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{{chembox new],
polytetrafluoroethylene (
PTFE) is a synthetic fluoropolymer which finds numerous applications. PTFE's most well known trademark in the industry is the
DuPont brand name
Teflon.
PTFE has an extremely low
coefficient of friction and is used as a non-stick coating for pans and other cookware. It is very non-reactive, and so is often used in containers and pipework for reactive and corrosive chemicals. Where used as a lubricant, PTFE significantly reduces friction, wear and energy consumption of machinery.
History
PTFE was invented accidentally by
Roy Plunkett of Kinetic Chemicals The story of Teflon The original patent number is US2,230,654.
Teflon was first sold commercially in 1946. By 1950, DuPont has acquired full interest in Kinetic Chemicals and was producing over a million pounds (450 t) per year in
Parkersburg, West Virginia. In 1954, French engineer
Marc Grégoire created the first pan coated with Teflon non-stick resin under the brandname of Tefal after his wife urging him to try the material which he was using on fishing tackle to be used on her cooking pans.[http://home.nycap.rr.com/useless/teflon/index.html Teflon History - Retrieved October 15, 2007 In the United States Kansas City, Missouri resident A. Trozzolo, who had been using the substance on a scientific instruments, marketed the first frying pan "The Happy Pan" in 1961. TEFLON MAKER: OUT OF FRYING PAN INTO FAME - New York Times - December 21, 1986
An early advanced use was in the
Manhattan Project as a material to coat valves and seals in the pipes holding highly reactive uranium hexafluoride in the vast
enriched uranium plant at
Oak Ridge, Tennessee, when it was known as
K416.
The common statement that PTFE is a spin-off from the
United States space program is an
urban legend.
Properties
s as it has very low friction and high heat resistance.
PTFE is a white solid at room temperature, with a
density of about 2.2 g/cm³. According to DuPont its melting point is 327 °C (620.6 °F), but its properties degrade above 260 °C (500 °F).http://www2.dupont.com/Teflon_Industrial/en_US/tech_info/techinfo_compare.html Fluoropolymer Comparison - Typical Properties] www2.dupont.com. Retrieved
10 September 2006.
The coefficient of friction of plastics is usually measured against polished steel. Coefficient of Friction (COF) Testing of Plastics MatWeb Material Property Data Retrieved 1 January 2007. PTFE's coefficient of friction is 0.1 or less, which is the lowest of any known solid material. PTFE's resistance to
van der Waals forces means that it is the only known surface to which a gecko cannot stick.http://socrates.berkeley.edu/~peattiea/research_main.html
PTFE has excellent dielectric properties. This is especially true at high radio frequency, making it suitable for use as an
Electrical insulation in
cables and
connector assemblies and as a material for printed circuit boards used at
microwave frequencies. Combined with its high melting temperature, this makes it the material of choice as a high-performance substitute for the weaker and lower melting point polyethylene that is commonly used in low-cost applications. Its extremely high bulk
resistivity makes it an ideal material for fabricating long life
electrets, useful devices that are the electrostatic analogues of
magnets.
Because of its chemical inertness, PTFE cannot be cross-linked like an
elastomer. Therefore it has no "memory," and is subject to
creep (deformation) (also known as "cold flow" and "compression set"). This can be both good and bad. A little bit of creep allows PTFE seals to conform to mating surfaces better than most other plastic seals. Too much creep, however, and the seal is compromised. Compounding fillers control unwanted creep, as well as to improve wear, friction, and other properties. Sometimes metal springs apply continuous force to PTFE seals to give good contact, while permitting some creep.
Property values
{| class="wikitable" cellpadding="4" cellspacing="0" border="1" style="border-collapse: collapse"|+ style="font-size:larger;font-weight:bold;"|Characteristics of PTFE (Teflon)|-! Property! Units! Value|-|
Density| align="center" | °C| align="center" | 327|-| [Young's modulus| align="center" | MPa| align="center" | 23|-| [Coefficient of friction (measured against polished stainless steel)]| align="center" || align="center" | ε=2.1,tan(δ)
Carcinogens in production
The
United States Environmental Protection Agency's scientific advisory board found in 2005 that perfluorooctanoic acid (PFOA), a chemical compound used to make Teflon, is a "likely
carcinogen." This finding was part of a draft report that has yet to be made final.{{cite web|url=http://www.epa.gov/sab/panels/pfoa_rev_panel.htm |publisher=Environmental Protection Agency |title= Perfluorooctanoic acid human health risk assessment review panel |accessdate=2005-05-20 --> DuPont settled for $300 million in a 2004 lawsuit filed by residents near its manufacturing plant in Ohio and West Virginia based on groundwater pollution from this chemical. Currently this chemical is not regulated by the EPA.
In January 2006, DuPont, the only company that manufactures PFOA in the US, agreed to eliminate releases of the chemical from its manufacturing plants by 2015, but did not commit to completely phasing out its use of the chemical. This agreement is said to apply to not only PTFE used in cookware but also other products such as food packaging, clothing, and carpeting. DuPont also stated that it cannot produce PTFE without the use of the chemical PFOA, although it is looking for a substitute.
PFOA is used only during the manufacture of the product—only a trace amount of PFOA remains after the curing process. DuPont maintains that there should be no measurable amount of PFOA on a finished pan, provided that it has been properly cured.
Similar polymers
Other polymers with similar composition are also known by the Teflon name:
They retain the useful properties of PTFE of low friction and non-reactivity, but are more easily formable. FEP is softer than PTFE and melts at 260°C; it is highly transparent and resistant to sunlight. FEP Detailed Properties Parker-TexLoc,
13 April 2006. Retrieved
10 September 2006.
See also
Notes
References
| last = Ellis| first = D.A.| last2 = Mabury| first2 = S.A.| last3 = Martin| first3 = J.W.| last4 = Muir| first4 = D.C.G.| coauthors = Mabury, S.A.; Martin, J.W.; Muir, D.C.G.| date = 2001| year = 2001| title = Thermolysis of fluoropolymers as a potential source of halogenated organic acids in the environment| journal = Nature| volume = 412| issue = 6844| pages = 321-324-->
External links
- The Chemical Heritage Foundation (2000). Roy J. Plunkett. Retrieved Oct 7, 2005.
- DuPont Teflon PTFE Material Data Sheet Retrieved Sept 6, 2006.
- DuPont (2005). Teflon News and Information. Retrieved Oct 7, 2005.
- PTFE vs FEP vs PFA vs ETFE vs PVDF The differences in Teflon tubing.
- DuPont (2005). Cooking Safety. Retrieved May 28, 2007.
- Environmental Working Group (2005). Canaries in the Kitchen - "Teflon Toxicosis" is deadly to pet birds. Are we at risk?. Retrieved Oct 7, 2005. More articles from EWG.
- Andrew Weil (2005-09-09). Teflon: The Sticky Business?
- Nature Publishing Group (2001-07-19). Thermolysis of fluoropolymers as a potential source of halogenated organic acids in the environment. Retrieved Oct 7, 2005.
- Organic Consumers Association / New York Times (2004-08-08). Dupont, Dupont Denies Poisoning Consumers with Teflon Products - Now in the Frying Pan. Retrieved Oct 7, 2005.
- Washington Post (2005-06-29 page A04). Compound in Teflon A 'Likely Carcinogen'. Retrieved Oct 7, 2005.
- CorpWatch / USA Today (2005-11-16). US: Engineer: DuPont hid facts about paper coating.
- CorpWatch / Associated Press (2005-11-29). US: EPA, DuPont in Settlement Over Chemical.
- CorpWatch / Associated Press (2005-12-14). US: DuPont fined more than $10M over Teflon.
- Los Angeles Times (2005-12-15). DuPont Settles Charges That It Hid Toxic Risk Data. Retrieved 2005-12-15.
- ABC News (2006-01-25). Government Moves to Curb Use of Chemical in Teflon.
- Washington Post (2006-01-26), Page A01. Harmful Teflon Chemical To Be Eliminated by 2015.
- Kopel, Dave (2004). Teflon Bullets. Retrieved Oct 7, 2005.
- "Teflon is Forever", Mother Jones, May/June 2007.
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