Designation:D4528−88(Reapproved2021)StandardClassificationforRubberCompoundingMaterials—Sulfur1ThisstandardisissuedunderthefixeddesignationD4528;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thisclassificationcoversthevarietyofsulfurgradesusedintherubberindustry.Typicalchemicalandphysicalpropertiesforsulfurareshown.Sulfurisprincipallyusedinunsaturatedrubbersasavulcanizingagent.1.2Thisinternationalstandardwasdevelopedinaccor-dancewithinternationallyrecognizedprinciplesonstandard-izationestablishedintheDecisiononPrinciplesfortheDevelopmentofInternationalStandards,GuidesandRecom-mendationsissuedbytheWorldTradeOrganizationTechnicalBarrierstoTrade(TBT)Committee.2.ReferencedDocuments2.1ASTMStandards:2D4569TestMethodforRubberCompoundingMaterials—DeterminationofAcidityinSulfurD4571TestMethodsforRubberCompoundingMaterials—DeterminationofVolatileMaterialD4572TestMethodforRubberChemicals—WetSieveAnalysisofSulfurD4573TestMethodforRubberChemicals—DeterminationofOilContentinOil-TreatedSulfurD4574TestMethodsforRubberCompoundingMaterials—DeterminationofAshContentD4578TestMethodsforRubberChemicals—DeterminationofPercentSulfurbyExtraction3.SignificanceandUse3.1Sulfurisoneoftheprincipalrubbervulcanizingagents.Itisacriticaladditive.Whenchemicallycombinedwithrubber,sulfurdevelopsbasicperformancepropertiesinthevulcanizedcompoundsuchas:tensilestrength,elongation,modulus,andhardness.Insoftorelasticrubbercompounds,sulfurisanessentialbutminoradditive.Insemi-hardrubberandebonite,sulfurbecomesamajorcompoundingmaterialwhileretainingitsroleasavulcanizingagent.3.2Themoststablemolecularformofsulfuratambientconditionsisaringstructurecontainingeightsulfuratoms.Dependingonconditionsthesemoleculesorientintooneoftwocrystallinestructures.Atroomtemperaturethecrystalsarerhombic...
