Bioinspired water-retaining and strong soybean flour-based adhesive for efficient preparation of plywood

The development of a water-retaining and high-bond-strength soybean flour (SF) adhesive is important to improve the efficient and clean preparation of plywood, promoting the substitution of aldehyde resin adhesives in the wood-based panel industry. Soybean protein isolate (SPI) was enriched on boron nitride (BN) to form protein-functionalized BN nanosheets (BS) with dense hydrogen bonds. Drawing inspiration from the strength and toughness of muscles, bionic structures based on BS and SF were designed to enhance adhesive bonding strength and toughness. A water-retaining agent epoxy hyperbranched polyester (EHP) was also synthesized to improve water retention and further enhance the bond strength of adhesives. Results show that the prepared adhesive with BS and EHP exhibits better initial viscosity and coating performance compared with unmodified SF adhesives. The prepressing intensity and wet shear strength of the prepared plywood increased by 227% and 400% to 0.72 and 1.05 MPa. In addition, EHP significantly improved the water retention of the adhesive from 0.5 h to 2 h. After 2 h, the wet shear strength decreased by 30.5% to 0.73 MPa, still meeting the interior use plywood requirement. Notably, this study provides a simple technique of water spraying to recover the dried adhesive layer, and the wet shear strength increased from 0.73 MPa to 0.87 MPa. This preparation strategy of biomass adhesive with water retention and low environmental load bear guiding significance for the efficient and clean production of the wood-based panel.