Synergism between bio-based oleate ester and low-concentration ZDDP under reciprocating contacts

Shu, Ju (author), Espejo, Cayetano (author), Kalin, Mitjan (author), Morina, Ardian (author)

In this study, a bio-based ester was experimentally tested under a reciprocating contact in terms of the tribological performance to assess the potential of bio-based materials as boundary lubrication additives for low Sulphated Ash, Phosphorus, and Sulphur (SAPS) lubricants. A synergy in tribological performance has been observed when the ethyl oleate was used with a low concentration of ZDDP, showing both lower friction and wear loss, compared to only ethyl oleate or Zinc dialkyldithiophosphates (ZDDP) as single additives in base oil. SEM-EDX and ToF-SIMS analyses confirm that the additive combination of ester and low-concentration ZDDP generates a more evenly distributed tribo-film than that for only ZDDP as an additive. Although the tribo-film thickness of the ester/ZDDP lubricant combination, measured with AFM, issmaller than that for only low- concentration ZDDP, the combination shows superior wear protection ability over ZDDP. Mass spectra from ToF-SIMS show that the main component of the film formed by the additive combination is zinc polyphosphate, while the film generated from low-concentration ZDDP consists of short-chain iron phosphate. It is proposed that the ethyl oleate present in the additive combination alleviates severe shear in the contact, which promotes the formation of a uniform tribo-film composed of glassy zinc polyphosphate. The formed tribo-film enhances the adsorption of ester fragments, improving the tribological performance compared to using only ester as an additive. The obtained results demonstrate the potential of bio-based esters to reduce ZDDP usage and move towards greener lubricants.

• Language: English
• Keywords: bio-based ester, ethyl oleate, low-concentration ZDDP, reciprocation
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2024
• Number of pages: Str. 1-11
• Numbering: Vol. 192, art. 109252
• PID: 20.500.12556/RUL-154702
• UDC: 539.92:547-326
• ISSN on article: 0301-679X
• DOI: 10.1016/j.triboint.2024.109252
• COBISS.SI-ID: 186544643
• Publication date in RUL: 23.02.2024

Record is a part of a journal

• Title: Tribology international
• Shortened title: Tribol. int.
• Publisher: Butterworth Scientific
• ISSN: 0301-679X
• COBISS.SI-ID: 26558976

Licences

• License: CC BY-NC 4.0, Creative Commons Attribution-NonCommercial 4.0 International
• Link: http://creativecommons.org/licenses/by-nc/4.0/
• Description: A creative commons license that bans commercial use, but the users don’t have to license their derivative works on the same terms.

Secondary language

• Language: Slovenian
• Keywords: ester na biološki osnovi, etil oleat, ZDDP z nizko koncentracijo, recipročnost

Projects

• Funder: EC - European Commission
• Funding programme: H2020
• Project number: 860246
• Name: GreenTRIBOS
• Acronym: GreenTRIBOS

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