Dual-Function Reactive Extrusion of Lignocellulosic Fibers for High-Performance Biodegradable Nanocomposite Films

The transition toward sustainable plastics calls for biodegradable polymers with enhanced performance and scalable processing routes. Plant-derived nanofibers are promising reinforcements, yet their adoption is hindered by energy-intensive isolation, incompatibility with hydrophobic matrices, and aggregation during drying. Here, we report a dual-function reactive extrusion strategy that combines nanofibrillation and surface modification in a single step. Lignocellulosic fibers are prefunctionalized with maleic anhydride to introduce carboxyl groups while retaining native lignin, and in-situ transesterification during melt compounding generates well-dispersed cellulose nanofibrils covalently bonded to PBAT. This integrated approach removes the need for costly nanocellulose isolation and drying while simultaneously ensuring compatibility and mechanical integrity through both chemical bonding and the hydrophobic contribution of lignin. The resulting composite films exhibit a 30% increase in stiffness while maintaining superior tensile strength and strain at failure, along with a 42% and 56% reduction in water vapor and oxygen permeability, respectively, compared to neat polymers. Additionally, the preserved lignin imparts over 90% antibacterial activity, enabling improved fruit preservation, while many film trials confirmed effective soil moisture retention and good biodegradability. Overall, this work establishes a scalable, industry-ready route to transform raw biomass into multifunctional nanofillers, providing a green pathway toward high-performance composite films for packaging and agricultural applications.