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Research Papers: Lubricants

Synthesis and Tribological Properties of S- and P-Free Borate Esters With Different Chain Lengths

[+] Author and Article Information
Guangbin Yang, Zhanming Zhang, Guihui Li, Jinfeng Zhang, Laigui Yu

Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004, P. R. China

Pingyu Zhang1

Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004, P. R. Chinapingyu@henu.edu.cn

1

Corresponding author.

J. Tribol 133(2), 021801 (Mar 18, 2011) (7 pages) doi:10.1115/1.4003304 History: Received June 28, 2010; Revised December 09, 2010; Published March 18, 2011; Online March 18, 2011

Three kinds of S- and P-free borate esters containing N with different alkyl chain lengths were prepared by using boric acid, ethanolamine, and alkyl-alcohol as the starting materials. The chemical structure of the products was analyzed by means of Fourier transformation infrared spectrometry, elemental analysis, and so on. The thermal stability of the products was evaluated by thermogravimetric analysis. The tribological properties of the synthesized borate esters as lubricating oil additives in liquid paraffin were evaluated using a four-ball friction and wear tester while the morphologies of the worn scars of the steel balls were observed using a scanning electron microscope. The chemical components on the worn surfaces of the steel balls were analyzed using an X-ray photoelectron spectroscopy. Results show that all the three kinds of synthetic borate esters as additives in liquid paraffin possess good antiwear performance and may be used as promising S- and P-free environmentally acceptable lubricating oil additives. Particularly, borate ester with short alkyl chain length at a low concentration in liquid paraffin was more effective in reducing wear, and the antiwear ability of the additives decreased with increasing alkyl chain length. The antiwear ability of the N-containing borate esters as additives in liquid paraffin might be closely related to the formation of hydrogen bonds via N with a high electronegativity and small atomic radius and the easy permeation of electron-deficient B on the rubbing steel surfaces.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 3

TG curves of S- and P-free borate esters (a) C8BN, (b) C12BN, and (c) C16BN

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Figure 4

Variation of the wear scar diameter of lower steel balls with additive concentration (four-ball tester, load 200 N, speed 1450 rpm, and duration 30 min)

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Figure 5

Variation of the friction coefficient with additive concentration (four-ball tester, load 200 N, speed 1450 rpm, and duration 30 min)

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Figure 6

Typical SEM micrographs of the worn steel surfaces lubricated with [(a) and (b)] liquid paraffin, [(c) and (d)] liquid paraffin with 0.1 wt %C8BN, [(e) and (f)] liquid paraffin with 0.1 wt %C12BN, and [(g) and (h)] liquid paraffin with 0.1 wt %C16BN (four-ball tester, load 200 N, speed 1450 rpm, and duration 30 min)

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Figure 7

[(a)–(e)] XPS spectra of the elements on the rubbed surface of the steel ball lubricated with liquid paraffin containing 10 wt %C8BN (200 N, 1450 rpm, and 30 min)

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Figure 1

The synthesis route to the N-containing and S- and P-free borate ester additives

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Figure 2

FT-IR spectra of S- and P-free borate esters (a) C8BN, (b) C12BN, and (c) C16BN

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