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Mechanical Behavior of Soybean Protein Fibers

By Deborah Nichols,2014-01-21 20:53
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Mechanical Behavior of Soybean Protein Fibers

    Mechanical Behavior of Soybean Protein

    Fibers

    JournalofDonghuaUniversity(Eng.Ed.)Vo1.26,No.1(2009)85 MechanicalBehavior0fSoybeanProteinFibersJ?

    YANGQing-bin(杨庆斌)h,SUNYa?ning(孙亚宁),

    1CoileofTea,tile,04ngdaoUniversity,ngdao266071,China 2CollegeofTextiles,DonghuaUniversity,Shahghai200051,China Abstract:Inordertounderstandtherelationshipbetween themechanicalpropertyandtheeffectofbleachingand dyeingtothesoybeanproteinfibers(SPF),fourmechanical modelsarechosen.Thetensileandrelaxationpropertyof thesoybeanproteinfibersareanalyzed.Thetensileand relaxationcurvesarefittedwiththesuitablemode1.It showsthattherelaxationpropertyofSPFisinaccordance withthestandardlinearsolidmode1.Estimatesofthe Hookcanspringmodulusat8%andat10%aredifferent,so sonicstructuralmodificationscouldbeproducedbythe strain.BIcachedfihersshowahigherlevelofrelaxation thanrawfibersanddvedfibems.Bleachinghasaremarkable influenceondecreasingtenacityatbreakforeachtest modality.Knottedandloopedmodalitiesdecreasefibet tenacityremarkablyinallthreesamples.

    Keywords:soybeanproteinfiber;tensileproperty; relaxationproperty

    ClCRuinbet:TS102.512Documentcode:A

    ArticleID:16725220(2009)01008504

    lntrOductiOn

    Thesoybeanproteinfiberisanewmaterialintextile. Thankstoitsfinedenier,lightspecificgravity,high strengthandsilklikelaster.ithassoexcellentcashmere handle,silksoftnessandheatresistantpropertiesthatit hasbeencalledmanmadecashmereandfoundwidelyused. Inordertounderstandtherelationshipbetween microstructureandthemechanicalpropertiesofSPF fibers,wehavestudiedstressrelaxationatdifferentstrain levelsandtheapplicationofdifferentmodelstostressstain

    curvesunderthreetensiletestconfigurations一——straight,

    knotted,andloopedfibersintroducingnonlinear modificationstothemodels.

    ManyresearchersB-s]haveanalyzedtheapplicationof oneofthemostsuitablemodelstobestcharacterizethe elasticpropertiesofyarns.TheVangheluwemodelismost suitabletoacrylicVonnelyarns,andboththeVangheluwe andZurekmodelsaremostsuitabletopolypropylene Inklonfibers.Furthermore,softieresearchers'have TIANLin(田琳),YUWeidong(于伟东)

    comparedthesemodelswithnewmodelstheyhave developed,wecalledthemodifiedVangheluweandZurek modelsandtheygivethebestresults.Inthispaper,we applythefourmodelstorawfibers,bleachedfibersand dyedfibersandcompareresultsbetweenmodelsand behavioraldifferencesforrawfibers,bleachedfibersand dyedfibers.

    1Experimenta

    1.1Materials

    Thetestsinvolvedrawfibers.bleachedfibersaswell asdyedfibers.Thebleachingprocessofsoybeanprotein

    fibersisfinishedbyusinghydrogenperoxideandurea,and theprocessisasfollows:hydrogenperoxide20g/L,Urea 10g/L,pHvalue1010.5,temperature80?,time

    9Ominandbathratio1:5O.TheSumifixHlFreactire dyestuffisusedindyeingofsoybeanproteinfibers.The suitabledyeingconditionissalt35g/L,alkali15g/L, temperature6O?andliquorratio1:30.Fiber

    characteristicsaresummarizedinTable1.Comparingitems 1and2,wecandeterminetheinfluenceofbleachingon viscoelasticbehaviorofthefibers,andcomparingitems1 and3,wecanassesstheinfluenceofdyeingonthe viscoelasticbehaviorofthefibers..

    Table1Characteristicsofthesoybeanproteinfibers 1.2Measurementandmethods

    Tensiletestsonstraight,knotted,andloopedfibers weredoneaccordingtotheGB/T9971998standard.Test

    conditionsinvolveda10mmeffectivespecimenlength, 10mm/mindeformationrate,andsamplesizeof30fibers. Fiberswererandomlyselectedfromasampleconditionedin astandardatmosphere48hoursbeforethetest,anda computerizedlnstron4206strengthmeterwasusedforthe Receiredd;tte:o00611l7

    *CoreespondenceshouldbcaddressedtoYANGOingbin.plofessor.E

    mail:qbyang620@yahoo.COW1.cn

    86JournalofDonghuaUniversity(Eng.

    Ed.)Vo/.26.No.1(2009)

    tests.Relaxationtestswerealsodoneonsinglestraight fiberssubjectedtorelaxationfor1minafterbeingstrained upto8%and10%atarateof10mm/min.Using

    nonlinearregressionprocedures,wefittedthe

    correspondingmodelstotherelaxationandload.elongation CEIrVeS.

    2ResultsandDiscussion

    2.1Relaxationbehavior

    ConsideringSPFasalinearviscoelasticfiber.whenit isStlbjectedtoaconstantlongitudinalstrain(atfixed

    temperature,theresultantlongitudinalstressPinthefiber isafunctionoftime.ThenP(t)atanyfixedtimeis

    ,andthestressrelaxation proportionaltothestrain(

    modulusR(r)maybedefinedbytheequation:

    R(t):P(t)/e(1)

    Foralinearviscoelasticfiber,R(t)isindependentof strainandrepresentsameasureofthemechanicaI propertiesofthematerial,whichissimilartothewaythe Young'smodulusmeasuresthemechanicalpropertiesofa purelyelasticmateria1.ThesimplestfunctionR(t)may takeforatheoreticalfiberinwhichonecharacteristic relaxationtimeTjsassociatedwithbondbreakdownunder strainisgivenby:

    R(r)Aexp(tiT)+B(2)

    TheresultsfortherelaxationmodulusR(t)upto1 minuteobtainedattwostrainlevelsaregiveninTable2. Table2RelaxationmodulusR(t)ine=8%and(:10%

    fortheSPF

    Therelaxationofstressassociatedwithanysecondary bondbreakdownisnotrepresentedbyasinglerelaxation timeT,butratherbyadistributionofrelaxationtimes. To

    understandthisprocedure.itisnecessarytoconsider mechanicalmodelsforthebehavior.Thetheoreticalfiber

    forwhichthestressrelaxationisgivenbyEq.(2),for purposesofmechanicalbehavior.bereplacedbythe standardlinearsolidmodelconsistingofaHookeanspring ofBm(x.tulusinparallelwithaMaxwellelementmadeup ofanotherHookeanspringofAinserieswithaNewtonian dashpotwithviscosity.IfwecalculateA,BandT,we canobtainthemodulusoftheHookeanspringAandthe viscosityoftheNewtoniandashpotoftheMaxwell elementbytheproductAxT,andthemodulusBofthe secondHookeanspringinparallelwiththeMaxwell element.

    BecauseEq.(2)isnonlinearinitspredictorvariables. anexactsolutionisnotavailableforit.Wehavetherefore usedanonlinearregressionprocedurewhichisaniterative searchalgorithmtodeterminetheestimatesthatminimize theresidualsumofsquares,i.e.,thequadraticvariationof theresultsarenotexplainedbythefittedmode1.Estimates ofthecoefficientsA.BandTandthedetermination coefficientRareshowninTable3.

    Table3Relaxationmodelfittingaccordingtodifferentfibers andstrainlevel

    EstimatesoftheHookeanspringmodulusat8%andat 1O%aredifferent.sosomestructuralmodificationscould bepr0ducedbythestrain.Therelaxationtimesarealsonot thesame.Itthereforeappearsthatthesecondarybond breakdownphenomenonshouldbeproducedatdifferent rate.Bleachedfibersshowahigherlevelofrelaxationthan rawanddyedfibers,sowecanconcludethatbleaching complicatesmacromolecularchainslippagewhenfibersare strained.Rawfibersshowahigherlevelofstressthan

bleachedfibersanddyedfibers.

    2.2MechanicaIproperties

    2.2.1Tenacityandelongationatbreakaccordingtotest configuration

    Table4showsthetenacityandelongationatbreak correspondingtoeachfibertypeandtestmodality.The strengthelongationcurvesofrawfibers,bleachedfibers anddyedfibersindifferentmodalitiesarelistedin Fig.1.Bleachinghasaninfluenceondecreasing tenacityatbreakforeachtestmodality.Knottedand loopedmodalitiesdecreasefibertenacityremarkablyin allthreesamples,andthesameOCCHFSwil:helongation atbreak.LoopedmodalitiesshowJowt2rtenacityand elongationatbreak.thelowestbeingthebleached fibersinloopedmodalities.

    JournalofDon~uaUniversity(Eng.Ed.)Vo1.26,No.1(2009)87 Table4Tenacityandelongationatbreakaccordingtotestconfiguration

    Z

    .J

    \

    D

    C

    ?

    O0.5

    3

    2.5

    z2

    \

    ?

1

    0?5

    0

    l1.522.5

    EIongation/mm

    (a)Strait

    4.5

    4

    3.5

    z3

    2.5

    2

    1.5

    l

    0.5

    O

    O0.5I1.5

    Elongation/n1m

    (b)Knotted

    OO.5l1.52

    Elongation/111111

    (c)Looped

    Fig.1Thestrength*elongationcurvesofSPFindifferentmodalities

    2.2.2Viscoelasticmodels

    TomodeltheSPFstress.straincurve,wehaveused fourviscoelasticmodels:theVangheluwemodel,the modifiedVangheluwemodel,theZurekmodelandthe modifiedZurekmodeI.

    TheVangheluwemodeIisformedbvaMaxwell elementwithviscosity'7andHookeanspringmodulusM.

    inparallelwithanonlinearspringwithCmodulus.Sincey isthedeformationrateandPoisthepre.tension.the relationshipbetweenstressPandelongation(isgivenby

    P(e)=Po+A(1--exp(Be))+Ce(3)

    WecaneasilyseethatA=,7),andB=M/A.There arethreevaluestobecalculated:A,whichequalstothe productofyandtheviscosityoftheMaxwellelement; B,whichistheinverseoftheMaxwelIrelaxationtimeT dividedbythedeformationratey;andC,whichisthe modulusofthenonlinearspringinparallelwiththe Maxwellelement.

    ThemodifiedVangheluwemodel:TheVangheluwe modelwasdevelopedmainlyforyarns,anditdoesnotfit aswellforfibers,wedevelopedanewmode1by introducinganexponentontheexponentialfunctionand thespringinparallelwiththeMaxwellelementwas consideredtohaveanonlinearbehavioridentifiedbya differentformofthesquareoftheelongation.The modifiedmode1isthus

    P(()=Po+A(1--exp(Be.))+Ce(4)

    Herewehavefivevaluestobecalculated:A,which asinVangheluwemodel,equalstotheproductofyand theviscosityoftheMaxwellelement;B,whichisthe inverseoftheMaxwellelementrelaxationtimeTdivided bythedeformationrateybutconsideringthespring modulustobeafunctionofe.;C,whichisthemodulusof thenonlinearspringinparallelwiththeMaxwellelement, beingafunctionofe;DandE,whicharetheexponents jlastdefined.

    TheZurekmodelincludesaninertialfrictionalsystem

    incorporatedinaparallelsystemcomposedofaHook's springandaNewtondamper.Thewholeisconnectedina rowtoanotherHook'sspring.Thebehavioroftheinertia1. frictionalsystemofmassandfrictionforceproportionalto thestrainhasbeendcscribedelsewhere.F0rthesakeof brevity.weomitherethemathematicaldevelopmentofthe modelandwepassdirectlytothefinalequation. P(()=AE+B+(C(一)exp(a())(5)

    AccordingtoEq.(5),thefirstpartP(x)A+B

    representsthelineardependenceoftenacityversus 98765432?O

    88JournalofDonghuaUniversity(Eng.Ed.)Vo/.26,No.1(2009) elongationintheyieldregionofthecurve.Agraphical methodcanbeusedtomakeanapproximateestimationof theparameters.ValuesofA,B,C,andarerelatedto therheologicalvaluesofthemode1.

    ThemodifiedZurekmodel:Applyingthesame

    criterionusedtomodifyVangheluwe'smodel,wemodified byconsideringanonlinearbehaviorofthespringinseries withthedashpot,theKepesskateandthelinearspring, beingproportionalto(..Therefore,thefinalequationis

    P(()=A(+B+(CeB)exp(ae.)(6)

    Itcontainsfiveparameterstobeestimated:A,B,C,, andD,P(()isthetenacityofthefiberatdifferentstrain (levels.

    Table5givesthecoefficientsofthebestfittingmodels accordingtofibertypeandtestmodality.

    Table5Bestequationsaccordingtofibertypeandtestmodality &

    Rawfiber

model

    Determination coefficientR2 Bleached

    fiber

    Deterrni"ion

    Dyedfn)er coefficientR2……

    Determination coefficientR2 Straight

    Knotted

    Looped

    A=0.7566

    B=36.8624 C=1.6541

    D=20.5874 E=1.9629

    A=16.2334 B=47.6405 C=8.O510

    =0.4864

    D=1.1692

    0.935

    0.95

    A=4.1530

    B=2.45870.96l C=1.4766

    A=25.2475 B=0.1053

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