Kinetcis and mechanism of HCN‐evolution from the oxidation of polyurethanes

Abstract

The oxidative degradation of aliphatic, aromatic, and secondary polyurethanes was investigated over a range of temperatures of 440–1000°C as a function of time and oxygen concentration. The degradation was studied with special emphasis on HCN‐evolution; its rate constants and Arrhenius equations were determined. In some of the temperature ranges reactions were diffusion controlled. At relatively low temperatures the oxidative rate constant was a linear function of oxygen concentration, whereas at higher temperatures oxidation of the evolved HCN took place in passage through the hot zone of the furnace; in addition, at these higher temperatures thermal degradation of the polymers and thermal decomposition of HCN in the hot zone occurred simultaneously with oxidation to an appreciable extent. The kinetics and mechanism proposed and quantitatively evaluated account well for the experimental results.

Oxidative and non-oxidative degradation of a TDI-based polyurethane foam: Volatile product and condensed phase characterisation by FTIR and solid state 13C NMR spectroscopy

“…[18,21,22] Wlodarczak [23] studied the thermo-oxidative degradation of a polyurethane foam from 6 which were identified included CO, CO 2 , methanol, C1-C4 aliphatic hydrocarbons, acetonitrile, acrylonitrile and HCN. Isothermal experiments conducted at intervals of 100°C revealed that the concentrations of HCN, hydrocarbons and CO 2 increased with increasing temperature, whilst the methanol, acetonitrile and acrylonitrile concentrations peaked at 500°C. Jellinek and Dunkle [24] studied the thermo-oxidative degradation of a number of polyurethanes synthesised from a variety of polyols and isocyanates. They proposed that for all polyurethanes a thermo-oxidative mechanism can be postulated based on the original mechanism proposed by Boland and Gee [16] involving the formation of hydroperoxides 10 which then degrade via radical chain reactions leading to deterioration of the polyurethane.…”

“…Jellinek and Dunkle [24] In this paper, we present data on the degradation of a TDI-based PU foam, with a focus on the characterisation of the condensed phase. Degradation studies were conducted to further probe the degradation behaviour of the polyurethane under non-oxidative environments.…”

Thermal Degradation of Polyurethane Bicomponent Systems in Controlled Atmospheres

“…In parallel to the formation of carbon dioxide, several studies have shown the formation of toxic gases (hydrocyanic acid, benzene etc) the nature of which depends on the initial chemical structure. They appear throughout the thermo-oxidative degradation of polyurethanes 7,8,26,27 .…”

Effect of blocking agents on the shock absorbing properties of the films of polyurethane adhesives

“…Polyurethane has excellent modulus even at low temperatures and finds usage in space applications (18,21). In view of its importance, the kinetics of formation (22), thermal degradation (23)(24)(25)(26). and their structure-property relationships (27)(28)(29)(30)(31)(32)(33) have been extensively reported.…”