Hydrophilic and Biodegradable PBAT Copolyesters Prepared from Chemically Recycled Resources

Poly(butylene adipate-co-terephthalate) (PBAT) is the most extensively researched and developed biodegradable material. Its application in the production of garments, packaging, and films is limited due to the lack of polar groups on its surface. To address the issue of insufficient hydrophilicity of PBAT, this paper presents modified PBAT that incorporates a hydrophilic chain segment (polyethylene glycol, PEG) during the polycondensation process. Regenerated bis(hydroxybutyl)terephthalate (BHBT), a precursor material for the synthesis of biodegradable PBAT, was produced through the chemical alcoholysis of poly(butylene terephthalate) (PBT). Hydrophilic PBAT was then prepared by condensation polymerization with recycled BHBT, BHAT (dihydroxybutyl adipate), and PEG. It has been demonstrated that the successful doping of hydrophilic PEG into the main chain of PBAT improves its hydrophilicity. This leads to a decrease in elongation at the break and tensile strength. Additionally, the contact angle decreases to 46.71°, while the surface free energy (γs) increases to 42.99 mJ/m2. Hydrophilic PBAT copolyesters exhibit an increase in gas permeability, with the highest permeability coefficient of water vapor (OSFWV = 1.358). In the visible light range of 400–800 nm, PBAT copolyesters exhibit higher transmittance than PBAT materials, resulting in greater transparency. Additionally, R-PBAT has a higher loss modulus and energy storage modulus than the PBAT copolyester in the range of 0.1–100 rad/s. The inclusion of PEG chain segments enhances the melt fluidity of the PBAT copolyester, facilitating processing. While over the course of 30 days, the addition of PEG had an effect on the degradation rate of PBAT, which remained at 34.44%.