Perfluorocarboxylic acids as additives for friction reduction in full-film EHD contacts : influence of additive chain length

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

Six perfluorinated, saturated and un-branched monocarboxylic acids (CF) with different chain lengths (8–18 C atoms) were used as additives to a polyalphaolefin base oil under full-film elastohydrodynamic (EHD) conditions in steel/steel and steel/sapphire contacts at ambient temperature. In the steel/steel contacts the longer alkyl chain lengths (CF14, CF16 and CF18) provided as much as 37 % friction reduction, while the shorter alkyl chain lengths (CF8, CF10 and CF12) resulted in up to 6 % friction reduction compared to the base oil. The CF16 and CF18 additives also maintained low friction during prolonged tests with more than 30 % and 17 % friction reduction, respectively. The steel/sapphire contacts had an up to 60 % friction reduction compared to the base oil. The Fourier-transform infrared spectroscopy, wetting, white-light interferometry and scanning electron microscopy confirmed that achieving a complete, coherent and uniform additive CF layer with a low polar surface energy is essential to provide effective boundary slip, which was found to be the responsible mechanism for such a large reduction in the friction. This additive-enabled EHD slip mechanism, confirmed at ambient temperature, is a noticeable improvement for the applicability of the EHL boundary-slip concept, since it enabled additive-based friction reduction also at low temperatures, which was so far obtained only at high temperatures with previously reported simple polar oleophobic additives. Moreover, the amount of friction reduction surpassed previously reported values.

• Jezik: Angleški jezik
• Ključne besede: additives, EHD contact, base oil, concentration, pressure, perfluoroalkyl acids, EHD lubrication, surface energy, additive films
• Vrsta gradiva: Članek v reviji
• Tipologija: 1.01 - Izvirni znanstveni članek
• Organizacija: FS - Fakulteta za strojništvo
• Status publikacije: Objavljeno
• Različica publikacije: Objavljena publikacija
• Leto izida: 2025
• Št. strani: 12 str.
• Številčenje: Vol. 211, art. 110892
• PID: 20.500.12556/RUL-169954
• UDK: 539.92
• ISSN pri članku: 1879-2464
• DOI: 10.1016/j.triboint.2025.110892
• COBISS.SI-ID: 240528387
• Datum objave v RUL: 26.06.2025

Gradivo je del revije

• Naslov: Tribology international
• Skrajšan naslov: Tribol. int.
• Založnik: Elsevier
• ISSN: 1879-2464
• COBISS.SI-ID: 62108419

Licence

• Licenca: CC BY-NC 4.0, Creative Commons Priznanje avtorstva-Nekomercialno 4.0 Mednarodna
• Povezava: http://creativecommons.org/licenses/by-nc/4.0/deed.sl
• Opis: Licenca Creative Commons, ki prepoveduje komercialno uporabo, vendar uporabniki ne rabijo upravljati materialnih avtorskih pravic na izpeljanih delih z enako licenco.

Sekundarni jezik

• Jezik: Slovenski jezik
• Ključne besede: aditivi, EHD kontakt, bazno olje, koncentracija, tlak

Projekti

• Financer: ARIS - Javna agencija za znanstvenoraziskovalno in inovacijsko dejavnost Republike Slovenije
• Številka projekta: P2-0231
• Naslov: Tribologija

• Financer: ARIS - Javna agencija za znanstvenoraziskovalno in inovacijsko dejavnost Republike Slovenije
• Številka projekta: J2-60050
• Naslov: Zmanjšanje trenja z naprednimi kontakti - FRAC