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Lubricants 2018, 6(2), 45; https://doi.org/10.3390/lubricants6020045

Tribological and Rheological Characterization of New Completely Biogenic Lubricating Greases: A Comparative Experimental Investigation

1
Laboratory of Machine Elements and Tribology, Department of Mechanical Engineering and Production, Faculty of Engineering Technology and Computer Science, Hamburg University of Applied Sciences (HAW-Hamburg), Berliner Tor 21, 20099 Hamburg, Germany
2
Pro2TecS-Chemical Product and Process Technology Research Centre, Complex Fluid Engineering Laboratory, Department of Chemical Engineering, University of Huelva, 21071 Huelva, Spain
*
Author to whom correspondence should be addressed.
Received: 22 March 2018 / Revised: 30 April 2018 / Accepted: 2 May 2018 / Published: 5 May 2018
(This article belongs to the Special Issue Lubricating Greases 2017)
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Abstract

Against the background of raw material shortage and the ever-expanding environmental consciousness, the use of biodegradable greases becomes more and more important. The aim of this experimental work is to investigate the tribological response of completely biodegradable greases. Complete biodegradable lubricating greases were formulated with high-oleic sunflower oil (HOSO) and/or castor oil, and different biodegradable thickener agents such as natural cellulose fibers of different lengths and some derivatives, as well as glyceryl and sorbitan stearates. To investigate the friction process, the model greases were tribologically examined with a nanotribometer at a normal force of 200 mN using a material combination of a steel ball on a steel disc. All frictional results, along with the volumes of wear tracks and micrographs of the main contacting area on the steel plate, are presented and discussed. In addition to this, rotational transient flow measurements were carried out on a rheometer at different temperatures to monitor the evolution of the shear stress with time at a constant shear rate, and to characterize the internal friction behavior by quantifying the energy density. All results were also analyzed from an energetic point of view. View Full-Text
Keywords: biogenic lubricating greases; tribology; rheology; friction; transient flow biogenic lubricating greases; tribology; rheology; friction; transient flow
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Acar, N.; Kuhn, E.; Franco, J.M. Tribological and Rheological Characterization of New Completely Biogenic Lubricating Greases: A Comparative Experimental Investigation. Lubricants 2018, 6, 45.

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