High-performance Esterified-Poly (vinyl alcohol)-Citric acid-Lignin resin and its application to Wet-spun nanocellulose Filament-Reinforced polymer composite

This paper reports an ultra-strong, tough and bio-based polyvinyl alcohol-citric acid-lignin resin applicable for all-green fiber-reinforced polymer composites for the first time. Through a facile solution mixing approach, the resin was optimized by varying the cross-linker - citric acid - followed by esterification at 180 °C. The treatment dramatically enhanced the tensile strength (269.8%), Young's modulus (273.5%), toughness (1222.8%), and hydrophobicity (48.5%). Moreover, the optimized resin showed an excellent adhesion strength (31.92 MPa) to cellulose. As proof of concept, the wet-spun nanocellulose filament was weaved into mats and utilized in composite fabrication with the resin via hand layup and hot press. The lightweight (1.253 ± 0.0613 gcm−3) yet strong structural biocomposite showed a record high bending strength of 363.42 MPa and flexural modulus of 39.89 GPa. Insights from this work offer a promising new avenue for utilizing bio-based resins and nanocellulose to engineer environment-friendly and robust structural composites.