Developing High-Performance Cellulose-Based Wood Adhesive with a Cross-Linked Network

Green, environment friendly, and sustainable biomass-based adhesive has been considered as an optimum alternative of petroleum-derived adhesive, yet poor water resistance restricts their advancement and popularization to a large extent. Herein, a hyperbranched cross-linking cellulose-based adhesive with a synergistic effect of covalent bonds and secondary bonds (mainly include hydrogen bond and hydrophobic effect) is synthesized based on the Maillard reaction between dialdehyde cellulose (DAC) and polyamines. The active aldehyde sites on the DAC skeleton anchor the amino group to form covalent bonds consuming a large number of hydrophilic groups, the remaining aliphatic segments of polyamines criss-cross to knit a hydrophobic network and endow the adhesive the ability to resist water erosion; integrant-exposed hydrophilic groups form intermolecular hydrogen bonds preferentially after curing and clustering due to the agglomeration effect of cellulose, which reduces the opportunity of forming hydrogen bonds with water molecules. The outstanding water resistance is manifested in two aspects: (1) the dry lap shear strength of modified adhesive increased from 1.47 to 3.29 MPa, making increments of 123.8% compared with the original DAC adhesive, the re-dry strength after 3 h of immersion in water of 63 °C or boiling achieved a breakthrough from 0 to 2.27 and 2.36 MPa; (2) the modified adhesive has a higher residual rate (above 77%) and a lower moisture absorption value (less than 22.2%) compared with the neat DAC adhesive (49 and 26.6%). The work provides an underlying approach to prepare wood adhesive with excellent bonding performance and eminent water resistance based on green and cheap raw materials and simple cooking chemistry.