High-performance biodegradable poly(lactic acid) composites with xylan and lignin copolymer

With the rising concerns over the growing plastic waste and the accumulation of microplastics, there has been increasing attention toward biodegradable plastics. Among the widely used biodegradable plastics, poly(lactic acid) (PLA) usage has been limited; it can biodegrade under certain compost conditions and possesses some brittleness along with high tensile strength and moderate barrier properties. In this study, xylan and lignin derived from lignocellulosic biomass were introduced to PLA to improve its mechanical properties and to confer additional beneficial effects. However, its amorphous nature and hydroxyl groups in xylan and lignin structure deteriorates compatibility with PLA matrices. Therefore, poly(caprolactone) (PCL) was grafted to xylan and lignin to enhance compatibility with the PLA matrix, and the reactions resulted in copolymers (Xylan-g-PCL and Lignin-g-PCL) with a newly appeared melting point (T_m) as crystallinity increased. Of the copolymers, the Xylan-g-PCL/PLA film had a higher elongation at break but weaker UV protection properties. Compared to neat PLA film, the copolymer films had higher biodegradability.