Astm D 5051 – 02 pdf free download

Standard Test Method for
Rubber Chemicals—Benzothiazyl Disulfide (MBTS)—Assay1

This standard is issued under the fixed designation D 5051; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of the last revision. A number in parentheses indicates the year of the last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.

1. Scope

1.1 This test method describes the determination of the assay of
benzothiazole disulfide (MBTS). It is based on the titration of free
iodine liberated upon the reduction of MBTS, with potassium
iodide (KI) in an acid medium.

1.2 The assay is determined as a mass percent.

1.3 Free 2-mercaptobenzothiazole (MBT) content is not
determined.

1.4 The values stated in SI units are to be regarded as the
standard.

1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

2. Referenced Documents

2.1 ASTM Standards:
D 1193 Specification for Reagent Water2
D 4483 Practice for Determining Precision for Test Method
Standards in the Rubber and Carbon Black Industries3

3. Summary of Test Method

3.1 In an acid medium, MBTS is reduced with KI to MBT
and free iodine. The free iodine is titrated with a standard sodium
thiosulfate solution.

3.2 MBTS is sparingly soluble in any organic solvent; while
MBT, formed during the reaction of MBTS with KI is very
soluble. Therefore after reagents are added as indicated in the
procedure, continue to stir till all MBTS has reacted.

4. Significance and Use

4.1 The test method is designed to assess the purity of
MBTS, which is used for rubber and latex vulcanization
acceleration. The amount of MBTS is of importance in
predicting performance in rubber compounds and for raw
material purchase and control.

4.2 This test method may be used as a quality control tool