外文翻译无规共聚聚丙烯在不同试验参数下对其机械性能的影响节选.docx
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外文翻译无规共聚聚丙烯在不同试验参数下对其机械性能的影响节选.docx
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外文翻译无规共聚聚丙烯在不同试验参数下对其机械性能的影响节选
中文3100字,2000单词,10500英文字符
出处:
SahinS,YaylaP.Effectsofprocessingparametersonthemechanicalpropertiesofpolypropylenerandomcopolymer[J].PolymerTesting,2005,24(8):
1012-1021.
本科生毕业设计(论文)外文译文
学院
专业
导师
学生
学号
Effectoftestingparametersonthemechanicalpropertiesofpolypropylenerandomcopolymer
SenolSahin,PasaYayla*
MechanicalEngineeringDepartment,EngineeringFaculty,KocaeliUniversity,41040Kocaeli,TurkeyReceived24January2005;accepted2March2005
Abstract:
Theeffectsoftemperatureontheimpactresistanceandhardnessofpolypropylenerandomcopolymerarestudiedforawiderangeoftemperatures.Thevariationsinthemechanicalpropertieswithawiderangeofstrainratesarealsoevaluated.Finally,thevariationsinmechanicalpropertiesasafunctionoftimeafterproductionarestudied.
Keywords:
Polypropylenerandomcopolymer;Mechanicalproperties;Storagetime;Strainrate
1.Introduction
Thereisavastliteratureonprocessing,morphology,testingandultraviolet(UV)degradationofpolypropylene(PP)[1–3].However,theliteraturelacksresultsontheeffectsofstoragetime,outdoorageingtimeandtheadditionofdifferentmasterbatchesatdifferentratiosonthemechanicalproperties.Thismaybeconnectedtothefactthatthoseinvestigationsareveryrigorousandtime-consuming.Forthesereasons,theaimofthispaperistostudytheinfluenceoftestingparametersonthemechanicalandthermalpropertiesofinjectionmouldedpolypropylenerandomcopolymer(PP-R)sampleswithdifferentstoragetimes.
2.Experiments
2.1.Materials
ThepolymerusedinthisstudyisanaturalcolourPP-R,producedbyBorealiss.a,tradenameRA130E,andsuppliedingranularform.ThepropertiesofthepolymeraregiveninTable1.
2.2.Specimenpreparation
Aspeciallydesignedinjectionmouldwasusedtoproducetestsamples.TheconfigurationofthemouldedtestsamplesisdepictedinFig.1.AllthetestsampleswereinjectionmouldedonaERATFE130/95injectionmouldingmachine.Table2showsthespecification,setparametersofthemachineandthemouldingconditions.Unlessotherwisementioned,beforetestingallthesampleswereconditionedatroomtemperatureforaperiodof30days.
2.3.Tensiletests
Thetensiletestsamplesweredumbbell-shapedwithdimensionsof156*1014mm,complyingwithISO527-1(1993)standard.Tensiletestsatvariousspeedswerecarriedoutonthesamples.AZwickZ10,screw-drivenuniversaltensile/compressiontestingmachineequippedwithadataacquisitionsystem,wasutilisedtocarryoutthetensiletests.Unlessotherwisementioned,a50mm/mintestspeedwasused.Forstrainrateeffectinvestigation,awiderangeofspeedsfrom1to1000mm/minwereused.Anextensometerwasutilisedtodeterminetheelasticmodules.Testswerecarriedoutatatemperatureof238C.Fromatleastthree
Table1
Typicalpropertiesofpolymerusedinthisstudy
specimensforeachtestseries,averagevaluesforyieldstress(Y),tensilestrength(Mpa),elasticmodulus(E),strain-toyield(Y),andstrain-to-break,3B,werededucedusingthetestingprogramofthecontrollingcomputer
2.4.Charpyimpacttests
Impactfractureenergyisanimportantparametercharacterizingtoughnessofmaterials.Impactvaluesrepresentthetotalabilityofthematerialtoabsorbimpactenergy,whichiscomposedoftwoparts:
(a)theenergyrequiredtobreakbonds,and(b)theenergyconsumedindeformingacertainvolumeofthematerial.Withconventionalimpacttestingequipment(withoutinstrumentation),itispracticallyimpossibletomeasureseparatelythesetwoparts.Instrumentedimpacttestingprovidesvaluableinformationonenergiesinvolvedinthefractureprocess,givingindividualevaluationofenergyforcrackinitiationandenergyrequiredtopropagatethecrackthroughthematerial,whichisnotpossiblewiththeconventionalCharpyimpacttest.Inmanymaterials,theformationofthecrackatthenotchrootoccursjustpriortooratthepeakload.Therefore,itisareasonableapproximationtodefinetheenergyuptothepeakloadasthe‘crackinitiationresistance’[4].Similarly,post-peakenergyisalsodefinedasthe‘crackpropagationresistance’ofthematerial.Formanyindustrialapplications,thetemperaturedependenceofimpactstrengthisveryinterestingandhasattractedconsiderableattention,notonlyfromindustry,butalsofromacademiccircles[5].
ThegeometryoftheCharpyimpacttestsampleswasrectangularwithdimensionsof80!
10!
4mm,conformingtotheISO179/1eA(2000)standard.Asingle-edge458V-shapednotch(tipradius0.25mm,depth2mm)wasmilledinthebarswithafly-cutterusingamillingmachine.
AseriesofCharpyimpacttestswerecarriedoutforawiderangeoftemperaturesaccordingtoISO179/1eU(2000).Forsettingthetesttemperature,amixtureofliquidnitrogenandacetoneatdifferentratioswasused.Thetestsampleswerekeptinthecoolingmediumforatleast30minbeforetesting.
TheCharpyimpacttestsofthenotchedspecimenswereconductedatawiderangeoftemperaturesrangingfromK75to858C,employingacreastInstrumentedCharpyImpactTester(Code6545/000)atanimpactspeedof2.93m/s.TheCharpyimpactenergyevaluationwasbasedonthelinearelasticfracturemechanics(LEFM)analysistodetermineimpactstrengthofmaterialsasproposedbyPlatiandWilliams[6].CharpyimpactenergyCvisgivenby
whereUistheabsorbedenergybythesample,BandDarethewidthandthicknessofthesamples,respectively,andFisthesamplegeometry-dependentcalibrationfactor.BearinginmindtheadvantagesofinstrumentedCharpyimpacttests,boththecrackinitiationenergy,whichisconsumeduptothemaximumforce,andthetotalimpactenergy,whichistheconventionalCharpyimpactenergy,dissipatedduringwholeimpactprocess,werecalculated.
2.5.Hardnesstest
Hardnessisdefinedastheresistanceofamaterialtodeformation,particularlypermanentdeformation,
Table2
Specificationandsetparametersoftheinjectionmouldingmachineusedinthisstudy
indentationorscratching.Ingeneral,themostwidelyusedmethodstomeasurehardnessareRockwellandShore.TheRockwellmethodisusuallyusedforhardermaterials,TheShore(orDurometer)method,regulatedbyISO868(2003),hasscalesforbothsofterrubbersandplastics.
Inthiswork,ShoreDhardnesstestswereperformedatdifferenttemperaturesusingaZwick3100ShoreDDurometerhardnesstester.Allresultsaretheaverageofthreemeasurements.
3.Resultsanddiscussion
3.1.Tensiletests
Thetensilebehaviourandultimatemechanicalpropertiesareveryimportantcharacteristicsofsemi-crystallinepolymers.Thesemacroscopicpropertiesareknowntoverycloselydependonthestrainrate,thusanunderstandingofstrainratedependenceoftheirdeformationbehaviourisimportantforencouragingtheirwideuseinengineeringandstructuralapplications[7].Strainratehasacomplicatedanddramaticeffectonmaterialsdeformationprocessesbecausetheenergyexpendedduringplasticdeformationislargelydissipatedasheat.Thisprocesswasobservedtobemoreprominentathigherloadingratesthatareassociatedwithadiabaticdrawingthanduringlowerloadingrateswhereisothermaldrawingoccurred[8].Ingeneral,threestagesofplasticdeformationweresuggestedintensiletestsofsemicrystallinepolymers[9,10]:
(1)pre-neckdeformationofmicro-spheruliticstructurethatproceedsinthewhole
sample,
(2)largedeformationintheneck,whichtransformsthemicro-spheruliticstructuretofibrillarstructure,andlastly(3)post-neckdeformationofthefibrillarstructure.Ingeneral,intheneck,thepolymericmaterialsoftensdrasticallyforaveryshortperiod,whichisassociatedwithadecreaseofplasticmodulus.However,astheneckdevelopsandexceedsalimitingzone,themorphologychangestothatofafibrillarstructurewithincreaseinplasticmodulus,termedasstrain-hardening.
Typicalstress–straincurvesofthePP-RsamplestestedatdifferentcrossheadspeedsaregiveninFig.2.Thetestsampleswerenotbrokenat600%elongationatcrossheadspeedsupto25mm/min,butforthehighertestspeeds,thesampleswererupturedatlower%elongationandhadavalueofabout38%atcrossheadspeedof1000mm/min.Atlowertestspeeds,thePP-Rsamplesformedaverymarkedandstableneckwithawidestress-whiteningzone;asthetestproceeded,theneckedzoneextendedthroughoutthewholetestgaugetothepointofruptureatverylargedeformationvalues.Atthisstage,duetostrain-hardeningtherewasagradualincreaseinthestressasthetestproceededuptorupture.Asthetestspeedincreased,thestress-whiteningzonenarrowedand,atveryhighcrossheadspeeds,theremainderofthegaugelengthwasnotplasticallydeformed.
Theeffectsofcrossheadspeedsonthevariationsin‘yieldstress’,‘yieldstrain’and‘elasticmodulus’aregiveninFigs.3–5,respectively.Thebehaviourofthesepropertieswithlog(crossheadspeed)waslinearandsuggestedthat,likeothersemi-crystallinepolymers,themechanicalpropertiesofPP-Risalsoverystrainrate-sensitive.Ithasbeenpointedoutthattheslopeinthesefiguresmightvaryfromonesemi-crystallinematerialtoanotherandcouldbeagoodindicationtodefinethestrainratedependencyofmaterial[11].
3.2.Impacttests
Theeffectoftemperatureonthevariationofforce–timesignalobtainedfrominstrumentedCharpyimpacttestsweredepictedinFig.6,showingremarkablechangeinnatureoftheforce–timesignalasthetemperaturechanges.Fig.6showsthatuptoabout25℃,almostalloftheenergyis
consumeda
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