High-Performance Gel-Spun Poly(vinyl alcohol) Fibers Reinforced by Organosolv Lignin-graft-poly(acrylic acid)

Water-soluble synthetic poly(vinyl alcohol) (PVA) polymers can be used as a raw material for high-performance solution-spun fibers. To enhance the biodegradability and physical properties of PVA fibers, lignin has been considered a low-cost, biobased filler/additive for PVA fibers. However, its amorphous structure and hydrophobic nature cause difficulty in developing lignin-reinforced PVA high-performance fibers due to the poor compatibility of amorphous lignin and linear semicrystalline hydrophilic PVA. Herein, the graft copolymerization of organosolv lignin (OL) and acrylic acid (AA) was performed at different reaction durations to yield hydrophilic lignin copolymers, which had enhanced compatibility with polar synthetic PVA. Chemically modified OL with reaction durations of 0, 12, and 24 h was incorporated into PVA fibers by gel spinning. With 5% modified OL from 24 h of reaction time, the composite fibers had an excellent tensile strength of 1.15 GPa, which was 61.4% higher than that of neat PVA fibers. This fiber's Young's modulus (13.09 GPa) and toughness (26 J/g) were also substantially enhanced when compared with those of the neat PVA fibers (Young's modulus of 8.97 GPa and toughness of 18.09 J/g). This work enables the high-value utilization of a modified lignin filler in synthetic fibers for potential applications in industrial or technical textile fields.