High‐strength, water‐resistant, formaldehyde‐free cellulose‐based thermosetting resin for wood bonding

Abstract Despite the continued dominance of detrimental formaldehyde‐based binders in the wood reconstituted products, there is a growing push to develop more environmentally friendly alternatives. Cellulose‐based biomass adhesives have been extensively researched and documented. However, their industrial application is limited due to inadequate water resistance and suboptimal coating ability. In this study, a cellulose‐derived wood binder with a hyperbranched entangling structure was synthesized by covalently cross‐linking branched polyethylenimine and oxycellulose through Schiff base formation. The dry/wet bonding strength of the prepared plywood was 2.07 and 1.52 MPa, respectively, exhibiting a remarkable increase and breakthrough compared to that of pure oxidized cellulose binder. This can be attributed to the formation of a water‐resistant Schiff base tangle network, which enhances the toughness of the adhesive. Notably, the pure cellulose adhesive tends to agglomerate on the wood surface, whereas the hyperbranched modified cellulose adhesive exhibits a more uniform coating ability. This study further demonstrates the reliable potential of tangle structures based on Schiff base reactions in the development of biomass‐based adhesives. Highlights A high bonding strength cellulose‐based wood adhesive was prepared. The Schiff base reactions have been used to construct cross‐linked structures. The cross‐linked network structure provides excellent water resistance. The cured cellulose‐based adhesive has excellent dry/wet bonding strength.