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. 2021 Jun 16;6(25):16343-16355.
doi: 10.1021/acsomega.1c00808. eCollection 2021 Jun 29.

Ester Oils Prepared from Fully Renewable Resources and Their Lubricant Base Oil Properties

Chenghong Hu  1 , Jia Ai  1 , Lin Ma  1 , Ping Wen  1 , Mingjin Fan  1 , Feng Zhou  2 , Weimin Liu  2
Affiliations

Ester Oils Prepared from Fully Renewable Resources and Their Lubricant Base Oil Properties

Chenghong Hu et al. ACS Omega. .

Abstract

The work reports on the physicochemical and tribological properties of gallate ester oils prepared from fully renewable resources, such as gallic acid and fatty acids. The ester structures were identified by proton nuclear magnetic resonance spectroscopy (1H NMR), carbon nuclear magnetic resonance spectroscopy (13C NMR) and high-resolution mass spectra (HRMS) data. The density at 20 °C (d 20), kinematic viscosity (KV), viscosity index (VI), pour point (PP), flash point (FP), thermal and oxidative stabilities, friction-reducing and antiwear properties of gallate ester oils were evaluated. The tribological properties of gallate ester oils as lubricants for steel, copper, and aluminum tribo-pairs can be compared with those of the commercially available lubricating oil tris(2-ethylhexyl) trimellitate (Phe-3Ci8), but their viscosity-temperature characteristics, thermal and oxidative stabilities are better than those of Phe-3Ci8. More importantly, they have much higher biodegradabilities than Phe-3Ci8. The study of the lubrication mechanism shows that the physical and/or chemical adsorption film formed by gallate ester molecules between friction pairs is the key factor for them to obtain friction-reducing and antiwear properties.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Increasing thermogravimetric (TG) curves of the gallate ester oils and Phe–3Ci8.
Figure 2
Figure 2
Increasing derivative thermogravimetric (DTG) curves of the gallate ester oils and Phe–3Ci8.
Figure 3
Figure 3
Constant TG curves of the gallate ester oils and Phe–3Ci8.
Figure 4
Figure 4
Evolution of cofficient of friction (COF)/time (a, c) and wear volume (WV) (b, d) of lower steel plates lubricated with the gallate ester oils and Phe–3Ci8 at room temperature (RT).
Figure 5
Figure 5
Evolution of COF/time (a, c) and WV (b, d) of lower copper plates lubricated with the gallate ester oils and Phe–3Ci8 at RT.
Figure 6
Figure 6
Evolution of COF/time (a, c) and WV (b, d) of lower aluminum plates lubricated with the gallate ester oils and Phe–3Ci8 at RT.
Figure 7
Figure 7
X-ray photoelectron spectroscopy (XPS) spectra of the wear spots lubricated with the samples on steel plates.
Figure 8
Figure 8
XPS spectra of the wear spots during Ar ion sputtering (a), lubricated with Phe–3Ci8 (b), 3C8–C3 (c), 3C8–Ci5 (d), 3C8–Ci8 (e), 3Ci8–Ci8 (f), 3C4–Ci8 (g), and 3C12–Ci8 (h).
Figure 8
Figure 8
XPS spectra of the wear spots during Ar ion sputtering (a), lubricated with Phe–3Ci8 (b), 3C8–C3 (c), 3C8–Ci5 (d), 3C8–Ci8 (e), 3Ci8–Ci8 (f), 3C4–Ci8 (g), and 3C12–Ci8 (h).
Figure 9
Figure 9
Contact resistances between the steel (a, b), copper (c, d) and aluminum (e, f) plates lubricated with the gallate ester oils and Phe–3Ci8.
Figure 10
Figure 10
Biodegradation rates (BRs) of the gallate ester oils and Phe–3Ci8.
Figure 11
Figure 11
Synthesis of the gallate ester oils.
See this image and copyright information in PMC

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