Cost-effective high-performance poly(butylene adipate-co-terephthalate)/sodium lignosulfonate composite films with enhanced biodegradability, UV protection and oxygen barrier properties.

Developing cost-effective biodegradable polymers with diverse properties remains critical for sustainable materials. This study presents a strategy to reduce poly(butylene adipate-co-terephthalate) (PBAT) costs using industrial byproduct sodium lignosulfonate (SL) with methylene diphenyl diisocyanate (MDI) as compatibilizer. The NCO groups of MDI react with hydroxyl groups of both SL and PBAT, ensuring homogeneous SL dispersion and strengthened interfacial interactions. SL/PBAT composite films with varying SL contents were prepared via melt-blending and blowing. The hydroxybenzene structure of SL significantly enhanced UV resistance. After 96 h UV exposure, tensile strength and elongation retention reached 77.76% and 75.51%, respectively, surpassing neat PBAT. Furthermore, the pronounced hydrophilicity of SL enhanced water absorption of the composite film, resulting in a mass retention of merely 37% after 42 days under soil burial degradation conditions. The rigid backbone and polar sulfonic groups improved oxygen barrier properties, reducing oxygen transmission rate from 50.27 to 23.67 cc·mm/m2·day·atm. This work not only enhance value of industrial lignin byproducts but also meets multiple performance requirements for sustainable packaging films. It provides a new strategy for advancing the application of PBAT films in food packaging, agricultural mulch, directly transplanted seeding cup and other biodegradable plastic products.