1、Designation: D 5051 06Standard Test Method forRubber Compounding MaterialsBenzothiazyl Disulfide(MBTS)Assay1This standard is issued under the fixed designation D 5051; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las
2、t revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 titration of freeio
3、dine 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 t
4、hisstandard.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.2.
5、Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterD 4483 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 fre
6、e 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 reacted.4. Sign
7、ificance 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 q
8、uality 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, having a sens
9、itivity 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,where such sp
10、ecifications 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 reag
11、ent water as definedby Types I, II, or III of Specification D 1193.7.3 Acetic Acid, 100 %, analytical reagent.7.4 Isopropanol, analytical reagent.7.5 Toluene, analytical reagent.1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommitte
12、e D11.11 on Chemical Analysis.Current edition approved Oct. 1, 2006. Published October 2006. Originallyapproved in 1990. Last previous edition approved in 2002 as D 5051 02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For A
13、nnual 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 Societ
14、y, 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 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Uni
15、ted States.7.6 Potassium Iodide (KI), analytical reagent.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 volumes isopropanol with 3 volumesto
16、luene.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 thenearest 0.1 mg and carefully transfer i
17、t to a 300-cm3Erlenm-eyer 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 will nowbe dissolved.9.4 Immedia
18、tely 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 as acetic acid isadded. If allowe
19、d 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(see 7.7) required for titra-tion
20、 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 of the sample and11.1.2 Results o
21、btained 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 D 4483. Please refer to this practicefor terminology and other statistical calculation details.12.2 The
22、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 rejection testing or any group o
23、fmaterials 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-ries participated in the ITP cond
24、ucting 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 second of theduplicates. A compl
25、ete statistical analysis according to D 4483was 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 values for MBTS.12.4 The D 4483
26、analysis revealed that one of the labora-tories 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 methodhas been established as the va
27、lue 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 reproducibility R, of this testmetho
28、d 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 populations.12.7 BiasIn test meth
29、od 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 be deter-mined.13. Keywords13
30、.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 Value (a) Sr r (r) SR R (R)IRM-
31、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 deviationR = reproducibility, in
32、measurement units(R) = reproducibility (relative) in percentD5051062ASTM 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 determination of the validity of any
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