Green flame retarding bismaleimide resin with simultaneously good processing characteristics, high toughness and outstanding thermal stability based on a multi-functional organic boron compound

Multi-function and green are two keywords of developing new flame retarding thermosetting resins, however, to achieve this target is still a big challenging today. Herein, a new kind of flame retarding bismaleimide resins with simultaneously good processing characteristics, high toughness and outstanding thermal stability were prepared by copolymerizing 4,4′-bismaleimidodiphenylmethane (BDM) with allyl triphenylborate (ATPB). The structure and integrated performances of BDM/ATPB resins were systematically studied and compared with the BDM/o,o′-diallylbisphenol A resin (coded as BD) that is almost known to be the best modified bismaleimide resin available. Results show that BDM/ATPB resins are solids with low softening points; they can be dissolved in acetone and have wide processing window, completely overcoming the poor processing characteristics of BDM. The properties of the BDM/ATPB system are dependent on the molar ratio of imide and allyl groups, and BDM/ATPB3 resin of which the molar ratio of imide to allyl groups (1:0.85) is the same as that of BD resin not only has significantly improved flame retardancy, reflected by obviously longer time to ignition, 1.5-3.0 times higher fire performance index, and greatly decreased heat releases, but also has about 10 °C higher initial decomposition temperature in both air and nitrogen atmospheres as well as about 1.2-1.3 times higher impact and flexural strengths, clearly demonstrating that ATPB is a multi-functional and green modifier for bismaleimide. The origin behind these attractive results of BDM/ATPB resins was intensively discussed.