Novel phosphorus-containing polyhedral oligomeric silsesquioxane designed for high-performance flame-retardant bismaleimide resins

A novel phosphorus-containing polyhedral oligomeric silsesquioxane (P-POSS) was developed, and incorporated into O, O′-diallylbisphenol A-modified bismaleimide (DBMI) to prepare slightly foaming flame-retardant materials (P-POSS/DBMI). The curing reaction, mechanical properties, thermal stability and flame retardancy of P-POSS/DBMI were systematically studied. The result of dynamic FTIR confirmed that the P-POSS could participate in the curing reaction of DBMI. In addition, it was proved that the material with a very low content of the P-POSS exhibited remarkably improved thermal stability and flame retardancy. When 6.0 wt.% P-POSS was introduced into DBMI matrix, char yield at 800 °C increased by ~31.5 %, meanwhile UL-94 V-0 rating and 35.4 LOI (limiting oxide index) were also obtained. And compared with DBMI, the flexural strength and impact strength of 6.0 wt.% P-POSS/DBMI were enhanced 42.3 % and 30.8 %, respectively. Interestingly, the impact strength of 2.0 wt.% P-POSS/DBMI increased to 30.5 kJ/m², about 136 % higher than that of DBMI.