广纺院纺织材料学英文课件03 Wool Fibers

Chapter10WoolFibersMorphologyStructuresofwoolfibersSubmicrostructureCotexcoreofthewoolfiber:90%ofthefibervolume,consistsofcountlesslong,spindle-shapedcellsheldtogetherbyintercellularcementWoolfibersunderpolarizedopticalmicroscopeStructuresofwoolfibersSubmicrostructureCotexcanbedividedinto2sections:Orthocotexcontaininglesscystine,andthuslessS-SbondsParacortexcontainingmorecystine,absorbinglesswater.twosectionsspiralaroundeachotheralongthefiberlength.thetwosectionsrespondtoheatandmoisturedifferentlyforming3-Dcrimp.StructuresofwoolfibersSubmicrostructureCotex:eachcortexcellcomposedofmacrofibrilsmicrofibrilsprotofibrils-keratinpolymermolecules(polypeptide)StructuresofwoolfibersKeratinpolymer:helixofaminoacidsStructuralcharacteristics18differentaminoacids:eachwith-N-C-C-backboneahelix:3aminoacidsperturn(right-handedhelix)Diversityofaminoacids:goodfordyeingPolargroupsinaminoacids:hydrophilicityCystineaminoacid:containssulfur:degradationbymothsandbeetlesBigsidegroupsandspiralmolecularconfiguration:hardtobepackedwellleadingtolowcrystallinity

(only25-30%)StructuresofwoolfibersIntermolecularbondingCross-linking:2cystineaminoacidsoneoneachofthetwoadjacentchainsformacystinelink,acovalentbond(S-Sbond),increasingstrengthandelasticity.Ionicbond:saltlinkageformedwhentwoaminoacidsareincloseproximity:responsibleforreactingwithaciddyes.Hydrogenbonds:betweenamidegroupsbuthaverelativelylowdensityduetomoreamorphousphaseandpackingdifficulties.PropertiesofwoolfibersMechanicalproperties:relativelylowstrengthortenacityhighelasticrecoveryhighflexibilityhighresiliencelowinitialmoduluslowabrasionresistancelowstiffnesslowtoughnesspropertieschangeaswaterabsorptionchangesPropertiesofwoolfibersComfortproperties:highheatofwettingduetomoreamorphousphasethanmanyotherfibers)slowtherateofevaporationofbodywaterwaterrepellentduetoepicuticle3-Dcrimptrapsmoreairreducingthermalconductivityairspace~2/3oftotalvolumelowlusterduetocrimpandscalesodorabsorbenthighpillingbuteasytoremoveMaintenanceofwoolfibersSoilcanbeeasilyremoved,butmayabsorblargequantitiesofoilysoilWashing:woolfibersareweakerinwaterandhavealowermodulusthuswillbeeasilystretchedshrinkswhenagitatedinwater:feltingshrinkagedegradesinmildalkalinesolutions,e.g.detergentsolutions.becausealkalinityweakenssalt&cystinelinkagesandincreasefelting:drycleaningrecommendedMaintenanceofwoolfibersWashing:Bleachesdegradeswoolandshouldnotbeused.DryheatmakesfiberbrittleRelativelyhighresistancetoacidDecompositionduetobacteria&enzymes,mothsandbeetlesharmwoolesp.whenstained:mothballsandcedarchestsrecommendedLowflammability:self-extinguishesduetohighwatercontent(needhighenergytogetridofwater)chemicalabsorption:easilyabsorbslargeamountofoil:goodforremoveoilspillageortoxicchemicals.Productionofwoolfibers55%producedinAustralia,formerUSSRandNewZealandclippedwoolorfleecewool:shearedfromthesheep(annuallydoneearlyspring),betterqualitypulledwool:pulledfromhide.chemicallyshed:fallingoffin2weeksoffeedingthechemicaltothesheepscoured:removewoolgrease,suint,sandandsomeplantmaterials(couldbe50%