Tests show that APP protects wood composites from fire and reduces smoke and zeolites enable further improvement. A synthetic aluminium silicate zeolite (hierarchically porous H4A) was loaded with ammonium polyphosphate, by in situ reaction of phosphoric acid and urea. 10% of either APP or APP-zeolite were tested included into wood resin of poplar sawdust pressed in phenol formaldehyde resin. Both APP and APP-zeolite reduced the peak heat release rate (cone calorimeter) by nearly 50% and delayed it from around 6 to 8 minutes. APP alone reduced the peak smoke production rate by around one third, and APP-zeolite reduced it by around half. Both also reduced carbon monoxide release.
“Reducing the fire toxicity of wood composites using hierarchically porous 4A (H4A) zeolite modified ammonium polyphosphate (APP) synthesized by a facile in-situ method”, Z. Zhang et al., Construction and Building Materials 262 (2020) 120754 https://doi.org/10.1016/j.conbuildmat.2020.120754