Styrene

OVERVIEW

Styrene (STY-reen) is a colorless to yellowish, oily liquid with a sweet, flowery odor at low concentrations and a sharp, penetrating, disagreeable odor at high concentrations. When exposed to light and air, it slowly polymerizes. Polymerization is the chemical reaction in which a small molecule, such as styrene, reacts with other molecules of the same kind to produce very large molecules, usually made of long chains. Styrene occurs naturally in very small amounts in certain foods, such as coffee, strawberries, and cinnamon; in the sap of some trees; and in the gaseous emissions from internal combustion engines, waste incinerators, and tobacco smoke.

KEY FACTS

OTHER NAMES:

Ethylbenzene; vinylbenzene; phenylethylene; styrol; styrolene; cinnamol

FORMULA:

C₆H₅CH=CH₂

ELEMENTS:

Carbon, hydrogen

COMPOUND TYPE:

Aromatic hydrocarbon (organic)

STATE:

Liquid

MOLECULAR WEIGHT:

104.15 g/mol

MELTING POINT:

−30.65°C (−23.17°F)

BOILING POINT:

145°C (293°F)

SOLUBILITY:

Insoluble in water; soluble in ethyl alcohol and acetone

HOW IT IS MADE

The first step in the preparation of styrene involves the reaction between benzene (C₆H₆) and ethylene (ethene; CH₂=CH₂), resulting in the formation of ethylbenzene (C₆H₅CH₂CH₃). The ethylbenzene is then dehydrogenated over a catalyst of iron(III) oxides at temperatures of about 600°C (1100°F). Dehydrogenation is the process by which hydrogen atoms are removed from a compound:

C₆H₅CH₂CH₃ − H₂ → C₆H₅CH=CH₂

COMMON USES AND POTENTIAL HAZARDS

About two-thirds of all the styrene produced in the United States is used in the manufacture of polystyrene. Polystyrene is a clear, colorless, hard plastic that is easily molded and made into a foam known as styrofoam. It is used in the insulation of electrical wires and devices, in containers for hot and cold foods and drinks, and for the insulation of buildings. Almost all of the remaining styrene is used in the production of other polymers, such as acrylonitrile-butadiene-styrene resins, styrene-acrylonitrile resins, styrene-butadiene rubber and latex, and various polyester resins.

The styrene fumes to which a person might be exposed are mild irritants to the skin, eyes, and respiratory tract. They may cause inflammation of the skin, eyes, nose, and throat. In larger amounts, they may adversely affect the nervous system causing nausea, tiredness, muscle weakness, depression, and concentration problems. Adequate studies on the carcinogenic properties of styrene have not been conducted, but the International Agency for Research on Cancer has called styrene a possible carcinogen. There are also no studies on the possible reproductive effects of exposure to styrene. In any case, the individuals most at risk for the health hazards of styrene are people who come into contact with the chemical in the workplace.

Interesting Facts

• In 2004, about 5.4 million metric tons (5.9 million short tons) of styrene were produced in the United States. It ranked 17th among all chemicals produced that year.

Words to Know

CARCINOGEN

A substance that causes cancer in humans or other animals.

RESIN

A natural or artificial soft solid material that is used as glue, ink, or in various plastics.

Styrene is also a moderate fire risk. In certain concentrations, it is also explosive. Again, these risks are of concern primarily to individuals who work with the pure compound in their jobs.

FOR FURTHER INFORMATION

"Material Safety Data Sheet: Styrene Monomer, Inhibited." Department of Chemistry, Iowa State University. http://avogadro.chem.iastate.edu/MSDS/styrene.htm (accessed on November 15, 2005).

"Styrene." International Chemical Safety Cards. http://www.cdc.gov/niosh/ipcsneng/neng0073.html (accessed on November 15, 2005).

"Styrene." National Safety Council. http://www.nsc.org/library/chemical/styrene.htmfx (accessed on November 15, 2005).

The Styrene Information and Research Center. http://www.styrene.org/ (accessed on November 15, 2005).

"ToxFAQs for Styrene." Agency for Toxic Substances and Disease Registry. http://www.atsdr.cdc.gov/tfacts53.html (accessed on November 15, 2005).

See AlsoPolystyrene