Epoxidized Safflower Oil, Glycerol, and Polyethylene Glycol-Modified Tapioca Starch and Poly(butylene adipate- co -terephthalate)-Based Blown Films: A Comparative Study on Its Preparation and Applications

Biodegradable poly(butylene adipate-co-terephthalate) (PBAT)/starch blends are promising alternatives to conventional plastics, although poor interfacial compatibility limits their applications. In this study, PBAT/starch and PBAT/thermoplastic starch (TPS) films containing glycerol, polyethylene glycol, and epoxidized safflower oil (ESFO) were prepared via direct melt blending and a two-step TPS process. Fourier transform infrared spectroscopy and solid-state 13C CP-MAS NMR analyses confirmed reactive compatibilization between ESFO, starch/TPS, and PBAT phases. The TPS-assisted route generated finer and more homogeneous morphologies, while ESFO reduced phase separation and improved interfacial adhesion. Consequently, ESFO-modified films exhibited superior tensile strength (∼26 MPa), elongation at break (∼655%), seal strength (∼14 N/in), lower water vapor permeability (∼2.2–2.5 mg mm/m2 day Pa), and improved viscoelastic behavior and thermal stability. Soil degradation studies further demonstrated the environmental compatibility of the developed films. The results provide valuable insights into the role of additives and processing routes in designing biodegradable PBAT/starch-based packaging materials.