Low-energy electron beam-induced cationic polymerization with onium salts

Demand for higher polymer performance with very short cure times has result ed in the development of low energy electron beam processes. This article p resents the results of such a process for curing two epoxy systems, namely 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylate and di-glycidy l ether of bisphenol A (DGEBA), using the cationic photoinitiator salts, tr iarylsulfonium hexafluoroantimonate, and diaryliodonium hexafluoroantimonat e, respectively. Glass transition temperature measurements were done using a modulated DSC method while the degree of conversion was measured using FT IR spectroscopy. Results indicate that for both epoxy systems a relatively low dosage of not more than 5 Mrad was sufficient to achieve up to 60% conv ersion, with up to 80% conversion achievable using 30 Mrad. The diaryliodon ium salt appeared to be more effective than the sulphonium salt in the abov e study. The effect of varying photoinitiator concentration and the resulti ng glass transition temperature has been studied. (C) 2001 John Wiley & Son s, Inc.