Designation:D5051−06(Reapproved2012)StandardTestMethodforRubberCompoundingMaterials—BenzothiazylDisulfide(MBTS)—Assay1ThisstandardisissuedunderthefixeddesignationD5051;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodcoversthedeterminationofassayofbenzothiazyldisulfide(MBTS).ItisbasedonatitrationoffreeiodineliberateduponreductionofMBTS,withpotassiumiodide(KI)inacidmedium.1.2Theassayisdeterminedasmasspercent.1.3Free2-mercaptobenzothiazole(MBT)contentisnotdetermined.1.4ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.5Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2D1193SpecificationforReagentWaterD4483PracticeforEvaluatingPrecisionforTestMethodStandardsintheRubberandCarbonBlackManufacturingIndustries3.SummaryofTestMethod3.1Inanacidmedium,MBTSisreducedwithKItoMBTandfreeiodine.Thefreeiodineistitratedwithstandardsodiumthiosulfatesolution.3.2MBTSissparinglysolubleinanyorganicsolvent;whileMBT,formedduringthereactionofMBTSwithKIisverysoluble.Thereforeafterreagentsareaddedasindicatedintheprocedure,continuetostirtillallMBTShasreacted.4.SignificanceandUse4.1ThetestmethodisdesignedtoassessthepurityofMBTS,whichisusedforrubberandlatexvulcanizationacceleration.TheamountofMBTSisofimportanceinpredictingperformanceinrubbercompoundsandforrawmaterialpurchaseandcontrol.4.2Thistestmethodmaybeusedasaqualitycontroltoolandforresearchanddevelopmentwork.5.Interferences5.1KI-reduciblecontaminantsinterferewiththeresults.6.Apparatus6.1ErlenmeyerFlask,300cm3.6.2GraduatedCylinder,5cm3...
