Fibre Length.pdf

Fibre Length

1. 1
Fibre Length
Evaluation of Textile Materials

2. 2
Why fibre length?
Quality assessment
Quality prediction
Fibre breakage study
M/C settings ??
Combing efficiency etc.
FibreLength

3. 3
FibreLength
Fiber length can be expressed as,
Staple length (STPL)
Mean length (ML)
Upper quartile length (UQL)
Effective length (EL)
Modal length (MoL)
Span length (SL)
Upper half-mean length (UHML)

4. 4
FibreLength
The parameters used to estimate fiber length
variations
Dispersion%
Uniformity index (UI)
Uniformity ratio (UR)
Short fiber content (SFC), and
Floating fiber index (FFI)

5. 5
Staple Length
ThestaplelengthisdefinedbyUSDAas“the
normallengthoftypicalportionofstaplefibers
havingrelativehumidityof65%andtemperature
of70°Fwithoutregardtovalueorquality.”

6. 6
Mean Length
The mean length of the fibers is defined as “the
average length of all fibers in the test specimen
based on weight–length data”.
It can also be calculated by number–length data
as an alternative.

7. 7
Upper Quartile Length
AccordingtoASTM,upperquartilelength(UQL)
isdefinedas“thefiberlengthwhichisexceeded
by25%offibersbyweightintestspecimen”.

8. 8
Effective Length
Theeffectivelengthislongerthantheaveragelength
andisameasureofthelengthofthemajorityoflonger
fibersinasample.
Theeffectivelengthisdescribedstatisticallyasthe
upperquartileofthefiberlengthdistributionobtainedby
ignoringshortfiberswhoselengthislessthanhalfof
theeffectivelengthoffibers.
Animation

9. 9
Modal Length
Themodallengthisthelengthofthehighfrequencyfiber
inthesampleobtainedfromthefiberlengthfrequency
diagram.
Themodallengthoflongstaplecottonishigherthanthe
meanstaplelengthduetotheprogressiveincreasein
skewnesswithincreasingstaplelengthinthefiberlength
distribution

10. 10
Span Length
Thespanlengthisthelengthoffibersata
distancespannedbyaspecificpercentageof
fibers(itcanbebynumberorbyweight)inthe
testbeard,consideringthereadingas100%at
thestartingpointofscanning.
Themostcommon spanlengthsused
commerciallyare2.5%and50%spanlength

11. 11
Span Length
Animation: Fibrogram

12. 12
Span Length
The2.5%spanlengthisdefinedasthelengthof
fiberatwhichonly2.5%oflongfibersareexcluded
Itprovidesthereferencelengthforrollersettingsto
beadjustedsothatfew,ifany,fibersarebroken
The2.5%spanlengthisclosetoupperhalf-mean
length(UHML)forlongstaplecotton
The50%spanlengthismorevaluableasa
potentialmeasureofyarnqualityandspinning
performance

13. 13
Animation: Fibrogram Analysis
Upper Half Mean Length

14. 14
Fibre Length Variation

15. 15
Dispersion%
LL´= Effective length
LL´-MM ´= NL ´= Inter-quartile range
Dispersion%=NL ´/LL ´
(for flatter middle zone, dispersion is minimum)
Animation

16. 16
Uniformity Index
The uniformity index (UI%) is the ratio of the mean
length to the upper half-mean length

17. 17
Uniformity Ratio
The uniformity ratio (UR%) is the ratio of the 50% span length
to the 2.5% span length.
Uniformity ratio (U.R.) = 50 % span length /2.5 % span length
= S
50% / S
2.5%
Uniformity ratio (U.R.) in %= [50 % span length /2.5 % span length ] *100
= [S
50% / S
2.5%] * 100
It is a smaller value
than the uniformity
index by a factor
about 1.8

18. 18
Short Fibre Content
Short fibre content (SFC%) is the percentage by
weightof fibers having a length less than half of an
inch.
It can also be measured in percentage by number
of fibers having a length less than half of an inch.

19. 19
Short Fibre Content
The%ofshortfibersincottonincreasesthecostof
processing(combing)andwaste%.
Alsocontributestoweakeryarnandlessefficient
spinning.
Longlengthfibersaremostlypreferredduetothereduced
numberoffiberendswithahigheryarnstrengthinthesame
length

20. 20
Floating Fiber Index
FloatingFiberIndex(FFI)isanalternativeto
shortfibercontent
Itexplainsthenumberofshortfiberswhichare
notclampedbetweenthenipsofapairofrollers
inthedraftingsystem
Thesefibersarefloatedonlongfiberstopass
throughthedraftingzonewithouttheinfluenceof
theapplieddraftingmechanism

21. 21
Methods of Measurement

22. 22
Bytrainedclassers
I.Selectingasampleandpreparingthe
fibresbyhanddoublinganddrawingto
giveafairlywellstraightenedtuftof
about½inchwide.
II.Thisislaidonflatblackbackgroundand
thestaplelengthismeasured.
Cotton FibreLength
a)Hand stapling method:

23. 23
III.Theshorterfibreswilllieinbodyofthe
tuftandextremeends(tips)willnotbe
thelimitsusedformeasurementof
staplelength.
IV.Theclasserchoosethelengthwhere
therearereasonablywelldefinededges.
V.Subjectiveinnature,sodifferencein
resultsbetweenclassers.
Cotton FibreLength
a)Hand stapling method …..cont

24. 24
b)Shirleyphotoelectricstapler
Forquickermeasurement oflength
(staplelength)
Objectivemeasuringtechniqueofearlier
staplelengthmeasuringmethod.(classer
judgesbyeye)
Cotton FibreLength

25. 25
b)ShirleyphotoelectricstaplerAnimation

26. 26
Fringesoffibresarepreparedbyhand
andcarefullyplacedoverblackvelvetpad
Thedensityofthefringeshouldbesuch
thattracesoftheblackvelvetcanbeseen
throughcentralpartwheredensityis
highest.
Thephotoelectricstaplerdetectsthe
distancebetweenthepointswherethe
densitygradientsaremaximum(oneither
side)
b)ShirleyPhotoelectricStapler

27. 27
Two photoelectriccellsconnected
oppositiontoeachother
Dependingonlightintensity,theopposed
cellspassacurrentwhichisproportionalto
thedifferenceintheintensity.
b)ShirleyPhotoelectricStapler…cont

28. 28
b)Shirleyphotoelectricstapler

29. 29
Variationincurrentareshowninsensitive
indicator
Asthefringeisadvancedinsidetheinstrument,
twomaximumdensitygradientpointwillbethere
andthisdistanceis“StapleLength”(max.
deflectionofgalvanometerinoppositedirection)
E.L. = P. E. Staple length ×1.1
b)ShirleyPhotoelectricStapler…cont

30. 30
SF%=(RB/OB)×100% and LL´=Effective length
LL´-MM ´= NL ´= Inter-quartile range
Dispersion%=NL ´/LL ´
(for flatter middle zone, dispersion is minimum)
c) Comb Sorter
Cotton FibreLength
OQ =½ OA OK = ¼ OP
KS =½ KK´ OL = ¼ OR
OM = ¾ OR
Animation

31. 31
American staple length = 0.91 ×Effective length (LL’)
c) Comb Sorter
Cotton FibreLength
OQ =½ OA OK = ¼ OP
KS =½ KK´ OL = ¼ OR
OM = ¾ OR

32. 32
Frequencydistributioninoppositeway,i.e.the
curveisknownbutthefrequencydistributionis
tobeobtained(Y-Axis:Fibrelengthin1/8
th
inch)
Mean Length from Comb Sorter

33. 33
Mean Length from Comb Sorter

34. 34
d)Singlefibrelengthmeasurement
Eachfibreistakenseparatelyandgently
straightenedovertheslide
Lengthisrecorded
otedious&timeconsuming;
onotusedinmillpractice,
ousedwherenumberoffibresaresmall
FibreLength

35. 35
e) Length measurementby weighing method
Aftercombing,thefibresareplacedonavelvet
pad.
Thenrankedintogroupssothatlengthrangein
eachgroupisabout3mm
Groupsarethenweighedonasensitive
balance.
Mean length = WL/ W
where L = Group length
W = Mass of fibrein length group
Upper Quartile Length ?-1/4
th
of the fibresby
mass is longer than that length
FibreLength

36. 36
f) Clamp tuft method (Weighing method)
Clamping
Combining to remove loose un-gripped
fibres
FibreLength

37. 37
Theprotrudingtuftsarecutfromedgeofthe
clampandweighed.
Theclampsthenopenedandfibresinsidethe
clampsareweighedseparately.
FibreLength
f) Clamped tuft method (Weighing method)
Total mass of combed tuft=
Mass of cut edge fibres + Mass of Clamped fibres

38. 38
Meanfibrelength/Totalmassofcombedtuft
=Widthofclamp(W)/Clampedtuftmass
Meanfibrelength(massbiased)
=W×Totalmassofcombedtuft
Massofclampedtuft
MeanfibrelengthαTotalmassofcombedtuft
FibreLength
f) Clamped tuft method
(Weighing method) …cont.

39. 39
g) Photoelectric method (Fibrograph)
Optical method of measuring the density
along the length of a tuft of parallel fibres.
Samples are prepared by “fibrosampler”
The Final Tuft
FibreLength (Cotton)
Animation

40. Fibre Sampling by Fibrosampler
40

41. 41
Assumptions:
Afibreiscaughtonthecombinproportionto
itslengthascomparedwiththetotallengthof
allfibresinthesample(longerfibrehasgreater
chance)
Thepointwhereitiscaughtisatrandomalong
itslength
FibreLength (Cotton)

42. 42
Typical Fibrogram
Superimposition
ofFibrogramand
SorterDiagram

43. 43
Typical Fibrograms (Cotton &Cut Staple Fibre )
Fibrograms Analysis

44. 44
Capacitive Method
FibreLength (Wool)
h) WIRA fibre diagram machine (length
for combed wool fibre)

45. 45
Parallelfibreshaveoneendsealed
betweenstripsofplastic
Measurementcarriedoutbypullingthe
fibres“draw”throughmeasuring
slots.
M/cmeasuresthecapacitanceasthe
‘draw’passes through slots.
(capacitanceisproportionaltoamount
ofmaterial)
WIRA fibre diagram machine

46. 46
MeanLength(ML)iscalculatedfromten
lengthreadingtakenat10%intervalbetween
5%and95%(=Li/10)
WIRA fibre diagram machine
Animation

47. 47
AutomaticversionofWIRAfibre
diagramm/c,withmodification.
Sampleispreparedbyfullyautomatic
m/cknownas“Fibroliner”.
i) Wool fibre length -by Almeter
(Capacitance method)

48. 48
Almeter -Fibroliner

49. 49
Duringmeasurement
thesampleismoved
(trappedbetweentwo
plasticfilms)ata
constantspeedwith
longestfibreentering
thecapacitorfirst.
Changeincapacity
causedbyamountof
fibre.
Wool fibre length -by Almeter
(Capacitance method)

50. 50
Thank You