Abstract
Abstract The influence of the initial temperature and thermal loss upon the oxygen index and burning rates of polymethylmethacrylate (PMMA), polystyrene (PS) and polyoxymethylene (POM) has been studied. It has been shown that the temperature profiles in the proximity of the burning surface are identical under the critical conditions for each of the polymers. Direct measurements of flame–polymer heat flows have shown that with an increase in initial temperature from 25° up to 200°C the heat flow decreases approximately by a factor of 2. An analogous situation is also observed with change in the thermal loss value in the condensed phase. These data are confirmed by linear pyrolysis experiments. In all experiments under critical conditions the oxygen concentration indicates the constant mass decomposition rate for each polymer. With a decrease in the outlet velocity of the combustibles below this value, which is specific to each polymer, extinction occurs.