Fire Safety Science Digital Archive

An analytical model is presented for the one-dimensional transient gasification of a noncharring thermoplastic material subjected to a specified, time-dependent external radiant heat flux. The model provides for temperature-dependent thermal properties and time-dependent radiative and convective heat losses from the surface. It assumes that the external radiant flux is absorbed only at the surface and that both the heat of vaporization and vaporization temperature can be specified and is constant. Calculated results are compared to experiments with poly (methy1 methacrylate) (PMMA). Agreement between theory and experiment is much better for a high (40 kw/m²) external radiant flux than for a low (17 kw/m²) external radiant flux. Under the latter condition, sub-surface absorption and degradation processes play a significant role but are not represented in the current model. Variable thermal properties, however, are shown to be non-crucial provided an appropriate effective temperature is chosen for their evaluation.