ASTM D 4936 - 10 (Reapproved 2015) Standard Test Method for Mercaptobenzothiazole Sulfenamide Assay by Reduction/ Titration

Current edition approved June 1, 2015. Published September 2015. Originally approved in 1989. Last previous edition approved in 2010 as D4936 – 10. — 8 p.
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)2,3 or 2-mercaptobenzothiazole.
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.
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).