Facile construction of polypyrrole microencapsulated γ‐Fe2O3 for simultaneously enhancing the flame retardancy and smoke toxicity suppression of intumescent flame‐retardant epoxy resins

Abstract

AbstractFor effectively strengthening the comprehensive properties of intumescent flame‐retardant epoxy resins (EPs), a microencapsulating γ‐Fe2O3 by polypyrrole (PPy) named PPy‐Fe2O3 was synthesized and used as a synergist to simultaneously enhance the flame retardancy, smoke toxicity suppression and mechanical strength of EP composites containing diaminodiphenylmethane modified ammonium polyphosphate (DDP). The results demonstrate that the mixture of PPy‐Fe2O3 and DDP exhibits a surprising synergistic effect on strengthening the comprehensive properties of EP composites. Specifically, EP composite containing 0.2 wt% PPy‐Fe2O3 and 9.8 wt% DDP achieves the UL94 V‐0 rating with a limiting oxygen index (LOI) value of 35.5%, while 10 wt% DDP only imparts a UL94 V‐1 rating and a LOI value of 34.0% to EP. Furthermore, 0.2 wt% PPy‐Fe2O3 shows a 11.0% reduction in peak smoke production rate and a 12.3% reduction in peak heat release rate of the EP/DDP system. The enhanced fire security of EP/DDP/PPy‐Fe2O3 is attributed to the formation of more phosphorus‐rich structures retained in the char, thus reducing the release of harmful gases including NH3, CO, and CO2, and generating more incombustible gases including H2O to weaken burning intensity. Meanwhile, the satisfactory compatibility of PPy‐Fe2O3 with epoxy matrix imparts a superior mechanical strength to EP composites.