A Mussel-Inspired Chitosan-Based Wood Adhesive with Boiling-Water Resistance and Flame Retardancy

Traditional biomass-based adhesives often suffer from low strength, poor boiling-water resistance, and limited functionality. In this study, inspired by the catechol-containing mussel byssal proteins, we developed a chitosan-based adhesive using chitosan (CS), tannic acid (TA), and Fe3+. Hydrogen bonding and metal coordination among CS, TA, and Fe3+ enhance the cross-linked network, thereby improving the adhesion performance, with a boiling-water shear strength of 1.40 MPa. Notably, the Limiting Oxygen Index (LOI) of poplar veneer treated with the CS-TA-Fe3+ adhesive was 29.70%, meeting the standards for flame-retardant materials. These results demonstrate the simultaneous enhancement of adhesion and flame retardancy, highlighting the potential of this system as a sustainable, multifunctional adhesive for construction and automotive applications.