Construction of hetero-structured nanohybrid relying on reactive phosphazene towards flame retardation and mechanical enhancement of epoxy resins

Abstract

We design a novel hetero-structured nanohybrid that can significantly improve flame retardancy and mechanical strength of epoxy resin (EP) at an ultralow filler loading. In this nanohybrid (SPGP), mesoporous SiO2 combined with organophosphorus compounds are grafted onto the surface of graphene oxide relying on the interface adhesion of polydopamine. As a result, the molecular chains of EP can be introduced into the channels of mesoporous SiO2 to form an interpenetrating network structure, thus leading to great dispersion of SPGP. In the case of introducing only 1 wt% SPGP, the impact strength of the composite is greatly increased by ∼100%, while the flame retardancy of the material is significantly improved with a high limiting oxygen index of 28%, low heat release, low CO production rate and smoke suppression. Furthermore, the mechanism analysis confirms that mesoporous SiO2, organophosphorus units, and graphene oxide in SPGP can synergistically promote the formation of the denser P–Si-containing hybrid char layer to enhance the barrier effect during combustion, thus suppressing fire hazards of EP. This work provides a new strategy for the design and manufacture of nanohybrids with high flame retardancy, mechanical reinforcement and low toxicity for polymers.