A facile method for cross-linking of methacrylated wood fibers for engineered wood composites

Chemical modifications are widely used to enhance the properties of wood composites and create a strong bonding mechanism for enhancing the dimensional stability, water resistance as well as decreasing carcinogenic formaldehyde emission. Esterification is the most-known modification way to enhance the durability of wood composites, but it does not improve mechanical performance. In this work, we demonstrated a two-step, easy and quick wood surface modification strategy based on microwave heating and UV crosslinking. Firstly, the fiber surface was reacted with methacrylic anhydride, then using methacrylated groups on wood, the fibers are covalently linked. As a proof-of-concept the fibers cross-linked within five minutes under UV radiation using benzophenone solution. Then, the effect of crosslinked wood fiber on the properties of mechanical and swelling of fiberboard were studied. Using SEM, FTIR-ATR, and swelling tests, we investigated the wood-based products' reaction mechanism, morphology, and internal bonding strength. The chemical cross-linking gives stronger bonding, compared to hydrogen bonding, between fibers even in wet conditions, resulting in a cross-linked foamlike structure. Also, wood panels were fabricated, compared to unmodified fibers, the internal bond strength and dimensional stability of fiberboards increased slightly. Overall, these results show that chemical cross-linking of wood fibers can be a fast and promising way to produce multi-functional wood composites.