Abstract

Prevulcanization inhibitors (PVI) provide an important delay in the curing reactions that occur in accelerated sulfur vulcanization. In this study, the reactions of N-(cyclohexylthio)phthalimide (CTP) with other curatives (excluding zinc oxide) were investigated in the presence and absence of rubber. The CTP has been shown to react very readily with 2-mercaptobenzothiazole (MBT) and this reaction has previously been credited with the delay observed. However, recent studies have shown that MBT is not formed until crosslinking has started. In a 2-bisbenzothiazole-2,2′-disulfide (MBTS) accelerated sulfur cure, CTP was shown not to delay the onset of crosslinking, but once crosslinking began, with the concurrent formation of MBT, the CTP reacted with the MBT inhibiting further polysulfide formation, pendent group formation and thus crosslinking. Crosslinking continues after the CTP has been consumed.