This test method is designed to assess the purity of 2-mercaptobenzothiazole sulfenamide accelerators. These products are used in combination with sulfur for the vulcanization of rubber.

The test method is suitable for assessing product specifications in that the property it measures is related to product performance. Since it is the primary property for comparison of product quality at different production facilities, good interlaboratory accuracy and precision is required.

Based on past experience, two significant sources of error in this test method are: (1) incomplete reduction and (2) titration end point assessment. Problems in these areas can be avoided by closely following the procedure.

1.1 This test method covers the determination of assay on mercaptobenzothiazole (MBT) sulfenamides. It is based on a titration of the basic amines liberated upon reduction of the sulfenamides with hydrogen sulfide gas (H₂S) ^, or 2-mercaptobenzothiazole.

1.2 Any free amine (HNR₂) or weak acid salts of the corresponding amine (HX·HNR₂) are titrated prior to reduction. This titer is used to calculate percent basic impurity (as free amine) in the sample.

1.3 With the indicated modifications, this test method is applicable to all MBT sulfenamides, that is, N-cyclohexyl-2-benzothiazolesulfenamide (CBS), N,N-diisopropyl-2-benzothiazyl sulfenamide (DIBS), 2 (morpholinothio) benzothiazole (MBS), N,N-dicylohexyl-2-benzothiazyl sulfenamide (DCBS), N-tert-butyl-benzothiazole-sulfenamide (TBBS), and 4-morpholinyl-2-benzothiazyl disulfide (MBSS).

1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

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. For specific hazard statements, see Section 9.