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The Impact of This Strategic Material
| Article
# : |
14007 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
2 / 1988 |
1,421 Words |
| Author
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Raymond B. Seymour
Raymond B. Seymour is Distinguished Professor of Polymer
Science at the University of Southern Mississippi in
Hattiesburg, Mississippi. |
Most of us are familiar with polyethylene in the form of sandwich and garbage bags, milk jugs, and squeeze bottles for catsup and mustard. Yet this versatile and inexpensive material serves a wide range of functions, including many high technology applications.
Almost everyone has heard of radar, but few recognize that this technology is partly dependent on polymers of ethylene and its derivatives. Radar, an acronym for radio detection and ranging, was invented in the 1930s. At that time, the available electrical shielding used between the two conducting tubes of a special radar cable was inferior.
The discovery of polyethylene, which was eventually used as an effective insulating material, took place on the very day that Hitler's troops invaded Poland. Hence, initially, polyethylene was considered a strategic material. Today polyethylene is still used in radar systems that are responsible for the safety of aircraft and ships and in automobile speed-trap radar systems. This little recognized use of polyethylene makes our lives safer.
Varying Properties
Polyethylene is produced by the polymerization of a colorless, flammable, unsaturated gaseous hydrocarbon, called ethylene, which is the world's most widely used petrochemical. In the polymerization process, hundreds of small molecules, called monomers, are joined together, sequentially, to form an extremely long chained molecule called a polymer or a macromolecule. Over the years, scientists have improved the polymerization process by experimenting with different catalysts and methods of production. This has led to polyethylenes with varying properties.
Many of these varying properties are due to the length of the polymer chain. The toughness and impact resistance of polyethylene increases dramatically as the chain length or molecular weight is increased, and consequently polyethylenes with long chain lengths are used for molding trash barrels, automotive seat backs, truck bed liners, tote boxes, canoes, and water filtration systems.
Such polyethylenes also have been used to make pipe with diameters as large as 48 inches and with a wall thickness of one inch. Polyethylene pipes are used to rejuvenate faulty sewer lines by inserting the pipe into unexcavated lines. Gasoline tanks made from these higher-density polyethylenes can be molded in intricate shapes so that formerly
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