Grease thixotropy: evaluation of grease microstructure change due to shear and relaxation
Abstract
Purpose
The thixotropy of lubricating grease thickened with lithium 12-hydroxystearate with mineral base oil was investigated. The thixotropy has a significant influence on the flow resistance and pressure drop in the structural components of lubrication systems, which is of major importance as today the latter are being centralized and automated. The paper aims to discuss these issues.
Design/methodology/approach
Rheometer studies on thixotropy were carried out and the grease microstructure was visualized using atomic force microscopy (AFM). Total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was used to study the physicochemical interactions which indicate the disintegration and recovery of the grease microstructure.
Findings
A qualitative assessment of the physicochemical interactions between lithium soap floccules was made and a theory of the self-ordering effect of lithium 12-hydroxystearate associated molecules during shearing and their aggregation and flocculation during relaxation has been proposed.
Originality/value
Because of the complexity of the disintegration and recovery of the lubricating grease thickener microstructure, there is still limited physical understanding of the mechanism of this process. Therefore, the present research was undertaken to identify the phenomena involved.
Keywords
Acknowledgements
The authors wish to sincerely thank Professor Ryszard Czarny from the Institute of Machine Design and Operation and Professor Małgorzata Komorowska from the Institute of Biomedical Engineering and Instrumentation, at Wrocław University of Technology, Wrocław, Poland for their help and fruitful discussions in the course of this research. Sincere thanks are also due to Grzegorz Trykowski from Nicolaus Copernicus University, Toruń, Poland for his effective technical support in taking the AFM microphotographs.
Citation
Paszkowski, M. and Olsztyńska-Janus, S. (2014), "Grease thixotropy: evaluation of grease microstructure change due to shear and relaxation", Industrial Lubrication and Tribology, Vol. 66 No. 2, pp. 223-237. https://doi.org/10.1108/ILT-02-2012-0014
Publisher
:Emerald Group Publishing Limited
Copyright © 2014, Emerald Group Publishing Limited