DuPont™ Styrofoam™ Brand Panel Core 20 Extruded Polystyrene (XPS) Foam Insulation* is a closed-cell high-performance core material. DuPont’s proprietary extrusion process enables precise control of parameters such as density, cell size and cell orientation. This yields foam boards that can meet the most demanding composite panel applications. Styrofoam™ Brand Panel Core 20 is supplied in sheets that have been carefully engineered and planed to precise tolerances for a superior bonding surface.