Chemical Properties
Heptafluoropropane is a liquefied gas and exists as a liquid at room
temperature when contained under its own vapor pressure, or as a
gas when exposed to room temperature and atmospheric pressure.
The liquid is practically odorless and colorless. The gas in high
concentration has a faint etherlike odor. Heptafluoropropane is
noncorrosive, nonirritating, and nonflammable.
Uses
HFC 227ea is being developed as a CFC replacement in
refrigerants, high temperature heat pumps, air-conditioning
systems; as a fire suppressant; and for pharmaceutical aerosols
and metered-dose inhalers.
Flammability and Explosibility
Nonflammable
Pharmaceutical Applications
Heptafluoropropane is classified as a hydrofluorocarbon
(HFC) aerosol propellant since the molecule consists only of carbon,
fluorine, and hydrogen atoms. It does not contain any chlorine and
consequently does not affect the ozone layer, nor does it have an
effect upon global warming. It is therefore considered as an
alternative propellant to CFCs for metered-dose inhalers (MDIs).
While some of its physical and chemical properties are known, little
has been published in regard to its use as a replacement for CFCs in
MDIs.
The vapor pressure of heptafluoropropane is somewhat
lower than that of tetrafluoroethane and dichlorodifluoromethane
but considerably higher than the vapor pressure used to formulate
most MDIs.
When heptafluoropropane is used for pharmaceutical
aerosols and MDIs, the pharmaceutical grade must be specified.
Industrial grades may not be suitable due to their impurity profile.
Similarly to tetrafluoroethane, heptafluoropropane is not a good
solvent for medicinal agents or for the commonly used surfactants
and dispersing agents used in the formulation of MDIs.
There are several MDIs formulated with this propellant worldwide
that contain a steroid as the active ingredient.
Safety
Heptafluoropropane is used as a fire extinguisher and is applicable
as a non-CFC propellant in various metered-dose inhalers.
Heptafluoropropane is regarded as nontoxic and nonirritating
when used as directed. No acute or chronic hazard is present when it
is used normally. Inhaling high concentrations of heptafluoropropane
vapors can be harmful and is similar to inhaling vapors of
other propellants. Deliberate inhalation of vapors of heptafluoropropane
can be dangerous and may cause death. The same
labeling required of CFC aerosols would be required for those
containing heptafluoropropane as a propellant (except for the EPA
requirement).
storage
Heptafluoropropane is a nonreactive and stable material. The
liquefied gas is stable when used as a propellant and should be
stored in a metal cylinder in a cool, dry place.
