Thermal oxidative degradation of cyanate- and amine-cured epoxy resins: Experiment and ReaxFF simulation

Thermal oxidative degradation behaviors of epoxy resin cured with cyanate ester and conventional amine are experimentally evaluated in terms of heat resistance and flame retardancy, and the degradation mechanisms are further investigated using ReaxFF molecular dynamics simulations. Thermogravimetric analysis revealed that both resins exhibit multi-step decomposition behavior, with the cyanate-cured resin showing nearly double the residual weight (char formation) compared to the amine-cured resin. ReaxFF thermal degradation simulations of a fully cured resin model, with and without oxygen, and fragmentation models were performed to elucidate the heat resistance properties associated with different molecular structures. The experimental and simulation results suggest that the degradation follows a two-step process: the first stage involves pyrolysis of the main chain, and the second stage involves oxidation of the resulting products. The high heat resistance of the triazine ring in the cyanate-cured resin delays the transition to the second stage of degradation, resulting in high thermal oxidation resistance.