详情
Freon�is a registered trade name of�DuPont�which
it uses for a number of�halocarbon�products. They are stable
nonflammable and nontoxic gases or liquids which have typically
been used as�refrigerants�and as�aerosol propellants.
These include the�chlorofluorocarbons�(CFCs) implicated in�ozone
depletion, but also include newer refrigerants which typically
include fluorine instead of chlorine and do not deplete the ozone
layer.
The first CFCs were synthesized by�Fr�d�ric Swarts�in the ***0s. In
the late ***0s a research team was formed by�Charles Franklin
Kettering�in�General Motors�to find a replacement for the dangerous
refrigerants then in use. The team was headed by�Thomas Midgley,
Jr.[1]�In ***8 they improved the synthesis of CFCs and demonstrated
their usefulness for such a purpose and their stability and
nontoxicity. Kettering patented a refrigerating apparatus to use
the gas, this was issued to�Frigidaire, a wholly owned subsidiary
of�General Motors.
[2]In ***0 General Motors �formed�Kinetic Chemicals�to produce
Freon. Their product was�dichlorodifluoromethane�and is now
referred to as \'Freon**2\', \'R**2\', or \'CFC**2\'. The number
after the R is a�refrigerant class number�developed �to
systematically identify single halogenated hydrocarbons, plus there
are R numbers assigned for other refrigerants besides
halocarbons.
Most uses of CFCs are now banned or severely restricted by
the�Montreal Protocol�as they are believed to be responsible for
ozone depletion.
[3]�Brands of Freon containing�hydrofluorocarbons�(HFCs) instead
have replaced many uses, but they too are under strict control
under the�Kyoto protocol�as they are super-greenhouse effect gases.
They are no longer used in aerosols, but to date no suitable
general use alternatives to the halocarbons have been found for
refrigeration which are not flammable or toxic, problems the
original Freon was devised to avoid.
