| Abstract: | The mechanism of flame retardant (FR) action of red phosphorus in polyacrylonitrile combustion was investigated by thermogravimetry, flash-pyrolysis GC-MS, and combustion methods. Red phosphorus was found to increase the thermal stability in air of polyacrylonitrile and to induce a char residue increment on this substrate. Both these effects disappeared when pyrolysis was carried out under nitrogen flow. Flash-pyrolysis GC-MS experiments showed that red phosphorus does not alter the pyrolysis product distribution of polyacrylonitrile, which implies that there is no specific interaction between polyacrylonitrile and red phosphorus. These data also showed that polymeric red phosphorus decomposes to volatile white phosphorus (P4) during pyrolysis. These observations allow us to propose a simple model for the mechanism of FR action of red phosphorus on polyacry-lonitrile at the molecular level. Combustion data for polyacrylonitrile-red phosphorus mixtures are in agreement with the proposed mechanism of FR action. |
