Fiber Science - Basics

1. Fiber Science
By Chamal Jayasinghe (B.Sc. Engineering (Textiles), AMIESL,
Classification of Textile Fibers , there properties and a brief description of manufacturing methods

2. Textile Fibers by Chamal Jayasinghe

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Fibers
Fibers are thin long strands which consist of natural or synthetic materials. Some of these fibers
can be used as a textile fiber when it full fills the needful parameters. Commonly used fibers
can be mentioned as follows.
Cotton , Linen , Silk , Polyester , Nylon , Viscose
Definition of Fiber
Fiber is a unit of matter characterized by flexibility, fineness and a high ratio of length to
thickness.
Basic demands required by a matter to be considered as textile fires are ,
a. Flexibility
b. Fineness
c. High Ratio of Length to Thickness
The most needful thing in a fiber is its length to diameter ratio which should be greater than
100. For example in cotton this ratio is 1400:1.
The present textile fibers can be classified according to their origin as below.

Fiber Classification



Natural

Man Made




Cellulose

Cellulose
Cotton

Regenerated
Jute

Viscose
Hemp Protein

Rayon Protein
Linen Wool

Tencel Regenerated

Silk

Soybean

Angora


Rubber Camel

Synthetic



Polyester



Nylon

Mineral

Polypropylene Mineral

Asbestos

Glass

Carbon

Metal


Steel


Gold


Silver

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Staple and Filament Fibers
Fibers with infinite (long) lengths are called filament fibers while fibers with short lengths
are called staple fibers. Cotton, Wool, Kapok are good examples for staple fibers while
polyester and nylon are examples for filament fibers.

Image 1.1 Filament and Staple Fibers
Internal Structure of a natural Fiber
Natural Fibers are created by natural polymerization, the basic unit which begins
polymerization calls monomer. Monomers joined together and create a Polymer. Polymers
join together and create Micro Fibrils. Micro fibrils lay parallel to each other and create
fibrils and then Fibers.







Image 1.2 How fibers are made in plant cells

Monomer
Polymer

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Amorphous and Crystalline areas
We can find two special areas in a fiber when look deep in to their polymer arrangements,
Those are crystalline and amorphous areas. In crystalline areas, polymer chains lye parallel and
close to each other. In amorphous areas, polymer chains lye randomly and unevenly.

Image 1.3 Crystalline and Amorphous areas of fibers
These crystalline areas are high in strength , yet has very less dye and moisture absorbency,
crystalline areas gives more strength to fibers.
In amorphous areas, polymers do not lye close to each other; these areas are less in strength
yet increase fiber qualities of flexibility, moisture & dye absorption. Basically the crystalline
area accounts for the strength of a fiber while the amorphous area accounts for the flexibility
of it.
Degree of Polymerization ( DP )
The degree of polymerization, or DP, is usually defined as the number of monomer units in a
macromolecule or polymer molecule.

Image.1.4 Monomers being polymerized

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2. Chemical and Physical properties of Fibers
Chemical constituent of polymer (monomer) is mainly responsible for the chemical properties
of textile fibers. Physical arrangement of polymer chains in fiber structure and polymer chain
length is mainly responsible for physical properties of fibers.
Physical Properties
1. Tenacity
2. Fineness
3. Moisture Absorption
4. Abrasion Resistance
5. Crease Recovery
6. Elongation
7. Elastic Recover
8. Resiliency
9. Luster
10. Flexibility
11. Uniformity
12. Specific Gravity
13. Softening and Melting Points

1. Tenacity (Measuring Unit = g / den)

Image 2.1 Yarn Being Ruptured by a force
 The strength of textile fibers is referred to as their tenacity. It is determined by
measuring the force required to rupture or break the fiber.
 Sufficient tenacity is required to withstand the mechanical and chemical processing as
well as make textile products which are durable.

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2. Fineness























Image 2.2 Vary of Fiber Diameter Depending on the source
 Fiber fineness governs the end use application of fiber.
For example: You may need a more fine fiber to create a shirt fabric than for creating a
trouser material
 Fibers used in clothing fabrics are below 5 decitex and rarely exceeds 15 decitex. .
 As the average number of fibers in the cross section is high, fine, staple fibers are more
suitable for producing regular yarns.
 Cloths made from fine fibers or filaments have a softer and smother handle
 Fabrics made with Fine fibers may have lower resistance to abrasion and can get easily
damaged.

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3. Moisture Absorption
 The ability of a fiber to absorb moisture is referred in moisture regain or moisture
content.
 The quantity of moisture picked up varies with the relative humidity and the
temperature of the atmosphere. The standard values are relative humidity of 65% and
temperature of 20
0
C.
 Depends on chemical nature and physical arrangement of fiber the moisture absorption
changes.
The moisture in a fiber is expressed in two methods
1. Moisture Absorption
2. Moisture Content
Below formulas are used in calculating them




The influence of moisture absorption of fibers.
 The comfort of the wearer.
 The amount of shrinkage that will occur during laundering.
 The speed with which the textile will dry after laundering.
 How fast it can neutralize the static electricity charges.









Moisture Content = Weight of Moisture x 100 %
Wet Mass
Moisture Regain = Weight of Moisture x 100 %
Dry Mass

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4. Abrasion Resistance (Measuring Unit = loss of weight per constant cycles of abrasion)

Image 4.1 A man’s trouser abraded at a highway accident
Fabrics are abraded when use against various materials, the ability of the fiber to
withstand these forces is called abrasion resistance.
 The life of a fabric is dependent on its resistance to abrasion.
 Nylon has an outstanding resistance to abrasion.
 Abrasion resistance is decided by its fiber composition yarn and fabric construction.

5. Crease Recovery (Measuring Unit = degrees in time)



Image 5.1 Fabrics with different crease recovery qualities

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To retain a good appearance of a fabric, the fabric must have a good crease recovery to
recover from unwanted creases occur in fabric usage and laundering.
6. Elongation (Measuring Unit = (ratio, or as a percentage))
The fibers should be able to extend when a force is applied on it , if it brittles in a force without
extended we can hardly use it as a textile fiber.

Lf = Extended Length, L0 = Normal Length
7. Elastic Recovery (Measuring Unit = (ratio, or as a percentage))
Elastic recover is very important for a fiber to come to it’s original position after extension. If
the elastic recovery is good, the fiber will have it’s original dimensions after the application of a
certain force.

8. Resiliency

Image 8.1 A sports women dressed up with more resilient dresses

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Resiliency refers to the ability of a fiber to come back to its original position after being creased
or folded. Good elastic recovery usually indicates good resiliency
Excellent resiliency is exhibited by polyester, wool and nylon fibers. Flax, rayon and cotton, on
the other hand, have a low resiliency.
9. Luster
Luster is amount of light reflected from the surface of the fiber
 Fine fibers provide a greater number of reflecting surfaces. Hence they have good
luster
 Fibers with a uniform diameter have a good luster.
 The shape of the cross section affects the degree of luster.
 Yarns made from continuous filaments are more lustrous than those made from
short fibers.
 Manufactured fibers can have their luster subdued by adding de-lustering agents.
10. Flexibility
Fibers should be flexible or pliable in order to be made into yarns and thereafter into fabrics
that permit freedom of movement. Certain end uses require greater flexibility, e.g.,
automobile seat belts.
11. Uniformity
Uniformity of fibers towards its length, ensure production of even yarns which can then
form fabrics of uniform appearance and consistent performance.
12. Specific Gravity
Specific gravity means the density of the fiber related to water density. In here the
water density is considered as 1 (Which is actually 1000 kg / m
3
). So if a actual density of a
fiber is 1300 kg / m
3
, it’s specific gravity is 1.3.
By looking at the specific gravity figures, we can easily distinguish whether the
fiber floats or sinks in water.
13. Softening & Melting Points
The temperature when a certain polymer starts to soft is called as the softening point
while the temperature that a polymer starts to melt is called as the melting point.

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3. Chemical Properties of fibers
1. Resistance to Acids
2. Resistance to Alkali
3. Resistance to Organic Solvents
4. Resistance to Sunlight
5. Resistance to Mildew
6. Resistance to Micro Biological Attacks
7. Resistance to Bleaching , Washing & Dry Cleaning

1. Resistance to Acids
The ability of a fiber to withstand certain concentrations of acids is called as resistance to acids.
Most protein (Wool; Silk; Kashmir) has good resistance to acids. While cellulosic fibers have less
resistance to them.
2. Resistance to Alkali
The ability of a fiber to withstand certain concentrations of bases is called resistance to alkali.
Most cellulosic fibers have good resistance to Alkalis. While protein fibers have less resistance
to alkalis.

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3. Properties of Specific Natural Fibers – Natural Fibers

For Further understand in to fibers; let’s consider some of the popular fibers in today
industry

3.1 Cotton – the miracle fiber







Image 3.1.1 Cotton fluff; and microscopic view of Cotton fiber
The above images shows how to cotton fiber is available in the tree and it’s longitudinal and
cross sectional views.
Cotton has been using as a textile fiber since more than 3000 years ago. It is the most popular
natural fiber in today textile industry. Cotton has many grate qualities which keeps it in its place
for centuries.
Cotton Harvesting
Cotton is grown as a small plant and harvested using large machineries specially designed for it.


Image 3.1.2 Cotton plant ready to harvesting and being harvested

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The above images show a cotton plant ready to harvest and a harvesting machine. Cotton is
widely cultivated in China, US , India , Australia Pakistan and many other countries.
Ginning
The next process after harvesting is removing the lint from the seed of the cotton. This is called
ginning. The cotton seed is used for making cooking oils and the crushed seed particles are used
as foods to animals.

Image 3.1.4 Cotton Ginning
After ginning cotton fibers are pressed and packed into bales and set off for spinning.

Image 3.1.5 Cotton Bales

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Properties of Cotton
Cotton fibres have twist, or convolutions, along the length of the fiber. The appearance of
cotton is unique among fibers. The chemical composition of cotton is the polymer cellulose.
untreated cotton fibers have kidney-shape appearance. The flatter fibers could be immature.
The hollow strip in the center of the fibers is called the lumen. The portion of the fiber between
the lumen and the outer wall is called the secondary wall composed of cellulose.


Image 3.1.6 Morphological Structure of Cotton Fiber
Mercerizing of cotton

Image 3.1.7 Cotton fiber cross
section before and after mercerizing

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Mercerization is the immersion of cotton in sodium hydroxide (sometimes called caustic soda),
causing the fibers to swell and the polymer chains to rearrange. The process improves luster,
strength, absorbency, and dye uptake.

Properties of cotton in detail
 Composition Cellulose –(87-90)%, Water-(5-8)% Others- natural impurities
 Obtain from cotton seeds.
 Length varies from (16-52) mm.
 Vary in color from white to light tan
 Moderately strong fiber-Low degree of orientation
Dry-strong (tenacity 3-5 g/denier)
Wet-stronger(tenacity 3.3-6 g/denier)
 Inelastic
 Poor resilience (easily make creases and wrinkles)
 Good absorbent fiber- (Due to countless H bonds.) Hydrophilic fiber (Moisture regain –
8.5 %)
 Good static resistance (due to good absorbency)
 Soft hand feeling- (much regular fiber).
 Attacked by mildew.
 Fiber turns to yellow when exposure to sunlight (The ultraviolet radiation in sunlight
breaks the chemical bonds in the polymer chain)
 Good abrasion resistance; durable
 Good heat conductor - cool to wear
 Cotton can be damage by acids.
 Cotton has good resistance to alkalis. (Textile processes such as scouring and bleaching
are generally carried out at a pH of between 10 and 11.)
 Does not melt. Decomposes slowly upon exposure to dry heat above 300 °
 Makes comfortable and durable garments.

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3.2 Flax
Flax is the name of the plant which is used to manufacture linen fiber.









Image 3.2.1 Flax plant and fiber
Properties of Flax
 Composition- cellulose, water and natural impurities
 Cellulosic bast fiber.
 Obtain from bast of flax plant.
 Used to produce linen fabrics.
 Stronger than cotton.
tenacity- dry- 5.5-6.5 g/denier,
tenacity- wet- 6.6-7.8 g/denier)
 Inelastic.(elasticity – 65%)
 Stiff handle.
 Make wrinkles and creases.(poor resiliency)
 Absorb water rapidly. (moisture regain- 12%)
 Expensive fiber.
 Good heat conductor- cool to wear.
 No pilling problems. (fibers are generally long and not as fine as cotton fibers
 Strong acids cause deterioration.
 Good resistance to alkalis
 Loses strength under sunlight
 The typical staple length of flax is ten to fifteen inches,
 Linen fabrics are used in table coverings, Draperies, upholstery, and apparel.

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3.3 Wool







Image 3.3.1 Sheep’s left and wool fiber microscopic side view at right.
Properties of Wool
 Natural protein (Keratin) fiber.
 Obtained from sheep.
 Color varies from off white to light cream.
 length of wool can range from 1.5 to 15 inches
 Weak fiber and strength decreases on wetting. (Tenacity dry– 1- 1.7 g/denier)
(Tenacity wet -0.8 – 1.6 g/denier)
 Crimp configuration.
 Good elastic recovery and resilience.
 Poor heat conductivity and warmth configuration.
 Very hygroscopic and can take up a high amount of moisture without felling damp.-
very hydrophilic (moisture regain – 13%-17%)
 Poor luster and expensive fiber.

Image 3.3.2 Structure of Wool fiber

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4. Man Made fibers and their production methods
The word “spinning” can be used to mean the conversion of staple fibers to yarn as well as to
mean the production of man-made filaments by extrusion.
All manmade polymers are solids at normal temperatures. The polymers in solid form must be
converted to liquid form polymer for creating fine fibers. For this purpose the molten polymer
needs to be forced through fine holes of the spinneret to form filaments.
The method used for each fiber depends upon the ease of conversion of the polymer from
solid to liquid state.
There are three methods of spinning manmade fibers:
Melt Spinning Polymer is converted in to liquid state by heating
Dry Spinning Polymer is dissolved in a suitable solvent which is later evaporated
Wet Spinning Solvent cannot be evaporated and must be removed by chemical means.


Image 4.1 Methods of manmade fiber manufacturing

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4.1 Melt spinning
Polymer is converted to liquid just by heating chips or pellets of it. The molten polymer is
pumped through the spinneret and the extruded filaments are hardened into solid filaments
after emerging.
 Nylon, polyester and olefin fibers are melt-spun fibers.

Image 4.1.1 Melt Spinning Process

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4.2 Dry Spinning
If Polymer is getting chemically damaged by heating, dry spinning is used. In this
method Polymers are dissolved in a suitable solvent which is evaporated in a later stage.
As the jets of solution emerge from the spinneret, a stream of hot air causes the solvent
to evaporate from the spinning solution, leaving solid filaments.
 Acetate, Triacetate and Acrylic fibers are produced by using this method.


Image 4.2.1 Dry Spinning Process

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4.3 Wet Spinning
This method is used when the solvent cannot be evaporated and must be removed by chemical
means. In wet spinning the solution of fiber-forming material is extruded into a coagulating
bath that causes the jets to harden as a result of chemical or physical change.
 Viscose, Acrylic, Rayon, Aramid, Modacrylic and spandex are produced by this method.


Image 4.3.1 Wet Spinning Process

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5. Properties of Specific Man Made Fibers
To get familiar with manmade fibers, let’s have a look in to properties of few of them.
5.1 Viscose
Viscose is manufactured by wet spinning method.







Image 5.1.1 Viscose fiber side view and cross section
Properties of Viscose
 Regenerated cellulose filament fiber.
 Raw materials are wood pulp or cotton linters.
 Very cheap.
 Fair strength. Less strength when wet.
(Tenacity dry - 2.4-3 g/denier)
(Tenacity wet – 1.1-1.5 g/denier)
 Wrinkle and crease.
 Moist absorbent. (moisture regain – 11-16)%
Cotton and viscose have same polymer. Fibers are made of the same polymer. But viscose
fibers have much lower crystalline than cotton
 High heat resistance
 The terms Polynosic and Modal refer to high-wet-modulus rayon.
 Easily damaged by strong acids
 Good resistance to most alkalis; loses strength in strong alkalis
 Lengthy exposure to sunlight weakens the fabric
 Greater affinity for dyes than cotton

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5.2 Polyester
Polyester is a manmade fiber manufactured by melt spinning method.








Image 5.2.1 Polyester fabric and microscopic view of fibers

Properties of Polyester
 Manmade synthetic fiber.
 Fine and translucent.
 Stronger fiber.(tenacity- 2.8-6.3 g/denier)
 Extremely crystalline.
 Completely hydrophobic.(moisture regain-0.4%)
 Good resiliency.
 Develop static charges readily.
 Attracts grease soils and airborne dust.
 The hydrophobic nature of polyester can also make it very difficult to remove oily stains
from it. Polyester is sometimes treated with a soil release finishes.
 Resistance to most acids
 Good resistance to most alkalis
 Good resistance to sunlight

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5.3 Nylon
Nylon is a manmade fiber which is made by melt spinning method.











Image 5.3.1 Nylon Fibers and a coat manufactured from nylon

Properties of Nylon

 Manmade synthetic fiber.
 Good strength.(tenacity 3.5-9 g/denier)
 Good elasticity.
 High Abrasion resistance
 Good resilience.
 Less absorbent.(moisture regain – 2.8-5)%
 Develop static charges.
 Poor heat conductivity.
 Dissolves in mineral and formic acids
 Good resistance to alkalis
 Loses strength when expose to sunlight

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Chart 2. Comparison of General Properties of Fibers based on their origin

Natural Cellulose Fibers Regenerated Cellulose Fibers Natural Protein Fibers Synthetic Fibers
Ex: Flax , Cotton , Jute , Linen Viscose , Rayon, Tencel Wool , Silk , Angora, Alpaca Polyester , Nylon

Good tenacity Tenacity is low than natural fibers Good Tenacity Better tenacity
Average moisture content Moisture content is higher than natural fibers
Moisture content little higher than natural
cellulose
Very low moisture content
Effected by acids Easily effected by acids Effected by acids with mild resistance
Acids and alkalis shows
different
Better resistant to alkalis Better resistant to alkalis Effected by alkalis effects on different fibers
Better resistant to dry cleaning
agents
Better resistant to dry cleaning agents Resist to dry cleaning agents Generally resist to dry cleaning
Burns like paper Burns like paper Shrink and burns - smell like hair burning Melt and burns
Withstand up to 200 C Withstand up to 260 C Withstand up to 120 C Withstand up to 140 C- 200 C
Effected by sunlight
Effected by sunlight - weaker than natural
cellulose
Tendency effect on sunlight
Sunlight effect is vary fiber to
fiber

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Chart 3. Properties of Conventional Textile fibers

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References
1. North Carolina State University
http://www.tx.ncsu.edu/
2. Association of Textile , Apparel and Material Professionals
https://www.aatcc.org














Please contact me for any comments @ [email protected]
Chamal Jayasinghe,
Assistant Technologist,
Sri Lanka Institute of Textiles and Apparel,
Rathmalana.