Wood Adhesive Based on Lignin-Crosslinked Epoxidized Carboxymethyl Chitosan with High Bonding Strength

Abstract Biobased wood adhesives are promising alternatives to conventional formaldehyde-containing adhesives. However, their practical application is still limited by complex preparation procedures and poor storage stability. In this work, a lignin-crosslinked epoxidized carboxymethyl chitosan adhesive (L-GCMCS) was developed via a one-pot, rapid in situ preparation process completed within 5 min. Carboxymethyl chitosan (CMCS) was first epoxidized through controlled prepolymerization with ethylene glycol diglycidyl ether (GDE). Subsequently, lignin was introduced to form a homogeneous adhesive system. The resulting adhesive exhibited a dry bonding strength of 3.62 ± 0.19 MPa and a wet bonding strength of 1.58 ± 0.16 MPa, both exceeding the Chinese industrial requirement of 0.7 MPa. Notably, the crosslinker accounted for only 6.6% of the total adhesive formulation. After 120 days of soil burial degradation, the cured adhesive lost 61.3% of its initial mass, demonstrating high biodegradability. These results demonstrate a fast, low-crosslinker-content, and sustainable strategy for high-performance wood adhesives and the value-added utilization of lignin.