Effect of red phosphorus and melamine polyphosphate on the fire behavior of HIPS

Pyrolysis and fire behavior of high impact polystyrene (HIPS) containing red phosphorus and melamine polyphosphate were investigated. The thermal and thermo-oxidative decomposition were characterized using thermogravimetry coupled with FTIR and MS, respectively. The fire behavior was monitored with a cone calorimeter using different external heat fluxes and determining the LOI. Red phosphorus reduced the heat release in HIPS due to radical trapping in the gas phase. The reduction in effective heat of combustion was accompanied by an increase of incomplete combustion products such as smoke and carbon monoxide. Melamine polyphosphate in HIPS acted in the condensed phase with barrier formation. The heat release rate was reduced, whereas the total heat evolved, smoke and carbon monoxide formation were not influenced significantly. Using both fire retardants, the resulting fire retardancy was characterized mainly by superposition.