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S.Yang,S.Gordon
5Fabricstructures:Woven,knitted,ornonwoven107
H.Gong,B.Ozgen
5.1Introduction
B.Kumar,J.Hu
8Easy-caretreatmentsforfabricsandgarments187 J.H.Xin,H.F.Lu
9Pilling-resistantknitwear217 L.Wang,X.Qian
PartThreeProductspecialization277
12Compressionandstretchfitgarments279 A.Yu,K.L.Yick
13Conductivetextiles305
K.(Kelvin)Fu,R.Padbury,O.Toprakci,M.Dirican,X.Zhang
14Insect-repellenttextiles335
J.H.Xin,X.W.Wang
15Camouflagefabrics349
Listofcontributors
K.Bilisik ErciyesUniversity,Kayseri,Turkey
R.J.Denning CSIROManufacturing,Geelong,VIC,Australia
M.Dirican NorthCarolinaStateUniversity,Raleigh,NC,UnitedStates
B.Fei HongKongPolytechnicUniversity,Kowloon,HongKong
K.(Kelvin)Fu NorthCarolinaStateUniversity,Raleigh,NC,UnitedStates
H.Gong UniversityofManchester,Manchester,UnitedKingdom
S.Gordon CSIROManufacturing,Geelong,VIC,Australia
C.Greb InstitutfuerTextiltechnikofRWTHAachenUniversity,Aachen,Germany
T.Gries InstitutfuerTextiltechnikofRWTHAachenUniversity,Aachen,Germany
J.Hu TheHongKongPolytechnicUniversity,HungHom,HongKong
Y.Ke JiangnanUniversity,Wuxi,China
B.Kumar IndianInstituteofTechnology,Delhi,India
M.Lengersdorf InstitutfuerTextiltechnikofRWTHAachenUniversity, Aachen,Germany
C.Lenz InstitutfuerTextiltechnikofRWTHAachenUniversity,Aachen,Germany
H.F.Lu TheHongKongPolytechnicUniversity,Kowloon,HongKong
N.Mao UniversityofLeeds,Leeds,UnitedKingdom
M.Miao CSIROManufacturing,Geelong,VIC,Australia
K.R.Millington DeakinUniversity,WaurnPonds,VIC,Australia
B.Ozgen EgeUniversity,Izmir,Turkey
R.Padbury NorthCarolinaStateUniversity,Raleigh,NC,UnitedStates
X.Qian TianjinPolytechnicUniversity,Tianjin,China
O.Toprakci NorthCarolinaStateUniversity,Raleigh,NC,UnitedStates
F.Wang TheHongKongPolytechnicUniversity,Kowloon,HongKong
L.Wang TianjinPolytechnicUniversity,Tianjin,China;RMITUniversity, Brunswick,VIC,Australia
X.W.Wang TheHongKongPolytechnicUniversity,Kowloon,HongKong
J.H.Xin TheHongKongPolytechnicUniversity,Kowloon,HongKong
S.Yang CSIROManufacturing,Geelong,VIC,Australia
K.L.Yick TheHongKongPolytechnicUniversity,HungHom,HongKong
A.Yu TheHongKongPolytechnicUniversity,HungHom,HongKong
X.Zhang NorthCarolinaStateUniversity,Raleigh,NC,UnitedStates
Preface
Producersandconsumerstodayarenotsatisfiedwithtextilesthatofferastandardperformance.Thisbookisaimedatassistingtextileengineersandproductdesignersto improvetheperformancestandardoftheirexistingproductsandtodevelopnewhighperformanceproducts.
Thedesignofhigh-performancetextilesstartswithselectingthemostsuitable fibers.Untilafewdecadesago,virtuallyalltextileshadbeenmadefromnaturalfibers obtainedfromplantsandanimals.Theadventofman-madefibershasenrichedthe materialssourcefortextileengineers.Syntheticfibersenteredtheworldofapparel andindustrialtextilesbyimitatingandblendingthemwithnaturalfibers,suchaswool andcotton.Manysyntheticfibersarenowhighlyspecializedandofferextremely high-performancepropertiesinchallengingapplicationsfarbeyondtraditional apparelandindustrialtextiles.
Textileengineeringresearchanddevelopmentinthelasthalf-centuryhavechangedthelandscapeofthetextileindustry.Whileringspinningisstillthedominantyarn manufacturingtechnology,unconventionalspinningmethods,suchasrotorspinning andair-jetspinning,arenowwidelyused.Shuttleloomsarereplacedbyshuttleless looms.Theuseofelectronicknittingmachinesiswidespread.Thenonwovenindustry hasexperiencedarapidexpansioninindustrialtextilesandapparelsduetothenew processingtechnologiessuchasspunlaceandduetothefastgrowthofsynthetic fibers.
Thefashionandtextileindustryhasalsoexperiencedrapiddevelopmentsinthe pastfewdecades.Syntheticdyesnowproduceamuchwidercolorgamutforbothnaturalandsyntheticfibers.Functionaltreatmentstofibers,fabrics,andevengarments todayprovidepropertiessuchaswrinklerecovery,waterrepellency,andflameretardancy.Withdecadesofdevelopmentincolorationandfinishing,producersandconsumersstartedthinkingoftheimpactofnewtechnologiesontheenvironment.The conceptofsustainabilityoftheecosystem,“greener”technology,biodegradability, andtheuseofnaturalproductshasbecomeatrend.Moreandmoreproductson themarketnowofferspecializedhigh-performanceproperties,suchasdirectional moisturetransfer,insectrepellency,andcamouflaging.
Inthisbook,thefirstthreechaptersdiscusstextilefibers,theirproperties,andsuitabilityfordifferenttextileend-uses. Chapter1 isaimedatprovidingaframeworkfor fiberselectionaccordingtotheirtechnicalattributes,influencesonproductcharacteristics,andrequirementsfortextileprocesses. Chapter2 reviewsfibersdevelopedin thelastfewdecadestofulfilltherequirementforgeneralusesandforspecializedhighperformancetextiles. Chapter3 dealswiththescienceandartoffiberblendingtomeet requirementsthatasingletypeoffibercannotfulfillsatisfactorily.
Chapters4–6 dealwiththeconversationoffibersintofit-to-purposeyarnsandfabrics. Chapter4 discussesfiber-to-yarnpropertypredictiontoolsbasedonthephysical andtheoreticalmodels. Chapter5 providessomebroadguidelinesforfabricdevelopmentbycomparingthecharacteristicsoffabricsproducedbydifferentcategoriesof fabric-formingmethods,namelyweaving,knitting,andnonwoven. Chapter6 attemptstolaydownthebasicprinciplesofmechanicsforunderstandingthefabric structure-propertyrelationship,particularlyinwovenfabrics.
Chapters7–11 reviewthemainperformancedeficienciesofcommonconsumer textilesandtechnologiesavailabletotextileengineersanddesignersforproduct improvementanddesign.
Mostgarmentsnowaredisposedbeforetheyarewornout.Colorfadingbecomes animportantreasonfordisposinggarments. Chapter7 discussestheinteraction betweenfiberanddye,thevariouschallengesthatinfluencethecolorfastnessofdyed fabricsinpractice,thefastnesspropertiesoffiber-dyesystems,colorfastnesstesting, andfinishingtreatmentstoimprovecolorfastness.Today’sbusyconsumersexpect thatgarmentsremainwrinklefreeafterdomesticlaunderingandtumbledrying. Chapter8 reviewsthechemistryandtechnologicalprogressesofeasy-caretreatments. Pillingisatraditionalperformanceproblemandtheproblemdeteriorateswiththe popularityofsofthandleknitwear. Chapter9 reviewsthemechanicsofpilling,influencesoffabricconstructiononpilling,treatments,andmanagementofknitwear pilling.
Apracticalimperativeofclothingistokeepthebodywarmincoldweather.Ifnot appropriatelydesigned,winterclothingcanbecomeheavyandbulky. Chapter10 beginswithadiscussiononthemechanismsofheattransferthroughfabrics,therelationshipbetweenheattransferandairgaptrappedwithintheclothingmicroclimate.It movesontodiscussthedesignofwarmfabricswithouttheunnecessaryweightand bulk.Sportsclothingisnownotonlywornbyathletesincompetitionbutalsoby almosteveryonetakingpartinexercisesandmanyotheractivities.Comingwiththis trendistherequirementforfabricstotransportsweatandheatefficiently. Chapter11 dealswiththemechanismsofwatervaporandliquidtransferthroughtextiles,theattributesoftextilematerialsthataffectthemoisturetransferprocess,andthemethods availabletodesignhigh-performancemoisturemanagementtextiles.
Theuseoftextilematerialsisnowfarbeyondapparelandhasbecomehighlyspecialized. Chapters12–18 discussanumberofhighlyspecializedtextilesthathave experiencedrapiddevelopmentandgrowthinrecentyears.
Chapter12 reviewscompressionandstretch-to-fitgarmentsusedinsportswearto improveathleticperformance,inthemedicaltreatmentsofhypertrophicscarsand venousdiseases,forbodyshaping,andasintimateapparel. Chapter13 discusses conductivetextilesmadeeitherfromconductivefibersorbydepositingconductive materialsontononconductivetextiles.Theend-usesforconductivetextilesare diverse,fromantistaticandelectromagneticshieldingtoelectronictextiles (eTextiles). Chapter14 dealswithinsect-repellentfabricsthataremadeintonets, uniforms,garments,andothertextilesforprotectinghumansfromthebiteofinsects orarthropodsintropicalandsubtropicalregions,rainforests,andotherenvironments ofinsectinhabitation.
Chapter15 reviewsthedevelopmentofcamouflagefabricsusedbythemilitary, hunters,gamewatchers,andthelike.Thischapterexploresthecurrentstateofcommercialdetectionsystemsandthecamouflagefabricsusedtodefeatthesesystems. Chapter16 dealswithfabricsdesignedfordefeatingballisticandstabthreatsfacing themilitaryandlawenforcementpersonnel.Itreviewstheprinciplesofdynamics behindbodyarmordesignandrecentdevelopmentsinballisticfibersandfabric structures.
Chapter17 beginswithanoverviewoftheperformancerequirementsofvarious filterfabricsandthetheoriesofdepthfiltration,surfacefiltration,andbloodfiltration. Itgoesontodiscusstheengineeringofwovenandnonwovenfilterfabricstoachieve optimumperformance. Chapter18 reviewsthefabricsdesignedforthereinforcement ofengineeringcomposites,especiallycarbonfiber-reinforcedpolymermatrixcomposites.Thechapterpresentswiderangesof2Dand3Dfabricpreformstructures,their characteristics,andmanufacturingtechnology.
Finally,weacknowledgethetimeandeffortsofourcontributors,whoareexperts intherespectiveareasdescribedinthisbook.
MengheMenghe
JohnH.Xin
TheHongKongPolytechnicUniversity May2017
PartOne Productdesign
Fiberselectionandsubstitution
M.Miao,S.Gordon CSIROManufacturing,Geelong,VIC,Australia
1
1.1Introduction
1.1.1Textilefibers
Theprimaryrawmaterialsfortextilemanufacturingarefibers.Traditionally,naturallyoccurringfiberswereusedintextiles.Theoriginsofthesenaturalfibersare mainlyplantsandanimalhairs.Naturalmineralfibersalsoexistsuchasasbestos, althoughnotcommonlyusedintextiles.
Themaincompositionofplantfibers(knownasvegetablefibers)iscellulose. Plantfibersgrowonseed(e.g.,cottonandkapok),asseedhairs,andwithintheleaves (e.g.,sisal)andstems(knownasbastfibers,e.g.,flaxandhemp)ofparticularplants. Cottonisthemostwidelyusednaturalfiber,accountingformorethanone-thirdofthe tonnageoffibersusedbytheworldtextileindustrytoday.
Themaincompositionofanimalfibersisprotein.Hairsofawiderangeofanimals, includingsheep(wool),goat(cashmere),camel,alpaca,rabbit,areusedtoproduce highlysought-aftertextileproducts.Silk,anotherhighlyvaluedtextilefiber,is producedbydrawingthesilkfilamentsfromsilkwormcocoons.Animalfibersare availableinmuchsmallerquantitiesthancotton.
Naturalpolymerssuchascelluloseandproteincanbeprocessedintosolutionsand extrudedintofibers.Thesefibersareoftenreferredtoasregeneratedfibers.Viscoseis animportantman-madefiber(MMF)regeneratedfromwoodcellulose.
Syntheticfibersaremadefrompolymersbuiltupfromchemicalelementsorcompounds.Thecompoundsthatareusedtomakethesefibersmostlycomefrom petroleum-basedchemicalsorpetrochemicals.About40%oftheworldtextilefiber consumptionispolyester.Othermaincommoditysyntheticfibersarenylon,acrylic, andpolyolefin.Environmentalandsustainabilityconcernsontheuseofpetrochemicalshavebeengrowinginrecenttime.Thishasledtothedevelopmentofnew fibersfromsustainablesources,forexample,polylacticacid(PLA)fiberfromcorn.
Fig.1.1A showsthehistoryofworldfiberdemandinmillionsoftons.Cottonhada dominantroleinthetextileindustryuntiltheturnofthemillennium.Theconsumption ofpolyesterpassedthatofcottonin2002andhascontinuedtogrowatasignificantly fasterratethanallotherfibertypes.In2014,theworldconsumerdemandforallfibers averaged11.4kg/capita(Fig 1.1B).VolumesvaryfromNorthAmericawithahighof 37kg/capitatoAfrica,theMiddleEastandIndiaat5kg/capita.
Fig.1.2 showsthepercentagechangeoffiberconsumptionbytype,between2007 and2010.Thedecreaseintheconsumptionofcottonandwoolwastakenupbythe increaseofpolyesterconsumption.
4EngineeringofHigh-PerformanceTextiles
Fig.1.1 Worldfiberdemandtrend.(A)Totalfiberdemand;(B)Globalfiberdemandpercapita (http://www.textileworld.com/textile-world/fiber-world/2015/02/man-made-fibers-continueto-grow/,accessed08.07.16).
Synthetic (noncellulosic) fibers
Fig.1.2 Compositionofworldapparelfiberconsumptionbyfibertype(FAO-ICAC,2013).
Withrapidprogressinpolymerscienceandfiberengineeringtechnologyoverthe lastthreetofourdecades,manynewMMFwithcharacteristicsthatsurpassnatural fibershaveemerged.ThesenewspecialtyfibersarecoveredinChapter2.
1.1.2Yarnproductionsystems
Historically,differentprocessing(spinning)systemsweredevelopedforcotton,wool, andtoalesserextent,forlinen(mainlyflax)andsilk.Amajordistinctionbetween themistheirabilitytodealwithdifferentfiberlengths.Woolcanbeprocessedon eithertheworstedorwoolensystems.Generallyspeaking,longwoolisprocessed ontheworstedsystem,whichinvolvescombing,repeatedgilling(pin-drawing) andhigh-draftspinning.Woolblendscontainingshorterfiberswithawidelengthdistributionareprocessedonthewoolensystem.Inthewoolensystem,fibersarefirst processedonacondensercardfollowedbylow-draftspinning.Cottonspinninghas alotofsimilaritieswithworstedspinning,butflat-cardingandrollerdrawing,instead ofroller-cardingandpin-drawing,areusedbecausecottonisconsiderablyshorterthan thewoolusedinworstedspinning.Therearedistinctdifferencesincharacteristicsof theyarnsprocessedbythesespinningsystems.
Cotton Wool Flax
Cellulosic fibers
Boththecottonandworstedsystemsconvertthefibers,viacarding,firstintoa sliverandthensubjecttheslivertohighratiodraftingthatattenuatesthesliverinto alighterassemblyoffibersthatisthentwistedintoayarn.Thefibersinspunyarnare mostlystraightandparallel,albeittwistedinahelicalmanner,givingacompact, smooth,andlustrousappearance.Becausewoolfibersaremuchcoarserandlonger thancottonfibers,thenumberoffibersinthesamelengthofyarnisfewer,withsubsequentlyfewerfiberendsonthesurface.Thismeansworstedyarnsaretypicallyless hairythancottonyarns.Suitingfabricisthetraditionalmarketforworstedyarn. Becauseofthelargequantitiesproduced,cottonyarnisusedwidelyinapparel,home textiles,andindustrialtextiles.
Thewoolenspinningsystemisamuchshortermanufacturingprocessthanworsted spinning.Thefiberwebformedonacardingmachineisdividedintostripsthatare rubbedtogethertoformslubbings,whicharestrandsofentwinedfibers.Theslubbings aretwistedintoyarnswithverylowdraft.Fibersinwoolenyarnsarecrossedandintertwined,incontrastwithparallelfibersinworstedyarns.Thislowfiberorientation givesacharacteristicmattedyarnstructurecontainingmanyairpockets.Typical productsfromwoolenyarnsareblankets,heavywintersuiting,andcarpets.
Man-madefibers(MMFs)wereinitiallymanufacturedtoimitatenaturalfibersfor textileapplications.ThefirstMMF,viscoserayon,wasintheformofamultifilament yarn,whichwasmarketedasartificialsilk.Flatfilaments(i.e.,parallel-laid)inamultifilamentyarncaneasilyseparate,causingprocessingproblems.Thus,multifilament yarnsusuallyarelightlytwistedorinterlacedtoimprovetheirprocessingperformance (MiaoandLui,1997).Multifilamentyarnscanbetexturizedtofurtherimpartstaple fiberyarncharacteristicsandspecialperformancessuchasstretch(Wilsonand Kollu,1987).
Man-madestaplefiberscanbeprocessedonthecottonorwoolspinningsystems dependingonthefiberlength.TheresultingMMFyarnsusuallybearsimilarcharacteristicsofthenaturalfiberyarnsprocessedonthesamesystem.Forthisreason,the cottonspinningsystemisknownasshortstaplespinningandthewoolspinningsystem (especiallytheworstedspinningsystem)isknownaslongstaplespinning.
Manycharacteristicsoftextilessuchasflexibility,softness,warmth,andaesthetics,derivefromtheslendershapeofthefibersandthewayinwhichthesefibers arearrangedinthetextileproducts.Thepriceoffiber,forexample,wool,canvary significantlydependingonitspropertiessuchasdiameter,length,color,andstrength. Selectionoffibersaccordingtotheirpropertiesisthefirststeptoproducing high-qualitytextileproducts.
1.2Fiberfineness
1.2.1Fibersaccordingtofineness
Aprimarycharacteristicoftextilefibersistheirhighflexibilityandtheirabilityto deformelasticallyunderalaterallyappliedload.Theflexibilityofaroundfiberis madepossiblebyitssmalldiameter(d ).Stiffness,theoppositeofflexibility,isproportionalto d4 . Forapparelfabrics,thefiberdiameteraffectsthetexture,drape,surface
6EngineeringofHigh-PerformanceTextiles
roughness,softnesstohandle,levelofmechanicalagitationtoskin(prickle),breathability,etc.Forsportandfiltrationfabrics,fiberdiameteraffectsthesizeandpopulation ofporesformedinthefabric,whichinfluencesfluidtransportproperties.Whenusedin polymer-matrixcompositematerials,fiberdiameterdeterminesthespecificinterfacial areabetweenthefiberandthematrixandthepermeabilityoffabricpreformto liquidresin.
Thefinenessofconventionalfibersismeasuredindifferentwaysdependingonthe fibertype.ThefinenessofMMFiscommonlymeasuredbyitslineardensity(weight/ length,intermsofdenier,decitex,millitex,andtex).Thefinenessofwoolfiberswas traditionallyassessedbythefinestyarncountthatcanbespunfromthefibers,andthis waschangedtoobjectivelymeasuredfiberdiameterusingmicroscopy,airflow,and imageanalysistechniques(OFDA,LaserScan)(Qietal.,1994;Sommerville,2000). Thefinenessofcottonfibersisassessedintermsofmicronaire,usingtheairflow method.However,themicronairevalueofcottondependsonitsaveragefineness andmaturity.Thelatterdescribesthethicknessofthecottonfiber’scellwall.The newCottonscopeinstrumentmeasurescottonlineardensity(millitex)independent ofmaturity(Gordonetal.,2012).
Silk,withalineardensityofabout1denier,isthefinestcommonlyusedtextilefiber. Cottonfibershaveakidney-shapedcross-sectionwithawidthofabout10–20 μm.The averagediameterofwoolfiberscanvaryfromlessthan15 μmtoabout50 μm.ConventionalMMFaremanufacturedtosimilardiametersasthesenaturalfibers,sothat theycanbeeasilyblendedwithnaturalfibersandprocessedonconventionalmachinery.Withtheadvanceofsyntheticfibermanufacturingtechnology,muchfinerfibers cannowbeproduced.Thespectrumoffiberdiameterisillustratedin Fig.1.3.
Microfibersaresyntheticfibersthatcanbefinerthansilk(aboutonedenieror decitex)(McIntyreandDaniels,1995).Thereareawiderangeofmethodsfor manufacturingmicrofibers(Mukhopadhyay,2002).Theshape,size,andcombination ofpolymersformicrofibersareselectedtoachievespecificcharacteristics,including softness,toughness,absorption,waterrepellency,electrostatics,andfilteringcapabilities.Microfibersareusedtoproduceman-madeleather(e.g.,ultra-suede),cleaning cloth,moisture-wickingandsoft-touchfabrics,andfiltrationmedia(e.g.,medical filters).
Conventional fibers > 1 decitex
Extruded fibers
Cotton Wool Silk
Direct extrusion
Melt blowing
Flash spinning
Bicomponent extrusion
islands-in-the-sea conjugate
Fig.1.3 Fiberfineness.
Bicomponent extrusion
Electrospinning
Catalytic synthesis (carbon nanotubes)
Self-assembly
Interfacial polymerization
Electrospinningisamethodforproducingsubmicronfibersfromavarietyofmaterials,forexample,polymersandcomposites.Inthepresenceofastrongelectricfield, anelectrostaticchargeisintroducedtoafinestreamofpolymersolutiondirectedata groundedcollectorplate.Theelectricallychargedjetofpolymersolutionaccelerates andthinsoutintheelectricfield.Ifasolventispresentitusuallyevaporatesbeforethe filamentreachesthecollectorplate.Mostelectrospunfibersareinthesubmicron diameterrange(100–500 μm)(Teoetal.,2016).Thepotentialapplicationsof electrospunfibersincludefiltration,cellgrowthscaffolding,energystorage,etc.
Nanofibers(<100 μm)havebeenthesubjectofintensiveresearchsincethe early1990s.Severalmethodsofmanufacturingnanofibershavebeeninvestigated (Pisignano,2013).Animportantfiberunderthiscategoryisthecarbonnanotube.Carbonnanotubesarethermallyandelectricallyconductive,andarethestrongestand stiffestmaterialsyetdiscoveredintermsoftensilestrengthandelasticmodulus (Yuetal.,2000).Thisstrengthresultsfromthecovalent sp 2 bondsformedbetween theindividualcarbonatoms.Carbonnanotubescanbemadeintononwovensheets (knownasbuckypapers)andmicrosizedyarns(Miao,2013).Awiderangeofpotential applicationshavebeeninvestigated,includingstrongtextileandcompositematerials, energystoragedevices,sensors,artificialmuscles,etc.
1.2.2Fiberfinenessandyarncountlimit
Withoutconsideringfibercurlingandyarnlengthcontractioncausedbytwistinsertion,thelineardensityofayarnisthesumofthelineardensitiesofallitsconstituent fibersintheyarncrosssection,whichisequaltothemeanfiberlineardensity multipliedbythenumberoffibersintheyarncrosssection.Modernstapleyarn manufacturingmachinerydoesnotarrangefibersendtoendintheresultingyarn. Thespinnercanonlycontroltheaveragenumberofalignedstaplefibers(n)inthe yarncrosssection,butnottheexactnumberoffibersinanyparticularcrosssection oftheyarn.Inanidealscenario,thenumberoffibersintheyarncrosssectionis randomwithastandarddeviationequaltothesquarerootoftheaveragefiber number(√ n)(Martindale,1945).Theirregularity(coefficientofvariation)ofthe yarnisreciprocalofthestandarddeviationoffibernumber(1=√ n).Yarnirregularity isaveryimportantqualityindicator.Tokeeptheyarnirregularityundercontrol,the averagenumberoffibersintheyarncrosssectionmustbesufficientlylarge(n > nmin). Therefore,thefinestyarnthatcanbespunisdirectlyrelatedtothemeanlineardensity ofthefiberused.Intheworstedindustry, nmin isgenerallyconsideredtobeabout 35–40,dependingonthemanufacturer’stoleranceofyarnirregularity.
Themassirregularityofacommercialyarnisalwaysgreaterthantheideal valuepredictedfromtheaveragefibernumber.Thisisbecause,first,theprocessing machineryisnotperfectandsecond,thefibersdonothaveidenticallineardensity. Vastamountsofcommercialdataarecollectedeachyearonyarnirregularityasa functionofyarnlineardensityandthedataarepublishedinUsterStatistics (https://www.uster.com/en/service/uster-statistics/).
1.2.3Woolaccordingtodiameter
Woolconstitutesabout2%oftheworldapparelfiberproduction.Wool’slimited supplycoupledwithitsexcellenttextileperformancepropertieshaveresultedinwool productsbeingpositionedattheluxuryendofmostmarkets.Owingtotherangeof sheepbreedsandwooltypesproduced,woolisprocessedintoawiderangeofend products.Endusesaredeterminedbythemainfibercharacteristics,withfiberdiameterbeingthemostimportantparameter. Fig.1.4 showstheapproximaterangeof applicationsfordifferentwoolsaccordingtofiberdiameter.
Animportantconsiderationofwoolselectionfornext-to-skingarmentsiswhether thefiberscauseapricklesensationthatarisesfromthemechanicalstimulationof specificnerveendings(Garnsworthyetal.,1988).Fiberscoarserthanabout30 μm arestiffenoughtoupholdaforcelargeenoughtotriggerthispricklesensation (Naylor,1992).Woolfibershaveanaturalspreadofdiametersandthepercentage offibersgreaterthan30 μmisoftenreferredtoas“pricklefactor”ofthewool.In theory,thepricklefactorcanbeachievedbyeitherreducingthecoarseedgeofthe diameterdistributionorbyreducingthemeanfiberdiameter.Inpractice,reducing thecoarseedgeofwooldiameterdistributionisdifficulttoachieveandchanging toafinerwoolisalwaysthechoicetoeliminatefabric-evokedprickle.
AnotheranimalhairfiberthatdeservesspecialmentionisCashmeredownfiber. Cashmerecommandssomeofthehighestpricesintheworldoftextiles.Cashmere hasafiberdiameterbetween12.5and16.0 μm.Worldproductionofcleancashmere isestimatedatabout6500tones( https://en.wikipedia.org/wiki/Cashmere_wool). Theappealofcashmereanditsunrivalle dstatusasaluxuryfiberisrootedfrom itsvisualappealandextremesoftness,scarcity,anditsmystique.Cashmereiscommonlyspunintowoolenyarns,whichare usedinknitwear.Manyknitwearproducersusecashmerebutbecauseofitscostoftenuseitinblendswithother fibersincludingMMF.Cashmereisalsousedinwovenaccessories(scarves,shawls, Carpets
andstoles),rugs(especiallytravelrugs and“throws”)andclothforluxurycoats, jackets,andsuitsforthemensweartrade.
1.3Fiberlength
Fabricsmadefromcontinuousfilamentyarnsgiveabrightandsmoothappearance. Filamentyarnswithverylowornotwist(flatfilamentyarn)retainalmostallthe strengthoftheindividualfilaments.Fabricsmadefromsuchyarnsareespeciallysuitableforapplicationsthatrequiremaximumstrengthandmodulus,suchasengineering compositesandbodyarmors.
Thebulkofappareltextilesaremadefromstaplefibers,althoughtheuseoffilamentpolyesteryarnisincreasing.Thesurfaceroughness,hairiness,porosity(bulk)of staplefiberyarnsgivedullappearance,“natural”texture,softhandle,andwarmthto thefinalfabrics.Fiberlengthanditsdistributioninfluencethechoiceofyarn manufacturingmethodandfurtherprocessingtechnologyandaffectthestructure andpropertiesofthespunyarn.
1.3.1Fiberlengthmeasurement
Therearemanywaystoexpressfiberlength.Staplelengthisthecharacteristicfiber lengthestimatedbysubjectivevisualassessmentofafibertuftpreparedbyhand.The word“staple”originatedfromthewoolindustry,whereawoolstapleisanaturally formedlockofwoolfiberinafleece(McIntyreandDaniels,1995).
Theobjectivemeasurementoffiberlengthstartswiththepreparationofafiber lengthdistributiondiagram(“fiberbeard”)usingdifferentinstruments,forexample, thecombsorter,thefibrographinstrument(cotton),andthealmeter(wool).When thewoolisprocessedintoasliverform(wooltop),thefiberlengthismeasuredby Hauteur,themeanfiberlengthcalculatedfromtheproportionsbylineardensity(cross section)ofthefibers.Thevariabilityofthefiberlengthisreportedasthecoefficientof variation(CVH%).However,inthewoolenindustry,barbe,themeanlengthbiasedby fiberweight,isused.Barbe,Hauteur,anditsCVhavethefollowingmathematical relation(McIntyreandDaniels,1995)
Cottonfiberlengthor“staple”lengthcanbedefinedintermsofspanlength,thatis, thelengthexceededbyastatedpercentoffibersbynumber,orbytheupperhalfmean length(UHML)value,bothdeterminedfromthefiberdiagramproducedbythe Fibrographinstrument.The2.5%spanlengthisthelengthexceededbythelongest 2.5%bynumberoffibers,whereastheUHMListhemeanlengthbynumberof thelongeronehalfofthefibersbyweight.Cottonfiberlengthvariationmaybe expressedbyauniformityindex,whichistheratioofmeanlengthtotheUHML orbytheuniformityratio,whichistheratiobetweenthe50%and2.5%spanlengths. Theshortfibercontent(percentageoffibershorterthanastatedlength)value measuredbytheFibrographishighlyvariablebetweensamples,instruments,and laboratoriesandassuchcannotbepricedortradedon.
Barbe ¼ Hauteur 1+ CV 2
(1.1)
