Tannic Acid-Modified Amylopectin-Rich Hydrogels with Enhanced Adhesion and Anti-Retrogradation Properties

Wood composites are widely used in furniture and construction industries, creating increasing demand for sustainable and formaldehyde-free wood adhesives. In this study, tannic acid (TA), a natural polyphenolic compound, was incorporated into an amylopectin (AP)-rich hydrogel derived from starch to develop an environmentally friendly wood adhesive with enhanced adhesion and multifunctionality. TA formed hydrogen-bonded networks with AP-rich hydrogels, improving the physicochemical properties of the hydrogel and suppressing starch retrogradation, thereby enhancing long-term structural stability. Owing to the polyphenolic structure of TA, the AP-rich/TA hydrogel exhibited excellent antioxidant and antibacterial activities. Furthermore, TA incorporation reduced hydrogel viscosity, improving spreadability and penetration into the wood substrate. After hot pressing, the adhesive achieved a bonding strength of approximately 1.3 MPa, attributed to enhanced interfacial hydrogen-bonding interactions between TA and wood surfaces. These combined effects resulted in significantly improved adhesion performance compared with the pristine AP-rich hydrogel. Overall, the AP-rich/TA hydrogel represents a sustainable and high-performance wood adhesive with excellent bonding strength, biological functionality, and potential to replace conventional petroleum-based adhesives.