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Teflon is the brand name of a polymer compound discovered by Roy J. Plunkett (1910-1994) of DuPont in 1938 and introduced as a commercial product in 1946. It is a thermoplastic fluoropolymer: Teflon is polytetrafluoroethylene (PTFE), a polymer of fluorinated ethylene, and the name is also used for a polymer with similar properties, perfluoroalkoxy polymer resin (PFA).
Teflon is polytetrafluoroethylene (PTFE), a polymer of fluorinated ethylene.
Teflon is also used as the trade name for a polymer with similar properties, perfluoroalkoxy polymer resin (PFA):
PTFE is sometimes said to be a spin-off from the US space program with more down-to-earth applications; this is an urban legend, as teflon cooking pans were commonplace before Yuri Gagarin's flight in 1961. PTFE was discovered serendipitously by Roy Plunkett of DuPont in 1938, while attempting to make a new CFC refrigerant, when the perfluorethylene polymerized in its storage container. DuPont patented it in 1941, and registered the Teflon trademark in 1944.
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 Uranium enrichment plant at Oak Ridge, Tennessee, when it was known as K416.
It was first sold commercially in 1946 and by 1950, DuPont was producing over a million pounds (450 t) per year in Virginia.
Teflon has been supplemented with another DuPont product, Silverstone, a three-coat fluoropolymer system that produces a more durable finish than Teflon. Silverstone was released in 1976.
Amongst many other industrial applications, PTFE is used to coat certain types of hardened, armour-piercing bullets, so as to reduce the amount of wear on the firearm's rifling. These are often mistakenly referred to as "cop-killer" bullets on account of PTFE's supposed ability to ease a bullet's passage through body armour. Any armour-piercing effect is, however, purely a function of the bullet's velocity and rigidity rather than a property of PTFE.
PTFE is an excellent electrical insulator with good dielectric properties. This is especially true at high radio frequencies, making it eminently suitable for use as an insulator in cables and connector assemblies and as a material for printed circuit boards. Combined with its high melting temperature this makes it the material of choice as a high performance substitute for the weaker and more meltable polyethylene that is commonly used in low-cost applications.
Due to its low friction, it is used for applications where sliding action of parts is needed: bearings, bushings, gears, slide plates, etc. In these applications it performs significantly better than nylon and acetal; it is comparable with UHMWPE, although UHMWPE is more resistant to wear than Teflon. For these applications, versions of teflon with mineral oil or molybdenum disulfide embedded as additional lubricants in its matrix are being manufactured.
Gore-Tex is a material incorporating teflon membrane with micropores.
Non-stick coatings on household frying pans have been shown to release toxic gases upon overheating. These gases are lethal to birds, and can cause flu-like symptoms in humans. This polymer fume fever in humans may last for more than a week in cases of moderate household exposure. This level of exposure can occur when a Teflon pan is left unattended on a high-power gas burner in a small unventilated apartment. In severe cases, decomposition chemicals can be lethal. Reports of Teflon's apparent toxicity may be misleading, however, as sufficient heat will thermally decompose most chemical substances. Teflon begins to deteriorate after the temperature of cookware reaches about 500 F (260 C), and begins to significantly decompose above 660 F (350 C). By comparison, cooking fats, oils and butter will begin to scorch and smoke at about 392 F (200 C), and meat is usually fried between 400-450 F (200-230 C), but hot spots in the pan can easily exceed this temperature. In recent years, under the threat of litigation, DuPont has become more forthcoming about the risks of using Teflon on hot surfaces, but has not stopped selling the product.
In January, 2006 DuPont, the only company that manufactures PFOA in the US, has 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 Teflon used in cookware but in other products such as food packaging, clothing and carpeting. DuPont also stated that it cannot produce Teflon without the use of the chemical PFOA, though it is looking for a substitute.
It is important to understand that PFOA is not part of the finished product of nonstick cookware or bakeware. While used during the manufacture of the product and while there is a small amount in the finished nonstick liquid product when it is shipped to the applicator, all of the PFOA is driven off in the curing process following the application of the PTFE spray to the pan's surface. The finished pan does not contain any measurable PFOA after proper curing. The consumer is never exposed to PFOA while using their nonstick pan. Retailers should feel confident in reassuring their customers that proper use of PTFE coated pans is perfectly safe.
| The above article is licensed under the GNU Free Documentation License. From Wikipedia, the free encyclopedia (https://en.wikipedia.org/wiki/teflon). 1/31/06 |
Teflon was first sold commercially in 1946, and by 1950 DuPont was producing over a million pounds (450 t) per year in Virginia. The story that PTFE is a spin-off from the United States space program is an urban legend — teflon cooking pans were commonplace before Yuri Gagarin's flight in 1961. DuPont later supplemented Teflon with Silverstone, a three-coat fluoropolymer system that produces a more durable finish, released in 1976. PTFE is an excellent electrical insulator with good dielectric properties, especially at high radio frequencies, making it suitable as an insulator in cables and connector assemblies and as a material for printed circuit boards; combined with its high melting temperature, it is the high performance substitute for weaker, more meltable polyethylene in low-cost applications. For sliding parts — bearings, bushings, gears, slide plates — it performs significantly better than nylon and acetal, and versions with mineral oil or molybdenum disulfide embedded as additional lubricants are manufactured for those uses.
The apparel connection runs through membranes and finishes. Gore-Tex is a material incorporating a Teflon membrane with micropores — the PTFE film's pores are large enough to pass water vapour from perspiration but small enough to block liquid rain, which is the working principle of waterproof-breathable outdoor clothing. PTFE-based finishes also give fabrics stain and water resistance, and expanded PTFE thread and fiber serve in severe industrial and outdoor applications. The toxicity discussion belongs with the material's heat limits: non-stick coatings release toxic gases upon overheating — lethal to birds and capable of causing flu-like polymer fume fever symptoms in humans — and Teflon begins to deteriorate at about 500 degrees F (260 degrees C), well above ordinary frying temperatures of 400-450 degrees F, though hot spots can exceed them. The EPA's scientific advisory board found in 2005 that perfluorooctanoic acid (PFOA), a chemical used to make Teflon, is a likely carcinogen; DuPont agreed in January 2006 to eliminate releases of the chemical from its manufacturing plants by 2015, while noting that PFOA is a manufacturing aid, not an ingredient of the finished coating.
PTFE has the lowest coefficient of friction of any known solid material, and it is very non-reactive, so it is used as a non-stick coating for pans and other cookware and in containers and pipework for reactive chemicals. Its melting point varies between 260 degrees C for FEP and 327 degrees C for PTFE, depending on which specific Teflon polymer is being discussed.
PTFE was discovered serendipitously by Roy Plunkett of DuPont in 1938, while attempting to make a new CFC refrigerant, when the perfluorethylene polymerized in its storage container. DuPont patented it in 1941 and registered the Teflon trademark in 1944; an early advanced use was in the Manhattan Project, coating valves and seals in pipes holding highly reactive uranium hexafluoride at Oak Ridge, Tennessee, where it was known as K416.
PFOA is not part of the finished product of nonstick cookware or bakeware. It is used during manufacture, and all of the PFOA is driven off in the curing process following application of the PTFE spray to the pan's surface, so the finished pan does not contain any measurable PFOA after proper curing and the consumer is never exposed to PFOA while using the pan. Teflon itself begins to deteriorate after cookware reaches about 500 degrees F (260 degrees C) and significantly decomposes above 660 degrees F (350 degrees C).