Interactive effect of oxygen diffusion and volatiles advection on transient thermal degradation of poly methyl methacrylate (PMMA)

A transient, one-dimensional model has been presented to formulate the substantial role of polymer gasification in the early stages of fire growth. The present model comprises the interaction between the oxygen diffusion and the released volatiles on the rate of polymer gasification, when the polymeric sample is subjected to an external radiative source. The model also includes different mechanisms affecting the degradation process such as in-depth thermal and oxidative decomposition, in-depth absorption of radiation and heat and mass transfer in the both gas and solid phases. The results for two different radiative heat sources (17 and 40 kW m⁻²) are reported and yielded realistic results, comparing to the published experimental data. It was found that an increase in the oxygen concentration will lead to a considerable decrease in the surface temperature as well as significant increase of gasification rate at 17 kW m⁻²; nevertheless this effect is less apparent at 40 kW m⁻².