Optimizing Chain Flexibility and Phase Morphology for High-Performance Bio-Based Packaging Films: A Comparative Study of Flexible PBAF Blended with Rigid/Amorphous PISO and Rigid/Crystalline PLGA

Bio-based packaging films face challenges in mechanical toughness, service temperature range, and gas barrier properties, which hinder widespread adoption. This study investigates polymer blends that combine flexible poly(butylene adipate-co-furanoate) (PBAF) with either rigid/amorphous poly(isosorbide succinate-co-oxalate) (PISO10) or rigid/crystalline poly(lactic-co-glycolic acid) (PLGA90) for food packaging applications. A stepwise (2 + 1) copolymerization process proves to be practical and scalable for synthesizing PBAF. PBAF65, selected for its broad service temperature range (−6.7 to 121.7 °C), serves as the flexible matrix in both blend systems. When incorporating 15 wt % content of either PISO10 or PLGA90, the blends show high elongation (∼700%), increased modulus (∼3-fold), and improved barrier properties (oxygen and water vapor BIFs of ∼4.3 and ∼0.7, respectively, compared to HDPE). The rigid/amorphous PISO10 promotes good miscibility with PBAF65 and maintains a high impact strength, in contrast to the reduced impact strength observed with rigid/crystalline PLGA90. Pilot-scale processing of the PBAF65/PISO10(15) film via twin-screw extrusion and blown film extrusion yields excellent dimensional stability, withstanding hot-fill (∼85 °C) and ice contact (∼5 °C) without defects. This study presents a case in which the selection of suitable rigid/amorphous or rigid/crystalline components enables the tailoring of flexible bio-based polymer blends for high-performance packaging applications, particularly in film form.