ASTMD3364-99 Standard Test Method for Poly(Vinyl ride) with Molecular Structural Implications

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Designation:D3364–99

StandardTestMethodfor

FlowRatesforPoly(VinylChloride)withMolecularStructuralImplications1ThisstandardisissuedunderthefixeddesignationD3364;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(e)indicatesaneditorialchangesincethelastrevisionorreapproval.

1.Scope

1.1ThistestmethodisanextensionofTestMethodD1238specifictothemeasurementofflowratesofpoly(vinylchloride)(PVC)compoundswhiledetectingandcontrollingvariouspolymerinstabilitiesassociatedwiththeflowrate.1.2Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.

NOTE1—ThereisnosimilarorequivalentISOstandard.

shipcanbeexpressedasfollows:

(Viscosity)(ShearRate)1−N=(shearstress)inwhichtheshearrateisexpressedas4Q/pR3anddependsonthepowerlawexponentN.

SinceQisthevolumetricflowrateintermsofcubicmillimetres/secondandRistheradiusofthedie,itfollowsthattheflowratevariesmuchfasterthantheviscosityasaresultofN.Thismeansthattheflowismuchmoresensitivetochangethantheviscosity.ForPVC,Nvariesfrom0.1to0.33.

3.2.3Flowratebythistestmethodistherateinmilligrams/minuteatwhichpolymerflowsthroughaspecificdie(seeFig.1)withatotalloadontheramof20kgatatemperatureof175°C.

4.SummaryofTestMethod4.1Conditions:

4.1.1InordertotestawidevariationofflowratescoveringsemirigidaswellasnonrigidPVCcompounds,thefollowingstandardconditionsareused:

Temperature

TotalloadonpistonApproximatepressureCharge

Pluggedorificewith120°entranceangle

175°C(347°F)20000g

2758kPa(400psi)2.1560.05g

2.ReferencedDocuments2.1ASTMStandards:

D883TerminologyRelatingtoPlastics2D1238TestMethodforFlowRatesofThermoplasticsbyExtrusionPlastometer2D3835TestMethodforRheologicalPropertiesofThermo-plasticswithaCapillaryRheometer3E177PracticeforUseoftheTermsPrecisionandBiasinASTMTestMethods4E691PracticeforConductinganInterlaboratoryStudytoDeterminethePrecisionofaTestMethod43.Terminology

3.1Definitions—Fordefinitionsrelatedtoplastics,seeTer-minologyD883.

3.2DefinitionsofTermsSpecifictoThisStandard:

3.2.1SeeTestMethodD3835,Sections5.1,5.2,and5.3.3.2.2Flowisthereciprocaloftheviscosity;therefore,theflowisdefinedasthevolumetricdisplacementthroughacontrolledorificeandisexpressedasshearrateovershearstress.

NOTE2—SincePVCobeysthepowerlawfunction,theaboverelation-ThistestmethodisunderthejurisdictionofASTMCommitteeD-20onPlasticsandisthedirectresponsibilityofSubcommitteeD20.30onThermalProperties(SectionD20.30.08).

CurrenteditionapprovedMarch10,1999.PublishedJune1999.OriginallypublishedasD3364–74.LastpreviouseditionD3364–94.2AnnualBookofASTMStandards,Vol08.01.3AnnualBookofASTMStandards,Vol08.02.4AnnualBookofASTMStandards,Vol14.02.

14.2BasisPrinciples:

4.2.1Thelowertemperature(relativeto190°C)ischosentominimizethermaldecomposition,maximizesensitivityoftheflowratetostructuralchangesinthePVCcompound,andtoallowawidelatitudeofusefulconditionsassociatedwiththeloadonthepiston.

4.2.2Modernextrusionplastometershavebeenredesignedtoaccomodatemuchhigherloads.Currentresearchformulti-weighttestinghasreachedlevelsof50kgandtheseareparticularlygoodforrigidPVC.Previously,flowratesforrigidPVCwerelimitedto190°C.RecentresearchhasshownthatrigidPVCcanberunat150°Cand50kgloads.ThisweightiseffectiveforallsemirigidPVCandevensomenonrigidcompounds.Forflowratesinexcessof10g/10min(1000mg/min),lowerweightsareused,forexample,colorconcen-tratesusedinPVCextrusionmayhaveflowratesinexcessof100g/10min(10000mg/min)andwillrequirea5-kgloadonthepiston.

4.2.3Whentheflowratesbecomeverysmallasinthecaseofthestiffestsemirigidcontaining25partsofplasticizer(flowratesbelow15mg/min),itmaybedesirabletousethedie(flat

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NOTE—Specifymaterialwhenordering.

FIG.1DieUsedforTestMethodD3364

entry8mm(0.315in.)long)inTestMethodD1238.Theflowissoslowthatlittlerheologicalinstabilityexists.Bychangingthedie,approximatelyatenfoldincreaseinflowisachieved.4.2.4Thechargesizeisimportant.ManyPVCcompoundsareelasticinnature,causingaseverelossinpressurefromthebottomofthepistonthroughthematerialtotheorificeofthedie.Evidenceindicatesthattheforcetoextrudemaybereducedbyasmuchas67%usinga9-gchargeand4.14MPa(600psi)onthepiston.

4.2.5ThepluggedorificeshouldbeusedinallPVCcompoundworksincetheamountofchargeislimitedandsincethepluggingforvarioustimeshasbeenobservedtogivesignificantvariationsintheflowrate.

5.SignificanceandUse

5.1Thistestmethodisusefulforquality-controltestsonPVCcompoundshavingawiderangeofmeltviscosities.Measurementsaremadeatshearratescloseto1s−1.

5.2InadditiontothepropertiesmentionedinTestMethodD1238,thistechniqueissensitivetoplasticizercontent,polymermolecularweight,polymerstability(boththermallyandrheologically),shearinstability,andgeneralcomposition.ThesensitivityofthematerialtotemperaturenecessitatesslightlytightercontrolsthanthosestatedinTestMethodD1238.

5.3Thesensitivityofthistestmethodmakesitusefulforcorrelatingwithprocessingconditionsandasanaidinpredict-ingchangesinprocessing.However,asaone-pointmeasureofflowrelativetoshearrate,itsonedrawbackisthatthesamePVCmeltflowvaluescanbeobtainedformaterialshavingdifferentprocessibility;thechanceofthishappeningismini-mized,however,ifthecompoundsaresimilarincomposition.5.4Correlationswithawiderangeofprocessingconditionshavesupportedtheconclusionsthatlittleornochangeincompositionoccursduringthetest.Thus,thistestisabletodetectandfollowprofoundchangeswhichoccurduringextrusion,injectionmolding,milling,ormixing.Thesechangesareduetothreetypesofmeasuredinstabilityinpolymers:

5.4.1Thermalinstabilityduetotemperatureeffect.

5.4.2Shearinstabilityduetobreakingofpolymerbonds.5.4.3Rheologicalinstabilityduetononuniformdistribu-tionsofwidelydifferentviscosityormolecularweightele-ments.

5.4.4Thus,implicationswithrespecttoPVCmolecularstructuralchangescanbedetectedandpredicted.

6.Apparatus

6.1Plastometer—TheapparatusisidenticaltothatusedinTestMethodD1238exceptforthedie.Analternativether-moregulatorissuggestedforimprovedtemperaturecontrol.6.2Die:

6.2.1ThedieisapproximatelythreetimesaslongastheoneusedinTestMethodD1238,amajorfactorincontrollinganyrheologicalinstabilityinthepolymer.Ifinstabilitystilloccurs,particularlyathighflowrates,dies2in.orlongercanbeusedtoimprovetheL/Dratio.ThedimensionsoftheregulardieareshowninFig.1.

6.3Thermoregulator—Althoughathermoregulatoridenti-caltothatusedinTestMethodD1238maybeused(provideditregulatesto17560.1°C),aunit5coupledwitha90°anglethermometer,dividedinto0.1°Cissuggestedforimprovedreproducibility.MostregulatorsdesignedforTestMethodD1238cannotcontrolbetterthan60.2°C.Thesensitivityofthistestmethodisillustratedbythefactthata19%changeinflowrateisobservedonatypicalPVCcompoundwitha1°Cchangeintemperatures.

6.4Thermometer,measuringthestandardtemperature,shouldrestonthetopoftheorificetoconformwithconditionsinaccordancewithTestMethodD1238(1⁄2in.abovetheshorterorifice).

7.Procedure

7.1Checkthatthetemperatureiscontrolledto60.1°Cintherangefrom174.9to175.1°C.

The“ThermoWatch”unit,manufacturedbyInstrumentsforResearchandIndustry,103FranklinAve.,Cheltenham,PA19012,hasbeenfoundsatisfactoryforthispurpose.

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7.2Theapparatusmustbeclean.

7.3Withthedieinplace,plugtheorifice(asharpenedwooddowelisasatisfactoryplug).

7.4Allowthedieandplugtoheatatleast3min.

7.5Startthestopwatchandcharge2.1560.05gofthePVCcompoundintothebore.Whenchargingiscomplete,packdownthePVCwiththephenolic-coatedchargingtoolbyrepeatedthrusts.

7.6Placethepistonintheboreandaddsufficientweightstomakethetotalmassincludingthepistonequalto20kg610g.Theentiretimeofchargingandpositioningofweightsshouldtakenolongerthan1minandpreferablylessthan1⁄2min.Ifchargingtimeisgreaterthan1min,cleanouttheinstrumentandrepeattheprocedure.

7.7Whenthestopwatchreadsexactly360s(6min),pulltheplugfromtheorifice.

7.8Atthistime(6min)andwithoutstoppingthestopwatch,cutofftheextrudedportionverycleanlywiththespatulaexactlywhenthesecondhandofthewatchreacheszero.Passthetipofthespatulaupwardalongonesideofthebeveledhole,lightlyacrossthebottomoftheorifice,anddownwardalongtheoppositeside.Makethecutquicklyandneatlyforbestprecision.Acleansharpcutisdesirablesothatsucceedingportionswillextrudestraight,notcurled.Itmaybenecessarytoreshapetheendofthecutofftooltoobtainthebestresults.7.9ThetimeforcuttingthespecimenshallbeinaccordancewithTable1.Asaguide,eachspecimenshouldbeabout20to30mmlong.

7.10Placethecutspecimenintheslottedtrayintheordertaken.

7.11Continuetotakespecimensuptoandincluding42minoruntilflowstops,whicheverissooner.

7.12Weighandrecordtheresultstotheclosest1mg.Averagethefivesuccessivemoststablevaluesneartheendoftherunandexpressasmilligramsperminute.ThisaveragevalueisthePVCflowrate.Donotusethefirsttwoorlasttwovaluessincethesearenormallyunstablevalues.

NOTE3—Occasionally,thevalueschangethroughouttherun.ThismaybeduetovariablelubricantconditionsatthemetalsurfacesorchemicalchangesinthePVCcompound.Undertheseconditions,averagethevaluesafterdiscardingthefirstthreevaluesandthelasttwo.Thecauseofthisunstableconditionshouldbestudiedandunderstood.

7.13Ofthefivestablespecimens,subtracttheweightofthefifthfromthatofthefirst.Dividethedifferencebytheaverageandmultiplyby100.ReportaspercentPVCinstability.Fluctuationsupanddownrepeatedlyduringaruncanindicatenonuniformmixingorabadchargingtechnique.

TABLE1TimeRequirementsforCuttingSpecimens

FlowRateRange,TimeIntervalmg/minBetweenCuts

TypicalType15to304minsemirigid30to502minsemirigid50to1001minsemirigid100to50030snonrigid400to150015snonrigid1000

to2000

10s

soft

7.14Determinethediameteroftheextrudateforthefirstandfifthstablespecimenswithamicrometer.Ifthedifferencebetweenthetwospecimensisgreaterthan0.15mm(0.006in.)(thenormalPVCswell,observedforawiderangeofPVCcompounds),reportthetotaldifferenceasPVCswellinginstability.Becarefulnottosqueezethespecimen;thespeci-menshouldfitthemicrometersettingeasily,butnotquitefallfree.

7.15Removetheweightsandpiston,andcleanthepistonwithacloth.

7.16Pushthedieoutofthetopofthecylinderwiththepush-outtool.PushoutanymoltenPVCintheorificewiththeorificebroach.Putthedie(hot)intomethylethylketoneinordertobreakthePVCskinawayfromtheorifice.Dryoffthecooleddiewithaclothandinspecttoseethattheorificeisclean.Atleasttwiceadaychecktheorificewiththe“go-no-go”gage.

7.17Cleanupthecylinder,replacethedie,andinserttheplug.Theinstrumentisnowreadyforthenexttest.Returnto7.4.

8.Calculation

8.1Thesimpleaverageofthefivevaluesisfirstpostedasthemilligramspertimescale.ThePVCmeltflowvalueisthenobtainedbyadjustingthevaluetomilligramsperminute(seeTable2).

8.2Theinstabilityismeasuredbysubtractingtheweightofthefifthorlastspecimenfromthefirstspecimen.Thevaluefortheinstabilitywillthenbepositiveornegative.Thus,

200mg/15s4thspecimen250mg/15s9thspecimen

8.3Calculatethesimpleaverageandtheinstabilityvalueasfollows:

instability5250mg/15s(1)

average5225mg/15s250

2255222.2%

where:

instability=FR42FR9

averageFR3100,FR4=flowrateof4thspecimen,andFR9=flowrateof9thspecimen.

NOTE4—Apositiveinstabilityprobablyindicatesthatcrosslinkingisoccurring.Anegativeinstabilityindicateseitheradegradationofthepolymerorachangeinthelubricantfunctionatthemetalsurfaceofthedie.

TABLE2MeasurementConversiontoMilligramsperMinute

TimeInterval,minFactorforObtainingFlowRate

inmg/minMultiplyBy

40.2520.501

1.000.50(30s)2.000.25(15s)4.000.167(10s)

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9.Report

9.1Reportthefollowinginformation:

9.1.1PVCflowrate,statingthedate,anyprocessinforma-tion,sampleidentification,weightonthepiston,anddie,9.1.2PercentPVCinstability,

9.1.3PVCswellinginstability,and

9.1.4Anychangeincolor,referencedtothetimeatwhichitoccurred.

10.PrecisionandBias10.1Precision:

10.1.1Table3isbasedonaroundrobin6conductedin1991inaccordancewithPracticeE691,involvingthreematerialstestedbysevenlaboratories.Foreachmaterial,allthesampleswerepreparedatonesource,buttheindividualspecimenswerepreparedatthelaboratorieswhichtestedthem.Eachtestresultwastheaverageoffiveindividualdeterminations.Eachlabo-ratoryobtainedthreetestresultsforeachmaterial.

NOTE5—Caution:ThefollowingexplanationsofrandR(10.1.2-10.1.2.3)areintendedonlytopresentameaningfulwayofconsideringtheapproximateprecisionofthistestmethod.ThedatainTable3shouldnotberigorouslyappliedtoacceptanceorrejectionofmaterial,asthosedataarespecifictotheroundrobinandmaynotberepresentativeofotherlots,

conditions,materials,orlaboratories.UsersofthistestmethodshouldapplytheprinciplesoutlinedinPracticeE691togeneratedataspecifictotheirlaboratoryandmaterials,orbetweenspecificlaboratories.Theprinciplesof10.1.2-10.1.2.3wouldthenbevalidforsuchdata.

Theround-robindatasupportingthesevaluesmaybeobtainedfromASTMHeadquarters.RequestRR:D-20-1042.

6TABLE3SummaryofPrecisionParameters(ValuesExpressed

inUnitsofMilligramsperMinute)

MaterialSemirigidFlexibleFlexible

AAverage108293439

SrA3.0513.8613.58

SRB8.0031.5935.48

rC8.5338.8038.04

RD22.3988.4599.35

10.1.2ConceptofrandR—IfSrandSRhavebeencalcu-latedfromalargeenoughbodyofdataandfortestresultsthatwereaveragesfromtestingfivespecimens,thefollowingapplies:

10.1.2.1RepeatabilityLimit,r—Incomparingtwotestre-sultsforthesamematerialobtainedbythesameoperatorusingthesameequipmentonthesameday,thetwotestresultsshouldbejudgednotequivalentiftheydifferbymorethanthervalueforthatmaterial.

10.1.2.2ReproducibilityLimit,R—Incomparingtwotestresultsforthesamematerialobtainedbydifferentoperatorsusingdifferentequipmentindifferentlaboratories,thetwotestresultsshouldbejudgednotequivalentiftheydifferbymorethantheRvalueforthatmaterial.

10.1.2.3Anyjudgmentmadeinaccordancewith10.1.2.1or10.1.2.2wouldhaveanapproximate95%(0.95)probabilityofbeingcorrect.

10.1.2.4Experiencehasshownthatthesingle-laboratoryprecisioncanbeimprovedbyafactoroftwoormorebycarefuloperatorcontrolofthesystematicerrorssuchasthedimensionsofthecomponentsofthemeltindexer,whentrulyuniformsamplesareusedforthedeterminations,andwhentheoperatorbecomesexperiencedinobservingdifferencesinasingleformulatedcompound.ThisstatementfurtherdefinestherepeatabilityofthismeasurementinaccordancewithPracticeE177.

10.2Bias—Theprocedureinthistestmethodhasnobiasbecausethevalueofthemeltflowrateisdefinedonlyinthetermsofthetestmethod.

11.Keywords

11.1chainshearing;crosslinking;degradation;fragmenta-tion;meltflowrate;poly(vinylchloride);rheology;shearinstability

Sr=within-laboratorystandarddeviationoftheaverage(median/otherfunc-tion).BSR=between-laboratoriesstandarddeviationoftheaverage(median/other).Cr=within-laboratoryrepeatabilitylimit=2.8Sr.DR=between-laboratoriesreproducibilitylimit=2.8SR.

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