Plastic
Plastics are a subspecies of a class of materials known as polymers. These are composed of large molecules, formed by joining many, often thousands, of smaller molecules (monomers) together. Other kinds of polymers are fibers, films, elastomers (rubbers), and biopolymers (i.e., cellulose, proteins, and nucleic acids). Plastics are made from low-molecular-weight monomer precursors, organic materials, which are mostly derived from petroleum, that are joined together by a process called "polymerization." Plastics owe their name to their most important property, the ability to be shaped to almost any form to produce articles of practical value. Plastics can be stiff and hard or flexible and soft. Because of their light weight, low cost, and desirable properties, their use has rapidly increased and they have replaced other materials such as metals and glass. They are used in millions of items, including cars, bullet-proof vests, toys, hospital equipment, and food containers. More than a hundred billion pounds of plastic were produced in 2000. Their increased use has resulted in concern with (1) the consumption of natural resources such as oil, (2) the toxicity associated with their manufacture and use, and (3) the environmental impact arising from discarded plastics.
Pollution Problems
Industrial practices in plastic manufacture can lead to polluting effluents and the use of toxic intermediates, the exposure to which can be hazardous.
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