Polystyrene is a polymer consisting of styrene molecules covalently bonded in a long carbon chain. It is a thermoplastic polymer which means that is flexible and may be deformed by heat. It can be colorless to yellow and it has a penetrating odor. It has excellent electrical insulation properties, a relatively high resistance to water and a high refractive index.
Polystyrene was first synthesized by E. Simons of Berlin in 1839. Simons, an apothecary, distilled storax resin with a solution of sodium carbonate. The product was an oily residue that Simons called styrol because he assumed that that he had made styrene oxide. After Simons's first discovery there was a flurry of activity among the German scientific community as they tried to pin down the structure of styrol. J. Blyth and A. W. Hofman confirmed that the carbon-to-hydrogen ratio of the compound was the same as in benzene and a compound called cinnamol. This suggested that cinnamol and styrol, or styrene, were the same compound. This hypothesis was lent credibility by H. Kopp's work showing the two compounds had very similar physical properties. The final barrier in confirming the two substances were the same was that styrene prepared by Simons' method was optically active whereas cinnamol was not. In 1874 Jacobus Van't Hoff (1852-1911) finally proved that the optical activity of styrene was due to impurities.
The full scale production of polystyrene would not have been possible without a crucial discovery by Charles Friedal (1832-1899) and James Crafts (1839-1917). In 1877, while attempting to produce amyl iodide by treating amyl chloride with aluminum and iodide, Friedal and Crafts discovered that the reaction produced large amounts of hydrocarbons. Until that time hydrocarbons could not be produced quickly. Their discovery showed that aluminum chloride is a catalyst that facilitates the production of ethylbenzene with fewer impurities. With fewer impurities the reaction proceeds quickly, making the production of styrene--and therefore polystyrene--more economically feasible.
Polystyrene is a very versatile material and it may be formed into sheets, beads, foamed, injection molded or extruded. People encounter it nearly every day in the form of coffee cups, coolers, insulation and, until recently, fast food packaging. Foamed polystyrene has long been a staple for cheap thermal insulation. Polystyrene is also a frequent additive to plastic housewares, toys, and furniture. Its monomer (single unit) form, styrene, is a major component of acrylonitrile-styrene-butadiene rubber (ASB), which is used in many automotive applications.
Polystyrene foam has fallen out of favor in the past few years. About 90 percent of the chlorofluorocarbons (CFCs) used to make the resin foam are released into the atmosphere during production thus posing a significant threat to the ozone layer. The foam's disposal poses even more problems. Over 25 billion foam cups are thrown away every year in the United States alone. Incineration of these produces toxic air pollution and hazardous ash. Burying them uses precious landfill space. To solve these problems scientists have investigated the possibility of recycling the material. This has led to the use of the foam for a variety of plastic products.
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