Perfluorinated Carbons (PFCs)

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Perfluorinated Carbons (PFCs)

Introduction

Perfluorinated carbons (PFCs) are human-made chemicals that are composed only of carbon and fluorine. PFCs do not deplete the ozone layer, but they are greenhouse gases with global warming potential ranging from 6,500 to 9,200 times more damaging than carbon dioxide, the leading cause of global warming. They also have lifetimes in the atmosphere that range from 2,600 years to over 50,000 years. PFCs that have escaped into the atmosphere could possibly remain there essentially forever.

Historical Background and Scientific Foundations

PFCs are colorless, non-flammable, and chemically almost non-reactive. Per is a prefix that means a compound has the maximum amount of an element that is possible in it, as in perfluorocarbons. PFCs have as many fluorine atoms as are possible to bond to a given number of carbons as the carbons are bonded to each other. All the PFCs are gases except one, and that one is a volatile liquid (a volatile liquid evaporates readily at normal room temperature and pressure). The number of carbon atoms determines how heavy an individual compound will be. The weight of a molecule is one of the factors that determines whether a compound will exist as a solid, liquid, or gas at room temperature. The heaviest PFC with six carbons is a volatile liquid at room temperature and pressure.

PFCs are primarily used where their properties make them the best choice for performance and system efficiency. They are also used in certain applications to replace hydrofluorocarbons (HFCs), but PFCs are costly to manufacture and so are not in as widespread use as hydrofluorocarbons (HFCs). The use of PFCs in place of HFCs is questionable. The Montreal Protocol banned ozone-depleting chlorofluorocarbons (CFCs). Their replacements, hydrochlorofluorocarbons (HCFC), are being phased out for the same reason. HFCs are replacing HCFCs because HFCs do not deplete the ozone layer. However, the HFCs are serious greenhouse gases, as are PFCs.

WORDS TO KNOW

CHLOROFLUOROCARBONS: Members of the larger group of compounds termed halocarbons. All halocarbons contain carbon and halons (chlorine, fluorine, or bromine). When released into the atmosphere, CFCs and other halocarbons deplete the ozone layer and have high global warming potential.

KYOTO PROTOCOL: Extension in 1997 of the 1992 United Nations Framework Convention on Climate Change (UNFCCC), an international treaty signed by almost all countries with the goal of mitigating climate change. The United States, as of early 2008, was the only industrialized country to have not ratified the Kyoto Protocol, which is due to be replaced by an improved and updated agreement starting in 2012.

SEMICONDUCTOR INDUSTRY: Global high-technology industrial sector that produces semiconductor-based electronic components, such as the microprocessor chips that are at the heart of most computers, personal music players, and other consumer electronics devices. The industry is a major emitter of the greenhouse gases perfluorocarbons, trifluoromethane, nitrogen trifluoride, and sulfur hexafluoride. U.S. semiconductor makers emitted the equivalent of 4.6 million metric tons of carbon dioxide in 2002, 37% less than in 1999 according to the U.S. Environmental Protection Agency.

Impacts and Issues

Perfluorocarbons are on the list of six main greenhouse gases cited under the United Nations Framework Convention on Climate Change, known as the Kyoto Protocol. The agreement was adopted by 171 countries at a conference in 1997 to significantly reduce overall emission of the identified greenhouse gases.

The major applications of PFCs are in the production of aluminum and in the manufacture of semiconductors (an element of microchips), with most of the PFCs entering the atmosphere because they have escaped during the manufacturing processes. In the semiconductor industry, PFCs are used in a number of the processes, including as a source of fluorine in specialized etching processes. The European Parliament and Council has directed that the efforts already being made to reduce the leakages of PFCs should be increased.

BIBLIOGRAPHY

Web Sites

“Products and Applications.” Fluorocarbons and Sulfur Hexafluoride. European Fluoride Technical Committee, 2007. <http://www.fluorocarbon.org> (accessed August 14, 2007).

“Perfluorocarbons.” Environmental Agency (UK), 2007. <http://www.environment-agency.gov.uk/> (accessed August 14, 2007).

Climate Change: In Context