A Si‐Containing Organophosphinic Acid Salt Endowing Epoxy Resin With Excellent Flame Retardancy, Smoke Suppression, and Toughness

Epoxy resin (EP) exhibits remarkable mechanical properties and notable chemical stability, making it suitable for widespread industrial applications. However, its inherent flammability limits its use in high‐safety environments. To address this limitation, a novel organophosphate flame retardant (DSZ) containing vinylsilazane flexible chains was synthesized for EP modification. The incorporation of 3 wt% DSZ enabled the flame‐retardant EP (FREP) to achieve a vertical combustion (UL‐94) V‐0 rating with a limiting oxygen index (LOI) of 32.4%, confirming high flame‐retardant efficiency. Cone calorimetry tests (CCT) demonstrated a 32.4% decrease in total smoke production for the 5 wt% DSZ formulation, which can be attributed to the synergistic effects of P–N–Si, which also enhanced smoke suppression. These improvements demonstrate the effectiveness of DSZ in elevating the fire safety of EP. Furthermore, the FREP exhibited a 78% increase in impact strength while its flexural and tensile properties remained unchanged. Collectively, DSZ enables simultaneous flame retardancy, smoke suppression, and mechanical reinforcement, significantly expanding the application scope of EP.