Flame retardancy, thermal decomposition and mechanical properties of epoxy resin modified with copper N, N’-piperazine (bismethylene phosphonate)

Abstract

A metal–organic phosphonate, i.e., copper N, N’-piperazine (bismethylene phosphonate) (CuPB) was synthesized and utilized to modify epoxy resin (EP). The flame retardancy, thermal decomposition and mechanical properties of EP/CuPB composites are overall evaluated, and the mechanism is tentatively discussed. The results reveal that EP containing 3.0 wt% CuPB (EP/CuPB-3) passes UL-94 V-0 grade with an increased limiting oxygen index of 28.5%. The peak heat release rate, total heat release, total smoke release and peak CO production rate of EP/CuPB-3 in cone calorimeter test are, respectively, reduced by 43.5%, 28.0%, 37.3% and 51.9%, compared to that of pure EP. Besides, a decreased mass-loss rate (16.2% min−1) and an increased char yield (26.8%) of EP/CuPB-3 in the thermogravimetric analysis are achieved as a result of the char-promotion function of CuPB. Satisfactorily, the thermal resistance of EP/CuPB composites is slightly improved with an increased glass transition temperature, and the mechanical properties including tensile and impact strengths are not much affected.