Dual modification of graphene by polymeric flame retardant and Ni(OH) 2 nanosheets for improving flame retardancy of polypropylene

To improve its dispersion and flame retardant efficiency, graphene oxide (GO) is dually modified with polymeric flame retardant and the nanomaterial with catalytic carbonation ability. Via the reactions between oxygen functional groups in GO and PCl groups in hexachlorocyclotriphosphazene, phosphazene-based flame retardant is grafted to GO. Due to the strong affinity of Ni2+ with NH2 groups in this phosphazene flame retardant, the decoration of Ni(OH)2 nanosheets on the graphene is facilitated. Transmission electron microscopy images confirm good dispersion and exfoliation state of graphene in polypropylene (PP) matrix. The incorporation of functionalized graphene oxide (FGO) results in the reduction of peak heat release rate, total heat release and smoke release of PP during the combustion. Flame mechanism of FGO is concluded according to the results of thermal decomposition and char analysis. This work provides a novel modification strategy for enhancing the dispersion and flame retardant efficiency of graphene.