Flammability limits of the polymer pyrolysates generated from flame retarded poly (ethylene terephthalate)

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Abstract
A device constructed and used to determine the flammability limits of pyrolysate–air mixtures as a function of percentage weight loss on pyrolysis has been employed to investigate the pyrolysate gases generated from poly (ethylene terephthalate) both in the presence and absence of chemical flame retardants. The chemicals tripropyl phosphate (TPP), dibromopropanol (DBP) and tris (2, 3 dibromopropyl) phosphate (TRIS) all influenced both the lower and upper flammability limits, with the largest effects being obtained when both phosphorus and bromine were present, followed by bromine only and then phosphorus only. The results indicate TPP has negligible condensed phase activity with only small gas phase action. DBP has no condensed phase activity but is a very active gas phase inhibitor. In contrast, TRIS has a detrimental effect upon the condensed phase reactions in that it is responsible for the formation of a more flammable pyrolysate gas mixture. Fortunately, its gas phase inhibition reaction is capable of reducing the overall flammability.