Plastic formulations, expanded

Expandable plastic n. A plastic formulated so as to be transformable into a cellular plastic by thermal, chemical, or mechanical means. 

Eoamable compositions in which the pressure within the cells is increased relative to that of the surroundings have generally been called expandable formulations. Both chemical and physical processes are used to stabilize plastic foams from expandable formulations. There is no single name for the group of cellular plastics produced by the decompression processes. The various operations used to make cellular plastics by this principle are extmsion, injection mol ding, and compression molding. Either physical or chemical methods may be used to stabilize products of the decompression process. 

Poly(vinylchloride). Cellular poly(vinyl chloride) can be produced from several expandable formulations as well as by decompression techniques. Rigid or flexible products can be made depending on the amount and type of plasticizer used (43). 

Today there are between 45 and 50 plastic materials. Physical volume, averaging a 13% per year growth rate for the past ten years, reached an estimated 16 billion pounds in 1968, higher than that of any metal except iron and steel, and approaching the total for non-ferrous metals. The number of formulas, grades, and types of these materials is greatly expanded by the use of plasticizers, fillers, and polymerization alternatives. All of these formulations are presumably different from one another and offer the user a broad material selection to fit his property and cost requirements. 

Unplasticized. Decreases to 1.30-1.32, depending on the formulation used when plasticized. General purpose, not expanded. 

This diversity presents a bewildering array of choices to a designer of plastic products. Table 4.1 illustrates the diverse choices available to a designer looking for a PS for a product application. First, he/she must select a grade and then a manufacturer. In each step shown in the table, available choices expand and the designer will select a low-cost formulation that has the required functionality. The number of available choices will also include various copolymers of styrene as well as blends of PS with other polymers (not inclnded in this estimate of choices). 

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