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1、Designation:D6048?07(Reapproved2012)StardPracticefStressRelaxationTestingofRawRubberUnvulcanizedRubberCompoundsThermoplasticElastomers1ThisstardisissuedunderthefixeddesignationD6048thenumberimmediatelyfollowingthedesigna

2、tionindicatestheyearofiginaladoptioninthecaseofrevisiontheyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperepsilon()indicatesaneditialchangesincethelastrevisionreapproval.INTRODUCTIONThereare

3、anumberoftechniquesusedtoidentifytheprocessabilityofrawrubberunvulcanizedrubbercompoundsthermoplasticelastomers(rubberrubberlikematerials).MostmeasureasingleaveragedvalueofnonNewtonianviscositywithsomedoingsoafteraperiod

4、ofsteadyshear.Thesetechniquesmaynotprovidesufficientinfmationwithregardstotheprocessabilityofaedmaterialasthey:(1)failtoprovideameasureoftheviscoelasticbehavi(2)destroystructureoftheedmaterialthroughthesteadyshearing.Str

5、essrelaxationtestingprovidesameasureoftheviscoelasticresponseofamaterialoveraperiodoftimewithoutdestroyingthestructureofthesample.Insuchtestingboththeinstantaneoustimedependentresponsetoanapplieddefmationaremeasured.Thei

6、nfmationfromthissingleexperimentcanthenbeusedtoexamineamaterial’sreactiontovariousdifferentprocessconditions.Thereareseveraldifferenttechniquesfmeasuringstressrelaxationpropertiesofrubberrubberlikematerials.Thispractices

7、ervestoprovidethereaderwithsomebackgroundinfmationaboutthosetechniquesintermsofthetheyoftestingtheinterpretationofresults.Manyconceptsareputfwardthatarenotdiscussedindepthftodosowouldrequireatextbooknotapractice.Thereade

8、ristherefeencouragedtoconsulttheidentifiedreferences.1.Scope1.1Thispracticecoversseveraldifferenttechniquesfdeterminingthestressrelaxationacteristicsofrubberrubberlikematerialsfthepossibleinterconversionofthisstressrelax

9、ationinfmationintodynamicmechanicalproperties.1.2Thetechniquesareintendedfmaterialshavingstressrelaxationmoduliintherangeof103to108Pa(0.1to1.5104psi)ftesttemperaturesfrom23to225C(73to437F).Notallmeasuringapparatusmaybeab

10、letoaccommodatetheentireranges.Thesetechniquesarealsointendedfmeasurementofmaterialsintheirrubberymoltenstatesboth.1.3Differencesinresultswillbefoundamongthetechniques.Becauseofthesedifferencesthetestreptneedstoincludeth

11、etechniquetheconditionsofthetest.Thisinfmationwillallowfresolvinganyissuespertainingtothetestmeasurements.1.4Thegeneralizeddeionsofapparatusarebasedonthemeasurementoffceasafunctionoftime.Mathematicaltreatmentofthatrelati

12、onshipproducesinfmationthatcanberepresentativeofmaterialproperties.Mathematicaltransfmationofthefcemeasurementswillfirstyieldstressrelaxationmoduliwithsubsequenttransfmationproducingdynamicmechanicalproperties.1.5Thevalu

13、esstatedinSIunitsaretoberegardedasthestard.Thevaluesgiveninparenthesesareprovidedfinfmationonly.1.6Thisstarddoesnotpurpttoaddressallofthesafetyconcernsifanyassociatedwithitsuse.Itistheresponsibilityoftheuserofthisstardto

14、establishappropriatesafetyhealthpracticesdeterminetheapplicabilityofregulatylimitationspritouse.2.ReferencedDocuments2.1ASTMStards:2D1566TerminologyRelatingtoRubber1ThispracticeisunderthejurisdictionofCommitteeD11onRubbe

15、risthedirectresponsibilityofSubcommitteeD11.12onProcessabilityTests.CurrenteditionapprovedMay12012.PublishedJuly2012.iginallyapprovedin1996.Lastpreviouseditionapprovedin2007asD6048–07.DOI:10.1520D604807R12.2FreferencedAS

16、TMstardsvisittheASTMwebsitewww.astm.gcontactASTMCustomerServiceat.FAnnualBookofASTMStardsvolumeinfmationrefertothestard’sDocumentSummarypageontheASTMwebsite.Copyright?ASTMInternational100BarrHarbDrivePOBoxC700WestConshoh

17、ockenPA194282959.UnitedStates15.SignificanceUse5.1Theprocessingbehavi(processability)ofrubberrubberlikematerialsiscloselyrelatedtotheirviscoelasticproperties.Theviscoelasticpropertiesaswellasthemechanicalpropertiesarerel

18、atedtothepolymericincludingmacromolecularmicromolecularstructure.Therefeadeterminationoftheviscoelasticityofamaterialwillprovideinfmationtopredictprocessingserviceperfmance.5.2Stressrelaxationtestingprovidesamethodologyf

19、investigatingtheviscoelasticityofrubberrubberlikematerials.Certainstructuralacteristicsthathavebeendemonstratedtobeevaluatedbythistestmethodare:(1)averagemolecularweight(2)molecularweightdistribution(3)linearitychainbran

20、ching(4)gelcontent(5)monomerratio.5.3Thispracticeisintendedtodescribevariousmethodsofmeasuringthestressrelaxationpropertiesofrawrubberunvulcanizedrubbercompoundsthermoplasticelastomersfdeterminingtheprocessabilityofthese

21、materialsthroughviscoelasticmeasurements.Factyperfmanceacteristicsthatthismethodologymaycrelatewithincludedieswellshrinkageextrusionratemillbingcarbonblackincpationtimemoldflow.6.Hazards6.1Therearenohazardsinherenttothet

22、echniquestobedescribed.Thereisnouseofreagentshazardousmaterials.Thedesignofthevariousdifferenttestapparatusmayhavecreatedpossiblepinchpointscautionshallbeexercisedaguardshallbeprovidedfthesesites.6.2Nmalsafetyprecautions

23、goodlabatypracticeshouldbeobservedwhenusinganyequipment.Thisisespeciallytruewhenperfmingtestsatelevatedtemperatureswhereelectricalheatersareused.7.TheyofStressRelaxation7.1MechanicalModelsofViscoelasticity:7.1.1Polymeric

24、materialsexhibitbothelasticityviscousresistancetodefmation.Thematerialscanretaintherecoverable(elastic)strainenergypartiallybuttheyalsodissipateenergyifthedefmationismaintained.Mechanicalanaloguesofaviscoelasticsolid(Fig

25、.1)aviscoelasticliquid(Fig.2)helpidentifythisbehavi.7.1.2InFig.1adashpotisconnectedinparallelwithaspring.ThisisknownasaVoigtelement.Ifdefmedthefceinthespringisassumedtobeproptionaltotheelongationoftheassemblythefceinthed

26、ashpotisassumedtobeproptionaltotherateofelongationoftheassembly.Withnofceactinguponittheassemblywillreturntoitsreferencestatethatisdictatedbytherestlengthofthespring.7.1.3Inthisexampleifasuddentensilefceisappliedsomeofth

27、ewkperfmedontheassemblyisdissipatedinthedashpotwhiletheremainderisstedinthespring.Theappliedfceisanalogoustothedefmingstresstheelongationisanalogoustotheresultingstrain.Theviscousresistancetodefmationrepresentedbythedash

28、potintroducestimedependencytotheresponseoftheassemblywherethisdependencyisdictatedbythespringdashpotconstants.Theassemblycannotrespondinstantaneouslytochangesinstressthisindicatesthattheviscoelasticsolidhasatimedependenc

29、y.7.1.4InFig.2adashpotisconnectedinserieswithaspring.ThisiscalledaMaxwellelement.UnliketheVoigtelementthereisnodictatedreferencestatesothattheassemblywilldefmindefinitelyundertheinfluenceofanappliedfceassumingthatthedash

30、pothasinfinitelengthaacteristicofaviscoelasticfluid.7.1.5Inthisexampleifasuddentensilefceisapplieditisthesameinboththespringthedashpot.Someofthewkperfmedontheassemblyisdissipatedinthedashpotwhiletheremainderisstedinthesp

31、ring.Thetotaldisplacementexperiencedbytheelementisthesumofthedisplacementsofthespringthedashpot.AswiththeVoigtelementrepresentingaviscoelasticsolidtheMaxwellelementrepresentsacombinationofviscouselasticproperties.Thisind

32、icatesthattheviscoelasticliquidisalsotimedependenthasaacteristictimeconstant.Howeverasthetimeconstantbecomessmallersmallertheelasticqualityoftheliquidbecomeslesslessappearstobehavemelikeapurelyviscousmaterial.7.1.6Theres

33、ponseofpolymerstochangesinstressstrainisactuallyacombinationofmultipleelementsofbothmechanicalmodelsonesuchexampleisillustratedinFig.3.Theresponseisalwaystimedependentinvolvesboththeelasticstageofenergyviscousloss.7.2Mol

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