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

Abstract

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.