PIN flame retardants based on ammonium phosphate were tested in laboratory produced papers and paper boards. In an older paper, fire resistance and smoke emission were tested for 9mm paper boards using FR-7 PIN flame retardant (Recytech) containing ammonium phosphate, ammonia, potassium hydroxide.
The FR was integrated into the paper during the production process from fibres. This showed a smoke coefficient (indicator of smoke opacity) reduced by around -75% at 10% FR loading and reduced by more than -90% at 20% loading. This PIN FR also significantly improved fire resistance, increasing time to ignition by over 50% and oxygen index by over 25%. In a more recent publication, a laboratory synthesised experimental phosphorus – nitrogen – (silica) mineral – carbon PIN flame retardant (silane modified ammonium polyphosphate diatomite = APPd) was tested as a flame retardant for two papers. This paper compares only modified and unmodified ammonium polyphosphate, concluding that the modified APPd resulted in significantly lower heat release rate but higher heat and peak carbon monoxide release.
“Effect of surface modification of ammonium polyphosphate–diatomite composite filler on the flame retardancy and smoke suppression of cellulose paper”, H. Zhao & L. Sha, J. Bioresources and Bioproducts. 2017, 2(1): 30-35. “Combustion and Mechanical Properties of Fire Retardant Treated Waste Paper Board for Interior Finishing Material”, H-S. Yang, J. Fire Sciences, vol. 20, Nov. 2002 http://dx.doi.org/10.1106/073490402031471