lengths.
Moreover, it has been well established that the bundle strength measured at 1/8
in. (3mm) gauge length has better correlation with yarn strength than the
strength values measured at other gauge lengths. Hence the use of 1/8 in.
(3mm) gauge length for bundle strength tests has now become very common.
The strength of cotton fibres is affected by the humidity of the atmosphere in
which it is conditioned and tested, the strength increasing with the rise in relative
humidity. On the basis of extensive studies on the variation of single fibre
strength with increase in relative humidity, it has been possible to arrive at
correction factors (Table) with the help of which one can calculate the single fibre
strength at the standard atmosphere of 65% RH from the strength obtained at
any ambient humidity.
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Table: Humidity Correction Factors for Single Fibre Strength
Relative
Humidity
(%)
30 40 50 60 70
0
1
2
3
4
5
6
7
8
9
1.218
1.211
1.294
1.196
1.189
1.181
1.174
1.168
1.160
1.153
1.146
1.140
1.134
1.127
1.120
1.114
1.107
1.101
1.096
1.089
1.083
1.077
1.071
1.065
1.059
1.054
1.048
1.043
1.037
1.031
1.026
1.020
1.016
1.010
1.005
1.000
0.994
0.989
0.984
0.980
0.975
0.970
0.965
0.960
0.955
0.951
0.951
0.951
0.951
0.951
Bundle strength measurements are also affected by factors such as the
condition of the leather in the jaws holding the fibres under test on the
instrument, jaw pressure, bundle alignment, fibre selection in the combing
process prior to clamping etc., some of which could give a ‘personal bias’ to the
results. In order to have a check on the results of bundle strength
measurements, it is necessary to test suitable control samples and keep the
instruments properly calibrated. The results on various samples tested could
then be corrected by a factor depending upon the test results on the control
sample.
SINGLE FIBRE STRENGTH
The tenacity of a fibre is dependent upon many factors related to its structure
and the conditions under which the test is carried out. The structural features
contributing to strength are the chain length of the molecules, their orientation
and the size and distribution of the crystallites. Testing conditions which affect
the strength values are as mentioned earlier, the gauge length used, the rate of
loading, the type of instrument employed and the relative humidity prevailing in
the testing room.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Table: Humidity Correction Factors for Single Fibre Strength
Relative
Humidity
(%)
30 40 50 60 70
0
1
2
3
4
5
6
7
8
9
1.218
1.211
1.294
1.196
1.189
1.181
1.174
1.168
1.160
1.153
1.146
1.140
1.134
1.127
1.120
1.114
1.107
1.101
1.096
1.089
1.083
1.077
1.071
1.065
1.059
1.054
1.048
1.043
1.037
1.031
1.026
1.020
1.016
1.010
1.005
1.000
0.994
0.989
0.984
0.980
0.975
0.970
0.965
0.960
0.955
0.951
0.951
0.951
0.951
0.951
Bundle strength measurements are also affected by factors such as the
condition of the leather in the jaws holding the fibres under test on the
instrument, jaw pressure, bundle alignment, fibre selection in the combing
process prior to clamping etc., some of which could give a ‘personal bias’ to the
results. In order to have a check on the results of bundle strength
measurements, it is necessary to test suitable control samples and keep the
instruments properly calibrated. The results on various samples tested could
then be corrected by a factor depending upon the test results on the control
sample.
SINGLE FIBRE STRENGTH
The tenacity of a fibre is dependent upon many factors related to its structure
and the conditions under which the test is carried out. The structural features
contributing to strength are the chain length of the molecules, their orientation
and the size and distribution of the crystallites. Testing conditions which affect
the strength values are as mentioned earlier, the gauge length used, the rate of
loading, the type of instrument employed and the relative humidity prevailing in
the testing room.
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INSTRUMENTS FOR MEASURING SINGLE FIBRE STRENGTH
There are various types of instruments available for carrying out single fibre
strength tests. They can be classified in mainly two types of instruments.
Universal Tensile Tester:
This is a robust and versatile instrument used for measurement of a variety of
mechanical properties. Its versatility rests in the fact that it is capable of
recording the tensile load-elongation curves of a range of samples from single
fibres to thick fabric strips, which cover a wide spectrum of mechanical
characteristics.
The specimen under test is clamped between two jaws. The upper jaw is
suspended from the ‘load cell’ which is the load sensing device, while the lower
jaw is mounted on the ‘cross-head’ which can be moved up and down at
controlled speeds. The crosshead speed, which decides the rate of extension of
the specimen, can be varied from 0.05 cm/min to 50 cm/min in 12 steps. The
choice of the suitable load cell from among the four cells which cover a range
from 2 g to 500 kg. is made in accordance with the load requirements of the
specimen under test. The load cell contains a bonded wire type of strain gauge
which consists essentially of a cantilever beam with a resistance wire bonded to
the surface. The upper jaw carrying the specimen is suspended from the free
end of the cantilever beam such that the tension developed in the specimen
leads to an infinitesimally small bending of the beam. As a result, the wire
bonded to the beam increases in length and hence in electrical resistance in
proportion to the tension in the specimen. Since this resistance wire forms one
arm of a wheatstone bridge circuit, which is excited by an oscillator and which
remains normally balanced, any tension in the specimen would cause disbalance
in the circuit. The resulting signal is amplified to operate a recorder pen. Thus
when the test specimen is extended, the recorder pen moves across the chart
through a distance proportional to the tension in the specimen. Since the
deflection of the end of the beam is infinitesimally small, the Instron works as a
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
INSTRUMENTS FOR MEASURING SINGLE FIBRE STRENGTH
There are various types of instruments available for carrying out single fibre
strength tests. They can be classified in mainly two types of instruments.
Universal Tensile Tester:
This is a robust and versatile instrument used for measurement of a variety of
mechanical properties. Its versatility rests in the fact that it is capable of
recording the tensile load-elongation curves of a range of samples from single
fibres to thick fabric strips, which cover a wide spectrum of mechanical
characteristics.
The specimen under test is clamped between two jaws. The upper jaw is
suspended from the ‘load cell’ which is the load sensing device, while the lower
jaw is mounted on the ‘cross-head’ which can be moved up and down at
controlled speeds. The crosshead speed, which decides the rate of extension of
the specimen, can be varied from 0.05 cm/min to 50 cm/min in 12 steps. The
choice of the suitable load cell from among the four cells which cover a range
from 2 g to 500 kg. is made in accordance with the load requirements of the
specimen under test. The load cell contains a bonded wire type of strain gauge
which consists essentially of a cantilever beam with a resistance wire bonded to
the surface. The upper jaw carrying the specimen is suspended from the free
end of the cantilever beam such that the tension developed in the specimen
leads to an infinitesimally small bending of the beam. As a result, the wire
bonded to the beam increases in length and hence in electrical resistance in
proportion to the tension in the specimen. Since this resistance wire forms one
arm of a wheatstone bridge circuit, which is excited by an oscillator and which
remains normally balanced, any tension in the specimen would cause disbalance
in the circuit. The resulting signal is amplified to operate a recorder pen. Thus
when the test specimen is extended, the recorder pen moves across the chart
through a distance proportional to the tension in the specimen. Since the
deflection of the end of the beam is infinitesimally small, the Instron works as a
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‘constant-rate-of-extension’ instrument when the crosshead is moved at a steady
rate. The crosshead and chart are driven synchronously through magnetic
clutches and convenient gears to provide a choice of constant and reversible
extension speeds. The chart movement can be varied to achieve a range of
extension magnifications. As a result of the simultaneous movement of the pen
and the chart, the former responding to the tension in the specimen and the
latter synchronized to the specimen extension; the trace on the chart represents
the load-elongation curve. The Instron is also equipped with an Integrator which
is a convenient device for obtaining the area under the load-elongation curve
which measure the work of rupture.
Bundle Strength:
The determination of strength on individual fibres, as discussed above, involved
considerable amount of time as tests have to be made on a large number of
fibres in view of the high variability in fibre strength. Moreover in actual practice,
fibres are not used individually but in groups, such as in yarns or fabrics. Thus,
bundles or groups of fibres come into play during the tensile break of yarns or
fabrics. Further, the correlation between spinning performance and bundle
strength is at least as high as that between spinning performance and intrinsic
strength determined by testing individual fibres. The testing of bundles of fibres
takes less time and involves less strain than testing individual fibres. In view of
these considerations, determination of breaking strength of fibre bundles has
assumed greater importance than single fibre strength tests.
INSTRUMENTS FOR BUNDLE STRENGTH DETERMINATION
In the past, various methods were tried for the determination of bundle strength.
In one of the methods (which was being used at this laboratory), a small tuft
containing about 80 to 120 fibres was taken and the ends fixed between two
pairs of paper strips by means of some good adhesive, taking care to see that
the test length was 1 cm; the paper strips were gripped between the jaws of a
schopper testing machine and the bundle broken in the usual manner. The
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
‘constant-rate-of-extension’ instrument when the crosshead is moved at a steady
rate. The crosshead and chart are driven synchronously through magnetic
clutches and convenient gears to provide a choice of constant and reversible
extension speeds. The chart movement can be varied to achieve a range of
extension magnifications. As a result of the simultaneous movement of the pen
and the chart, the former responding to the tension in the specimen and the
latter synchronized to the specimen extension; the trace on the chart represents
the load-elongation curve. The Instron is also equipped with an Integrator which
is a convenient device for obtaining the area under the load-elongation curve
which measure the work of rupture.
Bundle Strength:
The determination of strength on individual fibres, as discussed above, involved
considerable amount of time as tests have to be made on a large number of
fibres in view of the high variability in fibre strength. Moreover in actual practice,
fibres are not used individually but in groups, such as in yarns or fabrics. Thus,
bundles or groups of fibres come into play during the tensile break of yarns or
fabrics. Further, the correlation between spinning performance and bundle
strength is at least as high as that between spinning performance and intrinsic
strength determined by testing individual fibres. The testing of bundles of fibres
takes less time and involves less strain than testing individual fibres. In view of
these considerations, determination of breaking strength of fibre bundles has
assumed greater importance than single fibre strength tests.
INSTRUMENTS FOR BUNDLE STRENGTH DETERMINATION
In the past, various methods were tried for the determination of bundle strength.
In one of the methods (which was being used at this laboratory), a small tuft
containing about 80 to 120 fibres was taken and the ends fixed between two
pairs of paper strips by means of some good adhesive, taking care to see that
the test length was 1 cm; the paper strips were gripped between the jaws of a
schopper testing machine and the bundle broken in the usual manner. The
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bundle strength that was recorded on the machine was divided by the number of
fibres in the bundle to get an idea of the strength realized per fibre.
In this category mainly two instruments are in use.
1.Pressley Strength Tester
2.Stelometer
Pressley Strength Tester:
It works on the principle of inclined plane apparatus. Now this instrument is not
much in use because of service limiting factors.
Error is likely to occur on account of the fact that the tension applied to straighten
the fibres while keeping them in the clamps and the torque applied for tightening
the jaw screws would vary from operator to operator. This error can be reduced
by using a torque vice, in which tension is adjusted to about 8 lb-in. (1.5 kg/cm).
Further, as this instrument works on the principle of constant but increases with
the traverse of the moving load carriage further away from the initial position;
hence, for bundles having higher breaking strength, the rate of loading at
breaking point would be higher than that for bundles of lower strength. Also,
there is an increased likelihood of the rolling weight overshooting the breaking
point before coming to rest in the former case due to inertia.
Stelometer:
The Stelometer is a pendulum type of instrument in which, contrary to usual
practice, the pendulum weight remains stationary while the pendulum axis
moves through an arc. By means of a special dashpot device, the rotation of the
pendulum axis (beam) is controlled in such a manner that the rate of loading is
approximately constant. An arrangement has been provided to check the
calibration of the instrument and adjust the rate of loading. Normally, the rate of
loading used is 1 kg/sec. A pointer, freely mounted on the axis and driven by a
sensing pin mounted on the pendulum, moves over a scale graduated from 2 to
7 kg. indicating the breaking load. In addition, a smaller pointer suspended from
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
bundle strength that was recorded on the machine was divided by the number of
fibres in the bundle to get an idea of the strength realized per fibre.
In this category mainly two instruments are in use.
1.Pressley Strength Tester
2.Stelometer
Pressley Strength Tester:
It works on the principle of inclined plane apparatus. Now this instrument is not
much in use because of service limiting factors.
Error is likely to occur on account of the fact that the tension applied to straighten
the fibres while keeping them in the clamps and the torque applied for tightening
the jaw screws would vary from operator to operator. This error can be reduced
by using a torque vice, in which tension is adjusted to about 8 lb-in. (1.5 kg/cm).
Further, as this instrument works on the principle of constant but increases with
the traverse of the moving load carriage further away from the initial position;
hence, for bundles having higher breaking strength, the rate of loading at
breaking point would be higher than that for bundles of lower strength. Also,
there is an increased likelihood of the rolling weight overshooting the breaking
point before coming to rest in the former case due to inertia.
Stelometer:
The Stelometer is a pendulum type of instrument in which, contrary to usual
practice, the pendulum weight remains stationary while the pendulum axis
moves through an arc. By means of a special dashpot device, the rotation of the
pendulum axis (beam) is controlled in such a manner that the rate of loading is
approximately constant. An arrangement has been provided to check the
calibration of the instrument and adjust the rate of loading. Normally, the rate of
loading used is 1 kg/sec. A pointer, freely mounted on the axis and driven by a
sensing pin mounted on the pendulum, moves over a scale graduated from 2 to
7 kg. indicating the breaking load. In addition, a smaller pointer suspended from
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the above indicates the percentage elongation on an auxiliary scale. The
indicators can be read to nearest 0.01 kg and 0.1 percent for breaking load and
elongation respectively. The clamps, after removal of the protruding fibres, are
loaded in the slots on the top of the Stelometer and the beam is released. One
part of the Pressley clamps is held in the adjustable holder carried by the beam
while the other is held in a slot on the top end of the pendulum. The movement
of the beam applies tension to the bundle by pulling apart the two parts of the
clamps. As soon as the bundle breaks, the sensing pin falls away and the
pointer stops immediately. The breaking load can be read on the scale. The
broken fibres are collected from the clamps and the weight in milligrams
determined accurately. Six bundles are tested by two operators, on every
sample. The bundle tenacity is obtained by dividing breaking load by the weight
of the sample.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
the above indicates the percentage elongation on an auxiliary scale. The
indicators can be read to nearest 0.01 kg and 0.1 percent for breaking load and
elongation respectively. The clamps, after removal of the protruding fibres, are
loaded in the slots on the top of the Stelometer and the beam is released. One
part of the Pressley clamps is held in the adjustable holder carried by the beam
while the other is held in a slot on the top end of the pendulum. The movement
of the beam applies tension to the bundle by pulling apart the two parts of the
clamps. As soon as the bundle breaks, the sensing pin falls away and the
pointer stops immediately. The breaking load can be read on the scale. The
broken fibres are collected from the clamps and the weight in milligrams
determined accurately. Six bundles are tested by two operators, on every
sample. The bundle tenacity is obtained by dividing breaking load by the weight
of the sample.
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CORRECTION OF OBSERVED TEST RESULTS
Standard value for calibration cotton
Correction Factor =
Observed value for calibration cotton
After finding out the correction factor, the test values obtained on the instrument
are adjusted by this factor. Therefore, for any sample under test,
Adjusted value = Observed value x Correction factor
Breaking strength of bundle in kg x 11.81
Stelometer value at zero =
gauge length (g/tex) Weight of bundle in mg.
Breaking strength of bundle in kg x 15.0
Stelometer value at 1/8 in.=
gauge length (g/tex) Weight of bundle in mg.
FIBRE QUALITY INDEX
In order to decide the quality characteristics of the cotton required for spinning
different counts with desired CSP values, a single measure for the overall quality
of cotton has been established by SITRA. This measure known as Fibre Quality
Index (FQI), is derived from the following formula:
lu s m
FQI =
f
where,
lu =product of 2.5% span length (l) in mm and uniformity ratio % (u)
measured on Digital Fibrograph divided by 100
s =Bundle strength in g/tex at 3mm gauge length (Stelometer)
m =Maturity coefficient
f =Fibre fineness as determined on Micronaire and expressed as
Micronaire value (micrograms/in.)
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CORRECTION OF OBSERVED TEST RESULTS
Standard value for calibration cotton
Correction Factor =
Observed value for calibration cotton
After finding out the correction factor, the test values obtained on the instrument
are adjusted by this factor. Therefore, for any sample under test,
Adjusted value = Observed value x Correction factor
Breaking strength of bundle in kg x 11.81
Stelometer value at zero =
gauge length (g/tex) Weight of bundle in mg.
Breaking strength of bundle in kg x 15.0
Stelometer value at 1/8 in.=
gauge length (g/tex) Weight of bundle in mg.
FIBRE QUALITY INDEX
In order to decide the quality characteristics of the cotton required for spinning
different counts with desired CSP values, a single measure for the overall quality
of cotton has been established by SITRA. This measure known as Fibre Quality
Index (FQI), is derived from the following formula:
lu s m
FQI =
f
where,
lu =product of 2.5% span length (l) in mm and uniformity ratio % (u)
measured on Digital Fibrograph divided by 100
s =Bundle strength in g/tex at 3mm gauge length (Stelometer)
m =Maturity coefficient
f =Fibre fineness as determined on Micronaire and expressed as
Micronaire value (micrograms/in.)
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AT OPTIMUM TWIST MULTIPLIER
Achievable Lea CSP = 320 (ÖFQI + l) – 13C for carded counts
= [320 (ÖFQI + l) – 13C] (l+W/100)
for combed counts
where,
C = Count spun
W = % Waste extracted during combing
In the case of combed counts, the lea CSP would be more by 1% for every 1%
waste extracted at the combers.
FIBRE-YARN RELATIONSHIPS USING HVI TEST SYSTEM
(a)Prediction Expressions for Yarn lea CSP using HVI/FMT measured
fibre properties (ICC Mode):
SITRA has developed the following prediction expressions connecting
fibre properties measured by High Volume Instrument (HVI) and Shirley
Maturity Tester with yarn lea CSP.
Lea CSP = 280 ÖFQI + 700 – 13C (For carded counts)
Lea CSP = {280 ÖFQI + 700 – 13C} {l+W/100} (For combed counts)
Where,
C = Yarn count, Ne
W = % Comber Noil
Lsm
FQI =
f
Values of L, s, m are measured using HVI test system and that of m using
Shirley FMT.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
AT OPTIMUM TWIST MULTIPLIER
Achievable Lea CSP = 320 (ÖFQI + l) – 13C for carded counts
= [320 (ÖFQI + l) – 13C] (l+W/100)
for combed counts
where,
C = Count spun
W = % Waste extracted during combing
In the case of combed counts, the lea CSP would be more by 1% for every 1%
waste extracted at the combers.
FIBRE-YARN RELATIONSHIPS USING HVI TEST SYSTEM
(a)Prediction Expressions for Yarn lea CSP using HVI/FMT measured
fibre properties (ICC Mode):
SITRA has developed the following prediction expressions connecting
fibre properties measured by High Volume Instrument (HVI) and Shirley
Maturity Tester with yarn lea CSP.
Lea CSP = 280 ÖFQI + 700 – 13C (For carded counts)
Lea CSP = {280 ÖFQI + 700 – 13C} {l+W/100} (For combed counts)
Where,
C = Yarn count, Ne
W = % Comber Noil
Lsm
FQI =
f
Values of L, s, m are measured using HVI test system and that of m using
Shirley FMT.
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L = 50% span length, mm
s = Bundle strength, gm/tex
f = Fineness (Micronaire value in micrograms/inch)
m = Maturity ratio
If maturity ratio values are not readily available then, as an approximation,
the lea CSP values may be arrived at from following expression:
Lea CSP = 250 (ÖLs/f) + 590 – 13C
(b)Prediction Expressions for Yarn lea CSP using Fibre properties
measured by HVI test system (HVI Mode):
Lea CSP = 165 (ÖFQI) + 590 – (13C)(For carded counts)
Lea CSP = {165 (ÖFQI) + 590 – (13C)} {l+W/100} (For combed counts)
Where,
C = Yarn count, Ne
W = % Comber Noil
Ls
FQI =
f
Values of L, s, m are measured using HVI test system and that of m using
Shirley FMT.
L = Mean length, mm
s = Bundle strength, gm/tex
f = Fineness (Micronaire value in micrograms/inch)
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
L = 50% span length, mm
s = Bundle strength, gm/tex
f = Fineness (Micronaire value in micrograms/inch)
m = Maturity ratio
If maturity ratio values are not readily available then, as an approximation,
the lea CSP values may be arrived at from following expression:
Lea CSP = 250 (ÖLs/f) + 590 – 13C
(b)Prediction Expressions for Yarn lea CSP using Fibre properties
measured by HVI test system (HVI Mode):
Lea CSP = 165 (ÖFQI) + 590 – (13C)(For carded counts)
Lea CSP = {165 (ÖFQI) + 590 – (13C)} {l+W/100} (For combed counts)
Where,
C = Yarn count, Ne
W = % Comber Noil
Ls
FQI =
f
Values of L, s, m are measured using HVI test system and that of m using
Shirley FMT.
L = Mean length, mm
s = Bundle strength, gm/tex
f = Fineness (Micronaire value in micrograms/inch)
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MISCELLANEOUS PROPERTIES
1.Fibre Friction or Clinging Power:
Fibre friction is considered as an important factor that contributes to yarn
strength especially of the low twist yarns in which breakage often occurs
as a result of fibre slippage rather than fibre fracture. Prediction of
spinning value of cotton could therefore be rendered more accurate by
quantitative information on fibre friction. Three methods are employed for
determining fibre friction. In one method, which is a modification of
Adderley’s method, a 3/8 in. length of a group of 10 cotton fibres is pulled
between two pads made of parallelised fibres of the same cotton and
subjected to a known pressure. The force required to pull out the group of
10 fibres is measured by a mechanism similar to the one employed on the
0’ Neill single fibre strength tester. In another method frictional force is
determined at two angles of slippage (0
o
and 30
o
) by means of an
elaborate apparatus designed for this purpose. In the third method the
technique used for the application of pressure between fibre pads is
simplified and the force required to withdraw 20 parallel fibres is
determined.
2.Torsional Rigidity:
The resistance of a fibre to twisting is determined by its torsional rigidity.
This property is important in spinning where the difficulty of binding rigid
fibres together could result in the production of bulky yarns. The torsional
rigidity of a fibre is defined as the torque required to twist one centimeter
length of it through 360
o
. The torsional rigidity can be shown to be
proportional to the product of the rigidity modulus and the square of the
area of cross-section of the fibre, the constant of proportionality being
dependent on the cross-sectional shape.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
MISCELLANEOUS PROPERTIES
1.Fibre Friction or Clinging Power:
Fibre friction is considered as an important factor that contributes to yarn
strength especially of the low twist yarns in which breakage often occurs
as a result of fibre slippage rather than fibre fracture. Prediction of
spinning value of cotton could therefore be rendered more accurate by
quantitative information on fibre friction. Three methods are employed for
determining fibre friction. In one method, which is a modification of
Adderley’s method, a 3/8 in. length of a group of 10 cotton fibres is pulled
between two pads made of parallelised fibres of the same cotton and
subjected to a known pressure. The force required to pull out the group of
10 fibres is measured by a mechanism similar to the one employed on the
0’ Neill single fibre strength tester. In another method frictional force is
determined at two angles of slippage (0
o
and 30
o
) by means of an
elaborate apparatus designed for this purpose. In the third method the
technique used for the application of pressure between fibre pads is
simplified and the force required to withdraw 20 parallel fibres is
determined.
2.Torsional Rigidity:
The resistance of a fibre to twisting is determined by its torsional rigidity.
This property is important in spinning where the difficulty of binding rigid
fibres together could result in the production of bulky yarns. The torsional
rigidity of a fibre is defined as the torque required to twist one centimeter
length of it through 360
o
. The torsional rigidity can be shown to be
proportional to the product of the rigidity modulus and the square of the
area of cross-section of the fibre, the constant of proportionality being
dependent on the cross-sectional shape.
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As the determination of single fibre rigidity involves considerable testing
time, a quicker method has been developed. In this method, the rigidity is
determined on a bundle of fibres weighing about 1 mg and the single fibre
rigidity is estimated from the bundle rigidity by dividing the latter by the
number of fibres in the bundle. Although the values obtained by this
method are not identical with those obtained by measurement on single
fibres, there is a high correlation between the two and hence the bundle
method can be adopted to save time.
3.Lustre:
Luster and colour of cotton are two characteristics that appeal to the
aesthetic sense of the observer. Luster denotes the ability of the fibre to
reflect light preferentially in some directions whereas colour refers to the
hue and to the strength of the hue. While a white cotton does not
necessarily have to show lustre, a creamy or yellowish variety can be
highly lustrous. Lustre is measured by means of a lustre meter fabricated
for this purpose. In this instrument, the sample is illuminated at an angle
of 45
o
by a collight reflected from the sample is received by a photocell
and the intensity is obtained in terms of photo-current measured on an
ammeter. The intensity of specular reflection (45
o
) and the intensity of
diffuse reflection in the direction normal to the sample are noted. The
ratio of the two intensities are known as the contrast ratio is used to
express the lustre of the sample. The instrument can be used for tests on
fibre, yarn or fabric.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
As the determination of single fibre rigidity involves considerable testing
time, a quicker method has been developed. In this method, the rigidity is
determined on a bundle of fibres weighing about 1 mg and the single fibre
rigidity is estimated from the bundle rigidity by dividing the latter by the
number of fibres in the bundle. Although the values obtained by this
method are not identical with those obtained by measurement on single
fibres, there is a high correlation between the two and hence the bundle
method can be adopted to save time.
3.Lustre:
Luster and colour of cotton are two characteristics that appeal to the
aesthetic sense of the observer. Luster denotes the ability of the fibre to
reflect light preferentially in some directions whereas colour refers to the
hue and to the strength of the hue. While a white cotton does not
necessarily have to show lustre, a creamy or yellowish variety can be
highly lustrous. Lustre is measured by means of a lustre meter fabricated
for this purpose. In this instrument, the sample is illuminated at an angle
of 45
o
by a collight reflected from the sample is received by a photocell
and the intensity is obtained in terms of photo-current measured on an
ammeter. The intensity of specular reflection (45
o
) and the intensity of
diffuse reflection in the direction normal to the sample are noted. The
ratio of the two intensities are known as the contrast ratio is used to
express the lustre of the sample. The instrument can be used for tests on
fibre, yarn or fabric.
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CHAPTER – 6
TRASH
Trash cannot be termed as fibre property but it has its own importance as the
amount of trash present in cotton directly affects the cost of cleaned cotton. Even
if we keep commercial aspect aside trash affects the yarn quality considerably.
Even after removing the trash in Blowroom and Cards small amount of trash
remains in the sliver.
Infact removal of trash in Blowroom and Cards depends upon nature of trash.
Seed coats amongst all impurities are most difficult to remove.
Recent studies have confirmed tha6 remnant trash in sliver mostly consists of
seed coats and it is directly related with the uster neps and classimate faults.
MEASUREMENT OF TRASH
100g. of cotton sample ‘S’ to be analysed is weighed accurately and is passed
through the Trash Analyser giving L1g. of lint and T1g. of trash. The trash T1 is
collected and again processed giving L2g. of lint and T2g. of trash. The lint portions
L1 and L2 are weighed together and give the total lint content in the sample.
S (100 g)
Lint L1 Trash T1
Lint L2 Trash T2
L = Lint content % = L1 + L2
T = Trash content % = T2
Invisible Loss % = 100 – (L + T)
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 6
TRASH
Trash cannot be termed as fibre property but it has its own importance as the
amount of trash present in cotton directly affects the cost of cleaned cotton. Even
if we keep commercial aspect aside trash affects the yarn quality considerably.
Even after removing the trash in Blowroom and Cards small amount of trash
remains in the sliver.
Infact removal of trash in Blowroom and Cards depends upon nature of trash.
Seed coats amongst all impurities are most difficult to remove.
Recent studies have confirmed tha6 remnant trash in sliver mostly consists of
seed coats and it is directly related with the uster neps and classimate faults.
MEASUREMENT OF TRASH
100g. of cotton sample ‘S’ to be analysed is weighed accurately and is passed
through the Trash Analyser giving L1g. of lint and T1g. of trash. The trash T1 is
collected and again processed giving L2g. of lint and T2g. of trash. The lint portions
L1 and L2 are weighed together and give the total lint content in the sample.
S (100 g)
Lint L1 Trash T1
Lint L2 Trash T2
L = Lint content % = L1 + L2
T = Trash content % = T2
Invisible Loss % = 100 – (L + T)
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If the Trash T2 is still found to contain a sizable amount of lint, it is passed once
again through the Analyser giving L3g. of lint and T3g. of trash. Then lint content L
= L1 + L2 + L3 and Trash T = T3.
In general, two such 100 g. samples are analysed and the average calculated. It
is essential that the sample processed must be fairly representative of the bulk
sample.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
If the Trash T2 is still found to contain a sizable amount of lint, it is passed once
again through the Analyser giving L3g. of lint and T3g. of trash. Then lint content L
= L1 + L2 + L3 and Trash T = T3.
In general, two such 100 g. samples are analysed and the average calculated. It
is essential that the sample processed must be fairly representative of the bulk
sample.
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PRECAUTIONS
(1)While feeding the cotton, it is necessary to open it by hand and fed it
uniformly in a fairly thin fleece. For example, when feeding 100g. of
sample, half of it should be spread evenly on the feed table and as the
test proceeds the remaining sample should be added gradually.
(2)Hard lumps of trash or full seeds in the test sample must be collected by
hand and weighed along with the trash. If allowed to pass along with the
cotton, these are likely to damage the feed plate and licker-in wire points.
(3)A lever is provided for opening and closing the valve controlling the air
flow from the cage into the filter. This valve should be opened at the
beginning of a test. At the end of each test, the valve is closed so that all
the lint falls down into the lint box.
ANALYSIS OF TRASH
The visible trash so collected is passed through a set of wire meshy of mesh size
of BS 10 & BS 36 and is analysed as:
Trash over mesh 10 = Seed coats
Trash over mesh 36 = Leafy matter, kitties etc.
Trash below mesh 36 = Dust etc.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
PRECAUTIONS
(1)While feeding the cotton, it is necessary to open it by hand and fed it
uniformly in a fairly thin fleece. For example, when feeding 100g. of
sample, half of it should be spread evenly on the feed table and as the
test proceeds the remaining sample should be added gradually.
(2)Hard lumps of trash or full seeds in the test sample must be collected by
hand and weighed along with the trash. If allowed to pass along with the
cotton, these are likely to damage the feed plate and licker-in wire points.
(3)A lever is provided for opening and closing the valve controlling the air
flow from the cage into the filter. This valve should be opened at the
beginning of a test. At the end of each test, the valve is closed so that all
the lint falls down into the lint box.
ANALYSIS OF TRASH
The visible trash so collected is passed through a set of wire meshy of mesh size
of BS 10 & BS 36 and is analysed as:
Trash over mesh 10 = Seed coats
Trash over mesh 36 = Leafy matter, kitties etc.
Trash below mesh 36 = Dust etc.
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The Cleaning Efficiency of a Machine:
The cleaning efficiency helps to evaluate the performance of a machine. If it falls
below a certain level the machine needs to be checked. The removal of trash
particles such as seed & leaf particles, stalks, sand and dust from cotton is
quantitatively expressed as cleaning efficiency which can be estimated as follow:
About 200gm of sample is taken from the feed & delivery of a machine like Blow
room, Card or Beaters. These samples are analysed for trash content. This is
done by processing a 100gm of sample through a Trash Analyser and collecting
the trash obtained & weighing it accurately. Two samples must be analysed and
average trash content is calculated.
T1 – T2
Cleaning Efficiency % = x 100
T1
Where, T1 = % trash in the material fed
T2 = % trash in the material delivered
Speeds and Settings of Shirley Trash Analyser:
Speeds:
1.Taker-in … 900 rpm
2.Feed roller … 0.9 rpm
3.Cage … 800 rpm
4.Fan … 1500 rpm
5.Motor … 1400 rpm
Setting:
1.Feed plate to taker-in … 4/1000 inch (4 thou)
2.Streamer plate to taker-in … 5/1000 inch (5 thou)
(lead-in edge)
3.Streamer plate to taker-in … 7/1000 inch (7 thou)
(lead-off edge)
4.Stripping knife to taker-in… 4/1000 inch (4 thou)
(Bottom edge)
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
The Cleaning Efficiency of a Machine:
The cleaning efficiency helps to evaluate the performance of a machine. If it falls
below a certain level the machine needs to be checked. The removal of trash
particles such as seed & leaf particles, stalks, sand and dust from cotton is
quantitatively expressed as cleaning efficiency which can be estimated as follow:
About 200gm of sample is taken from the feed & delivery of a machine like Blow
room, Card or Beaters. These samples are analysed for trash content. This is
done by processing a 100gm of sample through a Trash Analyser and collecting
the trash obtained & weighing it accurately. Two samples must be analysed and
average trash content is calculated.
T1 – T2
Cleaning Efficiency % = x 100
T1
Where, T1 = % trash in the material fed
T2 = % trash in the material delivered
Speeds and Settings of Shirley Trash Analyser:
Speeds:
1.Taker-in … 900 rpm
2.Feed roller … 0.9 rpm
3.Cage … 800 rpm
4.Fan … 1500 rpm
5.Motor … 1400 rpm
Setting:
1.Feed plate to taker-in … 4/1000 inch (4 thou)
2.Streamer plate to taker-in … 5/1000 inch (5 thou)
(lead-in edge)
3.Streamer plate to taker-in … 7/1000 inch (7 thou)
(lead-off edge)
4.Stripping knife to taker-in… 4/1000 inch (4 thou)
(Bottom edge)
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5.Stripping knife to cage … 5/16 inch
(lead in edge)
6.Taker-in to cage … 13/64 to 15/64 inch
7.Separation sheet to cage … 1/4 inch
(Top edge)
8.Delivery plate to cage … 1/16 inch
Note:These settings will vary depending on the model of the machine.
CHAPTER – 7
THE MATURITY OF COTTON
Fibre maturity is another important characteristic of cotton and is an index of the
extent of development of the fibres. The maturity of cotton fibre varies not only
between fibers of different samples but also between fibres on the same seed.
Thus a ripened, full mature cotton boll contains fibers both mature and immature.
A cotton fibre consists of a cuticle, a primary layer and secondary layers of
cellulose surrounding the lumen or central canal. In the case of mature fibres,
the secondary wall thickening is very high and in some cases, the lumen is not
visible. In the case of immature fibres, due to some physiological causes, the
secondary wall thickening is practically absent, leaving a wide lumen throughout
the fibre. Hence to a cotton breeder, the presence of excessive immature fibres
in a sample would in dictate some defect in plant growth, either varietal or
environmental. To a technologist, the presence of excessive percentage of
immature fibres in a sample is undesirable as this causes waste, losses in
processing, lowering of the yarn appearance grade due to formation of neps
uneven dyeing etc.
The determination of fineness of a cotton is affected by maturity of the sample.
An immature fibre will show a lower weight per unit length than a mature fibre of
he same cotton, as the immature fibre will have less deposition of cellulose
inside the fibre. Hence it is essential to measure the maturity of a cotton whether
the observed fineness is an inherent varietal characteristic or is a result of
immaturity.
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5.Stripping knife to cage … 5/16 inch
(lead in edge)
6.Taker-in to cage … 13/64 to 15/64 inch
7.Separation sheet to cage … 1/4 inch
(Top edge)
8.Delivery plate to cage … 1/16 inch
Note:These settings will vary depending on the model of the machine.
CHAPTER – 7
THE MATURITY OF COTTON
Fibre maturity is another important characteristic of cotton and is an index of the
extent of development of the fibres. The maturity of cotton fibre varies not only
between fibers of different samples but also between fibres on the same seed.
Thus a ripened, full mature cotton boll contains fibers both mature and immature.
A cotton fibre consists of a cuticle, a primary layer and secondary layers of
cellulose surrounding the lumen or central canal. In the case of mature fibres,
the secondary wall thickening is very high and in some cases, the lumen is not
visible. In the case of immature fibres, due to some physiological causes, the
secondary wall thickening is practically absent, leaving a wide lumen throughout
the fibre. Hence to a cotton breeder, the presence of excessive immature fibres
in a sample would in dictate some defect in plant growth, either varietal or
environmental. To a technologist, the presence of excessive percentage of
immature fibres in a sample is undesirable as this causes waste, losses in
processing, lowering of the yarn appearance grade due to formation of neps
uneven dyeing etc.
The determination of fineness of a cotton is affected by maturity of the sample.
An immature fibre will show a lower weight per unit length than a mature fibre of
he same cotton, as the immature fibre will have less deposition of cellulose
inside the fibre. Hence it is essential to measure the maturity of a cotton whether
the observed fineness is an inherent varietal characteristic or is a result of
immaturity.
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Importance of Maturity:
The maturity of the fibre is concerned with development of the cell wall. The cell
wall thickening is highly sensitive to growing conditions. Adverse weather, poor
soil, plant diseases and pests etc., will increase the proportion of immature fibre
and lead to trouble in processing.
One of the main troubles causes by the presence of these thin walled immature
fibres is nepping. Apart from maturity, causes like small bits or fragments of seed
particles attached to the fibre also forms neps. Neps are created during
processing starting at the ginning stage. Further when rubbing of surfaces takes
place, as in carding, minute knots of tangled fibres are caused and the immature
fibres are more prone of this nepping effect. When fine cottons are being
process4d, the danger of nepping is even more acute, since even the mature
fibres are likely to cause neps by faulty processing. In addition, the neps so
formed are usually more prominent because of their size relative to the diameter
of the fine yarn.
Immaturity also affects the shade after dyeing. As the response of the primary
wall t certain classes of dyestuffs is less intense, the thinner the secondary wall
lighter will be the shade. Hence fine cotton tends to be lighter in shade than
coarse cotton. Apart from this the reflecting surfaces of the fibres of the
immaturity is with respect to the patches being shown or the weft bars seen in
the fabric when yarn made of immature fibres or yarn spun from cotton of
different maturity is used as warp and weft. The presence of neps in a yarn will
also form weak places and therefore the average strength of the yarn will be
reduced. Neps will show up as specks in the dyed cloth. So summarizing the
maturity, the following points are noted.
1.Maturity affects the quality of the yarn and also the processing. The
effects of immature fibres are seen especially in the spinning process.
Page 54 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Importance of Maturity:
The maturity of the fibre is concerned with development of the cell wall. The cell
wall thickening is highly sensitive to growing conditions. Adverse weather, poor
soil, plant diseases and pests etc., will increase the proportion of immature fibre
and lead to trouble in processing.
One of the main troubles causes by the presence of these thin walled immature
fibres is nepping. Apart from maturity, causes like small bits or fragments of seed
particles attached to the fibre also forms neps. Neps are created during
processing starting at the ginning stage. Further when rubbing of surfaces takes
place, as in carding, minute knots of tangled fibres are caused and the immature
fibres are more prone of this nepping effect. When fine cottons are being
process4d, the danger of nepping is even more acute, since even the mature
fibres are likely to cause neps by faulty processing. In addition, the neps so
formed are usually more prominent because of their size relative to the diameter
of the fine yarn.
Immaturity also affects the shade after dyeing. As the response of the primary
wall t certain classes of dyestuffs is less intense, the thinner the secondary wall
lighter will be the shade. Hence fine cotton tends to be lighter in shade than
coarse cotton. Apart from this the reflecting surfaces of the fibres of the
immaturity is with respect to the patches being shown or the weft bars seen in
the fabric when yarn made of immature fibres or yarn spun from cotton of
different maturity is used as warp and weft. The presence of neps in a yarn will
also form weak places and therefore the average strength of the yarn will be
reduced. Neps will show up as specks in the dyed cloth. So summarizing the
maturity, the following points are noted.
1.Maturity affects the quality of the yarn and also the processing. The
effects of immature fibres are seen especially in the spinning process.
Page 54 of 85
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
2.The large number of ends down in a ring frame is due to the immature
fibres.
3.The loss in yarn strength, the dyeing troubles are all due to the presence
of immature fibres.
In order to assess the quality of cotton with respect to maturity and its effect on
ends down, yarn strength, dyeing troubles and so on, some method of
measurement is required. The most important one amongst them being the
degree of thickening q. It may be expressed as the ratio of the actual cross
sectional area of the wall to the area of the circle with the same perimeter. The
reciprocal of this measures, 1/10 is called Immaturity ratio.
A
From the above figure, the degree of thickening q =
A
1
Where, A = Area of cross section of the cell wall
A
1
= Area of the circle of equal perimeter
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
2.The large number of ends down in a ring frame is due to the immature
fibres.
3.The loss in yarn strength, the dyeing troubles are all due to the presence
of immature fibres.
In order to assess the quality of cotton with respect to maturity and its effect on
ends down, yarn strength, dyeing troubles and so on, some method of
measurement is required. The most important one amongst them being the
degree of thickening q. It may be expressed as the ratio of the actual cross
sectional area of the wall to the area of the circle with the same perimeter. The
reciprocal of this measures, 1/10 is called Immaturity ratio.
A
From the above figure, the degree of thickening q =
A
1
Where, A = Area of cross section of the cell wall
A
1
= Area of the circle of equal perimeter
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
A
1
= pr
2
4p 4p
2
r
2
= x pr
2
=
4p 4p
Perimeter P = 2pr
\ P
2
= (2pr)
2
= 4p
2
r
2
P
2
\ A
1
=
4p
A 4pA
\ q= =
A
1
P
2
Direct measurement of this ratio is not a practicable routine test and is not
normally done. An indirect method known as Cotton fibre immaturity count is
used to determined the degree of cell wall thickening.
MEASUREMENT OF MATURITY
1.DIRECT METHOD
In these methods, the fibres after being swollen with 18 percent caustic
soda are examined under the microscope with suitable magnification. The
fibres are classified into different maturity groups depending upon the
relative dimensions of the cell wall and the lumen. However, the
procedures followed in different countries for sampling and classification
differ in certain respects.
i) Maturity Coefficient:
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
A
1
= pr
2
4p 4p
2
r
2
= x pr
2
=
4p 4p
Perimeter P = 2pr
\ P
2
= (2pr)
2
= 4p
2
r
2
P
2
\ A
1
=
4p
A 4pA
\ q= =
A
1
P
2
Direct measurement of this ratio is not a practicable routine test and is not
normally done. An indirect method known as Cotton fibre immaturity count is
used to determined the degree of cell wall thickening.
MEASUREMENT OF MATURITY
1.DIRECT METHOD
In these methods, the fibres after being swollen with 18 percent caustic
soda are examined under the microscope with suitable magnification. The
fibres are classified into different maturity groups depending upon the
relative dimensions of the cell wall and the lumen. However, the
procedures followed in different countries for sampling and classification
differ in certain respects.
i) Maturity Coefficient:
Page 56 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
A thin tuft of fibres in drawn by means of tweezers from a sliver
held in a comb sorter. Its thickness is so regulated that about 100
fibres are spread in a parallel array over a width of an inch in order
to facilitate the examination of each fibre separately under the
microscope. The tweezer end of the tuft is clamped first on the
narrower strip of the fibre mounting device called the ‘Maturity
slide’. The fibres are spread across the glass slide and the
overlapping fibres are again separated with the help of teasing
needle. The free ends of the fibres are then held in the clamp on
the second strip of the maturity slide, which is adjustable to keep
the fibres stretched to the desired extent.
The fibres are then irrigated with 18 percent caustic soda solution
and covered with a suitable cover slip.
The slide is then placed on the mechanical stage of a microscope
and examined. Beginning at one edge of the tuft, all fibres are
classed into three categories namely mature, half-mature and
immature, based on the ratio of lumen width (L) to wall thickness
(W) as indicated below:
Lumen width (L)
Category
Wall thickness (W)
L
Mature < 1
W
L
Half-mature 1 < < 2
W
L
Immature > 2
W
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
A thin tuft of fibres in drawn by means of tweezers from a sliver
held in a comb sorter. Its thickness is so regulated that about 100
fibres are spread in a parallel array over a width of an inch in order
to facilitate the examination of each fibre separately under the
microscope. The tweezer end of the tuft is clamped first on the
narrower strip of the fibre mounting device called the ‘Maturity
slide’. The fibres are spread across the glass slide and the
overlapping fibres are again separated with the help of teasing
needle. The free ends of the fibres are then held in the clamp on
the second strip of the maturity slide, which is adjustable to keep
the fibres stretched to the desired extent.
The fibres are then irrigated with 18 percent caustic soda solution
and covered with a suitable cover slip.
The slide is then placed on the mechanical stage of a microscope
and examined. Beginning at one edge of the tuft, all fibres are
classed into three categories namely mature, half-mature and
immature, based on the ratio of lumen width (L) to wall thickness
(W) as indicated below:
Lumen width (L)
Category
Wall thickness (W)
L
Mature < 1
W
L
Half-mature 1 < < 2
W
L
Immature > 2
W
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
About four to eight slides are prepared from each sample and
examined. The results are presented as percentages of mature,
half-mature and immature fibres in a sample. The results are also
expressed in terms of ‘maturity coefficient’ which is a unitary
expression signifying the multiple character of fibre maturity usually
represented by the percentage of mature, half-mature and
immature fibres, calculated from the formula:
(M + 0.6H + 0.4I)
Mc =
100
where Mc is the maturity coefficient, and M, H and I are the
percentage of mature, half-mature and immature fibres,
respectively, in the sample. Based on the maturity coefficient the
cottons are classed into different groups as shown in Table below.
Table: Classification of Cottons on the basis of Maturity
Coefficient
Category Range of maturity coefficient
Very immature
Immature
Average maturity
Good maturity
Very high maturity
Below 0.60
0.60 to 0.70
0.71 to 0.80
0.81 to 0.90
Above 0.90
ii)Percentage of Mature Fibres:
This is the US Standard (ASTM) method, in which the percentage
of mature fibres, Pm alone is determined.
Test specimen is prepared by any one of three following methods:
a)Array Method:
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
About four to eight slides are prepared from each sample and
examined. The results are presented as percentages of mature,
half-mature and immature fibres in a sample. The results are also
expressed in terms of ‘maturity coefficient’ which is a unitary
expression signifying the multiple character of fibre maturity usually
represented by the percentage of mature, half-mature and
immature fibres, calculated from the formula:
(M + 0.6H + 0.4I)
Mc =
100
where Mc is the maturity coefficient, and M, H and I are the
percentage of mature, half-mature and immature fibres,
respectively, in the sample. Based on the maturity coefficient the
cottons are classed into different groups as shown in Table below.
Table: Classification of Cottons on the basis of Maturity
Coefficient
Category Range of maturity coefficient
Very immature
Immature
Average maturity
Good maturity
Very high maturity
Below 0.60
0.60 to 0.70
0.71 to 0.80
0.81 to 0.90
Above 0.90
ii)Percentage of Mature Fibres:
This is the US Standard (ASTM) method, in which the percentage
of mature fibres, Pm alone is determined.
Test specimen is prepared by any one of three following methods:
a)Array Method:
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
From each length group, a bundle of about 100 fibres is taken
and spread uniformly on microscope slides. The series of
slides constitutes a test sample. A second set of slides is
prepared by another operator using fibres drawn from a
different array.
b)Laboratory Blended Sample:
Three slides of about 200 fibres each are prepared by each of
the two operators from a laboratory blended sliver of 50mm
length.
c)Fibrograph Beard:
Beards from two combs are removed and each one is divided
into two halves forming four sub-samples. From these sub-
samples, test specimens are prepared by the same procedure
as the one described in the case of the laboratory blended
sample.
The fibres laid parallel on the microscope slide are irrigated
with 18% caustic soda and are examined through a microscope
at 400 x magnification. They are classified into two categories,
mature and immature as shown below:
Lumen width (L)
Category
Wall thickness (W)
L
Mature < 2
W
L
Immature > 2
W
Page 59 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
From each length group, a bundle of about 100 fibres is taken
and spread uniformly on microscope slides. The series of
slides constitutes a test sample. A second set of slides is
prepared by another operator using fibres drawn from a
different array.
b)Laboratory Blended Sample:
Three slides of about 200 fibres each are prepared by each of
the two operators from a laboratory blended sliver of 50mm
length.
c)Fibrograph Beard:
Beards from two combs are removed and each one is divided
into two halves forming four sub-samples. From these sub-
samples, test specimens are prepared by the same procedure
as the one described in the case of the laboratory blended
sample.
The fibres laid parallel on the microscope slide are irrigated
with 18% caustic soda and are examined through a microscope
at 400 x magnification. They are classified into two categories,
mature and immature as shown below:
Lumen width (L)
Category
Wall thickness (W)
L
Mature < 2
W
L
Immature > 2
W
Page 59 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
From the total number of fibres and number of mature fibres,
the percentage of the mature (Pm) is calculated.
Pm = Mature Fiber/ Total Fibers x100
iii)Maturity Ratio:
In this method, which is also the British Standard method, the test
specimen is prepared either by the random sampling technique
(Zoning method) or the selective sampling technique (i.e. by
drawing fibres from various groups of the sorter pattern), and it is
recommended that test be made on five tufts of fibres from each
sample. Each tuft is taken separately on a slide and irrigated with
19% caustic soda. The swollen fibres are then examined under a
microscope magnification (100x) and classed into three groups,
viz. normal, thin-walled and dead. Rod-like fibres with no
convolution and no continuous lumen are classed as ‘normal’,
convoluted fibres with wall thickness one-fifth or less of the
maximum ribbon width are classed as ‘dead’, and the intermediate
ones are classed as ‘thin-walled’. A combined index known as
‘maturity ratio’ is used to express the results. Maturity ratio is
calculated by using the following equation:
N – D
Mr = + 0.70
200
where, Mr = Maturity ratio, N = Percentage of normal fibres and
D = Percentage of dead fibres.
Relationship between different Indices of Maturity:
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
From the total number of fibres and number of mature fibres,
the percentage of the mature (Pm) is calculated.
Pm = Mature Fiber/ Total Fibers x100
iii)Maturity Ratio:
In this method, which is also the British Standard method, the test
specimen is prepared either by the random sampling technique
(Zoning method) or the selective sampling technique (i.e. by
drawing fibres from various groups of the sorter pattern), and it is
recommended that test be made on five tufts of fibres from each
sample. Each tuft is taken separately on a slide and irrigated with
19% caustic soda. The swollen fibres are then examined under a
microscope magnification (100x) and classed into three groups,
viz. normal, thin-walled and dead. Rod-like fibres with no
convolution and no continuous lumen are classed as ‘normal’,
convoluted fibres with wall thickness one-fifth or less of the
maximum ribbon width are classed as ‘dead’, and the intermediate
ones are classed as ‘thin-walled’. A combined index known as
‘maturity ratio’ is used to express the results. Maturity ratio is
calculated by using the following equation:
N – D
Mr = + 0.70
200
where, Mr = Maturity ratio, N = Percentage of normal fibres and
D = Percentage of dead fibres.
Relationship between different Indices of Maturity:
Page 60 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Some workers have established the formulae connecting the three
commonly used measures of maturity such as maturity ratio (M r),
percentage of mature fibre (Pm) and maturity coefficient (Mc). These
formulae are useful for predicting one measure from another.
Pm = (Mc – 0.394) (3.434 – 1.783 Mc)
Pm = (Mr – 0.2) (1.5652 – 0.471 Mr)
Mr = (Mc – 0.301) (2.252 – 0.526 Mc)
2.INDIRECT METHOD
i) Polarised Light Methods:
These methods have been developed taking advantage of the
birefringence property of cotton fibres. In the simplest method,
about 200 fibres are mounted parallel to each other on a slide and
observed under a polarizing microscope. A selenite plate is placed
between the crossed polariser and analyser with the slow vibration
direction set at 45
o
to the polarized and parallel to the fibres. The
classification for maturity is made depending upon the interference
colours produced, the immature fibres appear blue or purple and
the mature fibres appear yellow or green. The number of immature
and mature fibres thus differentiated are counted and expressed as
percentages. Fairly good agreement is found between maturity
obtained by this method and caustic soda method.
ii)Air-flow Methods:
In this method, the Micronaire reading on a 40 grain sample is
noted, and then by adding to it a 10 grain sample, a composite
sample of 50 grains is prepared and tested. The authors have
Page 61 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Some workers have established the formulae connecting the three
commonly used measures of maturity such as maturity ratio (M r),
percentage of mature fibre (Pm) and maturity coefficient (Mc). These
formulae are useful for predicting one measure from another.
Pm = (Mc – 0.394) (3.434 – 1.783 Mc)
Pm = (Mr – 0.2) (1.5652 – 0.471 Mr)
Mr = (Mc – 0.301) (2.252 – 0.526 Mc)
2.INDIRECT METHOD
i) Polarised Light Methods:
These methods have been developed taking advantage of the
birefringence property of cotton fibres. In the simplest method,
about 200 fibres are mounted parallel to each other on a slide and
observed under a polarizing microscope. A selenite plate is placed
between the crossed polariser and analyser with the slow vibration
direction set at 45
o
to the polarized and parallel to the fibres. The
classification for maturity is made depending upon the interference
colours produced, the immature fibres appear blue or purple and
the mature fibres appear yellow or green. The number of immature
and mature fibres thus differentiated are counted and expressed as
percentages. Fairly good agreement is found between maturity
obtained by this method and caustic soda method.
ii)Air-flow Methods:
In this method, the Micronaire reading on a 40 grain sample is
noted, and then by adding to it a 10 grain sample, a composite
sample of 50 grains is prepared and tested. The authors have
Page 61 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
derived separate regression equations for the different species of
cottons connecting the maturity coefficient by the caustic soda
method and the difference in Micronaire readings between 40 grain
and 50 grain samples.
There are other techniques for measuring maturity using the
Micronaire instrument. As the fineness value determined by the
Micronaire is dependent both on the intrinsic fineness (perimeter of
fibre) and the maturity, it may be assumed that if the intrinsic
fineness is constant then the Micronaire value is a measure of the
maturity. For example, if samples of the same variety are tested, it
can be assumed that the intrinsic fineness would be the same and
hence a higher Micronaire value would indicate a higher maturity
value. This is especially so with regard to American Upland
cottons as there is little variation in intrinsic fineness between
different varieties. Hence, certain arbitrary Micronaire values have
been suggested to denote the maturity of a cotton; thus cottons
having a Micronaire value less than 3.5 are considered immature,
while those having over 4.0 are considered as mature.
iii)Dyeing Methods:
Mature and immature fibre differ in their behaviour towards various
dyes. Certain dyes are preferentially taken up by the mature fibres
while some dyes are preferentially absorbed by the immature
fibres. In this technique, the sample is dyed in a bath containing a
mixture of two dyes, namely, Diphenyl Fast Red 5 BL and
Chlorantine Fast Green BLL. The mature fibres take up the red
dye preferentially, while the thin-walled immature fibres take up the
green dye. An estimate of the average maturity of the sample can
be visually made from the amount of red and green dyed fibres.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
derived separate regression equations for the different species of
cottons connecting the maturity coefficient by the caustic soda
method and the difference in Micronaire readings between 40 grain
and 50 grain samples.
There are other techniques for measuring maturity using the
Micronaire instrument. As the fineness value determined by the
Micronaire is dependent both on the intrinsic fineness (perimeter of
fibre) and the maturity, it may be assumed that if the intrinsic
fineness is constant then the Micronaire value is a measure of the
maturity. For example, if samples of the same variety are tested, it
can be assumed that the intrinsic fineness would be the same and
hence a higher Micronaire value would indicate a higher maturity
value. This is especially so with regard to American Upland
cottons as there is little variation in intrinsic fineness between
different varieties. Hence, certain arbitrary Micronaire values have
been suggested to denote the maturity of a cotton; thus cottons
having a Micronaire value less than 3.5 are considered immature,
while those having over 4.0 are considered as mature.
iii)Dyeing Methods:
Mature and immature fibre differ in their behaviour towards various
dyes. Certain dyes are preferentially taken up by the mature fibres
while some dyes are preferentially absorbed by the immature
fibres. In this technique, the sample is dyed in a bath containing a
mixture of two dyes, namely, Diphenyl Fast Red 5 BL and
Chlorantine Fast Green BLL. The mature fibres take up the red
dye preferentially, while the thin-walled immature fibres take up the
green dye. An estimate of the average maturity of the sample can
be visually made from the amount of red and green dyed fibres.
Page 62 of 85
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Page 63 of 85
Fig. : Immature Fibre
Fig. : Immature Fibre
Fig. : Mature Fibre
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Page 63 of 85
Fig. : Immature Fibre
Fig. : Immature Fibre
Fig. : Mature Fibre
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 8
SOME PRECAUTIONS DURING COTTON FIBRE TESTING
1. FIBRE LENGTH
(a)Baer sorter:
Take a representative test specimen as per ISI method.
Prepare a uniform hand made sliver without applying much tension to
avoid fibre rupture.
Slightly twist the fibres before putting it over combs.
Straighten the edge of protruding sliver before transferring the fibre from
one side to another or over velvet board.
Straighten the edge of protruding sliver before transferring the fibre from
one side to another or over velvet board.
Comb the fibres 2-3 times before transferring.
Transfer all the fibres over velvet board.
Draw a line over transparent sheet just over the end of fibres.
Use a pointed pencil.
Page 64 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 8
SOME PRECAUTIONS DURING COTTON FIBRE TESTING
1. FIBRE LENGTH
(a)Baer sorter:
Take a representative test specimen as per ISI method.
Prepare a uniform hand made sliver without applying much tension to
avoid fibre rupture.
Slightly twist the fibres before putting it over combs.
Straighten the edge of protruding sliver before transferring the fibre from
one side to another or over velvet board.
Straighten the edge of protruding sliver before transferring the fibre from
one side to another or over velvet board.
Comb the fibres 2-3 times before transferring.
Transfer all the fibres over velvet board.
Draw a line over transparent sheet just over the end of fibres.
Use a pointed pencil.
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TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
(b)Fibrograph:
Warm up & calibrate the instrument according to the instruction manual
before testing.
Clean the Doffer of Fibro-sampler before and after sampling.
For best precision in testing, sample size should be between 600 to 900
fibres.
Brush the fibre beard to remove trash & loose fibres carefully because
light brushing will remove fewer loose fibre and heavy brushing will pull
out long fibres and disturb the random arrangement.
Press the sample uniformly with the heel of left hand side to protrude the
fibres through the hole of fibro sampler plate.
Use standard cotton for the correction.
2. MATURITY:
Prepare a uniform hand made sliver from random test specimen.
Spread the cotton fibres over glass slide separately or without over-
lapping.
Avoid the contact of NaOH solution with skin and use a glass rod.
Remove the air bubble by rubbing the glass slide to each other.
Focus the projectina over glass slide properly for better identification.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
(b)Fibrograph:
Warm up & calibrate the instrument according to the instruction manual
before testing.
Clean the Doffer of Fibro-sampler before and after sampling.
For best precision in testing, sample size should be between 600 to 900
fibres.
Brush the fibre beard to remove trash & loose fibres carefully because
light brushing will remove fewer loose fibre and heavy brushing will pull
out long fibres and disturb the random arrangement.
Press the sample uniformly with the heel of left hand side to protrude the
fibres through the hole of fibro sampler plate.
Use standard cotton for the correction.
2. MATURITY:
Prepare a uniform hand made sliver from random test specimen.
Spread the cotton fibres over glass slide separately or without over-
lapping.
Avoid the contact of NaOH solution with skin and use a glass rod.
Remove the air bubble by rubbing the glass slide to each other.
Focus the projectina over glass slide properly for better identification.
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TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
3. FINENESS:
Pass the test specimen through trash analyser before testing.
Level and calibrate the instrument according to the instruction manual.
Allow to stabilize the indicator before observation.
Take more observation if large variation is observed.
Use standard cotton foe the correction.
4. BUNDLE STRENGTH :
Level and calibrate the instrument according to instruction manual.
Use standard cotton for correction. Correction Factor should be within the
limit i.e., 1 ± 0.1.
Check the leather of fibre clamps.
Apply equal force and tension for each and every test.
Breaking strength of bundle should be between 3.0 kg. to 6.0kg.
Condition the standard cotton and test specimen before testing.
5. TRASH ANALYSIS:
Clean thoroughly the trash analyser before and after test.
Separate the seed from cotton sample manually.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
3. FINENESS:
Pass the test specimen through trash analyser before testing.
Level and calibrate the instrument according to the instruction manual.
Allow to stabilize the indicator before observation.
Take more observation if large variation is observed.
Use standard cotton foe the correction.
4. BUNDLE STRENGTH :
Level and calibrate the instrument according to instruction manual.
Use standard cotton for correction. Correction Factor should be within the
limit i.e., 1 ± 0.1.
Check the leather of fibre clamps.
Apply equal force and tension for each and every test.
Breaking strength of bundle should be between 3.0 kg. to 6.0kg.
Condition the standard cotton and test specimen before testing.
5. TRASH ANALYSIS:
Clean thoroughly the trash analyser before and after test.
Separate the seed from cotton sample manually.
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TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Condition the sample before and after trash analysis for weighing.
Manually open the big tufts of cotton before passing it through the trash
analyser.
Keep your fingers away from the feed rollers.
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Condition the sample before and after trash analysis for weighing.
Manually open the big tufts of cotton before passing it through the trash
analyser.
Keep your fingers away from the feed rollers.
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CHAPTER – 9
HIGH VOLUME INSTRUMENT
Zellweger Uster HVI test system measures seven important characteristics of
cotton and they are:
·Length
·Length uniformity
·Micronaire
·Bundle Strength
·Elongation
·Colour and reflectance
·Trash content (optical determination)
As per manufacturers claim, about 180 samples (each sample – 1test) can be
tested for all the above seven properties/hour with two operatives manning the
instrument.
However, as per practical experience in Indian Laboratories, about 100
samples/shift of 8 hours (each sample – 4 tests) could be conveniently tested
using HVI. Because of the high speed of testing, now technicians are in a
position to determine the raw material characteristics with reference to a large
enough sample.
High volume instruments are of two type.
Semi Automatic
Fully Automatic
In addition, automatic testing systems offer the following advantages:
·The results are practically independent of the operator error.
·The results are based on large volume samples and therefore more
significant.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 9
HIGH VOLUME INSTRUMENT
Zellweger Uster HVI test system measures seven important characteristics of
cotton and they are:
·Length
·Length uniformity
·Micronaire
·Bundle Strength
·Elongation
·Colour and reflectance
·Trash content (optical determination)
As per manufacturers claim, about 180 samples (each sample – 1test) can be
tested for all the above seven properties/hour with two operatives manning the
instrument.
However, as per practical experience in Indian Laboratories, about 100
samples/shift of 8 hours (each sample – 4 tests) could be conveniently tested
using HVI. Because of the high speed of testing, now technicians are in a
position to determine the raw material characteristics with reference to a large
enough sample.
High volume instruments are of two type.
Semi Automatic
Fully Automatic
In addition, automatic testing systems offer the following advantages:
·The results are practically independent of the operator error.
·The results are based on large volume samples and therefore more
significant.
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·The respective fibre data are immediately available.
·The data are clearly arranged in summarized reports (HVI test system has
microprocessors to format the test data for analysis, storage and retrieval)
·They make possible the best utilization of the raw material data.
·Problems as a result of the fibre material can be predicted & corrective
measures can be instituted before such problems can occur.
HVI test system enables testing of large volume of samples and arrive at a
correct estimate of the fibre properties within a short time so that appropriate
mixing can be prepared. Besides, quality of all individual bales and within bale
and between bale variations can be assessed. The bales can be categorized into
different lots depending on the actual fibre properties. The mills can
subsequently evolve a bale management system which would enable them to
maintain the quality at a consistent level at minimum cost.
The length, strength, length uniformity, elongation, Micronaire, colour, trash &
the NIR value of cotton fibres are all important in fibre research, in development
of improved fibre blends and in verifying that purchased fibre meet
specifications.
This test system offers precise and reliable automated operation with computer
controlled calibration and diagnostics. All functions are controlled by dedicated
microprocessors to simplify operation and to provide flexibility in testing
parameters.
Separate version of the software is available to measure properties of man-made
fibres. Included with the system are keyboard, monitor & balance. The monitor
display the menu selection, operating instructions and test results. As tests are
completed for each sample, the results can be transmitted to the printer of the
host computer system.
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·The respective fibre data are immediately available.
·The data are clearly arranged in summarized reports (HVI test system has
microprocessors to format the test data for analysis, storage and retrieval)
·They make possible the best utilization of the raw material data.
·Problems as a result of the fibre material can be predicted & corrective
measures can be instituted before such problems can occur.
HVI test system enables testing of large volume of samples and arrive at a
correct estimate of the fibre properties within a short time so that appropriate
mixing can be prepared. Besides, quality of all individual bales and within bale
and between bale variations can be assessed. The bales can be categorized into
different lots depending on the actual fibre properties. The mills can
subsequently evolve a bale management system which would enable them to
maintain the quality at a consistent level at minimum cost.
The length, strength, length uniformity, elongation, Micronaire, colour, trash &
the NIR value of cotton fibres are all important in fibre research, in development
of improved fibre blends and in verifying that purchased fibre meet
specifications.
This test system offers precise and reliable automated operation with computer
controlled calibration and diagnostics. All functions are controlled by dedicated
microprocessors to simplify operation and to provide flexibility in testing
parameters.
Separate version of the software is available to measure properties of man-made
fibres. Included with the system are keyboard, monitor & balance. The monitor
display the menu selection, operating instructions and test results. As tests are
completed for each sample, the results can be transmitted to the printer of the
host computer system.
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There are two ways of testing a sample. First one is the system testing which is
designed to allow linear measuring procedure that includes the length/strength,
Micronaire, colour/trash & NIR Modules. This procedure allows one operator to
perform all task. In this procedure only one test is performed for Micronaire &
NIR.
The second way is the module testing. There are different module for
length/strength, Micronaire, colour/trash & NIR. Testing is done in steps, but the
number of test for Micronaire & NIR can be increased.
The instrument is calibrated by using calibration cottons and standard colour tiles
provided with the instrument. The standard cottons are stored in an environment
of 27
0
C and 65% Relative Humidity because the moisture content of he cotton
affects its length, strength & Micronaire.
There are two kinds of cotton that can be used to calibrate HVI systems.
1.International Calibration Cotton (I.C.C).
2.High Volume Instrument calibration cottons (HVI). The HVI can be calibrated
on Stelometer level or pressley level.
ICC cotton are well blended card web. Two samples of these cotton are required
for Micronaire calibration, one with low Micronaire value & another with high
Micronaire value.
The word “Calibration” refers to adjustment of values. The HVI is calibrated
following engineering principle using hardware devices. After proper calibration,
adjustment to raw test values are made by means of automatic software
manipulation to cause test values to agree with designated values of standard
samples.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
There are two ways of testing a sample. First one is the system testing which is
designed to allow linear measuring procedure that includes the length/strength,
Micronaire, colour/trash & NIR Modules. This procedure allows one operator to
perform all task. In this procedure only one test is performed for Micronaire &
NIR.
The second way is the module testing. There are different module for
length/strength, Micronaire, colour/trash & NIR. Testing is done in steps, but the
number of test for Micronaire & NIR can be increased.
The instrument is calibrated by using calibration cottons and standard colour tiles
provided with the instrument. The standard cottons are stored in an environment
of 27
0
C and 65% Relative Humidity because the moisture content of he cotton
affects its length, strength & Micronaire.
There are two kinds of cotton that can be used to calibrate HVI systems.
1.International Calibration Cotton (I.C.C).
2.High Volume Instrument calibration cottons (HVI). The HVI can be calibrated
on Stelometer level or pressley level.
ICC cotton are well blended card web. Two samples of these cotton are required
for Micronaire calibration, one with low Micronaire value & another with high
Micronaire value.
The word “Calibration” refers to adjustment of values. The HVI is calibrated
following engineering principle using hardware devices. After proper calibration,
adjustment to raw test values are made by means of automatic software
manipulation to cause test values to agree with designated values of standard
samples.
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CHAPTER – 10
TESTING OF MAN-MADE FIBRES
SAMPLING OF MAN-MADE FIBRES
The reliability of the test results depends primarily upon how well the specimen
represents the original source material. Failure to provide an unbiased test
specimen that accurately represents the material from which it is drawn, will
produce misleading test results regardless of the accuracy and precision of he
test method.
Principle:
A representative sample is taken by abstracting small sub-samples from various
parts of the fibre lot and reducing each of them to a convenient number of fibres
by repeated blending and halving.
Sampling from a Bale:
In order to take representative sample from a bale, the side flaps, which are
perpendicular to the fibre layers, are opened. For example, in the case of a
‘Jailene’ bale, these flaps are those which are stitched to the bale sides and
bearing the bale number and other relevant fibre details. Fibre tufts are removed
from both the open sides of the bale, taking care that the sample includes
material from many layers.
Sampling Method:
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CHAPTER – 10
TESTING OF MAN-MADE FIBRES
SAMPLING OF MAN-MADE FIBRES
The reliability of the test results depends primarily upon how well the specimen
represents the original source material. Failure to provide an unbiased test
specimen that accurately represents the material from which it is drawn, will
produce misleading test results regardless of the accuracy and precision of he
test method.
Principle:
A representative sample is taken by abstracting small sub-samples from various
parts of the fibre lot and reducing each of them to a convenient number of fibres
by repeated blending and halving.
Sampling from a Bale:
In order to take representative sample from a bale, the side flaps, which are
perpendicular to the fibre layers, are opened. For example, in the case of a
‘Jailene’ bale, these flaps are those which are stitched to the bale sides and
bearing the bale number and other relevant fibre details. Fibre tufts are removed
from both the open sides of the bale, taking care that the sample includes
material from many layers.
Sampling Method:
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Take 16 single samples from various parts of the lot for establishing he final
sample. Lay the first and second sample together (doubling) and divide them by
pulling apart. Discard one half and divide and double the other half ten times to
achieve a thorough blending. Repeat the same procedure with the third and
fourth, fifth and sixth etc. samples until all the 16 samples are dealt with.
Double the resulting eight intermediary samples and divide them by pulling apart.
Discard one half and blend the other half by dividing and doubling ten times.
Treat the four intermediary samples in the same manner and continue until only
one sample remains. Blend this specimen by dividing and doubling until the
constituent fibres lie almost parallel as required for the final sample. Carry out
the dividing of the specimen with utmost care in order to avoid any stretching of
breaking of the fibre. This final sample or master sample is taken for testing the
fibre properties, by selecting at random fibres from various parts of the sample.
CONDITIONING OF SAMPLES TO STANDARD ATMOSPHERE
Principle:
Prior to testing, the sample is exposed to an atmosphere having a temperature
of 27 ± 2
o
C and a relative humidity of 65 ± 2% until moisture equilibrium is
reached.
Appliances:
Conditioning cabinet, if no conditioning room is available.
Method:
Place the specimen in a standard atmosphere having a temperature of 27 ± 2
o
C
and relative humidity of 65 ± 2%.
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Take 16 single samples from various parts of the lot for establishing he final
sample. Lay the first and second sample together (doubling) and divide them by
pulling apart. Discard one half and divide and double the other half ten times to
achieve a thorough blending. Repeat the same procedure with the third and
fourth, fifth and sixth etc. samples until all the 16 samples are dealt with.
Double the resulting eight intermediary samples and divide them by pulling apart.
Discard one half and blend the other half by dividing and doubling ten times.
Treat the four intermediary samples in the same manner and continue until only
one sample remains. Blend this specimen by dividing and doubling until the
constituent fibres lie almost parallel as required for the final sample. Carry out
the dividing of the specimen with utmost care in order to avoid any stretching of
breaking of the fibre. This final sample or master sample is taken for testing the
fibre properties, by selecting at random fibres from various parts of the sample.
CONDITIONING OF SAMPLES TO STANDARD ATMOSPHERE
Principle:
Prior to testing, the sample is exposed to an atmosphere having a temperature
of 27 ± 2
o
C and a relative humidity of 65 ± 2% until moisture equilibrium is
reached.
Appliances:
Conditioning cabinet, if no conditioning room is available.
Method:
Place the specimen in a standard atmosphere having a temperature of 27 ± 2
o
C
and relative humidity of 65 ± 2%.
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The time required for conditioning man-made fibres is usually 12 hours but in the
case of polyester staple fibre, the conditioning time of 6 to 8 hours is considered
adequate.
DETERMINATION OF FIBRE DENIER
By Microscope:
In this method fibre diameter is measured with the help of a microscope and the
following formula is used to compute out the denier.
Denier = pr
2
l d
Where, p = 3.14 r = radius of the fibre
l = length d = density of the material
By Cutting and Weighing Method:
Principle:
Determination of the weight of 10 bundles each comprising 50 fibres cut to a
length of 25 mm.
Appliances:
Staple cutter with cutting length of 25 mm; Precision torsion balance having a
range of 0.005 to 10 mg; Comb with support having 35 mm width and ten
needles per cm; Velvet covered plate and glass slide: 100 x 30 x 3 mm with
ground edges.
Method:
With dry fingers, take 10 fibre bundles of several mg each from the basic
sample. Parallelize the bundles by hand and then by means of the comb. Place
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
The time required for conditioning man-made fibres is usually 12 hours but in the
case of polyester staple fibre, the conditioning time of 6 to 8 hours is considered
adequate.
DETERMINATION OF FIBRE DENIER
By Microscope:
In this method fibre diameter is measured with the help of a microscope and the
following formula is used to compute out the denier.
Denier = pr
2
l d
Where, p = 3.14 r = radius of the fibre
l = length d = density of the material
By Cutting and Weighing Method:
Principle:
Determination of the weight of 10 bundles each comprising 50 fibres cut to a
length of 25 mm.
Appliances:
Staple cutter with cutting length of 25 mm; Precision torsion balance having a
range of 0.005 to 10 mg; Comb with support having 35 mm width and ten
needles per cm; Velvet covered plate and glass slide: 100 x 30 x 3 mm with
ground edges.
Method:
With dry fingers, take 10 fibre bundles of several mg each from the basic
sample. Parallelize the bundles by hand and then by means of the comb. Place
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the bundle into the staple cutter at right angles to the knives and under suitable
tension required for decrimping but without stretching the fibres.
Now cut-off a length or 25 mm Handle the remaining nine bundles in the same
way. Lay the 10 individual bundles on the velvet covered plate and cover them
with glass slide so as to allow the fibres to protrude slightly. Take five fibres from
each of the en such bundles and make a fresh tuft of 50 fibres. Produce such 10
bundles and weigh each bundle on the Precision torsion balance.
Calculations:
9000 x G 9000 x G
Denier = = = 7.2 x G
L x Z 25 x 50
Where, G = Weight of the fibre bundle in mg.
L = Length of the fibre bundle in mm.
Z = Total number of fibres in the bundle.
Determine the total mean and the coefficient of variation of the denier for the 10
bundles. The denier should be computed to three decimal places and coefficient
of variation to two decimal places.
By Vibromat:
Vibromat works on the vibration principle and serves to measure the fineness of
single fibres. The fibre is held in a clamp at one end, loaded with a preload
weight at the other end, and subjected to an acoustic oscillation which initiates a
transverse vibration in the fibre. The frequency of the vibration is the natural
frequency of the fibre. A photo-electric and an AD Transducer convert the fibre
vibration into an electrical signal the computer of the Vibromat determines from
this natural frequency and taking the preload account weight into account – the
fibre fineness in denier or decitex. The value is displayed on a monitor screen
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the bundle into the staple cutter at right angles to the knives and under suitable
tension required for decrimping but without stretching the fibres.
Now cut-off a length or 25 mm Handle the remaining nine bundles in the same
way. Lay the 10 individual bundles on the velvet covered plate and cover them
with glass slide so as to allow the fibres to protrude slightly. Take five fibres from
each of the en such bundles and make a fresh tuft of 50 fibres. Produce such 10
bundles and weigh each bundle on the Precision torsion balance.
Calculations:
9000 x G 9000 x G
Denier = = = 7.2 x G
L x Z 25 x 50
Where, G = Weight of the fibre bundle in mg.
L = Length of the fibre bundle in mm.
Z = Total number of fibres in the bundle.
Determine the total mean and the coefficient of variation of the denier for the 10
bundles. The denier should be computed to three decimal places and coefficient
of variation to two decimal places.
By Vibromat:
Vibromat works on the vibration principle and serves to measure the fineness of
single fibres. The fibre is held in a clamp at one end, loaded with a preload
weight at the other end, and subjected to an acoustic oscillation which initiates a
transverse vibration in the fibre. The frequency of the vibration is the natural
frequency of the fibre. A photo-electric and an AD Transducer convert the fibre
vibration into an electrical signal the computer of the Vibromat determines from
this natural frequency and taking the preload account weight into account – the
fibre fineness in denier or decitex. The value is displayed on a monitor screen
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together with the mean and the coefficient of variation of all the results in the
current series upto this point in time. For control purposes, after each
measurement the monitor also shows the cure of fibre vibration.
If the Vibromat is operated in conjunction with a Fafegraph, the fibre fineness is
measured first, then the fibre is transferred to the testing field of the
FAFEGRAPH and tenacity is tested.
The procedure can be rationalized by determining the fineness of each individual
fibre while the preceding fibre is being tensile tested so that two tests are
performed side by side.
DETERMINATION OF MEAN FIBRE LENGTH
Principle:
The length measured in this test is the length of the straightened fibre with the
crimp removed.
Appliances:
Glass plate; Forceps; Ruler with 1 mm markings and Magnifying glass.
Method:
Smear the glass plate with a small quantity of white petroleum jelly, liquid
paraffin or grease. Using the forceps, arrange a fibre in a straight line on the
glass plate and measure the length by using the ruler. In this way, test 100
measurements represents the mean fibre length. The magnifying glass would
reduce the strain involved in these measurements.
Note:
Exclude from the mean, all fibres which are longer by 10% than the specification
length. Such fibres are called ‘overlength fibres’ and these are estimated by
another method, which is given below.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
together with the mean and the coefficient of variation of all the results in the
current series upto this point in time. For control purposes, after each
measurement the monitor also shows the cure of fibre vibration.
If the Vibromat is operated in conjunction with a Fafegraph, the fibre fineness is
measured first, then the fibre is transferred to the testing field of the
FAFEGRAPH and tenacity is tested.
The procedure can be rationalized by determining the fineness of each individual
fibre while the preceding fibre is being tensile tested so that two tests are
performed side by side.
DETERMINATION OF MEAN FIBRE LENGTH
Principle:
The length measured in this test is the length of the straightened fibre with the
crimp removed.
Appliances:
Glass plate; Forceps; Ruler with 1 mm markings and Magnifying glass.
Method:
Smear the glass plate with a small quantity of white petroleum jelly, liquid
paraffin or grease. Using the forceps, arrange a fibre in a straight line on the
glass plate and measure the length by using the ruler. In this way, test 100
measurements represents the mean fibre length. The magnifying glass would
reduce the strain involved in these measurements.
Note:
Exclude from the mean, all fibres which are longer by 10% than the specification
length. Such fibres are called ‘overlength fibres’ and these are estimated by
another method, which is given below.
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DETERMINATION OF PERCENT OVERLENGTH FIBRES
Overlength Fibres:
Fibres having 10% more length than the specification length are called
overlength fibres.
Principle:
The percentage of fibres exceeding a certain approved length (specification
length + 10%) are sorted out. The ratio of the number of sorted fibres to the
number of tested fibres expresses the proportion of overlength fibres and is
reported in percentage.
Appliances:
Staple fibre sorter; Adjustable auxiliary equipment (stop) for pulling the fibre
bundles; Depressor; Special grip for sorting of staples; Black velvet pad;
Graduated foot rule (mm); and Analytical balance (mg graduation).
Method:
Take a fibre bundle from the representative sample comprising approximately
30,000 fibres, i.e., having an approximate weight of: G (mg) = 3.3 x specification
length x fibre denier.
Parallelize the fibres in the bundle by hand and divide the sample into bundles of
100-150 mg and test as follows:
Place the bundle in the decrimped condition in the gill section. Drop the gill pins
Until the first set of fibres project beyond the remaining gill section.
Set the sop opposite the first gill pin to the following distance:
Length of grip + Specification length of fibre + 8 mm (allowance of 2 mm made
for the length within the grip).
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
DETERMINATION OF PERCENT OVERLENGTH FIBRES
Overlength Fibres:
Fibres having 10% more length than the specification length are called
overlength fibres.
Principle:
The percentage of fibres exceeding a certain approved length (specification
length + 10%) are sorted out. The ratio of the number of sorted fibres to the
number of tested fibres expresses the proportion of overlength fibres and is
reported in percentage.
Appliances:
Staple fibre sorter; Adjustable auxiliary equipment (stop) for pulling the fibre
bundles; Depressor; Special grip for sorting of staples; Black velvet pad;
Graduated foot rule (mm); and Analytical balance (mg graduation).
Method:
Take a fibre bundle from the representative sample comprising approximately
30,000 fibres, i.e., having an approximate weight of: G (mg) = 3.3 x specification
length x fibre denier.
Parallelize the fibres in the bundle by hand and divide the sample into bundles of
100-150 mg and test as follows:
Place the bundle in the decrimped condition in the gill section. Drop the gill pins
Until the first set of fibres project beyond the remaining gill section.
Set the sop opposite the first gill pin to the following distance:
Length of grip + Specification length of fibre + 8 mm (allowance of 2 mm made
for the length within the grip).
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Pull the fibre by using the grip up to the stop. The overlength fibres will remain in
the gill even after taking the grip upto the stop. Remove these fibres and lay
them on velvet pad and confirm if they are overlength fibres by measuring their
length with the help of a ruler. Keep all these overlength fibres separately, taking
care that no such fibre is lost. Having pulled all the fibres projecting beyond the
gill section, lower the first gill, set the stop to the next gill and repeat the
procedure. Continue doing this until the fibre tuft remaining in the gill section is
smaller than the rated length + 10%.
Number of overlength fibres
% Overlength fibres = x 100
Total number of fibres tested
G x 9000
Total number of fibres is given by: N =
L x D
Where, G = Weight in mg.
L = Rated length
D = Denier
DETERMINATION OF FIBRE TENACITY AND ELONGATION AT BREAK
Principle:
The fibre is clamped in a tensile testing machine and stretched until it breaks.
The load applied and the extension taking place at breaking point are read.
Appliances:
Single fibre tensile testing machine working on the principle of constant rate of
extension (e.g., Fafegraph, Blace velvet plate, Forceps and Pretensioning weight
(equal to 0.05 g/den.).
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Pull the fibre by using the grip up to the stop. The overlength fibres will remain in
the gill even after taking the grip upto the stop. Remove these fibres and lay
them on velvet pad and confirm if they are overlength fibres by measuring their
length with the help of a ruler. Keep all these overlength fibres separately, taking
care that no such fibre is lost. Having pulled all the fibres projecting beyond the
gill section, lower the first gill, set the stop to the next gill and repeat the
procedure. Continue doing this until the fibre tuft remaining in the gill section is
smaller than the rated length + 10%.
Number of overlength fibres
% Overlength fibres = x 100
Total number of fibres tested
G x 9000
Total number of fibres is given by: N =
L x D
Where, G = Weight in mg.
L = Rated length
D = Denier
DETERMINATION OF FIBRE TENACITY AND ELONGATION AT BREAK
Principle:
The fibre is clamped in a tensile testing machine and stretched until it breaks.
The load applied and the extension taking place at breaking point are read.
Appliances:
Single fibre tensile testing machine working on the principle of constant rate of
extension (e.g., Fafegraph, Blace velvet plate, Forceps and Pretensioning weight
(equal to 0.05 g/den.).
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Method:
Place the representative tuft of the fibre sample on a black velvet plate and draw
a single fibre by using forceps. Attach pretensioning weight equal to 0.05 g/den
to one of the tips of the fibre and clamp the fibre, holding the other tip with the
forceps, in the jaws of the testing machine. Gauge length between the jaws
should be 10 mm and the breaking time should be adjusted to 20 + 2 seconds.
Load in grams and % extension values up to fibre break may be noted from the
counter or can be analysed from the load-elongation curves shown on the chart
of the Recorder. Test 200 fibres in the same way and take average of strength
in grams and % extension. Calculate CV% of load as well as elongation.
Determine the denier of the remaining tuft which is left on the velvet plate.
Average load in grams
Tenacity (gms/den) =
Average denier
Fafegraph, fabricated by Textechno, West Germany, is found to be an excellent
single fibre tensile strength testing machine which gives fool-proof test results
without any slippage of high tenacity polyester fibre from the jaws.
Precautions:
1.Never touch the middle of the fibre by hands or forceps. Attach the nipper
weight and use forceps at the tips only; otherwise the fibre will get
fractured in the middle and will give misleading results.
2.There should be no fibre slippage from any of the jaws while testing.
DETERMINATION OF FIBRE CRIMP STABILITY, CRIMPING ARCS AND
CRIMP REMOVAL
Crimping Arcs/cm:
The number of arcs per centimeter is counted with the aid of a microscope. One
arc is equal to full period.
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FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Method:
Place the representative tuft of the fibre sample on a black velvet plate and draw
a single fibre by using forceps. Attach pretensioning weight equal to 0.05 g/den
to one of the tips of the fibre and clamp the fibre, holding the other tip with the
forceps, in the jaws of the testing machine. Gauge length between the jaws
should be 10 mm and the breaking time should be adjusted to 20 + 2 seconds.
Load in grams and % extension values up to fibre break may be noted from the
counter or can be analysed from the load-elongation curves shown on the chart
of the Recorder. Test 200 fibres in the same way and take average of strength
in grams and % extension. Calculate CV% of load as well as elongation.
Determine the denier of the remaining tuft which is left on the velvet plate.
Average load in grams
Tenacity (gms/den) =
Average denier
Fafegraph, fabricated by Textechno, West Germany, is found to be an excellent
single fibre tensile strength testing machine which gives fool-proof test results
without any slippage of high tenacity polyester fibre from the jaws.
Precautions:
1.Never touch the middle of the fibre by hands or forceps. Attach the nipper
weight and use forceps at the tips only; otherwise the fibre will get
fractured in the middle and will give misleading results.
2.There should be no fibre slippage from any of the jaws while testing.
DETERMINATION OF FIBRE CRIMP STABILITY, CRIMPING ARCS AND
CRIMP REMOVAL
Crimping Arcs/cm:
The number of arcs per centimeter is counted with the aid of a microscope. One
arc is equal to full period.
Page 79 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Crimp Stability or Crimp Resistance:
For determination of crimp stability, the variation in length of a staple fibre during
loading and unloading is measured. The relation between the variation in length
by unloading and loading of the fibre is expressed in percent and defined as %
crimp stability.
Crimp Removal:
This is an indirect measure of crimp amplitude. For determination of the crimp
removal, the initial length of a crimped fibre and the increase in length after the
crimp removal are measured. The relation between the increase in length and
the initial length of the fibre is expressed in percent and defined as crimp
removal.
Appliances:
Crimp testing unit with microscope. Blace velvet plate, Forceps, Paper shapes
(e.g., from a puncture of adhesive paper tapes, each weighing 1 mg) and Grip
weights (0.05 + 0.01 g/den).
Method:
Take 50 fibres from the representative sample and place them individually on the
velvet plate. Stick a paper shape to one end of the fibre and clamp the fibre in
the grip by holding the fibre with forceps at the tip only. Looking through the
microscope, count the number of arcs and the length between the two nips.
Now attach gently the grip weight of 0.05 g/den to the paper shape; read the
stretched fibre length after one minute and then remove the grip weight and
allow the fibre to relax. Measure the fibre length after one minute of relaxation.
Test all the 50 fibres in the same way.
Clamp the fibre in the grip and at the other end attach a paper shape. Measure
the crimped length. Hang the grip weight of 0.3 g/den for 20 seconds or 0.05
g/den for one minute and record the stretched fibre length.
Page 80 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Crimp Stability or Crimp Resistance:
For determination of crimp stability, the variation in length of a staple fibre during
loading and unloading is measured. The relation between the variation in length
by unloading and loading of the fibre is expressed in percent and defined as %
crimp stability.
Crimp Removal:
This is an indirect measure of crimp amplitude. For determination of the crimp
removal, the initial length of a crimped fibre and the increase in length after the
crimp removal are measured. The relation between the increase in length and
the initial length of the fibre is expressed in percent and defined as crimp
removal.
Appliances:
Crimp testing unit with microscope. Blace velvet plate, Forceps, Paper shapes
(e.g., from a puncture of adhesive paper tapes, each weighing 1 mg) and Grip
weights (0.05 + 0.01 g/den).
Method:
Take 50 fibres from the representative sample and place them individually on the
velvet plate. Stick a paper shape to one end of the fibre and clamp the fibre in
the grip by holding the fibre with forceps at the tip only. Looking through the
microscope, count the number of arcs and the length between the two nips.
Now attach gently the grip weight of 0.05 g/den to the paper shape; read the
stretched fibre length after one minute and then remove the grip weight and
allow the fibre to relax. Measure the fibre length after one minute of relaxation.
Test all the 50 fibres in the same way.
Clamp the fibre in the grip and at the other end attach a paper shape. Measure
the crimped length. Hang the grip weight of 0.3 g/den for 20 seconds or 0.05
g/den for one minute and record the stretched fibre length.
Page 80 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Calculations:
(a)Crimp Stability:
Lg – Le
% Crimp stability = x 100
Lg – Lk
Where, Lk = Length (mm) of crimped fibre without grip weight
Lg = Length (mm) of crimped fibre after stretching of one minute
Le = Length (mm) of relaxed fibre measured after a minute of
relaxation.
The average of 50 values will give the average crimp stability.
(b)Crimping Arcs:
Kb
Crimping Arcs = x 10
Lg
Where, Kb = Number of crimping arcs in crimped length Lg (mm).
(c)% Crimp Removal:
Li
% Crimp removal = x 100
Lo
Where, Li = Increase in length of fibre after loading
Lo = Length of crimped fibre
The crimp removal is reported as a mean value obtained from the 50
individual values and expressed in percent to the first decimal place.
Page 81 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
Calculations:
(a)Crimp Stability:
Lg – Le
% Crimp stability = x 100
Lg – Lk
Where, Lk = Length (mm) of crimped fibre without grip weight
Lg = Length (mm) of crimped fibre after stretching of one minute
Le = Length (mm) of relaxed fibre measured after a minute of
relaxation.
The average of 50 values will give the average crimp stability.
(b)Crimping Arcs:
Kb
Crimping Arcs = x 10
Lg
Where, Kb = Number of crimping arcs in crimped length Lg (mm).
(c)% Crimp Removal:
Li
% Crimp removal = x 100
Lo
Where, Li = Increase in length of fibre after loading
Lo = Length of crimped fibre
The crimp removal is reported as a mean value obtained from the 50
individual values and expressed in percent to the first decimal place.
Page 81 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
DETERMINATION OF DEGREE OF WHITENESS OF MAN-MADE FIBRES
Principle:
The degree of remission of fibre flock is measured by the use of a blue filter.
The degree of remission, expressed in percent, and related to that of a freshly
smoked magnesium oxide standard represents the degree of whiteness.
Appliances:
Elrepho instrument with specimen dish, Hand gloves and Beaker.
Chemicals:
Methanol (chemically pure) or Freon-11 liquid.
Method:
Take approximately 15 grams of fibre from the representative sample. Wear
gloves and wash twice for 10 minutes in methanol or in Freon-11 to remove the
spin finish. Squeeze well and keep the washed sample on a clean filter paper
and allow the specimen to dry in the air.
Fill the fibre in the specimen dish taking care that high packing density is
ensured. Set the instrument against reference standard which is already
calibrated against magnesium oxide. Place the dish containing the washed fibre
sample under the test opening of the Elrepho device. Adjust the device with blue
filter in position 6 (pair of filters R46) and read the luminance factor directly on
the graduated drum.
After having carried out the first measurement, remove the fibre from the dish,
turn and replace it, and repeat the measurements in the same manner on the
rest of the sample. The mean of 10 individual measurements represents the
degree of whiteness, expressed in percent to one decimal place.
Page 82 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
DETERMINATION OF DEGREE OF WHITENESS OF MAN-MADE FIBRES
Principle:
The degree of remission of fibre flock is measured by the use of a blue filter.
The degree of remission, expressed in percent, and related to that of a freshly
smoked magnesium oxide standard represents the degree of whiteness.
Appliances:
Elrepho instrument with specimen dish, Hand gloves and Beaker.
Chemicals:
Methanol (chemically pure) or Freon-11 liquid.
Method:
Take approximately 15 grams of fibre from the representative sample. Wear
gloves and wash twice for 10 minutes in methanol or in Freon-11 to remove the
spin finish. Squeeze well and keep the washed sample on a clean filter paper
and allow the specimen to dry in the air.
Fill the fibre in the specimen dish taking care that high packing density is
ensured. Set the instrument against reference standard which is already
calibrated against magnesium oxide. Place the dish containing the washed fibre
sample under the test opening of the Elrepho device. Adjust the device with blue
filter in position 6 (pair of filters R46) and read the luminance factor directly on
the graduated drum.
After having carried out the first measurement, remove the fibre from the dish,
turn and replace it, and repeat the measurements in the same manner on the
rest of the sample. The mean of 10 individual measurements represents the
degree of whiteness, expressed in percent to one decimal place.
Page 82 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
DETERMINATION OF SPIN FINISH ON FIBRE
Principle:
The spin finish is readily extracted with Freon-11 liquid, which is then evaporated
and the leftover spin finish estimated as difference in weight.
Appliances:
One extraction tube with sintered disc and stopcock; Beakers (100 ml.) and
Vacuum oven.
Chemicals:
Freon-11.
Method:
Weigh about 10 grams of staple fibre accurately and fill loosely inside the tube
with the help of a glass rod. Pour two to three 20 ml portions of Freon-11 from
the top. After it passed through the fibre, drain the Freon extract from the tube
into a previously weighed beaker. The Freon-11 will evaporate immediately.
Then keep the beaker in the vacuum oven at 60
o
C for half an hour to drive out all
the moisture; cool to room temperature and weigh to a constant weight.
Calculations:
Weight of spin finish
% Spin Finish = x 100
Weight of sample
Weight of spin finish = Weight of beaker with the dry extract minus
the weight of dry beaker.
Page 83 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
DETERMINATION OF SPIN FINISH ON FIBRE
Principle:
The spin finish is readily extracted with Freon-11 liquid, which is then evaporated
and the leftover spin finish estimated as difference in weight.
Appliances:
One extraction tube with sintered disc and stopcock; Beakers (100 ml.) and
Vacuum oven.
Chemicals:
Freon-11.
Method:
Weigh about 10 grams of staple fibre accurately and fill loosely inside the tube
with the help of a glass rod. Pour two to three 20 ml portions of Freon-11 from
the top. After it passed through the fibre, drain the Freon extract from the tube
into a previously weighed beaker. The Freon-11 will evaporate immediately.
Then keep the beaker in the vacuum oven at 60
o
C for half an hour to drive out all
the moisture; cool to room temperature and weigh to a constant weight.
Calculations:
Weight of spin finish
% Spin Finish = x 100
Weight of sample
Weight of spin finish = Weight of beaker with the dry extract minus
the weight of dry beaker.
Page 83 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 11
CONTROL OF RAW MATERIAL QUALITY
Raw material forms biggest component in the cost of yarn. Total raw material
cost may range between 65-70% in case of yarn. Contribution of raw material is
quite significant from the quality viewpoint as well. On an average contribution of
raw material is 60% in case of yarn quality and all other factors i.e. machinery
and process parameters and supervisory skill may contribute about 40% in
normal condition.
The biggest problem in case of cotton is the variation in the raw material. Cotton
varies from variety to variety and in the same variety from station to station and
lot to lot in some station and from bale to bale in case of same lot number.
Earlier it was presumed that in case of manmade fibres there will not be any
variation and fibres will be supplied exactly as per specification. However,
studies conducted at NITRA has shown that variations are found in case of all
type of synthetic fibres. When all the things that is machinery set and processing
parameters are controlled, variation in yarn quality can be directly traced back to
the variation in fibre quality parameters. Impact of various fibre quality
parameters on yarn quality parameter is given below in the Table.
COTTON
S.No.Fibre Quality Parameters Yarn Quality Parameters
1. Mean length / Effective lengthYarn strength, Evenness, Hairiness
2 Length distribution Evenness, Hairiness
3 Short fibre content Evenness, Imperfections, Hairiness
4 Fineness Evenness
5 Fibre strength Yarn strength
6 Maturity co-efficient Neps
7 Trash % Imperfection particularly neps
Trash particles
8 Seed coats Neps
9 Colour Colour variation in within and between
lots
Page 84 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
CHAPTER – 11
CONTROL OF RAW MATERIAL QUALITY
Raw material forms biggest component in the cost of yarn. Total raw material
cost may range between 65-70% in case of yarn. Contribution of raw material is
quite significant from the quality viewpoint as well. On an average contribution of
raw material is 60% in case of yarn quality and all other factors i.e. machinery
and process parameters and supervisory skill may contribute about 40% in
normal condition.
The biggest problem in case of cotton is the variation in the raw material. Cotton
varies from variety to variety and in the same variety from station to station and
lot to lot in some station and from bale to bale in case of same lot number.
Earlier it was presumed that in case of manmade fibres there will not be any
variation and fibres will be supplied exactly as per specification. However,
studies conducted at NITRA has shown that variations are found in case of all
type of synthetic fibres. When all the things that is machinery set and processing
parameters are controlled, variation in yarn quality can be directly traced back to
the variation in fibre quality parameters. Impact of various fibre quality
parameters on yarn quality parameter is given below in the Table.
COTTON
S.No.Fibre Quality Parameters Yarn Quality Parameters
1. Mean length / Effective lengthYarn strength, Evenness, Hairiness
2 Length distribution Evenness, Hairiness
3 Short fibre content Evenness, Imperfections, Hairiness
4 Fineness Evenness
5 Fibre strength Yarn strength
6 Maturity co-efficient Neps
7 Trash % Imperfection particularly neps
Trash particles
8 Seed coats Neps
9 Colour Colour variation in within and between
lots
Page 84 of 85
TRAINING MANUAL
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
MANMADE FIBRES
S.No.Fibre Quality Parameters Yarn Quality Parameters
1 Mean length Yarn Evenness, Hairiness
2 Fineness Yarn Evenness, Hairiness
3 Crimp Yarn Evenness
4 Spin finish Yarn Hairiness
5 Fused fibres Yarn Imperfection
From the above Table we can see that how various fibre properties are affecting
different yarn quality parameters. Therefore depending upon the requirement of
quality we can select appropriate parameters of manmade fibres.
Cost of raw material can also be minimized by developing suitable software
which can incorporate data of quality as well as cost.
Page 85 of 85
FIBRE TESTING AND CONTROL OF RAW MATERIAL QUALITY
MANMADE FIBRES
S.No.Fibre Quality Parameters Yarn Quality Parameters
1 Mean length Yarn Evenness, Hairiness
2 Fineness Yarn Evenness, Hairiness
3 Crimp Yarn Evenness
4 Spin finish Yarn Hairiness
5 Fused fibres Yarn Imperfection
From the above Table we can see that how various fibre properties are affecting
different yarn quality parameters. Therefore depending upon the requirement of
quality we can select appropriate parameters of manmade fibres.
Cost of raw material can also be minimized by developing suitable software
which can incorporate data of quality as well as cost.
Page 85 of 85
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