Designation:D4818−21StandardClassificationforRubberCompoundingMaterials—VulcanizationAccelerators1ThisstandardisissuedunderthefixeddesignationD4818;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thisclassificationcoversvulcanizationacceleratorsanddefinestheirimportantchemicalandphysicalcharacteristics.Thepropertiesoutlinedhereinareusefulforqualitycontrol;theycanfrequentlybedirectlyorindirectlyrelatedtotheperformancecharacteristicsinrubbercompounds.1.2Thisinternationalstandardwasdevelopedinaccor-dancewithinternationallyrecognizedprinciplesonstandard-izationestablishedintheDecisiononPrinciplesfortheDevelopmentofInternationalStandards,GuidesandRecom-mendationsissuedbytheWorldTradeOrganizationTechnicalBarrierstoTrade(TBT)Committee.2.ReferencedDocuments2.1ASTMStandards:2D1519TestMethodsforRubberChemicals—DeterminationofMeltingRangeD1991TestMethodforRubberChemicals—2-Mercaptobenzothiazole(MBT)—AssayD4571TestMethodsforRubberCompoundingMaterials—DeterminationofVolatileMaterialD4574TestMethodsforRubberCompoundingMaterials—DeterminationofAshContentD4936TestMethodforMercaptobenzothiazoleSulfenamideAssaybyReduction/TitrationD5044TestMethodforRubberCompoundingMaterials—Free2-Mercaptobenzothiazole(MBT)inBenzothiazylDisulfide(MBTS)D5051TestMethodforRubberCompoundingMaterials—BenzothiazylDisulfide(MBTS)—Assay3.SignificanceandUse3.1Class1,Sulfenamides:3.1.1Asagroup,the2-benzothiazylsulfenamidesaretheprinciplesulfurvulcanizationacceleratorsusedintherubberindustrytoday.Theroleofthesematerialsinvulcanizationisdual.Theyprovidescorchtime(delayperiod)inthecrosslink-ingorvulcanizationoperationatprocessingtemperatures.Thedelayavoidsprematurecrosslinkingduringtheprocessing,forexample,mixing,extrusion,etc.Oncethemixedrubberisatthecuringtemperature,thesematerialspr...
