Soy Protein Adhesive Enhanced Through Supramolecular Interaction with Tannic Acid Modified Montmorillonite

The use of soybean meal (SM) as an alternative to petroleum-based resins in wood-based panels offers a solution to the problem of formaldehyde release. However, inherent drawbacks of soybean meal adhesives, such as poor toughness, low bond strength, and susceptibility to mold, have hindered their further development. In this study, a novel biomass adhesive, SM-MMT@TA, was developed based on supramolecular interactions between tannic acid (TA), montmorillonite (MMT), and soybean meal. Tannic acid was securely attached to the MMT surface through coordination bonds with Ca²⁺, Mg²⁺, and Al³⁺ ions, enhancing MMT's compatibility in the matrix via strong interfacial interactions. TA on the surface of MMT@TA effectively bonded with soy protein through strong hydrogen bonding, thereby increasing the crosslink density. As a result, the adhesive exhibited a wet shear strength of up to 1.75 MPa, which represents a 143.05 % increase compared to unmodified SM adhesive. Moreover, the moisture absorption rate of the adhesive was reduced to 26.79 %. Furthermore, abundant non-covalent interactions improved the adhesive's toughness, while natural polyphenols provided additional mold resistance. Overall, this study presents a new strategy for developing renewable, high-performance biomass-based adhesives.