Layer-by-layer assembly of nanomultilayer structures: Reinforcement of expanded char reduced the toxicity and fire hazard of epoxy resins

Abstract

Epoxy resins (EP) have been widely applied in chemical engineering, composite materials, and aerospace. Nevertheless, the high fire hazard of flammable epoxy resins, which release considerable hazardous substances and heat during combustion, limits their further application. In this work, a hierarchical structure (Gr/BPA@Si) based on graphene (Gr) assembled with hexagonal boron nitride nanosheets (h-BN) modified with polyaniline (PANI) and epoxy-based polyhedral oligomeric sesquisiloxane (EPOSS) was rationally combined with the conventional P-N-C intumescent system to construct an EP flame retardant. Concretely, the peak heat release rate (PHRR) and total heat release (THR) of the EP matrix incorporating 2 wt% Gr/BPA@Si (Gr/BPA@Si/EP) decreased by 26.7 % and 28.3 %, respectively, and the limiting oxygen index (LOI) increased from 24.7 % to 31.8 %. Moreover, the peak smoke production rate (PSPR) and total smoke release (TSP) were reduced by 27.8 % and 24.7 %, respectively, reflecting attenuated fire toxicity. Mechanistic investigation reveals that the enhanced flame retardancy and smoke suppression properties of the polymers were due to the synergistic effect of Gr/BPA@Si nanosheets and P-N-C intumescent system during the combustion process. This work presents a promising strategy for the development of polymer composites with high fire resistance and smoke suppression capability through the physical barrier effect formed by expansion.