Synthesis of Phosphorus-Nitrogen Synergistic Flame Retardant Containing Pyrimidine Ring/Vanillin for Improving Flame Retardancy, Smoke Suppressing, and Mechanical Properties of Epoxy Resin

In order to improve the flame retardancy, smoke suppressing, and mechanical properties of epoxy resins (EP), while pursuing low toxicity, environmental protection, and sustainable development, a reactive biobased flame retardant (TVD) containing P/N was synthesized by the one-pot method. The flame retardant, consisting of vanillin, 2,4,6-triaminopyrimidine, and DOPO as reactants, contained reactive groups in its structure and was introduced as a co-curing agent into the DDM-cured EP system. EP/TVD10 (at a phosphorus content of 0.58 wt%) achieved a UL-94 V-0 rating with an increased limit oxygen index (LOI) value of 34.2% (26.5% for pure EP), and the cone calorimetric test (CCT) results showed a decrease in total heat release (THR) values of 33.8% and a decrease in total smoke production rate (TSP) of 21.1% compared to pure EP. In addition, the introduction of TVD improved the mechanical properties of the epoxy resin, with an increase in flexural strength and modulus of 8.7% and 6.5% and a slight increase in impact toughness for EP/TVD10. These results indicate that TVD is a multifunctional and efficient bio-based flame retardant, which provides new ideas for the development of high-performance modified epoxy resin materials.