polytetrafluoroethylene polytetrafluoroethylene polytetrafluoroethylene names iupac name poly(1,1,2,2-tetrafluoroethylene) other names fluon, poly(tetrafluoroethene), poly(difluoromethylene), poly(tetrafluoroethylene), teflon identifiers cas number 9002-84-0 y abbreviations ptfe chebi chebi:53251 n chemspider none echa infocard 100.120.367 kegg d08974 n unii e1nc1jvs3o y comptox dashboard (epa) dtxsid7047724 properties chemical formula (c2f4)n density 2200 kg/m3 melting point 327 °c electrical resistivity 1018 ω·cm thermal conductivity 0.25 w/(m·k) hazards nfpa 704 (fire diamond) 1 0 0ox except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). n verify (what is yn ?) infobox references polytetrafluoroethylene (ptfe) is a synthetic fluoropolymer of tetrafluoroethylene and is a pfas that has numerous applications. the commonly known brand name of ptfe-based composition is teflon by chemours, a spin-off from dupont, which originally discovered the compound in 1938. polytetrafluoroethylene is a fluorocarbon solid, as it is a high-molecular-weight polymer consisting wholly of carbon and fluorine. ptfe is hydrophobic: neither water nor water-containing substances wet ptfe, as fluorocarbons exhibit only small london dispersion forces due to the low electric polarizability of fluorine. ptfe has one of the lowest coefficients of friction of any solid. polytetrafluoroethylene is used as a non-stick coating for pans and other cookware. it is non-reactive, partly because of the strength of carbon–fluorine bonds, 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 used as a graft material in surgery and as a coating on catheters. ptfe is one of the best-known and widely applied pfas commonly described as persistent organic pollutants or "forever chemicals". only since the start of the 21st century has the environmental impact and toxicity to human and mammalian life been studied in depth. history advertisement of the happy pan, a teflon-coated pan from the 1960s external audio "from stove tops to outer space... teflon touches every one of us some way almost every day.", roy plunkett, science history institute advertisement for zepel, the trade name used to market teflon as a fabric treatment ptfe thermal cover showing impact craters, from nasa's ultra heavy cosmic ray experiment (uhcre) on the long duration exposure facility (ldef). logo of teflon, the commonly known brand name of ptfe-based compositions manufactured by chemours polytetrafluoroethylene 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. by 1948, dupont, which founded kinetic chemicals in partnership with general motors, was producing over two million pounds (900 tons) of teflon brand polytetrafluoroethylene 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. in 1954, colette grégoire urged her husband, the french engineer marc grégoire, 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 brand name 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. non-stick cookware has since become a common household product, now offered by hundreds of manufacturers across the world. the brand name zepel was used for promoting its stain-resistance and water-resistance when applied to fabrics. 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 polytetrafluoroethylene 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 polytetrafluoroethylene for recycling. this radiation-induced chain scission allows it to be more easily reground and reused. corona discharge treatment of the surface to increase the energy and improve adhesion has been reported. production ptfe is produced by free-radical polymerization of tetrafluoroethylene. the net equation is n f2c=cf2 → −(f2c−cf2)n− because tetrafluoroethylene can explosively decompose to tetrafluoromethane (cf4) 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: 2− ⇌ 2 so•−4 the resulting polymer is terminated with sulfate ester groups, which can be hydrolyzed to give oh end-groups. granular ptfe is produced via suspension polymerization, where ptfe is suspended in an aqueous medium primarily via agitation and sometimes with the use of a surfactant. ptfe is also synthesized via emulsion polymerization, where a surfactant is the primary means of keeping ptfe in an aqueous medium. surfactants in the past have included toxic perfluorooctanoic acid (pfoa) and perfluorooctanesulfonic acid (pfos). more recently perfluoro 3,6 dioxaoctanoic acid (pfo2oa) and frd-903 (genx) are being used as an alternative surfactants. properties ptfe is often used to coat non-stick pans as it is hydrophobic and possesses fairly high heat resistance. ptfe is a thermoplastic polymer, which is a white solid at room temperature, with a density of about 2200 kg/m3 and a melting point of 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. at temperatures above 650–700 °c (1,200–1,290 °f) ptfe undergoes depolymerization. property value glass temperature 114.85 °c (238.73 °f; 388.00 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 coefficient of friction 0.05–0.10 dielectric constant ε = 2.1, tan(δ) < 5×10−2 dielectric constant (60 hz) ε = 2.1, tan(δ) < 2×10−2 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 (aluminium magnesium boride (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 from 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 from climbing out of formicaria. 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, until the 1990s, ptfe was not known to crosslink like an elastomer, due to its chemical inertness. therefore, it has no "memory" and is subject to creep. because of the propensity to creep, the long-term performance of such seals is worse than for elastomers that exhibit zero, or near-zero, levels of creep. in critical applications, belleville washers are often used to apply continuous force to ptfe gaskets, thereby ensuring a minimal loss of performance over the lifetime of the gasket. ptfe is an ultraviolet (uv) transparent polymer. however, when exposed to an excimer laser beam it severely degrades due to heterogeneous photothermal effect. processing 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 molten, ptfe does not flow due to its exceedingly high melt-viscosity. the viscosity and melting point can be decreased by inclusion of small amount of comonomers such as perfluoro (propylvinyl ether) and hexafluoropropylene (hfp). these cause the otherwise perfectly linear ptfe chain to become branched, reducing its crystallinity. some ptfe parts are made by cold-moulding, a form of compression molding. 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 360 to 380 °c (680 to 716 °f), allowing the fine particles to fuse (sinter) into a single mass. applications and uses ptfe-jacketed (white) shielded twisted-pair cables wire insulation, electronics the major application of ptfe, consuming about 50% of production, is for the insulation of wiring in aerospace and computer applications (e.g. hookup wire, coaxial cables). this application exploits the fact that ptfe has excellent dielectric properties, specifically low group velocity dispersion, 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, higher dispersion and lower-melting-point polyethylene commonly used in low-cost applications. bearings seals 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. electrets its extremely high bulk resistivity makes it an ideal material for fabricating long-life electrets, the electrostatic analogues of permanent magnets. composites 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. 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. chemically inert liners 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. tensioned membrane structures ptfe architectural membranes are created by coating a woven glass-fibre base cloth with ptfe, forming one of the strongest and most durable materials used in tensile structures. some notable structures featuring ptfe tensioned membranes include the o2 arena in london, moses mabhida stadium in south africa, metropolitano stadium in spain and the sydney football stadium roof in australia. musical instruments ptfe is often found in musical instrument lubrication products; most commonly, valve oil. lubricants 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