A Bio‐Based Branching Agent for Preparation of Crosslinked Poly(Butylene Succinate‐Co‐Terephthalate): Synthesis, Thermo‐Mechanical and Rheological Properties

To improve the mechanical strength, melt strength, and degradation performance of PBAT,a novel bio‐based polyalcohol branching agent (BA) was synthesized through a three‐step reaction using isomannide (1,4:3,6‐dianhydromannitol) as the precursor. This agent was subsequently employed to fabricate long‐chain‐branched poly(butylene succinate‐co‐terephthalate) (LCB PBAT) copolyesters via branching modification. The chemical structure of LCB PBAT was systematically characterized by 1 H NMR and 13 C NMR spectroscopy, while its thermal, mechanical, and rheological properties were comprehensively evaluated. Results demonstrate that the incorporation of a minor BA addition (0.2–0.8 mol%) significantly enhanced key thermal and mechanical parameters, including glass transition temperature (up to −25.1°C), melting point (up to 131.2°C), crystallization temperature (up to 103.2°C), and tensile strength (up to 23.26 Mpa). Notably, the crystallinity of LCB‐PBAT remained largely unchanged compared to linear PBAT. Rheological analyses revealed substantial improvements in melt processability, with the modified PBAT demonstrating a reduced loss tangent angle, enhanced elastic energy storage, and increased melt strength.