Degradable, Lightweight, and High-Performance Unidirectional Nanocellulose-Long-Filament-Reinforced Vanillin Epoxy Composites for Structural Applications

Degradable, lightweight, and high-strength green composite materials are in high demand for advanced applications. However, exploring robust composites with sustainability, hydrophobicity, and high strength is challenging. Herein, a biobased vanillin epoxy (VE)-containing imine network structure is reinforced with unidirectional nanocellulose long filaments (UD-NCLFs) by vacuum-assisted resin-transfer molding, followed by compression molding to fabricate a UD-NCLF-VE green composite. The UD-NCLF offers superior strength and stiffness along the direction of filament alignment, enhancing the structural efficiency and performance in the green composite. The developed UD-NCLF-VE green composite exhibits superior flexural properties compared to a neat VE thermoset due to strong and stiff UD-NCLF reinforcements along with good thermal and water-resistant properties. Additionally, the interfacial cross-linking of the hydroxyl groups of UD-NCLFs with the functional groups of biobased VE resin is studied. The composite also demonstrates excellent degradability in a 0.75 M HCl/methanol solution, providing a potential solution for landfill and plastic pollution.