Designation:D6338−10StandardClassificationSystemforHighlyCrosslinkedThermoplasticVulcanizates(HCTPVs)BasedonASTMStandardTestMethods1ThisstandardisissuedunderthefixeddesignationD6338;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.INTRODUCTIONThisclassificationsystemisintendedasameansforthecalloutofmaterialsforthefabricationofpartsorend-useitems.Itisnotintendedformaterialselection,whichshouldbeperformedbythosewithspecialexpertiseinthematerialsfield.Materialselectionshouldbemadeaftercarefulconsiderationof:partperformanceanddesign;theenvironmentinwhichthepartmustfunction;thematerialpropertiescoveredandnotcoveredbythisclassificationsystem;thedesiredservicelifetimeofthepart;thefabricationprocessforthepart;andmaterialandfabricationcosts.1.Scope*1.1Thisclassificationsystemcovershighlycrosslinkedthermoplasticvulcanizates(HCTPVs)forextrusion,moldingandotherfabricationmethods.HCTPVsarethermoplasticelastomers(TPEs)consistingoftwoormorepolymersystemsatleastoneofwhichisrubberyandhighly(>95%)crosslinkedandatleastoneofwhichisthermoplastic,witheachsystemhavingitsownphase.Thethermoplasticphasewilltendtobecontinuousandtherubberyphasediscontinuous.Thehighlevelofcrosslinkingandultrafineparticlesize(ca1µmdiameter)oftherubberyphasegiverisetopropertiesmorecloselyapproachingthoseofconventionalthermosetrubber,whencomparedtothesamethermoplastic/rubberypolymercompositionwithalowerlevel(#95%)ofcrosslinking.TheHCTPVpolymercompositionsmaycontainfillers,reinforcingagents,plasticizers,resins,antidegradants,colorantsandotherbeneficialconstituents.RecycledHCTPVsarenotcoveredinthisclassificationsystem.1.2Includedinthisclassificationsystemarethepropertiesnecessarytoidentifytherespectivecompositions.Forspecial-izedapplications,otherrequirementsmaybeneededtoidentifyspecificcharacteristics.1.3A...
