纺织材料的英文版系列文件(6个ppt)8.ppt

Chapter10WoolFibers,YipingQiuDonghuaUniversity,Morphology,Structuresofwoolfibers,SubmicrostructureCotexcoreofthewoolfiber:90%ofthefibervolume,consistsofcountlesslong,spindle-shapedcellsheldtogetherbyintercellularcement,Woolfibersunderpolarizedopticalmicroscope,Structuresofwoolfibers,SubmicrostructureCotexcanbedividedinto2sections:Orthocotexcontaininglesscystine,andthuslessS-SbondsParacortexcontainingmorecystine,absorbinglesswater.twosectionsspiralaroundeachotheralongthefiberlength.thetwosectionsrespondtoheatandmoisturedifferentlyforming3-Dcrimp.,Structuresofwoolfibers,SubmicrostructureCotex:eachcortexcellcomposedofmacrofibrilsmicrofibrilsprotofibrils-keratinpolymermolecules(polypeptide),Structuresofwoolfibers,Keratinpolymer:helixofaminoacidsStructuralcharacteristics18differentaminoacids:eachwith-N-C-C-backboneahelix:3aminoacidsperturn(right-handedhelix)Diversityofaminoacids:goodfordyeingPolargroupsinaminoacids:hydrophilicityCystineaminoacid:containssulfur:degradationbymothsandbeetlesBigsidegroupsandspiralmolecularconfiguration:hardtobepackedwellleadingtolowcrystallinity(only25-30%),Structuresofwoolfibers,IntermolecularbondingCross-linking:2cystineaminoacidsoneoneachofthetwoadjacentchainsformacystinelink,acovalentbond(S-Sbond),increasingstrengthandelasticity.Ionicbond:saltlinkageformedwhentwoaminoacidsareincloseproximity:responsibleforreactingwithaciddyes.Hydrogenbonds:betweenamidegroupsbuthaverelativelylowdensityduetomoreamorphousphaseandpackingdifficulties.,Propertiesofwoolfibers,Mechanicalproperties:relativelylowstrengthortenacityhighelasticrecoveryhighflexibilityhighresiliencelowinitialmoduluslowabrasionresistancelowstiffnesslowtoughnesspropertieschangeaswaterabsorptionchanges,Propertiesofwoolfibers,Comfortproperties:highheatofwettingduetomoreamorphousphasethanmanyotherfibers)slowtherateofevaporationofbodywaterwaterrepellentduetoepicuticle3-Dcrimptrapsmoreairreducingthermalconductivityairspace2/3oftotalvolumelowlusterduetocrimpandscalesodorabsorbenthighpillingbuteasytoremove,Maintenanceofwoolfibers,Soilcanbeeasilyremoved,butmayabsorblargequantitiesofoilysoilWashing:woolfibersareweakerinwaterandhavealowermodulusthuswillbeeasilystretchedshrinkswhenagitatedinwater:feltingshrinkagedegradesinmildalkalinesolutions,e.g.detergentsolutions.becausealkalinityweakenssalt&cystinelinkagesandincreasefelting:drycleaningrecommended,Maintenanceofwoolfibers,Washing:Bleachesdegradeswoolandshouldnotbeused.DryheatmakesfiberbrittleRelativelyhighresistancetoacidDecompositionduetobacteria&enzymes,mothsandbeetlesharmwoolesp.whenstained:mothballsandcedarchestsrecommendedLowflammability:self-extinguishesduetohighwatercontent(needhighenergytogetridofwater)chemicalabsorption:easilyabsorbslargeamountofoil:goodforremoveoilspillageortoxicchemicals.,Productionofwoolfibers,55%producedinAustralia,formerUSSRandNewZealandclippedwoolorfleecewool:shearedfromthesheep(annuallydoneearlyspring),betterqualitypulledwool:pulledfromhide.chemicallyshed:fallingoffin2weeksoffeedingthechemicaltothesheepscoured:removewoolgrease,suint,sandandsomeplantmaterials(couldbe50%of