Plastic

Name:
Plastic
Detailed information:
(1) Capable of being shaped or molded with or without the application of heat. Soft waxes and moist clay are good examples of this property.See Plasticity.(2) A high polymer, usually synthetic, combined with other ingredients, such as curatives, fillers, reinforcing agents, colorants, plasticizers, etc.; the mixture can be formed or molded under heat and pressure in its raw state and machined to high dimensional accuracy, trimmed, and finished in its hardened state. The thermoplastic type can be resoftened to its original condition by heat; the thermosetting type cannot.Plastics in general (including all forms) are sensitive to high temperatures, among the more resistant being fluorocarbon resins, nylon, phenolics, polyimides, and silicones, though even these soften or melt above 260C. Other types (cellulosics, polyethylene, acrylic polymers, polystyrene) are combustible when exposed to flame for a short time and still others (polyurethane) burn with evolution of toxic fumes.Engineering plastics are those to which standard metal engineering equations can be applied; they are capable of sustaining high loads and stresses and are machinable and dimensionally stable. They are used in construction, as machine parts, automobile components, etc. Among the more important are nylon, acetals, polycarbonates, ABS resins, PPO/styrene, and polybutylene terephthalate.Fibers, films, and bristles are examples of extruded forms. Plastics may be shaped by either compression molding (direct pressure on solid material in a hydraulic press) or injection molding(injection of a measured amount of material into a mold in liquid form). The latter process is most generally used, and articles of considerable size can be produced. Because of their dielectric properties, plastics are essential components of electrical and electronic equipment (especially for use within the human body).Plastics can be made into flexible and rigid foams by use of a blowing agent; these foams are light and strong, and the rigid type is machinable. They are collectively called cellular plastics. Plastics can also be reinforced, usually with glass or metallic fibers, for added strength. They are laminated to paper, cloth, wood, etc. for many uses in the packaging, electrical, and furniture industries; they also can be metal-plated. Plastic pipe is widely used for underground transportation of gases and liquids over long distances and intraplant.Several natural materials (waxes, clays, and asphalts) have rheological properties similar to synthetic products, but because they are not polymeric, are not considered true plastics. Certain proteins (casein, zein) are natural high polymers from which plastics are made (buttons and other small items), but they are of decreasing importance.Plastics have permeated industrial technology. Not only have they replaced and improved upon many materials formerly used, but they also have made possible industrial and medical applications that would have been impracticable with older technologies. Their major application areas are (1) automobile bodies and components, boat hulls; (2) building and construction (siding, piping insulation, flooring); (3) packaging (vapor-proof barriers, display cartons, bottles, drum linings); (4) textiles (carpets, cordage, suiting, hosiery, drip-dry fabrics, etc.); (5) organic coatings (paint and varnish vehicles); (6) adhesives (plywood, reinforced plastics, laminated structures); (7) pipelines; (8) electrical and electronic components; (9) surgical implants; (10) miscellaneous (luggage, toys, tableware, brushes, furniture, etc.).The Nobel Prize was awarded in 2000 for work on developing conducting plastics.For additional information refer to The Society of the Plastics Industry. See Polymer, High; Cellular Plastic; Reinforced Plastic; Foam, Plastic; Plastic Pipe. See Appendix III for a history of the industry.