Pyrolysis and ignition of polymers under approximated fire conditions

Pyrolysis rates and ignition temperatures of several polymers were determined in a special apparatus in which it was possible to simulate the surface exposure and sample heating rates (1 to 100°K/sec) to be expected under actual fire conditions. Sample pyrolysis occurred in air at a known, uniform temperature; and a direct measure of the ignition temperature was obtained. The rate of mass loss from samples was obtained at high, constant temperatures; and these data were described in terms of global but physically feasible mechanisms. These global descriptions were used to predict mass-loss-temperature relationships for heating at constant rates of temperature rise, and the predictions were compared to experimental measurements. The descriptions of pyrolysis were used to interpret the ignition data and to show that piloted ignition occurred when a combustible mixture is generated in the gas boundary layer at the exposed surface of the sample.