Abstract: A low pressure spraying assembly for mixing and initiating the reaction of a first liquid reactive polymeric material, such as an isocyanate terminated compound, with a second liquid reactive polymeric material, such as an hydroxyl terminated compound or polyol resin, to form a two part polymer, such as polyurethane, and spraying the polymer onto a surface. The spraying assembly includes a material circulating system and a spray gun assembly. The material circulating system comprises separate multiple diaphragm pumps, drive assemblies, flow meters and feedback controllers for each material. The spray gun assembly includes a manifold with a pair of fluid ports for receiving the first and second polymeric materials. A mixing device is mounted to the manifold for mixing the materials to form the two part polymer. A spray tip with an air cap is mounted to the distal end of the mixing device for spraying the polymeric material.