Study on the bonding performance and mildew resistance of soy protein-based adhesives enhanced by hydroxymethyl l-tyrosine cross-linker

Abstract

Soy protein-based adhesives are biodegradable and renewable and are widely used in wood based products. However, the application of soy protein (SP) adhesives is also limited by its poor mildew resistance, water resistance and bonding strength, so it is necessary to find ways to promote the comprehensive performance of SP adhesives. In this study, hydroxymethyl l -tyrosine (TYF) synthesized from l -tyrosine and formaldehyde was used to enhance the mildew resistance and bonding strength of the SP adhesive. The results showed that the cross-linking reactions of TYF and SP molecules and the condensation reactions between an appropriate amount of TYF molecules enhanced the force between SP molecules and made the cross-linked structure more stable and compact, resulting in a significant increase in the bonding strength of the SP adhesive modified by TYF. Compared with the plywood prepared by the SPI adhesive, the SP adhesive modified with 6 wt% TYF had the best bonding performance, and its dry and wet shear strength were increased by 49.3% and 110.1%, respectively. In addition, l -tyrosine Schiff base, which had antibacterial, bactericidal and antiviral effects, was produced by dehydration of TYF molecules, so the mildew resistance of SP adhesives modified by TYF was effectively enhanced.