Highly Absorbent Polymers-Inspired Biomass Adhesive with Enhanced Strength and Water Retention Properties

The depletion of fossil resources and the emission of harmful substances have spurred the need for biomass-based adhesives. Soybean meal, a renewable and eco-friendly material, offers a promising alternative to petroleum-based adhesives in wood products. However, water evaporation during curing often reduces the wettability and bond strength of soybean meal-based adhesives. Inspired by highly absorbent polymers, a soybean meal-based adhesive with enhanced water retention was developed by constructing multiple cross-linking networks and promoting hydrogen-bonding interactions between polyacrylamide (PAM) and thiolated sodium alginate (SASH). Notably, the SM-SASH-PAM5 adhesive retained 56% of its mass after 24 h in an open environment, prolonging its lifespan. The thinner adhesive layer (SM-SASH-PAM5) retained more than 76% of its mass after 30 min in a dry environment while maintaining 75.7% of its initial wet shear strength. In addition, it showed a 297.22% improvement in wet shear strength, reaching 1.07 MPa, and a 516.67% increase in prepressing bond strength, achieving 0.93 MPa compared to the original soybean meal adhesive. This strategy provides a versatile method for developing adhesives with excellent water retention, suitable for practical manufacturing applications.