A morphology study on Soy-based adhesive modified by Mg (NO 3 ) 2

Soy-based adhesive is being explored as a viable alternative to formaldehyde-based resins in the wood product industry due to growing environmental concerns. However, soy-based adhesive faces limitations, particularly in wet conditions, where it cannot rival the performance of formaldehyde-based resins. This study aims to enhance the adhesion properties of soy-based glue and elucidate the influence of protein association size on adhesive strength through a straightforward approach. The impact of Mg (NO3)2 salt on the morphology of soy protein isolate (SPI) suspension was examined. Concurrently, it was identified that a relationship exists between morphology, shear strength, and the zeta potential value of the adhesive in suspension, which can be applied for further formulation and predictive modeling of adhesive properties. The introduction of Mg2+ ions into isolated soy suspension induces the formation of protein associations by reducing electrostatic repulsive forces and increasing protein-protein interactions at a specific salt concentration, ultimately enhancing the cohesion properties of the soy-based adhesive. As a result, a significant improvement in shear strength was observed, increasing from 1.7 MPa to over 4 MPa at a neutral pH and reaching 6.9 MPa at pH 12.5.