Abstract
A modern lubricant contains various additives with different functionalities and the interactions or reactions between these additives could induce synergistic or antagonistic effects in tribological performance. In this study, sum frequency generation (SFG) spectroscopy was used to investigate competitive adsorption of lubricant additives at a solid/base oil interface. A silica substrate was used as a model solid surface. The lubricant additives studied here included two oil-soluble ionic liquids (ILs, [N888H][DEHP] and [P8888][DEHP]), an antiwear additive (secondary ZDDP), an organic friction modifier (OFM), and a dispersant (PIBSI). Our results showed that for mixtures of ZDDP and IL in a base oil (PAO4), the silica surface is dominated by the IL molecules. In the cases of base oils containing OFM and IL, the silica/lubricant interface is dominated by OFM over [N888H][DEHP], while it is preferentially occupied by [P8888][DEHP] over OFM. The presence of PIBSI in the mixture of PAO4 and IL leads to the formation of a mixed surface layer at the silica surface with PIBSI as a major component. The SFG results in this investigation provide fundamental insights that are helpful to design the formulation of new lubricant additives of desired properties.
| Original language | English |
|---|---|
| Article number | 98 |
| Pages (from-to) | 1-18 |
| Number of pages | 18 |
| Journal | Lubricants |
| Volume | 8 |
| Issue number | 11 |
| DOIs | |
| State | Published - Nov 2020 |
Bibliographical note
Publisher Copyright:© 2020 by the authors. Licensee MDPI, Basel, Switzerland.
Funding
Funding: This manuscript has been co-authored by UT-Battelle, LLC under contract no. DEAC05-00OR22725 with the U.S. Department of Energy. The U.S. Government retains, and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. Government purposes. The Department of Energy will provide public access to these results of federally sponsored research by the DOE public access plan (http://energy.gov/downloads/ doe-public-access-plan). This manuscript has been co-authored by UT-Battelle, LLC under contract no. DEAC05-00OR22725 with the U.S. Department of Energy. The U.S. Government retains, and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. Government purposes. The Department of Energy will provide public access to these results of federally sponsored research by the DOE public access plan (http://energy.gov/downloads/ doe-public-access-plan). Acknowledgments: This work was supported by the Vehicle Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy (DOE) as a subcontract to Pennsylvania State University through the Oak Ridge National Laboratory. The authors thank J. Dyck and E. Conrad from Solvay for providing phosphonium cation feedstocks, A.G. Bro and C. Dubin from ExxonMobil for providing the PAO base oil, O. Farng from ExxonMobil for providing the OFM, and PIBSI, and E. Bardasz from Lubrizol for providing the ZDDP.
| Funders | Funder number |
|---|---|
| U.S. Government | |
| U.S. Department of Energy | |
| Office of Energy Efficiency and Renewable Energy | |
| Oak Ridge National Laboratory | |
| UT-Battelle | DEAC05-00OR22725 |
Keywords
- Additives
- Base oil
- Ionic liquids
- Lubricants
- Sum frequency generation spectroscopy