Three birds with one stone: Halogen- and phosphorus-free flame-retardant thermosetting resins with high heat resistance and excellent mechanical properties based on simple biobased feedstocks

The preparation of halogen-free and phosphorus-free flame retardant thermosetting resins from simple biobased feedstocks is important for both environmental sustainability and practical industrial applications. Meantime, high performance thermoset resins need to have excellent heat resistance and mechanical properties. In this paper, the allyl monomers TAMT and TEC with s-triazine rings were synthesized from the basic biobased substrates vanillin and eugenol via simple synthetic route without column chromatographic purification throughout the reaction, and the structures of the monomers were investigated by nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS). Then TAMT and TEC were copolymerized with bismaleimide to produce the thermosetting resins poly(TA/B) and poly(TE/B) . Subsequently, the thermal, mechanical and flame retardant properties of the resins were investigated in detail, meanwhile, possible flame retardant mechanisms had also been put forward. The results showed that the newly produced s-triazine ring thermosetting resins poly(TA/B) exhibited excellent overall performance, specifically in terms of excellent heat resistance and mechanical properties, the glass transition temperature of the newly produced resin was more than 400 °C, and the initial thermal decomposition temperature was 434 °C, poly(TA/B) also exhibited excellent flame retardant properties, with reaching the UL94 V-0 level. The total heat release (THR) value was 6.9 kJ/g, which was much lower than that of the commercial bismaleimide resin (34.5 kJ/g). Using simple biobased feedstocks, halogen-free and phosphorus-free thermosetting resins with excellent heat resistance, mechanical properties, and flame retardancy were produced, which provided ideas and data support for the preparation of green and high-performance thermosetting resins.