Investigation into a bio-based adhesive in combination with fire retardants for particleboard manufacture

The sawmill industry generates substantial waste in the form of wood chips, shavings, and sawdust, which can be repurposed to manufacture particleboards. Conventional particleboards rely on formaldehyde-based adhesives, posing health risks due to formaldehyde emissions. Seeking alternatives, this study explored a bio-based adhesive system composed of citric acid and sorbitol (10 wt%) combined with 0–20 wt% fire retardants (imidazolium-based ionic liquid or ammonium dihydrogen phosphate) for particleboards made from residual sawmill processing. The objective was to assess the efficacy of the adhesive system in enhancing fire retardancy, moisture resistance, and mechanical properties of particleboards. Results indicate that incorporating ammonium dihydrogen phosphate significantly improves fire retardancy, evidenced by limiting oxygen index values of 50–78% and a thickness swelling after water immersion of 9.7%. However, with an internal bonding strength of max 0.24 MPa and modulus of rupture of max 4.3 MPa, the bio-based boards fell short of meeting standard requirements. Future research should focus on optimising the general citric acid and sorbitol-based adhesive formulations to overcome this limitation. Achieving sustainability and safety standards in particleboard production remains a critical objective for future research and industry implementation.