Teflon

Categories: Plastics | Organofluorides | Lubricants | DuPont

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. 

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  -(C - C)- 
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Teflon is also used as the trade name for a polymer with similar properties, perfluoroalkoxy polymer resin (PFA): 

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PTFE has the lowest coefficient of friction of any known solid material. It is used as a non-stick coating for pans and other cookware. PTFE is very non-reactive, and so is often used in containers and pipework for reactive chemicals. Its melting point varies between 260 °C (FEP) and 327 °C (PTFE), depending on which specific Teflon polymer is being discussed.

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 resists wear better 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.

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Toxicity

Mr. Pravin Choksi was the pioneer of the teflon industry in India. He established the Plastic Products Engineering Co. in November 1967 and truly revolutionised the industry.

Non-stick coatings on househould frying pans have been shown to release toxic gases upon overheating. These gases are lethal to avians, 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 all chemicals will decompose when heated enough. 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). Therefore, under normal usage, Teflon is not known to be harmful. The FDA has also found that consuming Teflon does not pose a health risk. 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.

The EPA's scientific advisory board found in 2005 that perfluorooctanoic acid, a chemical compound used to make Teflon, is a "likely carcinogen." This finding was part of a draft report [1] that has yet to be made final. DuPont settled for $300 million in 2004 a 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.

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External links

de:Polytetrafluorethylen fr:Teflon he:טפלון lt:Teflonas nl:Teflon id:Teflon ja:テフロン no:Polytetrafluoreten pl:Teflon pt:Teflon ru:Тефлон fi:Teflon sv:Teflon zh:聚四氟乙烯