Sustainable High-Performance Polylactide/Poly(butylene adipate- co -terephthalate) Blend Films via Integrating Interfacial Compatibilization with Biaxial Stretching

Abstract

A sustainable strategy integrating reactive compatibilization with biaxial stretching was developed to produce high-performance polylactide/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blend films. Pentamethylene diisocyanate (PDI) served as a reactive compatibilizer to enhance the interfacial compatibility of PLA/PBAT blends, while the thermo-mechanical field generated by biaxial stretching was utilized to tailor microstructure and properties. It was revealed that PDI significantly improved the stretchability of blends and affected the film surface quality. At low PDI contents, interfacial debonding between PLA and PBAT phases readily occurred, whereas excessive PDI contents promoted fragmentation and cavitation of the dispersed PBAT domains, both of which deteriorated the film quality. In contrast, the blend with 1.5 phr PDI exhibited balanced stress transfer and superior film-forming performance. Increasing the stretching rate further promoted molecular orientation and crystallinity while reducing surface roughness, thereby optimizing the comprehensive properties. The 7.0 × 7.0 biaxially stretched film fabricated with a stretching rate of 60%/s achieved a tensile strength of 113.9 MPa, representing a 172.5% improvement over the unstretched counterpart, while maintaining a high elongation at break of 176.0%. Owing to its dense surface structure and oriented microcrystals, the film exhibited low water vapor and oxygen permeability coefficients of 1.18 × 10–14 g cm/(cm2 s Pa) and 3.72 × 10–16 cm3 cm/(cm2 s Pa), respectively, while retaining high optical transparency of 86%. This work provides valuable insights into the development of PLA/PBAT biodegradable films with simultaneously enhanced mechanical and barrier properties, demonstrating considerable potential for industrial applications.