Study on the Synthesis and Properties of Biodegradable Poly(butylene diglycolate) Polyester

With increasing environmental requirements, biodegradable polymers have received widespread attention. Herein, we synthesized a series of poly(butylene diglycolate)s (PBDs), which was a novel biodegradable homopolyester, with number-average molecular weight (Mn) values between 13 and 97 K g·mol–1. The effects of Mn on the thermal and tensile properties of PBDs were comprehensively investigated. The glass transition temperature (Tg), melting temperature (Tm), and temperature of 5% weight loss (Td,5%) of PBDs were found to be approximately −26.4, 64.0, and 336 °C, respectively. PBD with 31 K g·mol–1 exhibits a brittle fracture feature, while obvious yielding behavior occurs when the Mn of PBD is higher than 45 K g·mol–1. Besides, PBD achieves stable mechanical properties when Mn reaches 51 K g·mol–1, with the elastic modulus, tensile strength, and elongation at break of 285, 27.1 MPa, and 290%, respectively, superior to those of linear low-density polyethylene (LLDPE). Furthermore, the crystal structures of PBD were recorded by WAXD and POM. The spherulites were observed after isothermal crystallization of PBD in a wide temperature range, and the maximum nucleation density was obtained after annealing at 20 °C. Significant hydrolysis of PBD in both buffer solution and artificial seawater was confirmed by monitoring the changes in residual weight, intrinsic viscosity, surface morphology, crystallinity, and chemical composition. Finally, PBD exhibits considerable biodegradability under composting and freshwater environments, with the residual weight reducing to 49.2 and 94.7% after 35 days, respectively. Due to the balanced mechanical and barrier properties and biodegradability, PBD has potential application prospects in packaging materials.