University of Arizona,
Keywords: guayule, resin, soy protein, adhesive
Summary:Soy protein (SP) adhesives have shown a significant potential as renewable bio-based adhesives for wood products. However, the market value limited by its low water resistance property. Therefore, improving water resistance of SP adhesives will increase its market interest. Utilization of natural product as water resistance enhancer for SP adhesive provides a sustainable solution for healthy and environmentally friendly wooden products. Guayule resin, an attractive by-product of the guayule rubber extraction, is a good candidate for this purpose. The aim of this preliminary study was to investigate the water resistance of SP adhesive enhanced by using guayule resin. The resin was modified with NaOH in hexane, acetone, and water solutions, and subsequently mixed with SP adhesive at different concentrations. An addition of 7.5% resin to SP adhesive showed the highest elastic modulus representing the highest intermolecular interactions. The highest water resistance also observed at SP-blended with 7.5% resin. The wet adhesion strength significantly increased by 70.5% compared to pure SP adhesive. The study of denaturing behavior of SP suggested that guayule resin strengthened SP network by interacting with 7S and 11S subunits of SP. The changes in SP properties were due to interactions between guayule resin and protein’s backbone and side chains. This study served as a strong motivator by enlightening research pertaining to the utilization of guayule resin as a bio-adhesives for wood industries.