Epoxy resin (EP) is valued for its adhesion and chemical stability, yet its inherent brittleness and flammability limit advanced applications. To address this, a novel reactive ionic liquid flame retardant, [PMoam]Ps, was developed as a co-curing agent. It integrates into the EP network, significantly enhancing flame retardancy. The modified composite achieves a limiting oxygen index (LOI) of 29.3%, a UL-94 V-0 rating, and shows reductions in peak heat release rate (PHRR) and total heat release (THR) of 35.8% and 38.6%, respectively. Simultaneously, the ionic liquid acts as an internal plasticizer, markedly improving mechanical performance. Compared to neat EP, the composite exhibits increases of 46.1% in tensile strength, 57.4% in flexural modulus, and 87.7% in impact strength. This work provides a promising strategy for developing high-performance epoxy composites with balanced flame retardancy and mechanical properties.
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