Decompression Expansion Processes, Physical Stabilization

Owens Corning manufactures a similar extruded polystyrene foam under the trade name FoamulaR. A single-screw tandem extrusion line is used to produce foam boardstock in a vacuum chamber connected to a barometric leg that acts as a vacuum seal [78]. Owens Corning also licenses their process to a number of international parties. 

More recently Pactiv, formerly Tenneco Packaging, has manufactured foamed polystyrene sheet and boardstock. A tandem extrusion line is used to produce polystyrene foam insulation products. 

Low-density polystyrene foam sheet was first produced by the extrusion of expandable polystyrene beads or pellets containing pentane as blowing agent [81,82]. Currently, polystyrene foam is extruded in a single-screw tandem line or in a twin-screw extruder. 

Two notable methods to produce microcellular foams include gas supersaturation in combination with an extrusion process developed by MIT/Trexel [84-86] and the continuous extrusion process by Dow [87,88]. Super-insulating materials are made by the encapsulation of a filler material inside a barrier film, aluminum foil, or metallized film. These materials exhibit 5-7 times the R-value of typical nonvacuum insulating materials depending on vacuum level and barrier and filler type. Uses for these VIPs (vacuum insulation panels) include refrigeration and controlled-temperature shipping containers. 

In the low-pressure process, a resin containing a blowing agent is forced into the mold, where it expands to fill the mold under pressures of 690-4100 kPa (100-600 psi). This produces structural foam products with a characteristic surface-swirl pattern caused by the collapse of cells on the surface of molded articles. 

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