The effect of curing cycles on curing reactions and properties of a ternary system based on benzoxazine,epoxy resin,and imidazole

A ternary blend (BEM) of benzoxazine (BA‐a), epoxy resin (E44), and imidazole (M) was prepared to study the effect of different curing cycles on curing reactions and properties of cured resins. Reactivity of two binary blends, E44 and BA‐a, with the catalyst M, was first investigated based on the curing kinetics. Results suggest that E44/M has lower reaction activation energy than BA‐a/M meaning the reaction of E44/M easily proceeds. To further figure out the sequences of the curing reactions of E44, BA‐a, and M in BEM, the curing behaviors of three BEM gels at 80, 140, and 180°C (defined as BEM‐80g, BEM‐140g, and BEM‐180g) were studied by DSC and FTIR techniques. For BEM‐80g, E44/M cured before BA‐a/M. For BEM‐180g, both curing reactions occurred simultaneously and the copolymerization of BA‐a and E44 was promoted. The crosslinked structures of cured BEM with different initial curing temperatures were strongly influenced by the reaction sequences. The T_gs, flexural properties and thermal stability of the copolymers with different curing cycles were compared. Good performance of this ternary system can be obtained by choosing suitable curing cycles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013