Simple mathematical models of char-forming polymers

Abstract

Char formation (particularly the formation of intumescent chars) is important in the fire retardance of polymers. A char has many desirable properties, ranging from providing thermal and physical barriers, to simply providing a spatial buffer between the combustible material and the heat source. A simple model of pyrolysis of char-forming polymers is developed and discussed. The definition of 'simple' in the title of this paper refers both to the mechanism by which char is formed and the mechanism by which volatile products escape to the surroundings. The physical situation that is considered is the essentially one-dimensional case of a horizontal specimen of material, insulated along its vertical sides, subject to an external heat flux and surface heat losses, such as in the cone calorimeter. The complications of modelling these systems are discussed, and results are presented for the deeradation of PVC.