Durably Flame‐Retardant Thermoplastic Poly (Ester Ether) Elastomers Modified by a Novel Bio‐Based Macromolecular Flame Retardant

To expand the application of thermoplastic polyester elastomer (TPEE), it is crucial to improve its flame retardancy. To do this, a novel bio‐based macromolecular flame retardant, PDVPA, was created from renewable vanillin, incorporating both Schiff base and spirocyclic diphosphate units. PDVPA demonstrates excellent thermal stability, with an initial decomposition temperature ( T 5% ) of approximately 330°C, ensuring it remains stable during composite processing without experiencing premature degradation. Moreover, PDVPA exhibits good interfacial compatibility with the TPEE matrix, allowing for even dispersion within the polymer. When incorporated at 20 wt% PDVPA, the TPEE/20PDVPA composite achieved a limiting oxygen index (LOI) of 30.2% and a UL‐94 V‐0 rating. Notably, its flame‐retardant properties stay intact even after 1 week of water immersion. The condensed‐phase flame‐retardant mechanism involves a synergy of char formation, driven by phosphorus‐containing acids from phosphodiester decomposition, along with high‐temperature crosslinking through CN bonds. This process produces dense, continuous char layers that serve as effective protective barriers, minimizing melt dripping during combustion. Overall, this macromolecular flame‐retardant strategy presents a promising approach to enhancing the fire safety of polymer materials.