Perfluorotetradecanoic acid as an additive for friction reduction in full-film EHD contacts : the role of functional group, base oil polarity, additive concentration and contact pressure

Polajnar, Marko (author), Požar, Tomaž (author), Kalin, Mitjan (author)

Perfluorinated tetradecanoic acid was added as an additive to a base oil and tested under full film elastohydrodynamic (EHD) contact conditions between a steel ball and a steel disc. By varying key performance parameters, we aimed to assess the feasibility and limitations of perfluorinated carboxylic acids in reducing friction in lubricated contacts. The results demonstrate that the tested perfluorinated additive is effective in reducing friction when blended with a non-polar synthetic poly-alpha-olefin oil. However, no significant friction reduction was observed when the same additive was used in a slightly polar synthetic ester. The carboxylic acid functional group plays a crucial role in the observed friction-reducing effect. Adjusting the additive concentration further plays an important role in reducing friction. A concentration of at least 0.35 wt.% is required to achieve a notable friction reduction of approximately 10%. Increasing the concentration beyond this threshold continues to improve the friction-reducing effect. Conversely, increasing the contact pressure has a detrimental impact on friction reduction. The greatest reduction in friction—over 20% compared to the base oil—was achieved at the lowest contact pressure tested (0.69 GPa).

• Language: English
• Keywords: additives, EHD contact, base oil, concentration, pressure
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 12 str.
• Numbering: Vol. 13, issue 6, art. 263
• PID: 20.500.12556/RUL-169952
• UDC: 539.92
• ISSN on article: 2075-4442
• DOI: 10.3390/lubricants13060263
• COBISS.SI-ID: 240516611
• Publication date in RUL: 26.06.2025

Record is a part of a journal

• Title: Lubricants
• Shortened title: Lubricants
• Publisher: MDPI
• ISSN: 2075-4442
• COBISS.SI-ID: 12353563

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: aditivi, EHD kontakt, bazno olje, koncentracija, tlak

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P2-0231
• Name: Tribologija

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: J2-60050