Modelling the effect of solid-phase additives on thermal degradation of solids

We model the effect of a simple solid-phase additive on the thermal degrada tion of a solid under thermally thick and thermally thin conditions. The ma thematical model simulates conditions in bench-scale tests (such as the con e calorimeter test) where a solid sample of typical cross-sectional area 10 0 cm(2) is exposed to a uniform external heat Aux and the mass loss rate an d effective heat of combustion are determined. We choose a simple model for the decomposition: the additive and solid decompose independently accordin g to first-order kinetics. We assume for simplicity that the thermal conduc tivity, density and specific heat capacity of the two solid phases are iden tical and hence the discussion centres on the role of the degradation mecha nisms of the components in relation to the overall degradation of the solid . (C) 1999 Elsevier Science Ltd. All rights reserved.