A High-Performance and Cost-Effective PBAT/Montmorillonite/Lignin Ternary Composite Film for Sustainable Production

Poly(butylene adipate-co-terephthalate) (PBAT) is recognized as a highly promising biodegradable plastic for film applications, and is aimed at replacing nonbiodegradable alternatives. To address the challenges of high cost and inadequate gas barrier performance in PBAT, cost-effective functional fillers have frequently been incorporated. However, the inherent incompatibility between fillers and the matrix results in a significant deterioration of mechanical properties. In this study, the compatibility of PBAT and montmorillonite was enhanced by incorporating lignin fractionated with organic solvents. Lignin fractionated with ethyl acetate showed the most substantial improvement in compatibility due to its lower glass transition temperature and higher content of hydroxyl groups. The fractionated lignin participated in the construction of multiple interactions, encompassing hydrogen bonds, silane-linked bonds, and nonbond interactions within the ternary composite. This enhanced compatibility and effectively preserved the remarkable mechanical properties of the composites, even under a high filler content. Even with the addition of 60 wt % fillers, the composite remained mechanically stable with a tensile strength of 15 MPa and an elongation at break of 217%, which were the best mechanical properties reported for highly filled PBAT composites. The resulting composite film could be mass-produced and displayed excellent gas barrier capabilities, with water vapor permeability and oxygen permeability reduced by up to 40% and 90%, respectively. Moreover, the production of this composite film resulted in a 35% cost reduction, alongside a lower environmental impact and reduced CO2 emissions. Therefore, the prepared ternary biodegradable composite film demonstrates exceptional performance, cost-effectiveness, and sustainability, rendering it as a feasible solution for packaging and mulching applications.