This specification covers only one class of foam, nominal density - 2.0 pounds per cubic foot (lb/ft³), rigid unicellular polyurethane foam, and the materials required for preparation by the foam-in-place technique. Intended Use: The mixture of the materials for foam-in-place preparation is readily pourable. Heat is developed immediately upon mixing and expansion takes place to fill the mold with a foam which becomes rapidly rigid. Material is primarily intended for the preparation of foam for buoyancy applications and the filling of void spaces which are susceptible to flooding.