Biaxially Stretched, Ribbon-Like PBAT Networks Confer High Strength and Toughness to Polylactic Acid Films

The inherent brittleness of polylactic acid (PLA) severely limits its practical application. Although blending with flexible polymers such as poly(butylene adipate-co-terephthalate) (PBAT) often improves ductility, it typically leads to a significant loss in mechanical strength, representing a long-standing strength-toughness trade-off. To overcome this dilemma, we propose a novel strategy for architecting an in situ PBAT network in the PLA matrix. Critically, a tailored processing protocol combining elongational flow with subsequent biaxial stretching is designed to enable the in situ formation, organization, and stabilization of a ribbon-like PBAT network within the PLA matrix at a low loading. This unique architecture leads to a remarkable combination of mechanical properties in the resultant PLA/PBAT film, which achieves a high tensile strength of 82.6 MPa, yielding a toughness of 120.1 MJ/m3. These values represent simultaneous improvements of 12.8% in strength and 2065.4% in ductility compared with pure PLA, effectively breaking the conventional trade-off. The underlying strengthening and toughening mechanisms are elucidated through morphological characterizations. This work provides a novel, industrially viable (via biaxial stretching) processing strategy for fabricating high-performance, fully biodegradable PLA-based films with great potential in sustainable packaging and beyond.