Plastics (Encyclopedia of Environmental Issues, Revised Edition)
Plastics are generally divided into two types: thermoplastics and thermosetting plastics. Thermoplastics can be repeatedly softened by heating and molded into shapes that harden upon cooling. Thermosetting plastics are also soft when first heated and can be molded into shapes, but when reheated, they decompose instead of softening. Both kinds of plastics are used widely around the world to make all kinds of products.
Because the primary raw material for making plastics is oil, the reliance on plastics is part of the world’s dependence on the drilling for and transport of oil, both of which are related to environmental problems, among them oil spills, tanker accidents, and air pollution from oil refineries. Another important way in which plastics affect the environment is in the difficulty they pose for disposal. The very properties that make plastics so useful—their stability and resistance to attack by chemicals and bacteria—make them almost indestructible. Unlike metal, wood, and paper, plastics do not corrode or decay. They contribute to unsightly litter along roadsides and can be found floating on the surfaces of the ocean everywhere. Because plastics are light, they account for a large proportion of the volume of the world’s solid waste. For example, while plastics account for only 7 percent of the total weight of solid waste generated in the United States, they make up about 20 percent of its volume.
A number of...
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Methods of Disposal (Encyclopedia of Environmental Issues, Revised Edition)
No single way has yet been found to solve the problem of disposal of plastics, but a number of methods have lessened the impacts of plastics on the environment. The first of these is recycling, which helps reduce the amount of new plastic that is made and the energy needed to make it. More than three-fourths of all plastics are thermoplastics that can be recycled through melting and remolding. In order for recycling to be successful, however, used plastic items must first be separated according to type. Different plastics melt at different temperatures, and molding machines work only if they are fed with pure materials. In 1988 the Society of the Plastics Industry developed a uniform coding system to simplify the sorting of waste plastic; most U.S. states require plastics manufacturers to place the codes on the items they make, and the system is now in use internationally.
Uses have been developed for recycled plastic that take advantage of this material’s low cost and durability. Plastic products with short service lives, such as packing foam, wrap, and containers, can be made into products with long lives, such as construction materials and plastic pipe. Recycled soft-drink bottles are used to make carpeting and insulation for parkas. Disposable cups and plates are converted to plastic “lumber.”
The incineration of plastics to produce energy is another approach to disposal, but this method has the drawback...
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Further Reading (Encyclopedia of Environmental Issues, Revised Edition)
Andrady, Anthony L., ed. Plastics and the Environment. Hoboken, N.J.: John Wiley & Sons, 2003.
Hill, Marquita K. “Solid Waste.” In Understanding Environmental Pollution. 3d ed. New York: Cambridge University Press, 2010.
Snyder, Carl H. The Extraordinary Chemistry of Ordinary Things. 4th ed. Hoboken, N.J.: John Wiley & Sons, 2003.
Wolf, Nancy, and Ellen Feldman. Plastics: America’s Packaging Dilemma. Washington, D.C.: Island Press, 1990.
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Plastics (Encyclopedia of Science)
The term plastic can be used as both an adjective and a noun. As an adjective, the term refers to any material that can be shaped or molded, with or without the application of heat. In this respect, objects such as soft waxes, asphalt, and moist clays are said to be plastic.
As a noun, the term describes a natural or synthetic polymer. A polymer is a material whose molecules consist of very long chains of one or two repeating units known as monomers. As an example, the synthetic polymer called polyethylene consists of thousands of ethylene units joined to each other in long chains. If the letter E is taken to represent an ethylene unit (monomer), then the polymer polyethylene can be represented as:
Although the term plastic is strictly defined as either a natural or synthetic material, it is probably understood by most people today to refer
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