|Other names |
Syncolon, Fluon, Poly(tetrafluroethene), Poly(difluoromethylene), Poly(tetrafluoroethylene), teflon
|Melting point||600 K, 327 °C|
|Thermal conductivity||0.25 W/(m·K)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. The best known brand name of PTFE-based formulas is Teflon by Chemours.Chemours is a spin-off of DuPont, which originally discovered the compound in 1938. Another popular brand name of PTFE is Syncolon® by Synco Chemical Corporation.
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 (Teflon).
Tetrafluoroethylene (TFE) is a fluoromonomer with chemical formula C2F4. It belongs to the family of fluorocarbons and is the simplest perfluorinated alkene. This gaseous species is used primarily in the industrial preparation of polymers.
The Chemours Company, commonly referred to as Chemours, is an American chemical company that was founded in July 2015 as a spin-off from DuPont. It has its corporate headquarters in Wilmington, Delaware, United States.
PTFE is a fluorocarbon solid, as it is a high molecular weight compound consisting wholly of carbon and fluorine. PTFE is hydrophobic: neither water nor water-containing substances wet PTFE, as fluorocarbons demonstrate mitigated London dispersion forces due to the high electronegativity of fluorine. PTFE has one of the lowest coefficients of friction of any solid.
Fluorocarbons, sometimes referred to as perfluorocarbons or PFCs, are, strictly speaking, organofluorine compounds with the formula CxFy, i.e. they contain only carbon and fluorine, though the terminology is not strictly followed. Compounds with the prefix perfluoro- are hydrocarbons, including those with heteroatoms, wherein all C-H bonds have been replaced by C-F bonds. Fluorocarbons can be perfluoroalkanes, fluoroalkenes and fluoroalkynes and perfluoroaromatic compounds. Fluorocarbons and their derivatives are used as fluoropolymers, refrigerants, solvents, and anesthetics.
Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Three isotopes occur naturally, 12C and 13C being stable, while 14C is a radionuclide, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity.
Fluorine is a chemical element with symbol F and atomic number 9. It is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. As the most electronegative element, it is extremely reactive, as it reacts with almost all other elements, except for helium and neon.
PTFE is used as a non-stick coating for pans and other cookware. It is nonreactive, partly because of the strength of carbon–fluorine bonds, and so it is often used in containers and pipework for reactive and corrosive chemicals. Where used as a lubricant, PTFE reduces friction, wear, and energy consumption of machinery. It is commonly used as a graft material in surgical interventions. It is also frequently employed as coating on catheters; this interferes with the ability of bacteria and other infectious agents to adhere to catheters and cause hospital-acquired infections.
The carbon–fluorine bond is a polar covalent bond between carbon and fluorine that is a component of all organofluorine compounds. It is the fourth strongest single bond in organic chemistry—behind the B-F single bond, Si-F single bond and the H-F single bond, and relatively short—due to its partial ionic character. The bond also strengthens and shortens as more fluorines are added to the same carbon on a chemical compound. As such, fluoroalkanes like tetrafluoromethane are some of the most unreactive organic compounds.
A lubricant is a substance, usually organic, introduced to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, transporting foreign particles, or heating or cooling the surfaces. The property of reducing friction is known as lubricity.
In medicine, a catheter is a thin tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgical procedure. By modifying the material or adjusting the way catheters are manufactured, it is possible to tailor catheters for cardiovascular, urological, gastrointestinal, neurovascular, and ophthalmic applications.
PTFE was accidentally discovered in 1938 by Roy J. Plunkett while he was working in New Jersey for DuPont. As Plunkett attempted to make a new chlorofluorocarbon refrigerant, the tetrafluoroethylene gas in its pressure bottle stopped flowing before the bottle's weight had dropped to the point signaling "empty." Since Plunkett was measuring the amount of gas used by weighing the bottle, he became curious as to the source of the weight, and finally resorted to sawing the bottle apart. He found the bottle's interior coated with a waxy white material that was oddly slippery. Analysis showed that it was polymerized perfluoroethylene, with the iron from the inside of the container having acted as a catalyst at high pressure. Kinetic Chemicals patented the new fluorinated plastic (analogous to the already known polyethylene) in 1941,and registered the Teflon trademark in 1945.
Roy J. Plunkett was an American chemist. He discovered polytetrafluoroethylene (PTFE), i.e. Teflon, in 1938.
E. I. du Pont de Nemours and Company, commonly referred to as DuPont, is an American conglomerate that was founded in July 1802 in Wilmington, Delaware, as a gunpowder mill by French-American chemist and industrialist Éleuthère Irénée du Pont.
Chlorofluorocarbons (CFCs) are fully halogenated paraffin hydrocarbons that contain only carbon (C), chlorine (Cl), and fluorine (F), produced as volatile derivative of methane, ethane, and propane. They are also commonly known by the DuPont brand name Freon. The most common representative is dichlorodifluoromethane. Many CFCs have been widely used as refrigerants, propellants, and solvents. Because CFCs contribute to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol, and they are being replaced with other products such as hydrofluorocarbons (HFCs) and R-134a.
By 1948, DuPont, which founded Kinetic Chemicals in partnership with General Motors, was producing over two million pounds (900 tons) of Teflon brand PTFE per year in Parkersburg, West Virginia.An early use was in the Manhattan Project as a material to coat valves and seals in the pipes holding highly reactive uranium hexafluoride at the vast K-25 uranium enrichment plant in Oak Ridge, Tennessee.
General Motors Company, commonly referred to as General Motors (GM), is an American multinational corporation headquartered in Detroit that designs, manufactures, markets, and distributes vehicles and vehicle parts, and sells financial services, with global headquarters in Detroit's Renaissance Center. It was originally founded by William C. Durant on September 16, 1908 as a holding company. The company is the largest American automobile manufacturer, and one of the world's largest. As of 2018, General Motors is ranked #10 on the Fortune 500 rankings of the largest United States corporations by total revenue.
Parkersburg is a city in and the county seat of Wood County, West Virginia, United States. Located at the confluence of the Ohio and Little Kanawha rivers, it is the state's third-largest city and the largest city in the Parkersburg-Marietta-Vienna metropolitan area. The population was 31,492 at the 2010 census. Its peak population was 44,797 in 1960. The city is about 14 miles south of Marietta, Ohio.
The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the U.S. Army Corps of Engineers. Nuclear physicist Robert Oppenheimer was the director of the Los Alamos Laboratory that designed the actual bombs. The Army component of the project was designated the Manhattan District; Manhattan gradually superseded the official codename, Development of Substitute Materials, for the entire project. Along the way, the project absorbed its earlier British counterpart, Tube Alloys. The Manhattan Project began modestly in 1939, but grew to employ more than 130,000 people and cost nearly US$2 billion. Over 90% of the cost was for building factories and to produce fissile material, with less than 10% for development and production of the weapons. Research and production took place at more than 30 sites across the United States, the United Kingdom, and Canada.
In 1954, Collette Grégoire, the wife of French engineer Marc Grégoire urged him to try the material he had been using on fishing tackle on her cooking pans. He subsequently created the first PTFE-coated, non-stick pans under the brandname Tefal (combining "Tef" from "Teflon" and "al" from aluminium).In the United States, Marion A. Trozzolo, who had been using the substance on scientific utensils, marketed the first US-made PTFE-coated pan, "The Happy Pan", in 1961.
Tefal is a French cookware and small appliance manufacturer owned by Groupe SEB. Its name is a portmanteau of the words TEFlon and ALuminium. The company is known for creating the non-stick cookware category and for frying products such as French fries more healthily with far less fat than is standard.
Marion A. Trozzolo was an innovator, inventor, entrepreneur, and professor of business at Rockhurst University in Kansas City, Missouri. He was the first manufacturer of teflon coated cookware in the United States, and was the developer of the Kansas City entertainment district River Quay.
However, Tefal was not the only company to utilize PTFE in nonstick cookware coatings. In subsequent years, many cookware manufacturers developed proprietary PTFE-based formulas, including Swiss Diamond International, which uses a diamond-reinforced PTFE formula;Scanpan, which uses a titanium-reinforced PTFE formula; and both All-Clad and Newell Rubbermaid's Calphalon, which use a non-reinforced PTFE-based nonstick. Other cookware companies, such as Meyer Corporation's Anolon, use Teflon nonstick coatings purchased from Chemours. Chemours is a 2015 corporate spin-off of DuPont.
In the 1990s, it was found that PTFE could be radiation cross-linked above its melting point in an oxygen-free environment.Electron beam processing is one example of radiation processing. Cross-linked PTFE has improved high-temperature mechanical properties and radiation stability. This was significant because, for many years, irradiation at ambient conditions has been used to break down PTFE for recycling. This radiation-induced chain scission allows it to be more easily reground and reused.
PTFE is produced by free-radical polymerization of tetrafluoroethylene.The net equation is
Because tetrafluoroethylene can explosively decompose to tetrafluoromethane and carbon, special apparatus is required for the polymerization to prevent hot spots that might initiate this dangerous side reaction. The process is typically initiated with persulfate, which homolyzes to generate sulfate radicals:
The resulting polymer is terminated with sulfate ester groups, which can be hydrolyzed to give OH end-groups.
Because PTFE is poorly soluble in almost all solvents, the polymerization is conducted as an emulsion in water. This process gives a suspension of polymer particles. Alternatively, the polymerization is conducted using a surfactant such as PFOS.
PTFE is a thermoplastic polymer, which is a white solid at room temperature, with a density of about 2200 kg/m3. According to Chemours, its melting point is 600 K (327 °C; 620 °F). It maintains high strength, toughness and self-lubrication at low temperatures down to 5 K (−268.15 °C; −450.67 °F), and good flexibility at temperatures above 194 K (−79 °C; −110 °F). PTFE gains its properties from the aggregate effect of carbon-fluorine bonds, as do all fluorocarbons. The only chemicals known to affect these carbon-fluorine bonds are highly reactive metals like the alkali metals, and at higher temperatures also such metals as aluminium and magnesium, and fluorinating agents such as xenon difluoride and cobalt(III) fluoride.
|Glass temperature||114.85 °C (238.73 °F; 388.00 K)|
|Melting point||326.85 °C (620.33 °F; 600.00 K)|
|Thermal expansion||112–125×10−6 K−1|
|Thermal diffusivity||0.124 mm2/s|
|Young's modulus||0.5 GPa|
|Yield strength||23 MPa|
|Bulk resistivity||1016 Ω·m|
|Coefficient of friction||0.05–0.10|
|Dielectric constant||ε = 2.1, tan(δ) < 5×10−4|
|Dielectric constant (60 Hz)||ε = 2.1, tan(δ) < 2×10−4|
|Dielectric strength (1 MHz)||60 MV/m|
|Magnetic susceptibility (SI, 22 °C)||−10.28×10−6|
The coefficient of friction of plastics is usually measured against polished steel.PTFE's coefficient of friction is 0.05 to 0.10, which is the third-lowest of any known solid material (BAM being the first, with a coefficient of friction of 0.02; diamond-like carbon being second-lowest at 0.05). PTFE's resistance to van der Waals forces means that it is the only known surface to which a gecko cannot stick. In fact, PTFE can be used to prevent insects climbing up surfaces painted with the material. PTFE is so slippery that insects cannot get a grip and tend to fall off. For example, PTFE is used to prevent ants climbing out of formicaria.
Because of its chemical inertness, PTFE cannot be cross-linked like an elastomer. Therefore, it has no "memory" and is subject to creep. Because of its superior chemical and thermal properties, PTFE is often used as a gasket material within industries that require resistance to aggressive chemicals such as pharmaceuticals or chemical processing.However, because of the propensity to creep, the long-term performance of such seals is worse than for elastomers which exhibit zero, or near-zero, levels of creep. In critical applications, Belleville washers are often used to apply continuous force to PTFE gaskets, ensuring a minimal loss of performance over the lifetime of the gasket.
Processing PTFE can be difficult and expensive, because the high melting temperature, 327 °C (621 °F), is above the initial decomposition temperature, 200 °C (392 °F). Even when melted, PTFE does not flow, but instead behaves as a gel due to the absence of crystalline phase and high melt viscosity.
Some PTFE parts are made by cold-moulding, a form of compression molding. 360 to 380 °C (680 to 716 °F), allowing the fine particles to fuse into a single mass.Here, fine powdered PTFE is forced into a mould under high pressure (10–100 MPa). After a settling period, lasting from minutes to days, the mould is heated at
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The major application of PTFE, consuming about 50% of production, is for wiring in aerospace and computer applications (e.g. hookup wire, coaxial cables). This application exploits the fact that PTFE has excellent dielectric properties,especially at high radio frequencies, making it suitable for use as an excellent insulator in connector assemblies and cables, and in 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 commonly used in low-cost applications.
In industrial applications, owing to its low friction, PTFE is used for plain bearings, gears, slide plates, seals, gaskets, bushings, and more applications with sliding action of parts, where it outperforms acetal and nylon.
Its extremely high bulk resistivity makes it an ideal material for fabricating long-life electrets, the electrostatic analogues of permanent magnets.
PTFE film is also widely used in the production of carbon fiber composites as well as fiberglass composites, notably in the aerospace industry. PTFE film is used as a barrier between the carbon or fiberglass part being built, and breather and bagging materials used to incapsulate the bondment when debulking (vacuum removal of air from between layers of laid-up plies of material) and when curing the composite, usually in an autoclave. The PTFE, used here as a film, prevents the non-production materials from sticking to the part being built, which is sticky due to the carbon-graphite or fiberglass plies being pre-pregnated with bismaleimide resin. Non-production materials such as Teflon, Airweave Breather and the bag itself would be considered F.O.D. (foreign object debris/damage) if left in layup.
Because of its extreme non-reactivity and high temperature rating, PTFE is often used as the liner in hose assemblies, expansion joints, and in industrial pipe lines, particularly in applications using acids, alkalis, or other chemicals. Its frictionless qualities allow improved flow of highly viscous liquids, and for uses in applications such as brake hoses.
Gore-Tex is a brand of expanded PTFE (ePTFE), a material incorporating a fluoropolymer membrane with micropores. The roof of the Hubert H. Humphrey Metrodome in Minneapolis, US, was one of the largest applications of PTFE coatings. 20 acres (81,000 m2) of the material was used in the creation of the white double-layered PTFE-coated fiberglass dome.
PTFE is often found in musical instrument lubrication product; most commonly, valve oil.
PTFE is used in some aerosol lubricant sprays, including in micronized and polarized form. It is notable for its extremely low coefficient of friction, its hydrophobia (which serves to inhibit rust), and for the dry film it forms after application, which allows it to resist collecting particles that might otherwise form an abrasive paste.
PTFE (Teflon) is best known for its use in coating non-stick frying pans and other cookware, as it is hydrophobic and possesses fairly high heat resistance.
The sole plates of some clothes irons are coated with PTFE (Teflon).
Other niche applications include:
Pyrolysis of PTFE is detectable at 200 °C (392 °F), and it evolves several fluorocarbon gases and a sublimate. An animal study conducted in 1955 concluded that it is unlikely that these products would be generated in amounts significant to health at temperatures below 250 °C (482 °F).
While PTFE is stable and nontoxic at lower temperatures, it begins to deteriorate after the temperature of cookware reaches about 260 °C (500 °F), and decomposes above 350 °C (662 °F). The degradation by-products can be lethal to birds, and can cause flu-like symptoms in humans—see polymer fume fever. Meat is usually fried between 204 and 232 °C (399 and 450 °F), and most oils start to smoke before a temperature of 260 °C (500 °F) is reached, but there are at least two cooking oils (refined safflower oil at 265 °C (509 °F) and avocado oil at 271 °C (520 °F)) that have a higher smoke point.
Perfluorooctanoic acid (PFOA, or C8) has been used as a surfactant in the emulsion polymerization of PTFE, although several manufacturers have entirely discontinued its use.
PFOA persists indefinitely in the environment.It is a toxicant and carcinogen in animals. PFOA has been detected in the blood of more than 98% of the general US population in the low and sub-parts per billion range, and levels are higher in chemical plant employees and surrounding subpopulations. The general population has been exposed to PFOA through massive dumping of C8 waste into the ocean and near the Ohio River Valley. PFOA has been detected in industrial waste, stain resistant carpets, carpet cleaning liquids, house dust, microwave popcorn bags, water, food and Teflon cookware. As a result of a class-action lawsuit and community settlement with DuPont, three epidemiologists conducted studies on the population surrounding a chemical plant that was exposed to PFOA at levels greater than in the general population. The studies concluded that there was an association between PFOA exposure and six health outcomes: kidney cancer, testicular cancer, ulcerative colitis, thyroid disease, hypercholesterolemia (high cholesterol), and pregnancy-induced hypertension.
Overall, PTFE cookware is considered an insignificant exposure pathway to PFOA.
The Teflon trade name is also used for other polymers with similar compositions:
These retain the useful PTFE properties of low friction and nonreactivity, but are more easily formable. For example, FEP is softer than PTFE and melts at 533 K (260 °C; 500 °F); it is also highly transparent and resistant to sunlight.
A thermoplastic, or thermosoftening plastic, is a plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling.
Polyvinylidene fluoride or polyvinylidene difluoride (PVDF) is a highly non-reactive thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride.
Perfluorooctanoic acid (PFOA) is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes and as a material feedstock, and is known as an emerging health concern and subject of regulatory action and voluntary industrial phase-outs. PFOA is considered a surfactant, or fluorosurfactant, due to its chemical structure consisting of a perfluorinated, n-octyl "tail group" and a carboxylate "head group". The head group can be described as hydrophilic while the fluorocarbon tail is both hydrophobic and lipophobic; The tail group is inert and does not interact strongly with polar or non-polar chemical moieties; the head group is reactive and interacts strongly with polar groups, specifically water. The "tail" is hydrophobic due to being non-polar and lipophobic because fluorocarbons are less susceptible to the London dispersion force than hydrocarbons.
Viton is a brand of FKM, a synthetic rubber and fluoropolymer elastomer commonly used in O-rings, chemical-resistant gloves, and other molded or extruded goods. The name is a registered trademark of The Chemours Company.
Nafion is a brand name for a sulfonated tetrafluoroethylene based fluoropolymer-copolymer discovered in the late 1960s by Walther Grot of DuPont. Nafion is a brand of the Chemours company. It is the first of a class of synthetic polymers with ionic properties that are called ionomers. Nafion's unique ionic properties are a result of incorporating perfluorovinyl ether groups terminated with sulfonate groups onto a tetrafluoroethylene (PTFE) backbone. Nafion has received a considerable amount of attention as a proton conductor for proton exchange membrane (PEM) fuel cells because of its excellent thermal and mechanical stability.
Polychlorotrifluoroethylene (PCTFE or PTFCE) is a thermoplastic chlorofluoropolymer with the molecular formula (CF2CClF)n, where n is the number of monomer units in the polymer molecule. It is similar to polytetrafluoroethene (PTFE), except that it is a homopolymer of the monomer chlorotrifluoroethylene (CTFE) instead of tetrafluoroethene. It has the lowest water vapor transmission rate of any plastic.
Silverstone is a non-stick plastic coating made by DuPont. Released in 1976, this three-coat (primer/midcoat/topcoat) fluoropolymer system formulated with PTFE and PFA produces a more durable finish than Teflon coating.
Krytox is a registered trademark of The Chemours Company. It refers to a group of colourless synthetic lubricants (oils and greases) with a variety of applications. Invented by researchers at DuPont, Krytox oils are fluorocarbon ether polymers of polyhexafluoropropylene oxide, with a chemical formula: F−(CF(CF3)−CF2−O)n−CF2CF3, where the degree of polymerization, n, generally lies within the range of 10 to 60. These compounds are collectively known by many names including perfluoropolyether (PFPE), perfluoroalkylether (PFAE) and perfluoropolyalkylether (PFPAE). A unique identifier is their CAS registry number, 60164-51-4.
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). ETFE has a relatively high melting temperature, excellent chemical, electrical and high-energy radiation resistance properties. When burned, ETFE releases hydrofluoric acid.
Polymer fume fever or fluoropolymer fever, also informally called Teflon flu, is an inhalation fever caused by the fumes released when polytetrafluoroethylene reaches temperatures of 300 °C (572 °F) to 450 °C (842 °F). When PTFE is heated above 450 °C the pyrolysis products are different and inhalation may cause acute lung injury. Symptoms are flu-like with chest tightness and mild cough. Onset occurs about 4 to 8 hours after exposure to the pyrolysis products of PTFE. A high white blood cell count may be seen and chest x-ray findings are usually minimal.
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 screw extrusion techniques. Fluorinated ethylene propylene was invented by DuPont and is sold under the brandname Teflon FEP. Other brandnames are Neoflon FEP from Daikin or Dyneon FEP from Dyneon/3M.
W. L. Gore & Associates, Inc. is an American multinational manufacturing company specializing in products derived from fluoropolymers. It is a privately held corporation headquartered in Newark, Delaware. It is best known as the developer of waterproof, breathable Gore-Tex fabrics.
Teflon is a registered trademark of the Chemours company used for polytetrafluoroethylene.
Perfluoroethers are a class of organofluorine compound containing one or more ether functional group. In general these compounds are structural analogous to related hydrocarbon ethers, but they exhibit also the distinctive properties of fluorocarbons.
A non-stick surface is a surface engineered to reduce the ability of other materials to stick to it. Non-stick cookware is a common application, where the non-stick coating allows food to brown without sticking to the pan. Non-stick is often used to refer to surfaces coated with polytetrafluoroethylene (PTFE), a well-known brand of which is "Teflon." In the twenty-first century other coatings have been marketed as non-stick, such as anodized aluminium, ceramics, silicone, enameled cast iron, and seasoned cookware. Superhydrophobic coating is the newest non-stick coating for sale.
Perfluoroalkoxy alkanes (PFA) are fluoropolymers. They are copolymers of tetrafluoroethylene (C2F4) and perfluoroethers (C2F3ORf, where Rf is a perfluorinated group such as trifluoromethyl (CF3)). In terms of their properties, these polymers are similar to polytetrafluoroethylene (PTFE). The big difference is that the alkoxy substituents allow the polymer to be melt-processed. On a molecular level, PFA has a smaller chain length and higher chain entanglement than other fluoropolymers. It also contains an oxygen atom at the branches. This results in a material that is more translucent and has improved flow, creep resistance, and thermal stability close to or exceeding PTFE. Similarly advantaged processing properties are found in fluorinated ethylene propylene (FEP), the copolymer of tetrafluoroethylene and hexafluoropropylene.