Chitosan, a renewable biopolymer derived from chitin, has faced limitations in adhesive applications due to its low strength and high water absorption. However, a team led by Qi Huang has developed a multifunctional bio-adhesive that addresses these issues by combining chitosan with boric acid and epoxidised rosin acid, resulting in a reinforced network. This new adhesive demonstrates impressive performance, with plywood achieving a dry shear strength of 2.71 MPa and a wet shear strength of 1.92 MPa. Particleboards bonded with this adhesive show a flexural strength of 21.00 MPa, an internal bond strength of 0.85 MPa, and minimal thickness swelling after water immersion. Molecular dynamics simulations have confirmed that the synergistic crosslinking enhances interfacial adhesion and overall network stability.
In addition to its strength, the adhesive offers excellent flame retardancy, achieving a limiting oxygen index of 81.10% and a char residue of 43.84% at high temperatures. Compared to traditional melamine–formaldehyde and phenol–formaldehyde resins, it has a significantly lower environmental impact and biodegrades over 95% within 15 days. This innovation presents a renewable and biodegradable alternative to petroleum-based adhesives in wood panel production.
