Bio-based poly(butylene diglycolate-co-furandicarboxylate) copolyesters with balanced mechanical, barrier and biodegradable properties: A prospective substitute for PBAT

Poly(butylene adipate-co-terephthalate) (PBAT) is a flexible aliphatic/aromatic copolyester commercialized for degradable plastics, while the slow degradation rates and poor barrier properties limit its applications. Consequently, it is highly desirable to develop materials with faster degradation rates and enhanced barrier properties. Here, we synthesized poly(butylene diglycolate-co-furandicarboxylate) (PBDF) copolyesters by transesterification and melt polycondensation. The NMR spectra confirmed their structure and composition. Besides, the thermal, mechanical, permeable and degradable properties were characterized thoroughly. It was found that the properties were dependent on chemical composition and crystallinity. Actually, the introduction of diglycolic acid (DGA) comonomer hinders the crystallization and all the copolyesters appear as semicrystalline polyesters except for PBDF80. Among them, PBDF40 possesses outstanding mechanical properties with an elastic modulus of 165 MPa, tensile strengths of 54 MPa, and elongations of break of 654%. Moreover, the CO2 and O2 barrier properties of PBDF40 are 68.6 and 45.9 times higher than those of PBAT. PBDFs also exhibit accelerated rates in hydrolysis and composting degradation, which could be attributed to the enhanced hydrophilicity due to the electronegativity of ether-oxygen atoms in DGA. In particular, the mass loss of PBDF40 reaches 46% and 42% after 28 days of CALB enzymatic degradation and 8 weeks of compost degradation, respectively. These results highlight that the synthesized polyesters, especially PBDF40, demonstrate potential application in food packaging.