Construction of porous g-C3N4@PPZ tubes for high performance BMI resin with enhanced fire safety and toughness.

• Innovation: novel g-C 3 N 4 @PPZ to promote flame retardant and toughness of BMI. • High-efficiency: PHRR and TSPR of BMI/g-C 3 N 4 @PPZ2.0 reduced by 52.1%, 53.8%. • The best impact strength of BMI/g-C 3 N 4 @PPZ increased by 184.0%. • Mechanism: the flame retardant and toughening mechanism was proposed. It's acknowledged that the inferior toughness of bismaleimide resin (BMI) is the crucial problem hindering its development and application especially in aerospace, mechanical and electronic fields. While the poor fire safety of toughened BMI is another problem urgently needed to be resolved. Therefore a novel g-C 3 N 4 @PPZ hierarchical architecture constituted of porous g-C 3 N 4 tubes modified by polyphosphazene was designed and fabricated to improve the fire safety and mechanical properties of BMI in this work. Especially compared to pure BMI, the peak heat release rate (PHRR) and peak smoke production rate (PSPR) of BMI with an incorporation of 2 wt% g-C 3 N 4 @PPZ (BMI/g-C 3 N 4 @PPZ2.0) are at 246.3 kW/m2 and 0.12 m2/s accompanying with 52.1% and 53.8% reduction respectively. The total heat release (THR) and total smoke production (TSP) of BMI/g-C 3 N 4 @PPZ2.0 are endowed with reductions of 29.4% and 42.9% as well, which demonstrates that the fire safety including heat and smoke hazards of BMI/g-C 3 N 4 @PPZ2.0 is significantly improved. With regard to the mechanical performance of BMI composites, the impact strength of BMI/g-C 3 N 4 @PPZ1.5 is 18.89 kJ/m2 which increases by 184.0% in comparison with that of pure BMI resin (6.65 kJ/m2). And it's found that the impact strength of BMI/g-C 3 N 4 @PPZ are still higher than pure BMI in hot-humid environment, which signifies that the BMI/g-C 3 N 4 @PPZ would be preferred in the industrial applications. Meantime the possible flame retardant and toughening mechanism of g-C 3 N 4 @PPZ in BMI is detailed investigated and proposed as well. [ABSTRACT FROM AUTHOR]