CoaedKniedFabrics上涂层针织物的力学性能

MechanicalPropertiesofPolyurethane

CoatedKnittedFabricsIntroductionSamplesandworkingmethodResultsanddiscussionConclusionsPart1introduction

Polyurethane-coatedknittedfabricsare

ofinterestbecausetheyexhibitseveral

positiveproperties,andyettheyarelittle

studied,especiallythoseusedinthe

garmentindustry.Theadvantagesof

polyurethanecoatingsincomparisonto

otherpolymersaregreaterresistanceto

abrasionandsplitting,increasedstrength

anddurability.

Polyurethanesareformedbythepolyaddition

reactionofapolyisocyanate

withapolyalcohol(polyol)inthepresence

ofacatalystandotheradditives.

Polyisocyanateisamoleculewithtwo

ormoreisocyanatefunctionalgroups,R-(N=C=O)n≥2andapolyolisamolecule

withtwoormorehydroxylfunctional

groups,R’-(OH)n≥2.Thereaction

productisapolymercontainingtheurethane

linkage,-RNHCOOR’-[3].Thereisachancetodevelopcoatedknitted

fabricsasprotectiveclothing,work

clothing,sportswearandcasualwear

more

comfortablethanclothesmadeout

ofcoatedwovenfabricbecausemovements

arelessrestrictedifclothingis

madeofelasticknittedmaterial.Coatedknittedfabricsaregenerallymore

stretchableandelasticthanwovenfabrics.Part2SamplesandworkingmethodSamplesSevenknittedfabricswithdifferent

structures(designationsKF1-KF7)were

chosentocoverawideintervalofvalues

ofthecharacteristicsofelongationand

breakingforcestested(Tables1&2).Theywerecoatedunderthesameconditions,

onthesamecoatingline,withthree

differentpolyurethanecoatings(designated

PU1-PU3).Thepolyurethanecoatingshave

nearlyequalaveragethicknessesand

weights,butdifferentmechanicalproperties

(Table3).Asdescribedabove,thetotalnumberof

coatedknittedfabricswas21(7knitted

fabrics×3polyurethanecoatings).WorkingmethodThistimeweobservedmechanical

propertiesbeforeandaftercoating,and

formedconclusionsonthepredictionof

theirbehaviour.Thebehaviourofknittedandcoated

knittedfabricsinthelinearapplication

offorcewascomparedwiththatofthesamespecimensinthecaseofspherical

forceapplication.Thesampleswerestatisticallyanalysed

(descriptivestatistics,hypothesistesting-t-test,regressionanalysis).Part3ResultsanddiscussionElongationofcoatedknittedfabricsin

relationtotheknittedfabricElongationinthewaledirectionTheknittedfabricselongatedfrom46.41%to309.93%,whichisaconsequenceoftheirdifferentstructures.Thecoatedknittedfabricselongatedinthewaledirectionfrom44.41%to382.44%.Thecoatedknittedfabrichasaconsiderablyhigheraverageelongationinthewaledirectioninrelationtotheknittedfabric-onaverageabout16%,apartfromtheleaststretchableknittedfabric(KF3),whichwasnotaffectedbythecoating.NamelytheKF3samplewasknittedinapower-netstructure(Table1),whereelongationinthewaledirectiondependsdirectlyonelongationpropertiesoftheverticallylaidyarn(andnotformedintoloops).Thet-testshowsthatthereisnostatisticallyconsiderabledifferencebetweenthemeanvaluesofelongationofthegroupsofsamplestested(p=0.92)ortheycanbeobservedasthesametypeofpolyestercoatingforelongationinthewaledirection.Regressionanalysisindicatestherelationshipbetweentheelongationoftheknittedfabricandthatofthepolyurethane-coatedknittedfabric.εcw=1.2312εkw-8.4717ThecoefficientofdeterminationR2=0.9915Itispossibletousetheregressionmodelobtainedforeasypredictionofthebehaviourofthecoatedknittedfabricandthechoiceofanappropriateknittedfabricsubstrate.ElongationinthecoursedirectionTheknittedfabricselongatedfrom34.96%to157.93%,whichisaconsequenceofthedifferentstructuresofknittedfabricsandyarnsused.Thecoatedknittedfabricselongatedinthecoursedirectionfrom96.15%to358.75%.Thecoatedknittedfabrichasaconsiderablyhigheraverageelongationinthecoursedirectioninrelationtotheknittedfabric-onaverageabout102%.Thet-testshowsthatthereisnostatisticallyconsiderabledifferencebetweenthemeanvaluesofelongationoftheknittedfabricscoatedwiththreedifferenttypesofPUcoating(p=0.72)fortheelongationinthecoursedirection.Regressionanalysisshowedthattherelationshipbetweentheelongationoftheknittedfabricandthecoatedknittedfabricinthecoursedirectionhaveonlyamediumcorrelation(r=0.79).Therelationshipbetweenvariablesisnotlinear.Exponentialregressionmodelεcc=103.53×e0.0064εkcwithacoefficientofdeterminationR2=0.6262,isthebestexplanationofelongationvarianceinthecoursedirectionofthesamplesofcoatedknittedfabrics(ecc)studiedwithregardtotheelongationofthesamplesofthesameknittedfabrics(ekc)examined.Itisinterestingtoinvestigatewhichelementstogetherwiththeelongationoftheknittedfabricaffecttheelongationofthecoatedknittedfabricinthecoursedirection.ThesamplesofcoatedfabricKF3,KF4andKF5showagreaterdifferenceintheelongationofthecoatedfabricanduncoatedfabric(Figure4,Table5)andmoresignificantlydeviatefromtheadaptedtheoreticalcurveoftheexponentialmodel.Theywereproducedfromalowthicknessknittedfabric(Table1).Theratiobetweenknittedfabricthicknessandcoatingthicknessincomparisonwithotherknittedfabricsislower(Table5)Thereisrelativelymorecoating,makingagreatercontributiontoelongationinsuchcoatedfabrics.Therelationshipbetweentheratioofthicknesses(Tr)andthatofelongation(er)clearlyshows(r=0.89)εtheelongationdecreasesifthereisrelativelylesscoatingonthecoatedfabric.Byusingmultiplelinearregression,amuchbetterrelationshipbetweentheelongationofthecoatedfabricinthecoursedirectionandbothvariables(elongationoftheknittedfabricandratioofknittedfabricthicknessandcoating)εcc=149.3042+2.032309εkc-44.866TrThecoefficientofmultiplecorrelation(R=0.91)indicatesastrongrelationshipbetweentheelongationofthecoatedknittedfabricinthecoursedirectionandthetwovariablesobserved.Inadditiontotheelongationoftheknittedfabric,theratiooftheknittedfabricthicknessandcoatingshouldbeconsidered.Technologicallythesefindingsshowhowextremelysensitiveitistopredictthebehaviourofcoatedknittedfabricswithaverythinsubstrate(thickness>0.4mm).ComparisonoftheelongationoftheknittedfabricandcoatedknittedfabricduringsphericalelongationTheknittedfabricselongatedfrom26to68mmuntilballbursting.Thecoatedknittedfabricselongatedfrom25to66mm.Thet-testshowsagainthatthereisnostatisticallysignificantdifferencebetweenthearithmeticmeansofthethreetypes(PU1-PU3)ofsamplestested(p=0.8372),andtheycanbeobservedasonegroupofsamples.Thelowerelongationofthecoatedknittedfabricduringsphericalelongation,onaverage8%.Itispossibletoconcludethatcoatingfixestheyarnandtheknittedfabricstructure,i.e.thepolyurethaneadhesivegluestheyarnwhichformsloops,henceitcannotmovefreelyanddeformthefabricstructurenoradapttosphericalelongation,causinganearlyburstofthecoatedknittedfabric.Thesamecoatedknittedfabric,whichwillshowbettercharacteristicsthantheknittedfabricitselfduringelongationinthecourseorwaledirection,exposedtosphericalelongationwillshowpoorercharacteristics.Themodeloflinearregressionεcb=0.7468εkb+6.1557withcoefficientofdeterminationR2=0.9292BreakingforceofthecoatedanduncoatedknittedfabricsBreakingforceinthewaledirectionBreakingforcesfrom104.6Nto907.5Nweremeasuredintheknittedfabricofdifferentstructures.Breakingforcesfrom136.7Nto1053Nweremeasuredinthecoatedknittedfabrics.Thecoatingcausedslightlyhigherbreakingforces––onaverage24%.Thet-testshowsagainthatthereisnostatisticallysignificantdifferencebetweenbetweenthebreakingforcesofthethreepolyurethane-coatedgroupsofsamplestested(p=0.93).LinearregressionmodelFcw=1.098Fkw+48.736,withthecoefficientofdeterminationR2=0.9802BreakingforceinthecoursedirectionoftheknittedfabricBreakingforcesfrom66.27Nto501.8Nweremeasuredintheknittedfabric.Theburstingofthecoatedknittedfabricsinthecoursedirectionoccurredatbreakingforcesfrom108.1Nto672.2N.Thecoatingcausedanincreaseinbreakingforcesinthecoursedirectionoftheknittedfabric-onaverageabout27%.Thet-testshowsagainthatthereisnostatisticallysignificantdifferencebetweenthebreakingforcesofthethreepolyurethane-coatedgroupsofsamplestested(p=0.88).RegressionmodelFcc=99.51×1,0039Fkc,withthecoefficientofdeterminationR2=0.9367BreakingforceofthesphericalburstoftheknittedfabricandcoatedknittedfabricBreakingforcesfrom73Nto1058Nweremeasuredintheknittedfabricsandfrom91Nto1228NinthecoatedknittedfabricsCoatingcausedanincreaseintheresistancetosphericalbursting-onaverageabout13%.thet-testshowsagainthatthereisnostatisticallysignificantdifferencebetweenthebreakingforcesofthethreepolyurethane-coatedgroupsofsamplestested(p=0.989).LinearregressionmodelFcb=1,1214Fkb+4,0992explainstherelationshipbetweentheoccurrencesobserved(Figure13).ThecoefficientofdeterminationR2=0.9956Part4ConclusionsAlthoughcoatingsignificantlychangesthemechanicalpropertiesofknittedfabrics,thepropertiesofcoatedknittedfabricsareprimarilydeterminedbythepropertiesoftheknittedsubstrate.Elongationinthecoursedirectionoftheknittedfabricsignificantlyincreasesaftercoating-onaveragebyabout102%,whiletheincreaseinelongationbycoatinginthewaledirectionislower,amountingtoabout16%.Elongationinthewaledirectionofcoatedknittedfabricscanbepredictedwithgreatcertaintyknowingthatoftheknittedfabric.Alinearregressionmodelexplains99.15%oftherelationshipbetweentheelongationoftheknittedfabricandcoatedknittedfabric.Elongationinthecoursedirectionofcoated