In general, polyurethane or polyisocyanurate foams are prepared by combining an isocyanate, a polyol or mixture of polyols, a blowing agent or mixture of blowing agents, and other materials such as catalysts,surfactants, and optionally, flame retardants, colorants, or other additives.It is convenient in many applications to provide the components for polyurethane or polyisocyanurate foams in prebl