Perfluoroalkoxy alkane

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PFA
PFA Structure.svg
Density [1] 2150 kg/m3
Flexural modulus(E)586 M Pa
Tensile strength(t)24 M Pa
Elongation at break300%
Folding enduranceNo break
Notch test
Melting point 315 °C
Maximum operating temperature260 °C
Water absorption (ASTM)<0.03 % after 24 hours
Dielectric constant (Dk) at 1M Hz 2.1
Dissipation factor at 1M Hz 0.0001
Arc resistance< 180 seconds
Resistivity at 50% R. H. > 1016 Ω m

Perfluoroalkoxy alkanes (PFA) are fluoropolymers. They are copolymers of tetrafluoroethylene (C2F4) and perfluoroethers (C2F3ORf, where Rf is a perfluorinated group such as trifluoromethyl (CF3)). The properties of these polymers are similar to those of polytetrafluoroethylene (PTFE). Compared to PTFE, PFA has better anti-stick properties and higher chemical resistance, at the expense of lesser scratch resistance. [2]

Contents

Properties

Unlike with PTFE, the alkoxy substituents allow the polymer to be melt-processed. [3] On a molecular level, PFA polymers have a smaller chain length and higher chain entanglement than other fluoropolymers. They also contain an oxygen atom at the branches. This results in materials that are more translucent and have improved flow and creep resistance, with thermal stability close to or exceeding PTFE. [4] Thus, PFA is preferred when extended service is required in hostile environments involving chemical, thermal, and mechanical stress. PFA offers high melt strength, stability at high processing temperatures, excellent crack and stress resistance and a low coefficient of friction. [1] Similarly enhanced processing properties are found in fluorinated ethylene propylene (FEP), the copolymer of tetrafluoroethylene and hexafluoropropylene. [5] However FEP is ten times less capable of withstanding repeated bending without fracture than PFA. [1]

Perfluoroalkoxy alkane is used to fabricate tubes to handle aggressive chemicals. Pfa tubing.jpeg
Perfluoroalkoxy alkane is used to fabricate tubes to handle aggressive chemicals.

Applications

PFA is commonly used as a material for piping and as fittings for aggressive chemicals, as well as the corrosion-resistant lining of vessels in the chemical-processing industry. Typical applications include the construction of gas scrubbers, reactors, containment vessels and piping. [6] In coal-fired power plants, it is used for lining heat exchangers. By channeling crude gas through a PFA-lined apparatus, the gas stream can be cooled below its condensation temperature without damaging the heat exchanger. Its use contributes to increasing the efficiency of the whole plant. [7]

PFA is also used to make sampling equipment in analytical chemistry and for geochemical or environmental in situ studies in the field, when it is particularly important to avoid chemical contamination from metallic ions at trace levels.

Production

Common trademarks include Teflon-PFA, Hostaflon-PFA and Chemfluor. [8]

Chemours claims to be the only U.S. producer of PFA at its Fayetteville Works plant in northern Bladen County. [9]

Environmental and health risks

The monomers of such perfluoroalkoxy alkane polymers, in common with other per- and polyfluoroalkyl substances, are widespread in the environment due to human production and release of the chemicals; so durable that they are referred to as "forever chemicals"; and have detrimental health concerns not yet fully understood. [10]

In 2023, the United States EPA proposed "the first (US national) standard to limit (PFAs) in drinking water;" albeit only six of >12,000 such chemicals were addressed. [11]

At high temperatures or in a fire, fluoroelastomers decompose and may release hydrogen fluoride. Any residue must be handled using protective equipment.[ citation needed ]

See also

Related Research Articles

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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.

<span class="mw-page-title-main">Thermoplastic</span> Plastic that softens with heat and hardens on cooling

A thermoplastic, or thermosoftening plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling.

<span class="mw-page-title-main">Polyvinylidene fluoride</span> Non-reactive thermoplastic fluoropolymer

Polyvinylidene fluoride or polyvinylidene difluoride (PVDF) is a highly non-reactive thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride. Its chemical formula is (C2H2F2)n.

<span class="mw-page-title-main">Perfluorooctanoic acid</span> Perfluorinated carboxylic acid

Perfluorooctanoic acid is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes and as a material feedstock. PFOA is considered a surfactant, or fluorosurfactant, due to its chemical structure, which consists of a perfluorinated, n-heptyl "tail group" and a carboxylate "head group". The head group can be described as hydrophilic while the fluorocarbon tail is both hydrophobic and lipophobic.

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 under the brand name "Teflon," trademarked by the DuPont Company.

<span class="mw-page-title-main">Nafion</span> Brand name for a chemical product

Nafion is a brand name for a sulfonated tetrafluoroethylene based fluoropolymer-copolymer discovered in the late 1960s by Dr. 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 chemical and mechanical stability in the harsh conditions of this application.

<span class="mw-page-title-main">Polychlorotrifluoroethylene</span> Chemical compound

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.

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<span class="mw-page-title-main">Fluorinated ethylene propylene</span> Polymer

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.

<span class="mw-page-title-main">ECTFE</span> Corrosion-resistant polymer

ECTFE (ethylene-chlorotrifluoroethylene) is an alternating copolymer of ethylene and chlorotrifluoroethylene. It is a semi-crystalline fluoropolymer, with chemical corrosion resistance properties.

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Perfluoroethers are a class of organofluorine compound containing one or more ether functional group. In general these compounds are structurally analogous to the related hydrocarbon ethers, except for the distinctive properties of fluorocarbons.

<span class="mw-page-title-main">Non-stick surface</span> Coating that prevents sticking

A non-stick surface is 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, silica, enameled cast iron, and seasoned cookware.

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<span class="mw-page-title-main">Hexafluoropropylene oxide</span> Chemical compound

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<span class="mw-page-title-main">Perfluorinated compound</span>

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<span class="mw-page-title-main">Fluorochemical industry</span> Industry dealing with chemicals from fluorine

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References

  1. 1 2 3 "PTFE, FEP, and PFA Specifications". Boedeker Corp. 2007. Retrieved 2007-12-22.
  2. "PTFE, FEP, PFA". Menden, Germany: TechnoFinish GmbH & Co. KG. Retrieved July 4, 2023.
  3. "PFA - Perfluoralkoxy". Glossary. Heidelberg, Germany: Reichelt Chemietechnik. 2014. Retrieved July 4, 2023. PFA ist zersetzungsfrei schmelzbar, so dass der Kunststoff durch thermische Formgebungsverfahren, wie Spritzgießen, Pressen und Extrudieren, bei Arbeitstemperaturen zwischen +320 °C und +420 °C zu Halbzeugen und Serienprodukten verarbeitet werden kann.
  4. "PFA Properties". Materials Overview. New Jersey, United States: Fluorotherm Polymers. February 13, 2017. Retrieved July 4, 2023.
  5. Siegemund, Günter; Schwertfeger, Werner; Feiring, Andrew; Smart, Bruce; Behr, Fred; Vogel, Herward; McKusick, Blaine (2002). "Fluorine Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_349..
  6. Dietrich Braun, für Einsteiger, Hanser, München, 2003.
  7. H. Saechtling: Kunststoff Taschenbuch, Hanser Verlag, Wien 1995, ISBN   3-446-17855-4.
  8. "Glossary: PFA - Perfluoralkoxy". Reichelt Chemietechnik. Retrieved 2019-06-22.
  9. Sorg, Lisa (September 6, 2022). "Chemours plans to expand its Fayetteville Works plant in northern Bladen County, where the company would ramp up production of PFA, a type of perfluorinated". NC Policy Watch. The Pulse. Retrieved 7 September 2022.
  10. Perkins, Tom (18 December 2021). "PFAS 'forever chemicals' constantly cycle through ground, air and water, study finds". Environment. The Guardian . Retrieved 4 July 2023.
  11. "Getting PFAs out of Water". Consumer Reports. Vol. 88, no. 8. July 2023. p. 5.