1.1 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
1.2 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.
1.3 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.
1.4 The methods do not distinguish thiurams and dithiocarbamates derived from the same amines.
1.5 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.
1.6 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.
1.7 Some compounding ingredients may interfere with method B. In such cases methods A or C shall be used.