ABSTRACT Although epoxy resins (EP) have been widely used in many fields, performing halogen‐free flame‐retardant modification on them while improving their mechanical properties still holds significant research value. Herein, a halogen‐free P/N/B‐containing modifier (DVB) was synthesized via mild nucleophilic substitution, esterification, and Schiff base reactions using diphenylphosphinyl chloride, vanilline, phenylboronic acid, and 3‐amino‐1,2‐propanediol as precursors. Its efficacy on bisphenol A epoxy resin/4,4′‐diaminodiphenylmethane thermosets was systematically evaluated, with comparisons to a phosphorus‐only intermediate (DV). At 3 wt% DVB loading (0.18 wt% P content), the modified EP exhibited a limiting oxygen index of 28.5% and achieved UL‐94 V‐0 classification. Relative to pristine EP, EP/5% DVB demonstrated a reduction of 41.8% in peak heat release rate, 27.7% in total heat release, and 30.0% in total smoke production, outperforming EP/5% DV (17.8%, 15.8%, and 12.2% reductions, respectively). Furthermore, EP/DVB thermosets displayed maximal improvements of 37.0% in flexural strength and 59.4% in impact strength, coupled with a glass transition temperature retention rate of 98%. Collectively, DVB presents considerable application potential for synergistically enhancing the flame retardancy and mechanical performance of epoxy resins.
Liu et al. (Tue,) studied this question.