Tribological behaviors of some novel dimercaptothiadiazole derivatives containing hydroxyl as multifunctional lubricant additives in biodegradable lithium grease
Abstract
Purpose
In order to meet the requests of exploring environmental-friendly and multifunctional lubricant additives, some novel dimercaptothiadiazole derivatives containing hydroxyl are prepared and used as antiwear (AW) and extreme-pressure (EP) additives in biodegradable lithium grease. The paper aims to discuss these issues.
Design/methodology/approach
The tribological performances of the grease samples containing these derivatives are evaluated by using a four-ball tester. X-ray absorption near edge structure (XANES) spectroscopy is used to analyze the chemistry of tribofilms under AW/EP regime, and thermal films are also considered for comparison.
Findings
The tribological tests show that these derivatives are all effective in reducing wear, especially at lower additive concentrations, but they are basically failed in reducing friction. They are also helpful in improving the EP characteristic of the base grease. The thermal films generated by these derivatives are composed of adsorbed organic sulfide and ferrous sulfate, though for short-chain derivatives, organic sulfide is the only component at 5.0 wt.%. Ferrous sulfide is the main component of the tribofilms formed by these derivatives at various additive concentrations. But for short-chain derivatives, these tribofilms consist of ferrous sulfide and ferrous disulfide at 5.0 wt.%, and the appearance of disulfide suggests that the interfacial temperature between the upper ball and three lower balls under these conditions is considerably low. The EP films generated by short-chain derivatives are all composed of organic sulfide and ferrous sulfide, while for long-chain derivatives, ferrous sulfide is the main component.
Originality/value
These low-toxic and oil-soluble dimercaptothiadiazole derivatives are effective in improving the tribological characteristic of the biodegradable lithium grease, and these heterocyclic derivatives may be good substitutes for some harmful traditional additives.
Keywords
Acknowledgements
The authors are grateful to the National Natural Science Foundation of China (Grant No. 20872092) and Beijing Synchrotron Radiation Facility (Grant No. SR06033) for the financial support to the work reported here.
Citation
Chen, H., Jiang, J., Ren, T., Zheng, L. and Zhao, Y. (2014), "Tribological behaviors of some novel dimercaptothiadiazole derivatives containing hydroxyl as multifunctional lubricant additives in biodegradable lithium grease", Industrial Lubrication and Tribology, Vol. 66 No. 1, pp. 51-61. https://doi.org/10.1108/ILT-08-2011-0065
Publisher
:Emerald Group Publishing Limited
Copyright © 2014, Emerald Group Publishing Limited