Curing properties of cycloaliphatic epoxy derivatives

In the cationic ring-opening polymerization of cyclic ethers, three major factors, i.e. ring strain, basicity and steric hindrance, are known to govern the reactivity. Considering from these three factors, cycloaliphatic epoxides seem to be the best candidate for the high performance formulations. In the commercial applications, 3,4-epoxycyclohexyl-3′,4′-epoxycyclohexene-carboxylate (ECC) is widely used as cycloaliphatic epoxy monomer. In ECC polymerization, the possibility of ester group participation was pointed out, which resulted in lower reactivity. The negative effect of ester group seems to be very important issue for improved reactivity.In this study, to clarify the effect of the ester group on the cationic polymerization, two di-functional monomers, 2,2-bis-(3,4-epoxycyclohexyl)-propane (CADE-1) and 3,3′-bicyclohexene-3,3′,4,4′-diepoxide (CADE-2), were selected as candidate for no-ester monomers and their reactivity in the photo-initiated cationic polymerization was investigated. Using photo-DSC and real time DRA method, reactivity comparison of them with ECC was conducted. High curing rate of CADEs, especially for low viscous CADE-2, was confirmed. The curing rate of highly viscous CADE-1 was effectively accelerated by addition of low viscous oxetane monomer.