A mussel protein-inspired biomimetic soy protein adhesive with strong moisturizing properties

Abstract

Soy protein adhesive is easy to lose water and dry, which leads to the decline of bonding performance and unstable production, restricting its large-scale application. The traditional method of improving the moisturizing performance of adhesive by adding hydrophilic substances often leads to a significant decline in the bonding performance of adhesive. This study addresses this issue by synthesizing a hyperbranched polymer (HBP) and combining it with SPI and the crosslinker triglycidylamine (TGA) to create a high-moisture-retaining, strong adhesive. The hydrophilic HBP, rich in phenolic hydroxyl groups, forms an extensive hydrogen-bonding network that significantly enhances water retention. During hot pressing, phenolic hydroxyl groups react with the epoxy crosslinkers, forming dense aromatic ether linkages, which greatly improve cohesive strength. The resulting adhesive showed 63.43 % mass retention after 40 h at 25 °C/60 % RH, an 86 % improvement over pure SPI adhesive. Veneers coated with the SPI/T/HBP₃ adhesive after 2 h of air exposure and hot pressing, retained 83.52 % / 80.40 % of dry/wet bonding strength of the directly hot-pressed values, outperforming SPI/Gly adhesive (76.36 %/67.26 %). After 300 days of cyclic aging (40 °C, 100 % RH), the adhesive maintained dry/wet bonding strengths of 2.04 MPa and 1.70 MPa, respectively. This study provides new strategies for large-scale application of soybean protein adhesives and enhances biomass adhesives.