Tetrafluoroethylene (TFE) is a
fluorocarbon
Fluorocarbons are chemical compounds with carbon-fluorine bonds. Compounds that contain many C-F bonds often have distinctive properties, e.g., enhanced stability, volatility, and hydrophobicity. Several fluorocarbons and their derivatives are ...
with the
chemical formula
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...
. It is a colorless gas. Its structure is . It is used primarily in the industrial preparation of
fluoropolymer
A fluoropolymer is a fluorocarbon-based polymer with multiple carbon–fluorine bonds. It is characterized by a high resistance to solvents, acids, and bases. The best known fluoropolymer is polytetrafluoroethylene under the brand name "Teflon, ...
s. It is the simplest
perfluorinated alkene
In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins.
The Internationa ...
.
It was first reported as "dicarbon tetrafluoride" in 1890.
Properties
Tetrafluoroethylene is a synthetic colorless, odorless gas that is insoluble in water. Like all unsaturated fluorocarbons, it is susceptible to
nucleophilic
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they a ...
attack. It is unstable towards decomposition to
carbon
Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
and
carbon tetrafluoride
Tetrafluoromethane, also known as carbon tetrafluoride or R-14, is the simplest perfluorocarbon (Carbon, CFluorine, F4). As its IUPAC name indicates, tetrafluoromethane is the perfluorinated counterpart to the hydrocarbon methane. It can also be c ...
() and prone to form explosive peroxides in contact with air.
Industrial use
Polymerization of tetrafluoroethylene produces
polytetrafluoroethylene
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a corporate spin-of ...
(PTFE) polymers such as
Teflon
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from ...
and
Fluon
Ethylene tetrafluoroethylene (ETFE) is a fluorine-based plastic. It was designed to have high corrosion resistance and strength over a wide temperature range. ETFE is a polymer and its source-based name is poly (ethene-co-tetrafluoroethene). It i ...
. PTFE is one of the two fluorocarbon resins composed wholly of fluorine and carbon. The other resin composed purely of carbon and fluorine is the
copolymer
In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are som ...
of TFE with typically 6–9%
hexafluoropropene
Hexafluoropropylene is the fluoroalkene with the formula CF3CF=CF2. It is the perfluorocarbon counterpart to the hydrocarbon propylene. It is mainly used to produce copolymers with tetrafluoroethylene. Hexafluoropropylene is used as a chemical i ...
(HFP), which is known as FEP (
fluorinated ethylene propylene
Fluorinated ethylene propylene (FEP) is a copolymer of hexafluoropropylene and tetrafluoroethylene. It differs from the polytetrafluoroethylene (PTFE) resins in that it is melt-processable using conventional injection molding and Plastic extrusio ...
copolymer). TFE is also used in the preparation of numerous copolymers that also include hydrogen and/or oxygen, including both fluoroplastics and
fluoroelastomers
A fluoroelastomer is a fluorocarbon-based synthetic rubber. Fluoroelastomers generally have wide chemical resistance.
Composition
Several compositions of fluoroelastomers exist including FKM (by ASTM D1418 standard, equivalent to FPM by ISO/DIN 1 ...
. Typical TFE-based fluoroplastics include ETFE, the alternating 1:1 copolymer with ethylene, and PFA, which is a random copolymer similar to FEP but with a minor amount of a perfluoroalkyl vinyl ether (PAVE) rather than HFP.
DuPont
Dupont, DuPont, Du Pont, duPont, or du Pont may refer to:
People
* Dupont (surname) Dupont, also spelled as DuPont, duPont, Du Pont, or du Pont is a French surname meaning "of the bridge", historically indicating that the holder of the surname re ...
uses primarily perfluoro(methylvinylether), whereas
Daikin
is a Japanese multinational conglomerate company headquartered in Osaka. Daikin is the world's largest air conditioner manufacturer.
History
Daikin Industries Ltd was founded in 1924 as by Akira Yamada. In 1953, Daiflon or polychloro ...
uses primarily perfluoro(propylvinylether) in manufacturing PFA. There are numerous other fluoropolymers that contain tetrafluoroethylene, but usually not at greater than 50% by weight.
Manufacture
TFE is manufactured from
chloroform
Chloroform, or trichloromethane (often abbreviated as TCM), is an organochloride with the formula and a common solvent. It is a volatile, colorless, sweet-smelling, dense liquid produced on a large scale as a precursor to refrigerants and po ...
.
Chloroform is fluorinated by reaction with
hydrogen fluoride
Hydrogen fluoride (fluorane) is an Inorganic chemistry, inorganic compound with chemical formula . It is a very poisonous, colorless gas or liquid that dissolves in water to yield hydrofluoric acid. It is the principal industrial source of fluori ...
to produce
chlorodifluoromethane
Chlorodifluoromethane or difluoromonochloromethane is a hydrochlorofluorocarbon (HCFC). This colorless gas is better known as HCFC-22, or R-22, or . It was commonly used as a propellant and refrigerant. These applications were phased out under ...
(R-22).
Pyrolysis
Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology
The word ''pyrolysis'' is coined from the Gree ...
of chlorodifluoromethane (at 550–750 °C) yields TFE, with
difluorocarbene
Difluorocarbene is the chemical compound with formula CF2. It has a short half-life, 0.5 and 20 ms, in solution and in the gas phase, respectively.Douglas A Jean Osteraas "Difluorocarbene Modification of Polymer and Fiber Surfaces," ''Journal ...
as an intermediate.
:
:
Alternatively, it can be prepared by pyrolysis of
fluoroform
Fluoroform, or trifluoromethane, is the chemical compound with the formula . It is a hydrofluorocarbon as well as being a part of the haloforms, a class of compounds with the formula (X = halogen) with C3v symmetry. Fluoroform is used in divers ...
(which is also produced from chloroform and HF):
:
Laboratory methods
A convenient, safe method for generating TFE is the
pyrolysis
Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology
The word ''pyrolysis'' is coined from the Gree ...
of the
sodium
Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...
salt
In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...
of
pentafluoropropionic acid:
:
The
depolymerization Depolymerization (or depolymerisation) is the process of converting a polymer into a monomer or a mixture of monomers. This process is driven by an increase in entropy.
Ceiling temperature
The tendency of polymers to depolymerize is indicated by ...
reaction – vacuum pyrolysis of PTFE at in a
quartz vessel – is a traditional laboratory synthesis of TFE. The process is however challenging because attention must be paid to pressure, as well as the avoidance of
perfluoroisobutene
Perfluoroisobutene (PFIB) is the perfluorocarbon with the formula . Classified as a perfluoroalkene, it is the fluorinated counterpart of the hydrocarbon isobutene. This colorless gas is notable for its high toxicity.
Production and reactions
...
. PTFE polymer
cracks, and at a pressure below exclusively is obtained. At higher pressures the product mixture contains
hexafluoropropylene
Hexafluoropropylene is the fluoroalkene with the formula CF3CF=CF2. It is the perfluorocarbon counterpart to the hydrocarbon propylene. It is mainly used to produce copolymers with tetrafluoroethylene. Hexafluoropropylene is used as a chemical i ...
and
octafluorocyclobutane
Octafluorocyclobutane, or perfluorocyclobutane, C4F8, is an organofluorine compound which enjoys several niche applications. Octafluorocyclobutane is a colourless gas and shipped as a liquefied gas. It is the perfluorinated analogue of cyclobutane ...
.
Reactions
Tetrafluoroethylene is a reactive molecule that participates in myriad reactions. Owing to the presence of four fluorine substituents, its reactions differ strongly from the behavior of conventional alkenes such as
ethylene
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...
. Tetrafluoroethylene dimerizes, giving
octafluorocyclobutane
Octafluorocyclobutane, or perfluorocyclobutane, C4F8, is an organofluorine compound which enjoys several niche applications. Octafluorocyclobutane is a colourless gas and shipped as a liquefied gas. It is the perfluorinated analogue of cyclobutane ...
. Even normal alkenes and dienes add tetrafluoroethylene in a
+2manner.
1,3-Butadiene
1,3-Butadiene () is the organic compound with the formula CH2=CH-CH=CH2. It is a colorless gas that is easily condensed to a liquid. It is important industrially as a precursor to synthetic rubber. The molecule can be viewed as the union of two ...
gives 3-vinyl-1,1,2,2-tetrafluorocyclobutane.
Safety
The main hazard associated with TFE is that of explosion, especially if oxygen is present. TFE reacts with oxygen at low temperatures to form an explosive oxide,
the detonation of which is usually sufficient to trigger explosive decomposition of TFE to C and . Explosions can also be caused by
adiabatic compression
An adiabatic process (''adiabatic'' ) is a type of thermodynamic process that occurs without transferring heat between the thermodynamic system and its Environment (systems), environment. Unlike an isothermal process, an adiabatic process transf ...
if the TFE is handled under high pressure, which it typically is in an industrial setting. If pressurised TFE is allowed into a vessel or pipework at a lower pressure, then the atmosphere in the vessel will be compressed by the TFE, causing it to heat up, potentially to the point where it might detonate the TFE. This has been known to cause explosions. In industry, pipework is flushed with pressurized nitrogen, before the introduction of TFE, both to exclude oxygen and prevent adiabatic compression.
TFE is an
alkylating agent Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting ...
, albeit a weak one, and as such is expected to be a carcinogen.
LD50(rat, inhalation) = 40000 ppm.
The
International Agency for Research on Cancer
The International Agency for Research on Cancer (IARC; ) is an intergovernmental agency forming part of the World Health Organization of the United Nations.
Its role is to conduct and coordinate research into the causes of cancer. It also cance ...
classifies TFE as probably carcinogenic to humans based on animal studies.
See also
*
Tetrachloroethylene
Tetrachloroethylene, also known as perchloroethylene or under the systematic name tetrachloroethene, and abbreviations such as perc (or PERC), and PCE, is a chlorocarbon with the formula . It is a non-flammable, stable, colorless and heavy liqu ...
*
1,1,1,2-Tetrafluoroethane
1,1,1,2-Tetrafluoroethane (also known as norflurane ( INN), R-134a, Klea 134a, Freon 134a, Forane 134a, Genetron 134a, Green Gas, Florasol 134a, Suva 134a, HFA-134a, or HFC-134a) is a hydrofluorocarbon (HFC) and haloalkane refrigerant with th ...
*
Fluorochemical industry
The global market for chemicals from fluorine was about US$16 billion per year as of 2006. The industry was predicted to reach 2.6 million metric tons per year by 2015. The largest market is the United States. Western Europe is the ...
References
External links
National Toxicology Program Chemical RepositoryTetrafluoroethylene, hexafluoropropylene and vinylidene fluoride terpolymer – aka THV, melt-processable members of the fluorocarbon family*
{{Authority control
Perfluoroalkenes
Monomers
IARC Group 2A carcinogens
Organic compounds with 2 carbon atoms