Influence of post-curing on solid state¹³C NMR spectra of electron beam-irradiated epoxy resins

In this work, difunctional epoxy resins were cured using electron beam (EB) irradiation. After EB curing, the specimens were cured thermally and the effect of post-curing on the network structure was investigated using nuclear magnetic resonance (NMR) spectroscopy. Decreases in the abundances of extant oxirane and secondary alcohol groups after post-curing were confirmed from analyses of solid-state ¹³C NMR spectra. These phenomena could be explained by the fact that the crosslinking density increased through the re-cross-linking that occurred during post-curing. In terms of the cure mechanism we believe that the main cure reactions during EB curing were the reactions mediated by the protonic acids and oxonium cations.