A Chinese research team has developed an eco-friendly wood adhesive based on chitosan and modified rosin acid. The formulation achieves high mechanical strength, flame retardancy and rapid bio-degradability, offering a viable alternative to formaldehyde-based resins.

Chitosan, a renewable bio-polymer derived from chitin, offers excellent environmental compatibility, but has so far been limited in adhesive applications due to low strength and very high water uptake.

A team led by Qi Huang has now developed a multifunctional bio-adhesive (CS-BA-ERA) that overcomes these drawbacks by combining chitosan (CS), boric acid (BA) and epoxidised rosin acid (ERA) into a reinforced network.

The adhesive delivered strong performance: plywood achieved a dry shear strength of 2.71 MPa and a wet shear strength of 1.92 MPa. Particleboards bonded with CS-BA-ERA reached a flexural strength of 21.00 MPa, an internal bond strength of 0.85 MPa and only 11.06 % thickness swelling after 24 hours of water immersion.

Molecular dynamics simulations confirmed that synergistic crosslinking improved interfacial adhesion and overall network stability. Beyond strength, the adhesive provides excellent flame retardancy, achieving a limiting oxygen index of 81.10% and a char residue of 43.84% at 599.60°C.

Compared with conventional melamine-formaldehyde and phenol-formaldehyde resins, it shows a significantly lower environmental impact and undergoes over 95% bio-degradation within 15 days. This research highlights a renewable and biodegradable alternative to petroleum-based adhesives for wood panel production.

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