Thermal degradation of linear polyurethanes and model biscarbamates

Thermal degradation of model biscarbamates, polyurethanes and poly(urethane‐ureas) has been investigated by pyrolysis at atmospheric pressure. The biscarbamates were prepared from phenyl, benzyl, and cyclohexyl isocyanate and ethylene glycol. The polyurethanes and poly(urethane‐ureas) were prepared from tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), and 4,4′‐dicyclohexylmethane diisocyanate (H12‐MDI) and poly(oxyethylene glycols) of various molecular weights. Rate constants for thermal degradation were obtained by measuring carbon dioxide evolution. The thermal degradation of all materials showed that the stability increased in the following manner: aromatic < aralkyl < cycloaliphatic. The separation and identification of the products of the thermal degradation gave an insight into the mechanisms involved in the pyrolysis of aromatic, aralkyl, and cycloaliphatic biscarbamates and the influence of temperature on these mechanisms.