Effect of Silica Fillers on the Curing Reaction of Epoxy-imidazole Thermoset Resin

Epoxy-imidazole thermosetting resins undergo a complex reaction mechanism when heated, involving two simultaneous processes: exothermic addition polymerization and endothermic reactions, during which the catalyst, imidazole, is regenerated. Consequently, the relationship between conversion and glass transition temperature (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$T_{\mathrm{g}}$</tex>) varies depending on the curing conditions. In this study, we examined the effect of silica fillers on the properties of epoxy-imidazole systems. Fast scanning calorimetry indicated that the reaction in silica filler-containing samples is delayed. Molecular dynamics simulations revealed that epoxy groups tend to localize near the OH groups on the silica filler surface, suggesting that polymer chain growth is suppressed due to the strong interaction between epoxy groups and OH groups of silica. This research provides valuable insights into the epoxy-imidazole reaction mechanism, facilitating further material development and enhancing its industrial applications.