Foamed plastics are plastics whose apparent density is decreased substantially by the presence of numerous cells disposed throughout its mass. Foamed plastics are also known as cellular plastics or expanded plastics. Foamed plastics are two phase systems where dispersion medium is synthetic rubber or plastic and dispersed medium is a gas. During manufacturing, a fluid polymer is expanded into a cellular state followed by proper stabilization. During heat treatment of polymer, a blowing agent is used. This blowing agent gets entrapped into the polymer structure. Some examples of polymers used here are polystyrene, PVC, polyethylene, styrene-acrylonitrile copolymers etc. Blowing agents used here are pentanes, hexanes, halocarbons etc. Frothing process can also be utilized for the production of cellular polymers. Here a gas is dispersed in a fluid to produce a foam, which is then stabilized. Foamed plastics are widely used nowadays for thermal and electrical insulation, for the packaging of delicate instruments, for making pillows and mattresses and for providing buoyancy in boats and sea-borne cables.
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