ASTM_D_5051_-_06_2021e1.pdf

Designation:D505106(Reapproved 2021)1Standard Test Method forRubber Compounding MaterialsBenzothiazyl Disulfide(MBTS)Assay1This standard is issued under the fixed designation D5051;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1NOTECorrected 3.2,6.2,9.2,and 12.2 editorially in November 2021.1.Scope1.1 This test method covers the determination of assay ofbenzothiazyl disulfide(MBTS).It is based on a titration of freeiodine liberated upon reduction of MBTS,with potassiumiodide(KI)in acid medium.1.2 The assay is determined as mass percent.1.3 Free 2-mercaptobenzothiazole(MBT)content is notdetermined.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD4483 Practice for Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustries3.Summary of Test Method3.1 In an acid medium,MBTS is reduced with KI to MBTand free iodine.The free iodine is titrated with standard sodiumthiosulfate solution.3.2 MBTS is sparingly soluble in any organic solvent,whileMBT,formed during the reaction of MBTS with KI,is verysoluble.Therefore,after reagents are added as indicated in theprocedure,continue to stir until all MBTS has reacted.4.Significance and Use4.1 The test method is designed to assess the purity ofMBTS,which is used for rubber and latex vulcanizationacceleration.The amount of MBTS is of importance inpredicting performance in rubber compounds and for rawmaterial purchase and control.4.2 This test method may be used as a quality control tooland for research and development work.5.Interferences5.1 KI-reducible contaminants interfere with the results.6.Apparatus6.1 Erlenmeyer Flask,300 cm3.6.2 Graduated Cylinder,5 cm3,25 cm3,50 cm3.6.3 Magnetic Stirrer,with hot plate.6.4 Buret,50-cm3capacity.6.5 Analytical Balance,having a sensitivity of 60.1 mg.7.Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended that1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand Rubber-like Materials and is the direct responsibility of Subcommittee D11.11on Chemical Analysis.Current edition approved Nov.1,2021.Published January 2022.Originallyapproved in 1990.Last previous edition approved in 2017 as D5051 06(2017).DOI:10.1520/D5051-06R21E01.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1?all reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades may beused,provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated,referencesto water shall be understood to mean reagent water as definedby Types I,II,or III of Specification D1193.7.3 Acetic Acid,100%,analytical reagent.7.4 Isopropanol,analytical reagent.7.5 Toluene,analytical reagent.7.6 Potassium Iodide(KI),analytical reagent.7.7 Sodium Thiosulfate(Na2S2O3)(0.1 N).7.8 Starch Indicator SolutionSlurry 2 g of soluble starchwith 10 cm3of water and dilute with 90 cm3of boiling water.7.9 Hydrochloric Acid(HCl)(2 N).7.10 Solvent:Mix 5 volumes isopropanol with 3 volumestoluene.8.Sampling8.1 Depending upon the purposes of the testing,samplingshall be at the discretion of the analyst to obtain as represen-tative a sample as