In situ Loaded Nanoscale Red Phosphorus on Mesoporous Silica for Simultaneously Improved Flame Retardancy and Toughness of Epoxy Composites

Nanoscale red phosphorus (NRP) was synthesized via a phosphorus-amine dissolution method and immobilized onto mesoporous silica nanospheres (MSNs) to obtain hybrid NRP@MSN particles with improved dispersion stability. Epoxy resin (EP) composites containing 2 wt% fillers were prepared to evaluate their thermal and flame-retardant behaviors. Compared with EP, the NRP@MSNs/EP composite significantly enhanced fire safety, resulting in a 52.8% reduction in the peak heat release rate, a 13.9% decrease in total smoke production, and a 165% increase in char yield. Mechanical testing revealed a notable toughening effect under impact loading. The improved flame retardancy originates from the combined nano-barrier effect of MSNs and the catalytic charring and radical-quenching functions of NRP. This work demonstrates an efficient strategy for stabilizing NRP and highlights its strong potential as an environmentally friendly flame retardant for EP systems.