Bismaleimide with high thermal stability, toughness and flame retardancy modified by synergistic hyperbranched flame retardant

Usually, the incorporation of traditional linear molecule flame retardant will bring negative impact on the thermal stability of bismaleimide (BMI), which limited the application of BMI in high-end fields. Based on this problem, a synergistic hyperbranched polymer (HPTDM) containing phosphorus/nitrogen/silicon was used as a novel flame retardant for cured BMI system. Due to the specific hyperbranched structure, the HPTDM itself had high thermal stability. And the elements of nitrogen, silicon and phosphorus can significantly improve the efficiency of flame retardants through synergistic effects. Surprisingly, the addition of flame retardants did not greatly affect the thermal stability of pure BMI, and the BMI/HPTDM-0.5 with the phosphorus content of as low as 0.05 wt% could achieve a maximum reduction of 34.4% in total heat release (THR). Furthermore, the modified BMI resin demonstrated superior toughness owing to the novel hyperbranched structure, and the impact strength of BMI/HPTDM-1.0 was 90.2% higher than the pure BMI. This article provided a novel strategy for designing hyperbranched flame retardant and promoted the BMI in the field of high temperature.