HomePage | Recent Changes | Preferences

CFCs (ChloroFluoroCarbons) are a family of artificial compounds, formerly used widely in industry, for example as refrigerant?s, propellants and cleaning solvents. Since the discovery of their destructive effects on the [ozone layer]?, their use has been generally prohibited.

CFCs were developed by the American engineer Thomas Midgley as a replacement for ammonia (then a common refrigerant). The new compound developed had to have a low boiling point, a lack of toxicity and be generally non-reactive. In a demonstration for the American Chemical Association, Midgley flamboyantly demonstrated all these properties by inhaling a breath of the gas and using it to blow out a candle.

Midgley specifically developed CCl2F2. However one of the attractive features of CFCs is that there exists a whole family of the compounds, each having a unique boiling point which can suit different applications. As well as refrigerants, CFCs have been used as propellants in aerosol cans, cleaning solvents for circuit boards, and as blowing agents for making expanded plastics (such as those used to store fast-foods.)

There has been a movement since the end of the eighties and throughout the nineties to ban CFCs because of their destructive effect on the ozone layer. This damage was, however, first discovered in the seventies, due mainly to the work of scientists [Sherry Rowland]? and [Mario Molina]?. It turns out that one of CFCs most attractive features - its unreactivity - has been instrumental in making it one of our worst pollutants. CFC's lack of reactivity gives it a lifespan long enough to diffuse up in to the upper stratosphere?. Here the sun's UV radiation is strong enough to break off the chlorine atom, which on its own is a highly reactive free radical. This catalyses the break up of ozone in to oxygen:

 Cl + O3 -> ClO + O2

 ClO + O -> Cl + O2

CFCs are such a big problem because the chlorine is regenerated at the end of these reactions, making it able to keep on reacting with millions of other ozone molecules. The ozone hole produced is able to let through UV light, which causes cancer in humans.

CFC also stands for the Computer Film Company one of the earliest digital film special-effects companies.

HomePage | Recent Changes | Preferences
This page is read-only | View other revisions
Last edited December 14, 2001 6:35 am by Sodium (diff)