1 This International Standard specifies methods using gas chromatography (GC) and thin layer chromatography (TLC) for the separation and identification of the following classes of accelerators in vulcanized and unvulcanized compounds:
— thiazoles
— sulfenamides
— thiurams and dithiocarbamates
— guanidines
— dithiodimorpholine
2 When 2-mercaptobenzothiazole (MBT) is identified and no sulfenamides are present, it is not possible to establish if the original accelerator was MBT and/or its salts or 2,2'-dibenzothiazoledisulfide (MBTS) as each of these accelerators may be produced from the others during the vulcanization process.
3 When sulfenamides are identified, it is not possible to establish if MBT and/or its salts and MBTS are present as these accelerators may be produced from 2-mercaptobenzothiazole sulfenamides during the vulcanization process.
4 The methods do not distinguish thiurams and dithiocarbamates derived from the same amines.
5 From the morpholine identification it is not possible to determine if the initial accelerator is 2-morpholinothio-benzothiazole (MBS) or dithiomorpholine as morpholine may be formed from MBS and dithiodimorpholine during the vulcanization process.
6 The separation of accelerator compounds from unvulcanized compounds is relatively straightforward whereas separation from vulcanized compounds is difficult due to the lesser ability of solvents to penetrate the vulcanized matrix.
7 Some compounding ingredients may interfere with method B. In such cases methods A or C shall be used.