Synthesis of a novel type of high-efficiency boron-containing Schiff base flame retardant for epoxy resin

Boron-containing Schiff base flame retardant ((E)-2-([2,4-dihydroxybenzylidene]amino)ethyl dihydrogen borate (B-HIBD) was prepared easily and successfully. Thermogravimetric analysis (TGA) showed that when the additive amount was only 3 wt%, the introduction of B-HIBD significantly improved the thermal stability of epoxy resin (EP) composites. The cone calorimeter test showed that compared with pure EP, the peak of heat release rate (PHRR), total heat release (THR), smoke production rate (SPR)，total smoke production (TSP) ，and the releasing of CO for 3 wt% B-HIBD/EP reduced by 58.2, 18.3, 65.9, 51.2, and 28.4%, respectively, showing that B-HIBD could significantly enhance the fire safety of EP composites. This promotion has been embodied not only in the catalysis function of the Schiff base group containing benzene ring but also in borate participating in the carbon-forming process, promoting the dehydration and carbonization of the EP surface and delaying the transfer of mass and heat in the combustion process, which enhance performance for flame retardant. So it is an efficient strategy to develop a novel type of high-efficiency boron-containing Schiff base flame retardant to improve the fire safety for EP.