The reactions of 2-(4-morpholinothio)- and 2-(4-morpholinodithio) benzothiazole in the absence of polyisoprene

2-(4-morpholinothio)benzothiazole (MOR) and 2-( 4-morpholinodithio) benzoth iazole (MDB) were heated with sulfur and ZnO in a DSC. The products formed at various temperatures were identified and analyzed by HPLC. At temperatur es below 200 degrees C, decomposition of the accelerator in the absence of other curatives was slow, degradation products being mainly 2-bisbenzothiaz ole-2,2'-disulfide (MBTS) and 2-mercaptobenzothiazole (MBT). A rapid exothe rmic decomposition above 200 degrees C resulted in the formation of MBT (or its amine salt) and 2-(4-morpholino)benzothiazole (MB). MOR and MDB reacte d with sulfur to form higher polysulfides. MDB was shown to react more read ily with sulfur than MOR and the delayed action of MOR in rubber can theref ore not be ascribed to a stable polysulfide as suggested by other authors. Neither MOR nor MDB was found to react with ZnO. A limited reaction between MBT and ZnO was observed. (C) 1999 John Wiley & Sons, Inc.