Due to the adverse health effects of formaldehyde-based adhesives and their fossil origin, there is an ongoing search for appropriate bio-based adhesives for particleboards. Although there are some possible solutions, their use in construction is limited partly due to their low moisture resistance and flammability. The latter can be improved by adding various fire retardants. A particleboard with improved fire resistance was produced using citric acid and sorbitol as an adhesive in combination with ammonium dihydrogen phosphate as a fire retardant. Intending to optimise the properties of a laboratory-produced three-layer particleboard, the test procedures focused on thickness swelling, internal bond, MOR/MOE in bending, as well as exposure to small flame impingement and elevated temperatures in hot plate test. An improvement in properties was noticeable with increasing adhesive content, while particle size did not significantly influence the results. The addition of ADP had a negative effect on mechanical properties but improved the thickness swelling. Boards with added ADP showed greater mass loss when exposed to 400 °C. A possible decomposition of ADP at elevated temperatures into phosphoric acid and ammonia gas may have contributed to more significant smoke development and extinguishing the flame when subjected to minor flame impingement.

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