Vanillin-derived epoxy-coated flexible cellulose nanofiber film for multifunctionality and energy harvesting applications

Abstract

Cellulose nanofiber (CNF), a state-of-the-art sustainable material, often suffers from high hydrophilicity, flammability, and emaciated UV-blocking properties, hampering its broad growth in high-performance applications. This paper reports a novel multifunctional bio-based-epoxy-coated CNF film promising to cope with the addressed challenges. Key to this approach is the etherification reaction, which favors excellent compatibility between CNF film and vanillin-derived epoxy (VDE) resin, resulting in a robust crosslinked network structure with a remarkable adhesion strength (16.12 ± 0.7 MPa), tensile strength (211.6 ± 7.2 MPa), and Young's modulus (8.6 ± 0.4 GPa). A thin VDE layer coating on CNF (VDE/CNF) film significantly presented the film's hydrophobicity of around ⁓93.0 ± 1.5° and UV shielding performance of ⁓100%. Additionally, the coated VDE/CNF film exhibited higher thermal stability (213 °C) and char residue (36%) than the CNF film. Most importantly, despite the high flammability nature of CNF film, the VDE/CNF film passed a V-0 rating under the UL-94 test with a limited oxygen index of 31.8%. The VDE/CNF film was utilized for a triboelectric nanogenerator (TENG) to demonstrate its broad technological impact. Notably, the VDE/CNF-TENG exhibited a significant output power of 18.33 μW. This critical approach offers a promising way to extensively utilize sustainable and multifunctional VDE/CNF nanocomposite materials for high-performance applications.

Keywords

• Bio-based epoxy resin
• Cellulose nanofibers
• Mechanical properties
• Wettability
• UV shielding
• Flame retardancy