Abstract: Disclosed is a polyurethane elastomer having a density of from about 100 to about 1100 kg/m.sup.3, and an abrasion loss of less than about 300 mg, as determined in accordance with Test Method A of ISO 4649. Such elastomer can be prepared by reacting a urethane-modified polyisocyanate with at least one polyol in the presence of from about 0.1 to about 10 parts per 100 parts by weight of polyol' of a liquid polybutadiene comprising 1,2-butene, 2,3-(trans)butene and 2,3-(cis)butene moieties, wherein the 1,2-butene content is less than about 50 percent, based on total butene content, and the 2,3 (cis)-butene content is greater than the 2,3-(trans)butene content.

Abstract: This invention relates to a process of preparing polyurethane polymers by reaction of an isocyanate composition having an isocyanate equivalent weight of from 180 to 300 and comprising in from at least 50 weight percent a prepolymer, with an active hydrogen-containing substance in the presence of water which provides for at least 50 mole percent of the total blowing requirement. The prepolymer is obtained by reacting a molar excess of a polyisocyanate comprising, in from at least 70 weight percent, 4,4'-methylene diphenylisocyanate with an isocyanate-reactive composition containing (a) a branched diol or triol having a molecular weight of from 60 to 300, and (b) a polyoxyalkylene polyol or mixtures thereof having an average functionality of from 2 to 4 and a molecular weight of from 3000 to 12000, wherein the parts by weight ratio of (a):(b) is from 0.01:1 to 0.25:1.