3. Production of extruded expanded polystyrene (EPS-E or XPS)

The most common extrusion process for EPS-E is known as direct gazing or physical expansion. It produces sheets from 20 to 200 mm thick, and foils from 0.5 mm thick. Sheet density is very low (≈ 0.07 kg/m ³ ). Figure 18 shows a schematic diagram of the extruder.

Crystal polystyrene granules are melted under pressure in an extruder, then nucleating agent(s) and liquid or gaseous blowing agent(s) are mixed with the molten polymer. The mixture is kept under pressure and pushed through the die. As it exits the die, the expanding agent creates expanding cells. The resulting expanded plate or sheet is then cooled....