Polymeric foams are composite materials that consist of a solid polymer matrix surrounding gas-filled voids (bubbles). Polymeric foams can be produced from a variety of materials, the two most common being polystyrene and polyurethane, and are generally used in applications that require a lightweight structure having a moderate degree of mechanical strength. These lightweight structures are often much more cost effective than the equivalent solid polymers and can also offer additional advantages e.g. thermal insulation properties. Polymeric foams can be open or closed cell. In open cell foam the pores in the foam structure are all linked together in one continuous interconnected network. In closed cell foam the individual pores are not linked but are rather separate from one another.
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