High-efficiency flame-retardant epoxy resin using phosphoraphenanthrene/thiazole-based co-curing agent

To alleviate the fire hazard of epoxy resin (EP), an efficient flame retardant (ADM) containing phosphophenanthrene and thiazole groups is synthesized and used as co-curing agent for 4,4 & PRIME;-diaminodiphenyl methane to prepare EP/ADM composites. EP/4 mass% ADM composites with phosphorus content of only 0.25 mass% reach UL-94 V-0 rating and the limiting oxygen index value is high to 35.8%. The results reveal that the peak heat release rate, total smoke production, and total heat release of EP/4 mass% ADM composites are reduced by 24%, 14.4% and 16.7%, respectively, in comparison with those of pure EP. The improvement in flame retardancy is mainly attributed to the decomposition of DOPO which produces HPO & BULL; and PO & BULL; to capture the reactive radicals in the gaseous phase. The thiazole group releases hindered amine groups and inactive gas with a dilution effect in the gaseous phase thus further enhancing the effect of the phosphophenanthrene group. Besides, ADM helps to increase the glass transition temperature (T-g) of EP/ADM composites, which is 176 & DEG;C for EP/4 mass% ADM composites, which is higher than the value (172 & DEG;C) of EP.