APP with bio-based cobalt phytate reduce heat release, smoke production, density and toxicity from polyurethane foam. The recognised workhorse PIN flame retardant, ammonium polyphosphate (APP), was dosed at 33% loading in polyurethane rigid foam during foaming reaction, and at 27% with 6% cobalt phytate (a commercially available metal salt of bio-sourced phytate, a phosphorus-rich molecule found in plant seeds). The phytate improved compatibility of APP with the foam and improved foaming, possibly by reacting with isocyanate. APP showed peak heat release 34% lower than neat polyurethane, and APP + cobalt phytate 43% lower. APP alone had little impact on smoke, whereas APP + cobalt phytate reduced total smoke production by 42%.and maximum smoke density by 27%, as well as significantly reducing emissions of the toxic gases carbon monoxide and hydrogen cyanide. Analysis showed that the cobalt phytate improved the density and graphitisation of the char layer.
“Effect of ammonium polyphosphate/cobalt phytate system on flame retardancy and smoke & toxicity suppression of rigid polyurethane foam composites”, B. Zhang et al., J. Polymer Research (2021) 28:407 https://doi.org/10.1007/s10965-021-02763-z