Dielectric Properties and Kinetic Study on the Degradation of Bismaleimide Resin

Summary Bismaleimide, a thermosetting resin, is attracting interest in the aerospace industry due to its epoxy‐like processability, but better high‐temperature performance than epoxy. As this industry shifts towards using higher overall percentages of fiber‐reinforced polymer‐matrix composites, understanding how these systems degrade, in particular the polymer matrix component, becomes increasingly important. Additionally, these materials are now being exposed to a wider variety of environmental and physical conditions, as new areas of usage, for both primary and secondary roles, are being explored. In this context, the thermo‐oxidative degradation kinetics of bismaleimide are explored. Two model‐free isoconversional methods, the Friedman and Ozawa‐Flynn‐Wall methods, are used to analyze results from thermogravimetric analysis at a variety of heating rates (5, 10, 20, and 50 °C/min) from room temperature to 800 °C. From these methods, the activation energies associated with particular degradation steps have been determined. Additionally, the dielectric properties of the bismaleimide resin were measured as a function of frequency (0.10 Hz to 1 MHz) and temperature (–140 °C to 160 °C) using spectroscopic techniques. One primary dielectric relaxation (gamma) was observed in the temperature and frequency ranges used and modeled using a Havriliak‐Negami model. The associated activation energy of the relaxation was calculated to be 41.31 kJ/mol.