1、Designation: D5051 06 (Reapproved 2012)Standard 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,
2、 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 ofbenzothiazyl disulfide (MBTS). It is based on a titr
3、ation 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 ar
4、e 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 and health practices and determine the applica-bility of regulatory limitations p
5、rior 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 In an acid medium, MBTS is reduced with KI to MBTand free io
6、dine. 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 till all MBTS has re
7、acted.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 b
8、e 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,5cm3.6.3 Magnetic Stirrer, with hot plate.6.4 Buret, 50-cm3capacity.6.5 Analytical Balance,
9、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 thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,
10、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
11、 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.1This test method is under the jurisdiction of ASTM Committee D1
12、1 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 D5051 06. DOI: 10.1520/D5051-06R12.2For referenced ASTM standards, visit the ASTM w
13、ebsite, 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 s
14、uggestions 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.1Copyright ASTM Internati
15、onal, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7.7 Sodium Thiosulfate (Na2S2O3) (0.1 N).7.8 Starch Indicator SolutionSlurry2gofsoluble starchwith 10 cm3of water and dilute with 90 cm3of boiling water.7.9 Hydrochloric Acid (HCl) (2 N).7.10 Solvent: Mix 5 vol
16、umes 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 possible of the lot to be tested.9. Procedure9.1 Accurately weigh about 0.5 g of the test specimen to theneares
17、t 0.1 mg and carefully transfer it to a 300-cm3Erlen-meyer flask.9.2 Add 50 cm3of solvent to the specimen, which may notdissolve completely.9.3 With stirring, add the reagents in the following se-quence: 50 cm3of distilled water, about6gofKI,25cm3of2 N HCl, and 25 cm3of acetic acid (see 3.2). Sample
18、 will nowbe dissolved.9.4 Immediately titrate (see Note 1) the liberated iodinewith 0.1 N Na2S2O3solution. Toward the end of the titration,add5cm3of starch indicator solution. The end point proceedsfrom blue-violet to yellow to colorless (milky).NOTE 1The final titration must be carried out as soon
19、as acetic acid isadded. If allowed to stand, a reduction of free iodine will occur, giving alower MBTS assay.9.5 Obtain a blank titration by proceeding from 9.2 to 9.4.10. Calculation10.1 Calculate the percent MBTS as follows:Percent MBTS 5A 2 B! 3 N 3 0.33248!2 W3 100 (1)where:A = volume of Na2S2O3
20、(see 7.7) required for titra-tion of the sample, cm3,B = volume of Na2S2O3required for titration of theblank, cm3,N = normality of the Na2S2O3solution,W = mass of the test specimen in g, and0.33248 = millimole mass of MBTS.11. Report11.1 Report the following information:11.1.1 Proper identification
21、of the sample and11.1.2 Results obtained from two individual determinationsand their average, reported to the nearest 0.1 %.12. Precision and Bias412.1 This precision and bias section has been prepared inaccordance with Practice D4483. Please refer to this practicefor terminology and other statistic
22、al calculation details.12.2 The precision results in this precision and bias sectiongiven an estimate of the precision of this test method with thematerials (rubbers, etc.) used in the particular interlaboratoryprogram as described below. The precision parameters shouldnot be used for acceptance or
23、rejection testing or any group ofmaterials without documentation that the parameters are appli-cable to the particular group of materials and the specifictesting protocols of the test method.12.3 A Type 1 interlaboratory test program (ITP) wasconducted in 1997 on a sample of IRM-MBTS. Six laborato-r
24、ies participated in the ITP conducting duplicate tests on eachof 2 successive test days. A test result for the assay is the valueobtained from one analysis operation. The database generatedby this ITP was divided into two parts; Part 1 used the first ofthe duplicates on each day and Part 2 used the
25、second of theduplicates. A complete statistical analysis according to D4483was conducted for each part. The analysis results of each partwhere then combined (averaged) for the final values as given inthis section. Thus the precision results pertain to between daysingle determinations for the assay v
26、alues for MBTS.12.4 The D4483 analysis revealed that one of the laborato-ries had excessive within-laboratory variation (high k-value)and the results from this laboratory were deleted. The precisionis therefore based on a five laboratory ITP.12.5 RepeatabilityThe repeatability r, of this test method
27、has been established as the value tabulated in Table 1.Twosingle test results, obtained under normal test method proce-dures, that differ by more than this tabulated r (for any givenlevel) must be considered as derived from different or non-identical sample populations.12.6 ReproducibilityThe reprod
28、ucibility R, of this testmethod has been established as the value tabulated in Table 1.Two single test results obtained in two different laboratories,under normal test method procedures, that differ by more thanthe tabulated R must be considered to have come from differentor non-identical sample pop
29、ulations.12.7 BiasIn test method terminology, bias is the differ-ence between an average test value and the reference (or true)test property value. Reference values do not exist for this testmethod since the value (of the test property) is exclusivelydefined by the test method. Bias cannot therefore
30、 be deter-mined.13. Keywords13.1 mercaptobenzothiazole; mercaptobenzothiazoledisulfide4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D11-1083.TABLE 1 Precision for MBTS AssayAMean Within-LaboratoryBBetween LaboratoryMaterial Va
31、lue (a) Sr r (r) SR R (R)IRM-MBTS 96.79 0.134 0.380 0.39 0.397 1.12 1.16APrecision results for 5 laboratories, mean value in percent assay for MBTS.BSr = repeatability standard deviationr = repeatability, in measurement units(r) = repeatability (relative) in percentSR = reproducibility standard devi
32、ationR = reproducibility, in measurement units(R) = reproducibility (relative) in percentD5051 06 (2012)2ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that
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