Lignin-Based Dual-Cross-Linked Adhesives with Strong Adhesion Performance and Multienvironmental Adaptability

Wooden products (such as plywood) are expected to meet the needs of different application scenarios. Wood adhesive is essential for the adhesion strength, weather resistance, and environmental health performance of wood-based composite. However, sustainability of raw materials, a simple production pathway, and reliance on extreme environments are still issues that traditional adhesives urgently need to address. Herein, we propose a lignin-based, formaldehyde-free adhesive system through a simple one-pot strategy. This study lay not merely in the use of lignin as an adhesive precursor, but in the construction of a dual-cross-linked network through the synergistic integration of glyoxal-induced covalent cross-linking and Cu2+-mediated coordination chelation. This structural design enabled the adhesive to achieve both high bonding strength and multienvironmental adaptability. The plywood bonded with the optimized adhesive exhibited dry and wet bond strengths of 2.8 and 1.4 MPa, respectively. Remarkably, the bonding strength loss remained within an acceptable range (0.9–2.3 MPa) in the extreme temperature range (−196 to 100 °C). Additionally, the prepared plywood exhibited a long-lasting solvent resistance. The strength properties retained nearly 100% after 24 h of solvent immersion, without significant strength loss compared with the sample after being exposed to air. Environmental impact assessment demonstrated that the synthetic approach developed herein possesses excellent environmental compatibility. This work presented a simple and distinctive strategy for synthesizing green, sustainable, multienvironmental adaptive adhesives.