ASTM_D_4936_-_10_2015.pdf

Designation:D493610(Reapproved 2015)Standard Test Method forMercaptobenzothiazole Sulfenamide Assay by Reduction/Titration1This standard is issued under the fixed designation D4936;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.1.Scope1.1 This test method covers the determination of assay onmercaptobenzothiazole(MBT)sulfenamides.It is based on atitration of the basic amines liberated upon reduction of thesulfenamideswithhydrogensulfidegas(H2S)2,3or2-mercaptobenzothiazole.1.2 Any free amine(HNR2)or weak acid salts of thecorresponding amine(HXHNR2)are titrated prior to reduc-tion.This titer is used to calculate percent basic impurity(asfree amine)in the sample.1.3 With the indicated modifications,this test method isapplicable to all MBT sulfenamides,that is,N-cyclohexyl-2-benzothiazolesulfenamide(CBS),N,N-diisopropyl-2-benzothiazyl sulfenamide(DIBS),2(morpholinothio)benzo-thiazole(MBS),N,N-dicylohexyl-2-benzothiazyl sulfenamide(DCBS),N-tert-butyl-benzothiazole-sulfenamide(TBBS),and4-morpholinyl-2-benzothiazyl disulfide(MBSS).1.4 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.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 and health practices and determine the applica-bility of regulatory limitations prior to use.For specific hazardstatements,see Section 9.2.Referenced Documents2.1 ASTM Standards:4D4483 Practice for Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustries3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 IpOH/Tol solvent,ntitration solvent containing fivevolumes isopropanol and three volumes toluene.3.1.2“lot”sample,na production sample representativeof a standard production unit.3.1.3 potassium hydrogen phthalate acidimetric standard,nFisher P-243.53.1.4 primary titrant,n0.25 to 0.30 N aqueous hydrochlo-ric acid(HCl).3.1.5 reducing solution,nIpOH/Tol solvent saturated withhydrogen sulfide gas(H2S)at 25C(about 1.1 g H2S/100 mLsolvent).3.1.6 test unit,nthe actual material used in the analysis.Itmust be representative of the“lot”sample.3.2 Abbreviations:3.2.1 THAMtris(hydroxymethyl)aminomethane alkali-metric standard(Fisher T-395).34.Summary of Test Method4.1 Procedure AFor CBS,TBBS,MBSS,MBS-90,andMBS,a weighed specimen is dissolved in the appropriatesolvent,the“free amine”blank is titrated with standard acid,and the sulfenamide is reduced with H2S.That is,BtSNR21H2SBtSH1HNR21S(1)where:Bt=the 2-benzothiazole radical.BtSH=2-mercaptobenzothiazole.HNR2=free amine.1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.11 on Chemical Analysis.Current edition approved June 1,2015.Published September 2015.Originallyapproved in 1989.Last previous edition approved in 2010 as D4936 10.DOI:10.1520/D4936-10R15.2Goodyear Paper,Industrial and Engineering Chemistry Production Researchand Development,Vol 2,1963,p.16.3Elastomerics,August 1981,pp.3444.4For 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.5The sole source of supply of the apparatus known to the committee at this timeis Fisher Scientific Co.,711 Forbes Ave.,Pittsburgh,PA 15219.If you are aware ofalternative suppliers,please provide this information to ASTM InternationalHeadquarters.Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 The liberated amine is then titrated with standard acid to anindicator end point.4.2 Procedure BFor sulfenamides of hindered amines(DIBS and DCBS),it is necessary to measure the liberatedamine by back titration at 40 to 45C.Excess hydrochloric acid(HCl)is added,then back titrated with standard sodiumhydroxide(NaOH).4.3 Procedure CThis alternative is appropriate for allsulfenamides.A weighed specimen is dissolved in ethanol,the“free amine”blank is titrated with standard acid,and thesulfenamide reduced with MBT.That is,BtSNR21BtSHBtSSBt1HNR2(2)where:BtSSBt=benzothiazole disulfide.The liberated amine is captured in a known amount ofstandard acid and the excess acid back titrated with standardsodium hydroxide.5.Significance and Use5.1 This test method is designed to assess the purity of2-mercaptobenzothiazole sulfenamide accelerators.Theseproducts are used in combination with sulfur fo