Pyrolysis Kinetics of a Polyurethane Foam by Thermogravimetry; A General Kinetic Method

Abstract

Kinetic studies on the decomposition of a flexible polyurethane foam based on tolylene diisocyanate and a polyether polyol of propylene oxide have been carried out with the thermogravi-metric technique (TGA). In dry nitrogen the decomposition proceeds in two overall steps. At the end of the first step, which follows a diffusion-controlled rate law, the cellular structure collapses to a viscid liquid. The viscid liquid decomposes further in accord with a random nucleation rate law. The activation parameters which provide very good fits to the experimental TGA curves at heating rates of 2 and 20°/min are A₁ = 3.4 × 10¹⁹min⁻¹, E₁ = 52 kcal/mole, and A₂ = 6.8 × 10¹²min⁻¹, E₂ =39 kcal/mole. A general approach for the derivation of kinetic parameters for such complex reactions is presented.