THE MECHANISM OF EPDM PEROXIDE VULCANIZATIONS IN THE PRESENCE OF TRIALLYLCYANURATE AS A COAGENT

Using FT-IR spectroscopy as a major tool, the reaction mechanism for E PDM peroxide vulcanisations in the presence of triallylcyanurate (TAC) as a coagent was elucidated. It was established that due to the incom patibility of TAC with the elastomer matrix, the coagent resides in sm all domains. During peroxide vulcanisation polyaddition of TAC molecul es and grafting to the elastomer matrix takes place, followed by therm osetting of coagent domains and covulcanisation of these domains with the elastomer matrix. Polyaddition of TAC proceeds via a cyclopolymeri sation mechanism. Although cyclisation is inefficient with respect to crosslinking, this reaction does not inhibit the formation of coagent bridges, because a third allyl moiety is available for covulcanisation . The formation of coagent bridges is found to be the predominant fact or in increasing the crosslinking efficiency, which implies that suppr ession of macroradical side reactions by the coagent, only plays a min or role.