Closed Cell Foam
Closed cell foam is a plastic that contains foam cells which are sealed, or "closed" and packed together. This foam is very dense and has high compressive strength. Because the cells are not broken in this foam and gas and liquid molecules do not freely travel from cell to cell, when exposed to heated gas the cells expand, filling the material and making closed cell foam an excellent heat insulator. Closed cell properties can be combined with other foam materials such as polyethylene and polyurethane to create certain foam products. For example, closed cell polyurethane foam is what foam mattresses and pads for couches and chairs are made out of, while closed cell polyethylene foam is a good choice for packaging materials and nautical flotation devices.
Whether or not closed cell foam is appropriate for an application depends on the application environment. Closed cell foam is commonly used in building applications for residential homes, industrial buildings, office buildings, schools and outdoor or marine environments. Open cell foam is not ideal for outdoor applications or wet environments because of its porosity, or tendency to soak up water, whereas closed cell foam is impermeable to moisture, providing protection and insulation. However, because closed cell foam is so dense, more material is required, making open cell foam an economical choice for dry environments. Closed cell foam is best used for framing because of its dense nature, but it may also be used for applications such as soundproofing due to closed cell foam's ability to repel sound waves, which bounce off the foam's closed cells instead of spreading throughout the material, as happens with open cell foam.
Closed cell foam has varying degrees of hardness, depending on the material's density. A normal closed cell foam sheet can support between 2 and 3 pounds per cubic foot. Because the cells are not broken within closed cell foam, the material is strong and rigid and often strong enough to be walked on. The advantages of closed cell foam compared to open cell foam include its strength and greater resistance to the leakage of air or water vapor. These properties make closed cell foam a good material to use for any type of heat insulation or outdoor insulation. Closed cell foam may be fabricated into many shapes, sizes and colors for various padding, insulating and soundproofing applications.