ASTM_D_5044_-_06_2012.pdf

Designation:D504406(Reapproved 2012)Standard Test Method forRubber Compounding MaterialsFree2-Mercaptobenzothiazole(MBT)in Benzothiazyl Disulfide(MBTS)1This standard is issued under the fixed designation D5044;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 procedure for estimation ofthe acidic impurities in benzothiazyl disulfide(MBTS).1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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.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 A sample of MBTS is dissolved in solvent.Afteraddition of an acetate buffer,water,and starch solution,thesolution is titrated with iodine.3.2 MBTS is sparingly soluble in any organic solvent.MBT,major impurity in MBTS,is very soluble.Stirring thereforewill dissolve MBT,MBTS could stay undissolved.4.Significance and Use4.1 2-Mercaptobenzothiazole(MBT)is usually the majorimpurity in MBTS.Free MBT may be determined by this testmethod.4.2 MBT and MBTS are used for rubber and latex vulcani-zation acceleration.The amount of MBT in MBTS may be ofimportance in predicting performance in rubber compoundsand for raw material purchase and control.4.3 This test method may be used as a quality control tooland for research and development work.5.Apparatus5.1 Erlenmeyer Flask,300-cm3.5.2 Graduated Cylinders,10-cm3,50-cm3,250-cm3.5.3 Buret,10-cm3.5.4 Analytical Balance,having a sensitivity of 60.1 mg.6.Reagents6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended thatall 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.6.2 Purity of WaterUnless otherwise indicated,referencesto water shall be understood to mean reagent water as definedby Types I,II,or III of Specification D1193.6.3 Isopropanol,analytical reagent.6.4 Toluene,analytical reagent.6.5 Acetic Acid,100%analytical reagent.6.6 Sodium Acetate,analytical reagent.6.7 Water,distilled.6.8 Iodine Solution(0.1 N).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 May 1,2012.Published July 2012.Originally approvedin 1990.Last previous edition approved in 2006 as D5044 06.DOI:10.1520/D5044-06R12.2For 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.3Reagent Chemicals,American Chemical Society Specifications,AmericanChemical Society,Washington,DC.For suggestions on the testing of reagents notlisted by the American Chemical Society,see Analar Standards for LaboratoryChemicals,BDH Ltd.,Poole,Dorset,U.K.,and the United States Pharmacopeiaand National Formulary,U.S.Pharmaceutical Convention,Inc.(USPC),Rockville,MD.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.9 Starch Indicator SolutionSlurry 2 g of soluble starchwith 10 cm3of water and dilute with 90 cm3of boiling water.6.10 Sodium Acetate SolutionDissolve 60 g of sodiumacetate in water to make 600 cm3of solution.6.11 Acetate-BufferAdd 100 cm3acetic acid(see 6.5)to600 cm3sodium acetate solution(6.10).6.12 SolventMix 5 volumes Isopropanol with 3 volumestoluene.7.Sampling7.1 Sampling shall be at the discretion of the analyst toobtain as representative a sample as possible of the lot to betested.8.Procedure8.1 Accurately weigh about 1 g of the test specimen to thenearest 0.1 mg and carefully transfer to a 300-cm3Erlenmeyerflask.8.2 Add 50 cm3of solvent to the specimen which may notdissolve completely.8.3 With stirring,add the reagents in the following se-quence:150 cm3distilled water,10 cm3acetate buffer,and5 cm3starch solution.8.4 Titrate immediately with 0.1 N iodine solution until thecolor change from colorless to light violet is stable for 1 min.(See 3.2)8.5 Obtain a blank titration by proceeding