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Introduction:
The term"cellular plastics" encompasses a range of materials with widely varying properties and fields of applications. Virtually any polymer, thermoplastic or thermoset, can be made into a cellular or foamed form with the resulting products having densities ranging from 60 pounds per cubic foot (pcf) all the way down to 0.1 pcf. Basically, cellular plastics can have either of two structural configurations: (a) the closed-cell type, in which each individual cell, more or less spherical in shape, is completely enclosed by a wall of plastic, or (b) the open-cell type, in which the individual cells are intercommunicating. The foams can be ridged, semiridged, or flexible. Cellular plastics can be produced in the form of slabs, blocks, boards, sheets molded shapes, and sprayed coatings. Some can also be "foamed-in-place" in an open cavity. As originally conceived, most foamed plastics were completely cellular in structure; today, it is possible to arrange the cells so that a product may have essentially solid skin surface and a cellular core.
What causes plastics to expand into "foam?" Two principal methods are employed, physical and chemical.
Structural Foam is an injection molding process whereby a blowing-agent is used to provide a cellular structure to increase the rigidity of the part as well as eliminate sink-marks which are common to large injection molded parts.
Process:
The types of processes used, are adaptations of standard processes such as: Compression molding, Transfer molding, Injection molding, Extrusion, Blow molding, Calendering, Laminating, Cold molding, Casting, Plastisol casting, Thermoforming, Reinforcing, Foam molding, Foam casting, etc.
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