Curing reaction and phase behavior of bismaleimide-polyethersulfone multi-phase system

The curing process and curing kinetics of bismaleimide-polyethersulfone (BMI-PES) multi-phase systems were investigated by DSC using the non-isothermal method at different heating rates. The apparent activation energy and the pre-exponential factor of the curing BMI-PES resin systems were calculated by Kissinger method, and the reaction series were computed by means of Crane formula, and the kinetic equation was concluded. The curing reaction kinetics formula of BMI-PES resin was presented and validated with the homologous experiment. The microphase structure evolution of the curing BMI-PES resin systems with the curing temperature as well as curing time was investigated by SEM. The results indicate that autocatalytic phenomenon exists in the curing reaction process of BMI-PES system and PES resin participates in the curing process of BMI resin. With the increasing of the heating rate of BMI-PES, the curing characteristic temperatures of BMI-PES systems shift toward higher temperature values while the curing enthalpy values are almost constant. With the increasing of the PES content, the curing rate increases accordingly, while the enthalpy decreases, and the curing peak temperature is almost constant. Based on the curing kinetics study, the apparent activation energy of BMI-PES curing reaction increases while the pre-exponential factor and the reaction series are not changed. The curing process of the curing reactions follows the first order reaction. The experimental cure degree is fitted highly well with the theoretical one in the initiation of curing reaction at 200℃. The SEM results suggest that phase inversion structure exists in BMI-PES resin system after 180℃.