<scp>EP</scp> ‐modified flame retardant: A new strategy for synergistically enhancing the flame retardancy and mechanical properties of <scp>TPU</scp>

Abstract In this article, EP‐SMAE was synthesized by reacting the reactive groups of bisphenol A diglycidyl ether (DGEBA) with phosphorus‐containing Schiff base derivatives (SMAE) to enhance the fire safety of thermoplastic polyurethane (TPU). The experimental results demonstrated that TPU/5EP‐SMAE achieved a Limiting Oxygen Index (LOI) value of 27.8%, reaching the UL 94 V‐0 classification. Further addition of EP‐SMAE improves the anti‐drip performance of TPU, a benefit that SMAE alone does not provide. The EP modification of SMAE promotes the formation of a denser and more ordered char layer while preserving SMAE's gas‐phase flame inhibition. In TPU, EP‐SMAE demonstrates biphasic flame retardancy and significantly alleviates the negative impact of SMAE on mechanical properties. The tensile strength of TPU/5EP‐SAE was 18.9 MPa, which is higher than the 8.8 MPa of TPU/5SMAE. This study presents an effective method to enhance the flame retardancy of TPU while preserving its mechanical properties. Highlights EP‐SMAE enhanced the fire resistance performance of SMAE in TPU. TPU/5EP‐SMAE reached a LOI of 27.8%, passing UL 94 V‐0 rating. Adding 15EP‐SMAE inhibited the dripping of TPU. EP‐SMAE exerted a dual‐phase flame inhibition effect. EP‐SMAE reduced the adverse impact of SMAE on mechanical properties.