perfluoroalkoxy alkane

Unlike with PTFE, the alkoxy substituents allow the polymer to be melt-processed.{{cite web |last= |year=2014 |title=PFA - Perfluoralkoxy |url=https://www.rct-online.de/de/HmswGlossar/detail/id/15 |access-date=July 4, 2023 |website=Glossary |publisher=Reichelt Chemietechnik |publication-place=Heidelberg, Germany |quote=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.}} 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.{{cite web |last= |date=February 13, 2017 |title=PFA Properties |url=https://www.fluorotherm.com/technical-information/materials-overview/pfa-properties/ |access-date=July 4, 2023 |website=Materials Overview |publisher=Fluorotherm Polymers |publication-place=New Jersey, United States}} 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. Similarly enhanced processing properties are found in fluorinated ethylene propylene (FEP), the copolymer of tetrafluoroethylene and hexafluoropropylene.{{Ullmann|first1=Günter |last1=Siegemund|first2=Werner|last2=Schwertfeger|first3=Andrew|last3=Feiring|first4=Bruce|last4=Smart|first5=Fred|last5=Behr|first6=Herward|last6=Vogel|first7=Blaine |last7=McKusick|title=Fluorine Compounds, Organic|year=2002|doi=10.1002/14356007.a11_349}}. However FEP is ten times less capable of withstanding repeated bending without fracture than PFA.

Image:pfa tubing.jpeg

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.Dietrich Braun, [https://books.google.com/books?id=Xp0TRVDTCNAC&q=PFA%27%27Kunststofftechnik&pg=PA32 für Einsteiger], Hanser, München, 2003. 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.H. Saechtling: Kunststoff Taschenbuch'', Hanser Verlag, Wien 1995, {{ISBN|3-446-17855-4}}.

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.

{{Expand section|date=October 2024}}

PFA is produced as a copolymer of tetrafluoroethylene and a perfluoroether, usually perfluoro(methyl vinyl ether). Preparation of the perfluoroether precursors is more complex than partially fluorinated vinyl ethers, which can be made from the reaction of tetrafluoroethylene with alkoxides:

:{{chem2|RO- + F2C\dCF2 -> F2C\dCFOR + F-}}

However, the instability of α-fluoroalcohols makes preparation of most perfluoroalkoxides impractical. Instead, production of vinyl perfluoroethers can be achieved by pyrolysis of a perfluoro(2-alkoxy carboxylate) salt.{{cite journal|doi=10.1021/jo01258a067 |title=Synthesis of perfluoroalkyl vinyl ether acids and derivatives |date=1969 |last1=Sullivan |first1=Raymond |journal=The Journal of Organic Chemistry |volume=34 |issue=6 |pages=1841–1844 }}{{cite patent|country=US|number=3180895|title=Fluorocarbon ethers|assign=DuPont|inventor=John Ferguson Harris Jr. and Donald Irwin McCane|gdate=1965-04-27}}

This reaction, called dehalocarbonylation, proceeds by the elimination of {{chem2|CO2}} from the carboxylate, forming a carbanion intermediate that then undergoes elimination of fluoride to form the alkene.{{cite journal|doi=10.1126/science.abm8868 |title=Low-temperature mineralization of perfluorocarboxylic acids |date=2022 |last1=Trang |first1=Brittany |last2=Li |first2=Yuli |last3=Xue |first3=Xiao-Song |last4=Ateia |first4=Mohamed |last5=Houk |first5=K. N. |last6=Dichtel |first6=William R. |journal=Science |volume=377 |issue=6608 |pages=839–845 |pmid=35981038 |bibcode=2022Sci...377..839T }} The vinyl ether can also be prepared directly from an acyl fluoride by using sodium carbonate:{{cite book |last1=Grot |first1=Walther |title=Fluorinated Ionomers |date=2011 |publisher=Elsevier Science & Technology Books |location=San Diego |isbn=9781437744583 |edition=2nd |page=15 |url=https://books.google.com/books?id=E8H1Hwd5GXUC&pg=PA15}}

:{{chem2|ROCF(CF3)COF + Na2CO3 -> ROCF\dCF2 + 2 CO2 + 2 NaF}}

Common trademarks include Teflon-PFA, Hostaflon-PFA and Chemfluor.{{cite web |url=https://www.rct-online.de/en/HmswGlossar/detail/id/15 |title=Glossary: PFA - Perfluoralkoxy |website=Reichelt Chemietechnik |access-date=2019-06-22}} Chemours claims to be the only U.S. producer of PFA at its Fayetteville Works plant in northern Bladen County.{{cite web |title=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 |last1=Sorg |first1=Lisa |url=https://pulse.ncpolicywatch.org/2022/09/06/chemours-plans-to-expand-its-fayetteville-works-site-public-info-sessions-scheduled/ |website=NC Policy Watch |publisher=The Pulse |access-date=7 September 2022 |date=September 6, 2022}}

{{for|the environmental and health risks of the broad class of PFAs|Per- and polyfluoroalkyl substances#Health and environmental effects}}

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.{{Cite news |last=Perkins |first=Tom |date=18 December 2021 |title=PFAS 'forever chemicals' constantly cycle through ground, air and water, study finds |newspaper=The Guardian |department=Environment |url=https://www.theguardian.com/environment/2021/dec/17/pfas-forever-chemicals-constantly-cycle-through-ground-air-and-water-study-finds |access-date=4 July 2023}}

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.{{Cite magazine |last= |date=July 2023 |title=Getting PFAs out of Water |magazine=Consumer Reports |volume=88 |issue=8 |page=5}}

At high temperatures or in a fire, fluoroelastomers decompose and may release hydrogen fluoride. Any residue must be handled using protective equipment.{{Citation needed|date=July 2023}}

• Fluoropolymer
• Perfluoroether

{{reflist}}

Category:Fluoropolymers

Category:Thermoplastics

Category:Organofluorides