AbstractDifferential thermal analysis and thermogravimetric analysis were used to evaluate the thermal properties of several types of polyurethane elastomers. The composition of the polymers investigated was changed by varying the substrate, or soft segment, diisocyanate and extender. The data indicated that within the limits of the compositions under study, polyurethanes were thermally stable to their melting points, however, above the melt they were susceptible to oxidation unless stabilized by the addition of an antioxidant. On the differential thermograms the absence of a pronounced endothermic peak at the melting point, characteristic of non‐crystalline polymers, was observed. The decomposition of polymers made with 4,4′‐diphenylmethane diisocyanate (MDI) occurred above 400°C. and was at least a two‐step process, while the decomposition of polymers containing toluene diisocyanate (TDI) occurred below 400°C. and appeared to be a one‐st