Biobased Phosphorus-Nitrile Flame Retardant from Vanillin for Thermoplastic Poly(ester ether) Elastomers: Enhanced Fire Safety and Antidripping Performance

Thermoplastic poly(ester ether) elastomers (TPEE) are renowned for their exceptional mechanical strength and thermal stability. However, their intrinsic flammability and severe melt dripping behavior limit their application in safety-sensitive contexts. To address these challenges, phosphorus-containing flame retardants have emerged as a promising solution due to their superior flame retardant efficacy. In this study, a novel bioderived phosphorus-nitrile flame retardant, DMVP, was synthesized from renewable vanillin and subsequently introduced into TPEE through melt blending processes. Notably, the modified composites demonstrated excellent flame resistance and antidripping performance, achieving a UL-94 V-0 rating and a limiting oxygen index of 30.5% with the incorporation of 20% DMVP. Furthermore, the TPEE/20DMVP showed a 21.4% decrease in peak heat release rate and a 25.3% reduction in total heat release compared to neat TPEE in cone calorimetric tests. These improvements in flame retardancy and antidripping properties of the TPEE/DMVP composites can be attributed to a synergistic flame retardant mechanism operating in both the gas phase and condensed phase, including free radical termination chain reactions and dilution effects in the gas phase, as well as catalytic charring effects in the condensed phase, which are further augmented by the chemical cross-linking of nitrile groups. Hence, this multifaceted synergistic flame retardant strategy provides an efficient approach for developing high-performance and fire safety polymers.