AbstractLinear polyurethaneimide elastomers (PUI) were obtained from polyether‐ or polyester‐diols, diphenylmethane diisocyanate or bitolylene diisocyanate and pyromellitic acid dianhydride. It was found that these polymers have considerably better mechanical properties than typical linear polyurethanes (PU). The elastic modulus and stress at break increase with contents of the hard polyimide segments. The softening temperatures and thermal stability of the PUI at 500°C were higher than the ones of PU with similar hard segment contents. Electric properties of PUI were close to the ones of conventional PU. It was shown that cellular PUI had considerably lower dielectric constant.Tg's of the soft segments PUI were less thanTg's corresponding to PU. It is connected with greater phase separation of the hard imide segments from the soft polyether– or polyester–urethan
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