Evolution of HCN during high‐temperature thermal degradation of polyurethanes

Abstract

AbstractThe thermal degradation of an aliphatic, aromatic, and secondary polyurethane has been studied over a range of temperatures from 500 to 1000°C with respect to the kinetics and mechanism of HCN evolution. This evolution shows a rapid linear increase of evolved HCN with time, passing into a plateau when the polymer has been consumed. In high temperature ranges, thermal decomposition of the evolved HCN also takes place, and in some temperature regions the degradation is diffusion controlled. Overall, the process is governed by a depolycondensation reaction which is the slowest step in a sequence of reactions. The reaction sequence is kinetically evaluated and the respective rate constants, diffusion constants, and energies of activation are presented. The reaction mechanism accounts well for the experimental results in spite of some simplifications which had necessarily to be applied.