at most 0°Cas measured by dynamic mechanical analysis using the peak of the tan delta curve as the T$_{g}$. The polyurethane of the invention often exhibits excellent thermal properties. These are manifested by comparing the storage moduli of the polyurethane, as measured by dynamic mechanical analysis in the manner described in the following examples, at 150°Cand 200°C.An advantage of this invention is that the absolute values of the storage moduli tend to be high (at a given % hard segment) at 150°C,and in that there is 71ittle loss of storage modulus when the polyurethane is further heated to 200° C. In specific embodiments, the storage modulus at 150°Cis at least 5 x 10 7 Pa, at least 7.5 x 10 7 Pa or at least 9.0 x 10 7 Pa, and the ratio of the storage modulus at 200°Cto that at 150°Cis at least 0.75 or at least 0.85. In some embodiments this ratio is at least 0.90. A cast elastomer product of the invention may be a static or dynamic type, static elastomers being products that are not subjected to frequent deformation during use (such as gasketing materials and certain types of rollers) and dynamic elastomers being products that are subjected to frequent deformation as they are used. The elastomer of the invention is useful, for example, as gaskets and seals, tubing, rollers for many applications such as coating rollers, nip rollers, drive belts, squeeze rollers, business machine rollers, pulleys, conveyor wheels, fork truck wheels, tricycle wheels, caster wheels, industrial tires, rod wipers, snow plow blades, chute and cyclone liners, agitator blades and many more. The invention is useful, for example, as a sealant or adhesive. For use as a sealant or adhesive, the reactants preferably are formulated into a two- component system, one component containing the polyisocyanate (more preferably an isocyanate-terminated prepolymer or quasi-prepolymer) and the other component containing at least one of polyol b-1) and b-2). A preferred sealant or adhesive formulation, for example, includes A) an isocyanate component comprising an isocyanate-terminated prepolymer or quasi prepolymer having an isocyanate content of at least 1%, at least 2.6% or at least 4% by weight up to 20% by weight, up to 15%, up to 12% or up to 10% by weight, which is a reaction product of polyol b-1) and the starting organic polyisocyanate; and B) a curative component comprising or entirely constituted by polyol b-2). A reaction mixture is formed by mixing the A) and B) components, preferably at ratios such that an isocyanate index of at least 90, at least 95 or at least 98 to at