1, 3‐Propanediol (PDO)-based biodegradable copolyesters with elevated Tg, improved mechanical properties and spinnability as intrinsic alternatives to PBAT

Commercial poly(butylene adipate-co-terephthalate) (PBAT), a biodegradable aromatic–aliphatic copolyester, is considered a promising alternative to conventional plastics in various fields. However, its relatively low mechanical strength and low glass transition temperature (T g ) often restricts broader applications. In this study, bio-based 1,3-propanediol (PDO) was employed to completely replace 1,4-butanediol in PBAT, and a series of poly(trimethylene terephthalate- co -trimethylene adipate) (PPAT) copolyesters were synthesized via melt polycondensation. Structural characterization confirmed the targeted copolyester compositions and random chain segments (R ≈ 1), with intrinsic viscosities of 0.89-1.01 dL/g. Crystallographic analysis revealed that the crystallinity of PPATs varied with the adipic acid/dimethyl terephthalate molar ratio while preserving a monoclinic crystal structure. Notably, PPAT55 exhibited a significantly higher T g (−7.8 °C) than PBAT (−26.1 °C), and all copolyesters showed good thermal stability for melt processing. Importantly, PPAT55 fibers achieved a tensile strength of 0.71 cN/dtex after threefold drawing, representing a 51.06% enhancement over PBAT fibers. Furthermore, the increased aliphatic segment content promoted by hydrolytic susceptibility, as demonstrated by enzymatic degradation tests, with PPAT55 showing a 9.93% mass loss after 42 days, demonstrating satisfactory biodegradability comparable to PBAT. The degradation mechanism was further elucidated at the molecular level through theoretical calculations. This work provides a feasible strategy for developing high-performance sustainable polyester materials with good spinnability.