Abstract: Disclosed is an aromatic diisocyanate prepolymer combined with a dibasic ester, preferably a mixed dialkyl ester of adipic, glutaric and succinic acids, which when used with amine or polyol curatives to make solid, non-foamed elastomeric polyurethane and/or polyurethane/urea products reduces viscosity and improves wettability of the castable polyurethane prepolymer without loss of cured physical properties. This improved wettability of the liquid prepolymer is useful for impregnation of fabrics, preferably polyesters, during the manufacture of a polyurethane coated fabric type belting.