Fabrication of high-strength and tough PLA/PBAT composites via in-situ copolymer formation using an adaptable epoxy extender.

Developing biodegradable polymers with superior mechanical performance offers a sustainable solution to address the severe environmental challenges posed by conventional plastics. Poly(lactic acid) (PLA) and poly(butylene adipate-co-terephthalate) (PBAT), two prominent biodegradable plastics, exhibit complementary mechanical properties. However, their inherent incompatibility and significant viscosity mismatch cause significant challenges for effective blending via the conventional methods. Herein, we propose an innovative strategy that integrates kinetic and thermodynamic principles to fabricate PLA/PBAT composites with high strength and high toughness. An adaptable ternary copolymer, presenting strong affinity with both PLA and PBAT segments, was employed as an epoxy chain extender (EE) to covalently couple PLA and PBAT under high shear conditions. The high-shear reactor reduced the size of the dispersed phase and significantly expanded interface area, providing abundant reaction sites for EE. This enabled the in-situ generation of abundant PLA-PBAT copolymers, as evidenced by increased melt viscosities and higher molecular weight of the resulting products. By optimizing the EE content to 2.5 wt%, PLA/PBAT composite achieved an exceptional balance between strength (47.6 MPa) and toughness (229.3 MJ/m), representing improvements of 47 % and 34-fold, respectively, over conventional PLA/PBAT blend. This work provides a scalable and robust platform for developing high-performance biodegradable composites from immiscible polymers.