AbstractThe dependence of thermal stability of poly(ester‐urethane) elastomers on their composition was investigated. For polyurethanes of hard segment content above 3070, hydroquinone di(β‐hy‐droxyethyl) ether (HQEE) is the choice for good thermomechanical stability while the stability of bisphenol‐A‐based polymers is rather poor. The temperature sensitivity of modulus was essential in the range of ‐30‐24OC, while in the range of 24–70°C i t is moderate. The modulus in the low temperature region depends on the nature of polyesterdiol. Its drop with temperature is lower for poly(hexamethy1ene carbonate) glycol (PHC)‐based polyurethanes than poly(ethy1ene‐adipate) glycol (PEAd)‐based ones. In the high temperature region it also depends on the nature and amount of hard segments. The thermal stability of 4,4′‐dicyclohexylmethane diisocyanate (SMD1)‐based polyurethanes is inferior to the one for 4,4′‐diphenylmethanediisocyanate (MD1)‐derived polymers.