Preparation and Properties of a Fully Biobased Adhesive Based on Epoxidized Soybean Oil

Adhesives are indispensable materials in industrial production, with continuously growing market demand. However, conventional adhesives, primarily derived from petroleum and hazardous substances such as formaldehyde and toluene, pose significant environmental and health risks due to their tendency to release toxic compounds. Inspired by the synthesis of epoxy resin adhesives and the adaptive hydrophobic–hydrophilic interactions of marine mussels, this study presents an eco-friendly, fully biomass-derived adhesive with high performance and multifunctionality. The adhesive was developed through the synergistic interaction of epoxidized soybean oil (ESO), tannic acid (TA), and citric acid (CA), forming a biomimetic physicochemical cross-linked network. TA contributes to the formation of a stable hydrogen-bonding network with ESO while exhibiting antimicrobial properties by inactivating mold cell surface enzymes and proteins. Meanwhile, CA acts as an efficient nucleophile, undergoing ring-opening reactions with epoxy groups in ESO. The synergistic effects of these components significantly enhance the adhesive’s water resistance and antimicrobial performance. Experimental results demonstrate exceptional bonding performance at aluminum plate interfaces, achieving a maximum shear strength of 5.780 MPa. Remarkably, the adhesive retains outstanding water resistance, maintaining a shear strength of 4.658 MPa after 24 h of immersion in deionized water. Furthermore, it exhibits excellent mold resistance, showing no signs of fungal growth after 7 days of testing. The adhesive also shows a remarkable ability for mold shaping through effectively bonding with materials such as sand and wood chips. Given its fully biomass-derived composition, this adhesive offers notable advantages, including environmental benign, abundant raw materials, scalability, and simple preparation process, making it a promising candidate for sustainable material applications.