Biaxial Stretching of PBAT/PLA Blends for Improved Mechanical Properties

Biodegradable polymers offer a promising solution to the growing issue of global microplastic pollution. To effectively replace conventional plastics, it is essential to develop strategies for tuning the properties of biodegradable polymers without relying on additives. Biaxial stretching promotes anisotropic crystallization in polymer domains, thereby altering the mechanical performance of polymer blends. In this study, we employed a design of experiment (DoE) approach to investigate the effects of biaxial stretching at three drawing temperatures (Tds) and draw ratios (λs) on a biodegradable blend of poly(lactic acid) (PLA) and poly(butylene adipate-co-terephthalate) (PBAT), aiming to optimize both the strength and ductility. The DoE analysis revealed that the composition, the λ, the interaction between the λ and composition, and the interaction between the Td and composition significantly affect the elongation at break (εBreak). For the stress at break (σBreak), the most influential factors were the interaction between the λ and PLA concentration; a three-way interaction among the λ, PLA, and Td; the Td; the λ; and finally the PLA concentration alone. The optimal εBreak and σBreak were achieved at a λ = 5 × 5 and Td = 110 °C, with a composition of 10% PLA and 90% PBAT. The stretched samples exhibited higher crystallinity compared to the pressed samples across all compositions. This work demonstrates that in addition to the composition, the processing parameters, such as the λ and Td, critically influence the mechanical properties, enabling performance enhancements without the need for compatibilizers or toxic additives.