Experimental and Numerical Study of the Thermal Degradation of PMMA

Abstract

Thermal degradation of PMMA subjected to a radiant heat flux was studied both experimentally and numerically. Very accurate measurements of mass loss rate and temperature profiles were performed for three constant heat fluxes: 1.5,2.3 and 3.0 W·cm-'. The results show that the mass loss rate cannot be directly related to the surface temperature and a contribution of the sub-surface region of the sample to the rate of gasification must be taken into account in a thermal degradation odel. A heat source term was introduced in the conduction equation and a kinetic equation was used to locally calculate the mass loss rate in each slab of the solid. The density and the thermal conductivity of the material were assumed temperature independent while for the specific heat the values measured by differential scanning calorimetry in the range 20-400·C were retained. The predictions of the model are in very close agreement with the experimental results for the evolution with time of both the temperature profile in the solid and the mass loss rate.