A Boron‐Containing Ammonium Polyphosphate for Epoxy Resins with Enhanced Flame Retardancy and Reduced Smoke Release

Epoxy resin (EP) has been widely used in coatings, adhesives, and composites. However, EP is flammable with severe smoke production. The addition of flame retardant fillers into EP can effectively improve its flame retardancy, but often brings mechanical reduction to EP. Herein, a high‐effective boron‐containing flame‐retardant (2‐phenyl‐1,3,2‐dioxaborolan‐4‐yl) methanamine ammonium polyphosphate (PBMA‐APP) is synthesized and introduced into EP to improve the fire resistance and the impact toughness. With the addition of 6% PBMA‐APP, the fire performance of EP is significantly improved. The Underwriters Laboratories‐94 rating is increased to V‐0, the total heat release and total smoke production (TSP) are reduced by 30% and 32%, respectively. It is proposed that the synergistic effect among B, N, and P in PBMA‐APP promoted the char formation of EP. The addition of 6% PBMA‐APP into EP causes little effect on tensile strength but increases the impact strength of EP to 11.2 kJ m⁻². This work has proposed a possible strategy to develop a high‐efficient flame retardant for thermosetting resins.