Perfluoropolyether
{{Short description|Class of chemical compounds}}
Perfluoropolyethers (PFPEs) are a class of organofluorine compound. Some types are synthetic liquid lubricants that have been used in the aerospace industry for over 30 years.{{cite web |title=Spontaneous Dewetting of a Perfluoropolyether |publisher=National Aeronautics and Space Administration |author=Bradley Shogrin |date=August 1995 |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950026498.pdf |accessdate=November 29, 2017}} The main properties of PFPE are being temperature resistant between {{Convert|-58|C|K}} and {{Convert|257|C|K}} (depending on specific composites), having very low outgassing compared to other fluids (vapour pressure of {{val|6|e=-8|ul=Torr}}) and having a dielectric strength of around 15.7 MV/m.{{Cite web|url=http://www.solvay.com/en/markets-and-products/featured-products/Fomblin-PFPE-Lubricants.html|title = Fomblin® PFPE Lubricants}}
Perfluoropolyethers consists of a polymer chain in which monomers consisting of perfluoro-alkyl groups are joined by ether linkages. The bonds between carbon and oxygen or fluorine are strong.{{cite news |title=Brief Introduction of PFPE Synthesis Methods |author=Fluorochemie |publisher=Fuzhou Topda New Material Co., Ltd. |url=https://www.fluorochemie.com/brief-introduction-of-pfpe-synthesis-methods.html |accessdate=June 27, 2022}} Perfluoropolyethers are a type of PFAS.{{cite journal |last1=Kwiatkowski |first1=Carol F. |last2=Andrews |first2=David Q. |last3=Birnbaum |first3=Linda S. |last4=Bruton |first4=Thomas A. |last5=DeWitt |first5=Jamie C. |last6=Knappe |first6=Detlef R. U. |last7=Maffini |first7=Maricel V. |last8=Miller |first8=Mark F. |last9=Pelch |first9=Katherine E. |last10=Reade |first10=Anna |last11=Soehl |first11=Anna |last12=Trier |first12=Xenia |last13=Venier |first13=Marta |last14=Wagner |first14=Charlotte C. |last15=Wang |first15=Zhanyun |last16=Blum |first16=Arlene |title=Scientific Basis for Managing PFAS as a Chemical Class |journal=Environmental Science & Technology Letters |date=11 August 2020 |volume=7 |issue=8 |pages=532–543 |doi=10.1021/acs.estlett.0c00255|doi-access=free |hdl=20.500.11850/438999 |hdl-access=free }}
The thermal and chemical stability of PFPEs along with a vapor–liquid equilibrium of 230 °C when mixed with the right composites make it a suitable candidate for vapor phase soldering technologies.{{Cite web |url=https://www.asscon.de/d/pages/aktuelles/pdf/lead-free%20proc.pdf |title=Archived copy |access-date=2020-08-23 |archive-date=2021-02-27 |archive-url=https://web.archive.org/web/20210227165041/https://www.asscon.de/d/pages/aktuelles/pdf/lead-free%20proc.pdf |url-status=dead }}
History
Perfluoropolyethers were developed in the early 1960s for the USAF, who needed a lubricant that would not react with liquid or gaseous oxygen (O2).{{Cite web |title=HUSKEY Specialty lubricants |url=https://www.huskey.ru/APPLICATIONS%20AND%20BENEFITS%20OF%20PERFLUOROPOLYETHER.pdf |publisher=HUSK-ITT Corporation}}
Manufacture
Each type of perfluoropolyether is synthesized differently: PFPE-K is obtained from HFPO by anionic polymerization. For PFPE-Y and PFBE-Z, photooxidation of hexafluoropropylene and tetrafluoroethylene, respectively, is applied. PFPE-D is synthesized by anionic ring-opening polymerization of 2,2,3,3-tetrafluorooxetane. PFPE-A is obtained by an initial esterification of polyethylene glycol with a perfluoroacyl fluoride. Then, it is converted into a fully fluorined polymer using direct fluorination.{{Cite book |url=https://www.oecd.org/chemicalsafety/risk-management/synthesis-report-understanding-perfluoropolyethers-and-their-life-cycle.pdf |title=Synthesis Report on Understanding Perfluoropolyethers (PFPEs) and Their Life Cycle |date=2024 |publisher=OECD}}
File:PFPE-K.svg|PFPE-K
File:PFPE-Y.svg|PFPE-Y
File:PFPE-Z.svg|PFPE-Z
File:PFPE-D.svg|PFPE-D
File:PFPE-A.svg|PFPE-A
Properties
PFPEs are chemically inert to many acids and oxidants (like fuming sulfuric acid (oleum, SO3), chlorine gas, oxygen) and solvents, etc.
PFPEs are nonflammable, and exhibit unusually high load carry capabilities.{{Cite book |last=Ash |first=Michael |url=https://www.worldcat.org/oclc/747426845 |title=Handbook of green chemicals |date=2004 |publisher=Synapse Information Resources |others=Irene Ash |isbn=978-1-934764-29-9 |edition=2 |location=Endicott, NY |oclc=747426845}}{{Rp|page=275}}
Toxicity
Do not breathe gas/fumes/vapor/spray.{{Cite book |last=Ash |first=Michael |url=https://www.worldcat.org/oclc/747426845 |title=Handbook of green chemicals |date=2004 |publisher=Synapse Information Resources |others=Irene Ash |isbn=978-1-934764-29-9 |edition=2 |location=Endicott, NY |oclc=747426845}}{{Rp|page=1906}} As this is a large class of chemicals, refer to the specific chemical's safety data sheet.
Applications
Generally, PFPEs may be used as lubricant in all sorts of bearing, plug valves, gaskets, chains, and joint bearing applications, where oxygen inertness of a material is a requirement. Examples include aircraft fuel systems, mechanical components of devices used in airspace, deep space or high vacuum and at cryogenic temperatures.
PFPEs may be used in mold release agent for plastic injection molding.
As top coating lubricant on computer disc drives and Scanning Electron Microscope{{r|:1|p=275}}
As anti-galling compounds.
As fluid medium in ferrofluidic seals.
= Semiconductor industry =
In the semiconductor industry, PFPEs may be used as a vacuum grease or in plasma etching equipment, or for robots used in semiconductor wafer handling, clean rooms, and other commercial environments.
See also
- Krytox, a PFPE-based lubricant