REACTIONS OF 2-(4-MORPHOLINOTHIO)BENZOTHIAZOLE AND 2-(4-MORPHOLINODITHIO)BENZOTHIAZOLE IN THE PRESENCE OF POLYISOPRENE

2-(4-Morpholinothio)benzothiazole (MOR) and 2-(4-morpholinodithio)benz othiazole (MDB) were reacted, in combination with sulfur and ZnO, in t he presence of polyisoprene (IR). Samples were heated in a DSC at 2.5 degrees C/min and characterized by swelling experiments. The products formed at various temperatures were analyzed by HPLC. Crosslinking onl y occurred once all the benzothiazole sulfenamide had been consumed, t he onset of vulcanization characterized by a considerable increase in 2-mercaptobenzothiazole (MBT) concentration. Crosslinking occurred ear lier in all corresponding MDB formulations. Higher crosslink densities were recorded with addition of ZnO. The delayed action experienced in MOR systems was attributed to an exchange reaction between benzothiaz ole-terminated pendent groups and MOR and not due to the stability of the disulfide, MDB. (C) 1997 John Wiley & Sons, Inc.