Solid, rapid-setting, rigid polyurethanes

A rigid, non-cellular, solid composition having a density of at least 1 g/cc, a percent elongation of less than 100 and which is demoldable within about 5 minutes, without the application of an external source of heat, after admixture in the absence of a catalytic quantity of a catalyst for urethane formation and also in the absence of a chemically hindered aromatic diamine of the components of a rapid-setting polyurethane-forming composition comprising

• A. an amine initiated polyol having an OH equivalent weight of from about 50 to less than about 250 and from about 3 to about 8 hydroxyl groups;
• B. an organic aromatic polyisocyanate;
• C. a liquid modifier compound having a boiling point above about 150.degree. C selected from the group consisting of organic phosphates, organic phosphites, organic phosphonates and mixtures thereof;
• and
• wherein Components (A) and (B) are present in quantities such that the NCO:OH ratio is from about 0.8:1 to about 1.5:1 and Component (C) is employed in quantities of from about 5% to about 60% by weight of the combined weight of components (A), (B) and (C).