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Glycol - Uses

ethylene polymer polyester chemical

In the 1993 ranking of chemicals according to the quantity produced in the United States, ethylene glycol ranked 30th, with 5.23 billion lb (2.37 × 109 kg). Much of this ethylene glycol is used as antifreeze in automobile radiators. The addition of ethylene glycol to water causes the freezing point of the latter to decrease, thus the damage that would be caused by the water freezing in a radiator can be avoided by using a mixture of water and ethylene glycol as the coolant. An added advantage of using such a mixture is that its boiling point is higher than that of water, which reduces the possibility of boil-over during summer driving. In addition to ethylene glycol, commercial antifreeze contains several additives, including a dye to reduce the likelihood of the highly toxic ethylene glycol being accidentally ingested. Concern over the toxicity of ethylene glyco-the lethal dose of ethylene glycol for humans is 1.4 ml/kg-resulted in the introduction, in 1993, of antifreeze based on non-toxic propylene glycol.

The second major use of ethylene glycol is in the production of poly(ethylene terephthalate), or PET. This polymer, a polyester, is obtained by reacting ethylene glycol with terephthalic acid (IUPAC name: 1,4-benzenedicarboxylic acid) or its dimethyl ester (Figure 4).

Poly(ethylene terephthalate) is used to produce textiles, large soft-drink containers, photographic film, and overhead transparencies. It is marketed under various trademarks including DACRON®, Terylene®, Fortrel®, and Mylar®. Textiles containing this polyester are resistant to wrinkling, and can withstand frequent laundering. Poly(ethylene terephthalate) has been utilized in the manufacture of clothing, bed linen, carpeting, and drapes.

Other glycols are also used in polymer production; for example, tetramethylene glycol is used to produce polyesters, and diethylene glycol is used in the manufacture of polyurethane and unsaturated polyester resins. Propylene glycol is used in the manufacture of the polyurethane foam used in car seats and furniture. It is also one of the raw materials required to produce the unsaturated polyester resins used to make car bodies and playground equipment.

Resources

Books

Bailey, James E. Ullmann's Encyclopedia of Industrial Chemistry. New York: VCH, 2003.

Budavari, Susan, ed. The Merck Index. 11th ed. Rahway, NJ: Merck, 1989.

Loudon,G. Mark. Organic Chemistry. Oxford: Oxford University Press, 2002.

Szmant, H. Harry. Organic Building Blocks of the Chemical Industry. New York: Wiley, 1989.


Arthur M. Last

KEY TERMS

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Diol

—An aliphatic organic compound containing two hydroxyl (OH) groups.

Intermolecular hydrogen bonding

—The attractive force between a hydrogen atom in one molecule and a strongly electronegative atom, such as oxygen, in a second molecule.

IUPAC

—International Union of Pure and Applied Chemistry, the world oranization known for its efforts to standardize chemical names and symbols.

Polyester

—A polymer in which the identical repeating units are linked by ester groups.

Poly(ethylene terephthalate)

—A polymer formed by the reaction of ethylene glycol and terephthalic acid (or its dimethyl ester).

Polymer

—A compound of high molecular weight whose molecules are made up of a number of identical repeating units.

Polyurethane

—A polymer formed through the reaction of a glycol with a diisocyanate.

Unsaturated polyester resin

—A product in which long-chain polyester molecules containing carbon-carbon double bonds have been joined (cross-linked) to other identical molecules.

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