The oligomer of the invention is prepared in a series of or simultaneous reaction steps, employing an aliphatic polyisocyanate, and typically an aliphatic diisocyanate; that is, with the isocyanate groups connected to an aliphatic group or moiety, particularly an alkyl moiety of the polyisocyanate, which is reacted with an amine polyol, and preferably with a primary amine polyol, in an exothermic-