High-Strength, Multifunctional, and Long Nanocellulose Hybrid Fibers Coated with Esterified Poly(vinyl alcohol)–Citric Acid–Lignin Resin

In natural fiber-reinforced polymer composites, strong and tough nanocellulose long fibers (NCLFs) are in high demand. Despite the availability of diverse cellulose nanofiber (CNF) preparations, efficient production of continuous high-strength NCLFs remains a challenge. This study reports a synergistic approach that entails wet spinning and coating CNF with a bio-based and hydrogen-bonded polyvinyl alcohol–citric acid–lignin (H-PCL) resin followed by esterification at 180 °C to form esterified poly(vinyl alcohol)–citric acid–lignin (E-PCL)–NCLF. Morphology assessments on the cross-sectional images of E-PCL-NCLF by scanning electron microscopy revealed a homogeneous coating of H-PCL resin with an average coating thickness of 0.8 μm. The prepared fiber showed a dramatic increase in the mechanical properties with a Young's modulus of 31.20 GPa (49% increase), a tensile strength of 684.61 MPa (138% increase), and a toughness of 12.90 MJ/m3 (10% increase) with a strain at break of 3.26%. The reported approach imparted multifunctional characteristics in the prepared EPCL-NCLF regarding high hydrophobicity, antioxidant activity, and thermal stability. These remarkable enhancements make the prepared EPCL-NCLF a promising candidate for all-green natural fiber-reinforced polymer composites.