Novel epoxy formulations for high energy radiation curable composites

It has been widely recognised that high energy radiation can be effectively applied to the cure of epoxy resins in applications as composite matrices or structural adhesives with improvements in product quality and/or reduction in production costs. In the presence of suitable initiators, polymerisation of epoxies occurs via cationic mechanism, thus restricting the choice of the resin system components to species which do not contain electron donor groups. The present investigation is aimed to identify suitable co-monomers to be formulated with an epoxy resin, resulting in different cure reaction kinetics and application properties of the cured resin. In particular, four different anhydride types, three dicarboxylic and one tetracarboxylic, have been formulated at the same weight ratio with a diglydilether of bisphenol F and a photo-initiator. Resin samples, irradiated at different integrated doses, have been characterised with solubility tests, dynamic-mechanical thermal analysis and three point flexural tests, showing a response which is strongly affected by the specific chemical structure of the anhydride co-monomer. Post-irradiation thermal treatments carried out on samples irradiated at the lower dose suggest different reaction patterns, with different controlling factors depending on the activation mechanism (temperature or γ-rays).