One‐Pot Melt Polycondensation for Upcycling Degraded Poly(butylene succinate) Into Intrinsically Flame‐Retardant Polyesters

ABSTRACT Aiming at the issue of resource waste associated with waste poly(butylene succinate) (PBS), this work proposes the direct utilization of waste polymers as reaction raw materials for upcycling to produce high‐value polyesters with flame‐retardant properties. The flame‐retardant structures were covalently incorporated into the PBS molecular chains through a one‐pot melt polycondensation process to concurrently achieve flame‐retardant enhancement and an increase in the molecular weight of waste PBS. Adding 10 mol% CEPPA into PBS significantly enhanced flame retardancy by increasing the limiting oxygen index from 21.0% to 29.9% and enabling the material to achieve a UL‐94 V‐0 rating with no dripping, demonstrating an efficient gas‐solid phase synergistic effect. Meanwhile, the viscosity‐average molecular weight increased significantly from 26 kDa for the waste PBS to over 42 kDa, demonstrating the exceptional efficacy of this approach in reconstructing degraded PBS segments. This work presents a viable strategy for upcycling waste PBS into functional polyesters that exhibit superior thermal, mechanical, and flame‐retardant properties.