Descriptions E.P.S. (Expandable Poly Styrene) is a lightweight,Website: , rigid, plastic foam insulation material produced from solid particles of polystyrene. Expansion is achieved by virtue of small amounts of pentane gas dissolved into the polystyrene base material during production. The gas expands under the action of heat, applied as steam, to form perfectly closed cells of EPS. These cells occupy approximately 40 times the volume of the original polystyrene bead. The EPS beads are then molded into appropriate forms suited to their application. Products made from foamed polystyrene are nearly ubiquitous, for example packing materials,insulation,and foam drink cups.