Lubricating Greases

A special issue of Lubricants (ISSN 2075-4442).

Deadline for manuscript submissions: closed (31 August 2015) | Viewed by 45373

Special Issue Editors


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Guest Editor
Chemical Product and Process Technology Research Center (Pro2TecS), Department of Chemical Engineering and Materials Science, ETSI, University of Huelva, 21071 Huelva, Spain
Interests: rheology; bio-sourced materials; bio-lubricants; lubricating greases; colloids; biopolymers; tribology; gels with emphasis on oleogels and organogels
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
CIQSO—Center for Research in Sustainable Chemistry and Department of Chemistry, University of Huelva, 21071 Huelva, Spain
Interests: organic synthesis; natural products; supramolecular chemistry in water media; bioactive compounds; photoactive organic compounds
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Although lubricating greases are widely used in many specific applications, their market only constitutes a very low percent of the total amount of lubricants processed in the world. This may be one of the reasons why, up to now, not much attention has been paid to innovation and research on lubricating grease formulations and related functional properties. On the other hand, it is worth mentioning that the mechanical response of greases in a lubricated contact is not yet fully understood. This is due to its complex rheological behavior in comparison with other liquid lubricants. Since lubrication is mainly a deformation and flow problem, the knowledge of the rheological properties of lubricating greases may contribute to elucidate one of the unresolved problems in tribology: the effect of viscoelasticity on lubrication characteristics and, consequently, the way in which a lubricating grease behaves under operating conditions. Suitable structural and physical characteristics may be reached from a proper selection of the ingredients but, also, from a process optimization.

The relationship among composition, microstructure and functional properties is another important issue which deserves more investigation as well as the development of new formulations with improved characteristics. In this sense, mostly in the last two decades, lubricant customers are aware of the negative effects that traditional lubricants exert on the environment and, therefore, are demanding new green products able to reduce this impact.

This special issue aims to collect and disseminate the latest developments and trends in the field of lubricating greases including physical, chemical, microstructural and rheological characterization, tribological response and associated mechanisms, technical information and modeling on grease behavior in lubricated contacts (bearings, seals, etc.), processing of greases and pumpability, development of new formulations including bio-greases and new thickeners agents, etc.

Prof. Dr. José M. Franco
Prof. Dr. Jesús F. Arteaga
Guest Editors

Manuscript Submission Information

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Keywords

  • lubricating grease
  • rheology
  • tribology
  • bearing
  • thickeners
  • additives
  • biodegradable greases
  • grease composition
  • grease microstructure

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Published Papers (6 papers)

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Research

135 KiB  
Article
Eco-Friendly Multipurpose Lubricating Greases from Vegetable Residual Oils
by Ponnekanti Nagendramma and Prashant Kumar
Lubricants 2015, 3(4), 628-636; https://doi.org/10.3390/lubricants3040628 - 21 Oct 2015
Cited by 32 | Viewed by 7618
Abstract
Environmentally friendly multipurpose grease formulation has been synthesized by using Jatropha vegetable residual oil with lithium soap and multifunctional additive. The thus obtained formulation was evaluated for its tribological performance on a four-ball tribo-tester. The anti-friction and anti-wear performance characteristics were evaluated using [...] Read more.
Environmentally friendly multipurpose grease formulation has been synthesized by using Jatropha vegetable residual oil with lithium soap and multifunctional additive. The thus obtained formulation was evaluated for its tribological performance on a four-ball tribo-tester. The anti-friction and anti-wear performance characteristics were evaluated using standard test methods. The biodegradability and toxicity of the base oil was assessed. The results indicate that the synthesized residual oil grease formulation shows superior tribological performance when compared to the commercial grease. On the basis of physico-chemical characterization and tribological performance the vegetable residual oil was found to have good potential for use as biodegradable multipurpose lubricating grease. In addition, the base oils are biodegradable and non toxic. Full article
(This article belongs to the Special Issue Lubricating Greases)
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473 KiB  
Article
Influence of Base Oil Polarity on the Transient Shear Flow of Biodegradable Lubricating Greases
by Martin Fiedler, Rubén Sánchez, Concepción Valencia, Claudia S. Leopold, Erik Kuhn and José M. Franco
Lubricants 2015, 3(3), 611-627; https://doi.org/10.3390/lubricants3030611 - 9 Sep 2015
Cited by 3 | Viewed by 7376
Abstract
The scope of this study is to elucidate the physical mechanisms influencing the transient flow behavior of lubricating greases based on biogenic oleochemicals from a polarity point of view. This includes the mutually interacting influence of base oil polarity and thickening agents on [...] Read more.
The scope of this study is to elucidate the physical mechanisms influencing the transient flow behavior of lubricating greases based on biogenic oleochemicals from a polarity point of view. This includes the mutually interacting influence of base oil polarity and thickening agents on the rheologically-measured mechanical structural degradation in transient shear flow. Due to the high temperature dependence of Keesom forces in the background of polar-active bond mechanisms, the analysis of the transient flow response as a function of temperature allows to attribute the observed influences to differences in base oil polarity. In general, clay-thickened greases show a greater tendency to be rheologically influenced by base oil polarities than soap-thickened lubricating greases. Full article
(This article belongs to the Special Issue Lubricating Greases)
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2007 KiB  
Article
Correlation between System Entropy and Structural Changes in Lubricating Grease
by Erik Kuhn
Lubricants 2015, 3(2), 332-345; https://doi.org/10.3390/lubricants3020332 - 24 Apr 2015
Cited by 28 | Viewed by 5133
Abstract
Lubricating greases are colloid disperse systems consisting of a base oil and a thickener (additional additives). The lubricant is modeled as a tribological system, and the reaction of a fluid friction stress is investigated. The energetic situation of the volume element is analyzed [...] Read more.
Lubricating greases are colloid disperse systems consisting of a base oil and a thickener (additional additives). The lubricant is modeled as a tribological system, and the reaction of a fluid friction stress is investigated. The energetic situation of the volume element is analyzed and the system entropy described. The description of the structural degradation and the used entropy was realized with the help of rheometer tests. Full article
(This article belongs to the Special Issue Lubricating Greases)
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1629 KiB  
Article
Grease Aging Effects on Film Formation under Fully-Flooded and Starved Lubrication
by Tiago Cousseau, Beatriz Graça, Armando Campos and Jorge Seabra
Lubricants 2015, 3(2), 197-221; https://doi.org/10.3390/lubricants3020197 - 9 Apr 2015
Cited by 24 | Viewed by 10220
Abstract
Several film thickness measurements were performed with three fresh and aged lubricating greases, their base and bled oils under a wide range of operating conditions using a ball-on-disc test rig with optical interferometry. The analysis of the film thickness measurements is in agreement [...] Read more.
Several film thickness measurements were performed with three fresh and aged lubricating greases, their base and bled oils under a wide range of operating conditions using a ball-on-disc test rig with optical interferometry. The analysis of the film thickness measurements is in agreement with the observations of several authors and adds some important aspects regarding separate film properties in EHL contacts. At full film lubrication and moderate to high speeds, the bled oil showed a similar behavior of its lubricating greases. At fully-flooded condition, low speeds and thin films, it was observed that the thickener lumps play a major role on film formation, overcoming the bled oil effects. A relationship between thickener type and film formation was evidenced. The same trends were observed under starved lubrication, where the thickener type that contributes the most to locally increase the film thickness follows the order of PP > Ca > Li. The aging process of the greases was shown to change their rheological response in different manners—softening or hardening—depending on the grease formulation. Grease aging increased the film thickness under fully-flooded and starved lubrication, regardless of the level of degradation. Full article
(This article belongs to the Special Issue Lubricating Greases)
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528 KiB  
Article
Recycled and Virgin HDPEs as Bleed Inhibitors and Their Rheological Influences on Lubricating Greases Thickened with PP and mPP
by Ravi Dixena, Eltepu Sayanna and Rajendra Badoni
Lubricants 2014, 2(4), 237-248; https://doi.org/10.3390/lubricants2040237 - 18 Dec 2014
Cited by 10 | Viewed by 6950
Abstract
Polypropylene (PP) thickened lubricating grease exhibits high oil bleed tendency at low temperatures, which makes it a promising candidate for low temperature applications. At elevated temperatures, PP thickened lubricating grease exhibits excessive oil bleeding, which limits its use at high temperatures. Excessive oil [...] Read more.
Polypropylene (PP) thickened lubricating grease exhibits high oil bleed tendency at low temperatures, which makes it a promising candidate for low temperature applications. At elevated temperatures, PP thickened lubricating grease exhibits excessive oil bleeding, which limits its use at high temperatures. Excessive oil bleed adversely affects the lubricating performance of the PP thickened grease. The present work is focused on the study of the oil bleed tendency of PP and Maleated Polypropylene (mPP) thickened greases at various temperatures by incorporating virgin and recycled high density polyethylene (HDPE) into the thickener system. Grease containing various percentages of PP and mPP thickeners were prepared and modified with different percentages of virgin and recycled HDPE. Polymers were characterized through differential scanning calorimetry (DSC) techniques. The oil bleed performance of these greases was evaluated by the conical sieve method (ASTM D 6184) at various temperatures. Storage (G′) and loss modulus (G″) of greases was determined by rheometry at 25 °C. Incorporation of HDPE and recycled HDPE in PP thickened grease decreased oil bleeding compared to the base grease. Full article
(This article belongs to the Special Issue Lubricating Greases)
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566 KiB  
Communication
Detection of Elemental Composition of Lubricating Grease Using Laser Induced Breakdown Spectroscopy
by Cherry Dhiman, Martha N. Reddy, Kamal Gulati and Mohd. Shahid Khan
Lubricants 2014, 2(4), 223-236; https://doi.org/10.3390/lubricants2040223 - 18 Dec 2014
Cited by 5 | Viewed by 6815
Abstract
The elemental composition of lubricating soft grease used in rail engines are studied using laser induced breakdown spectroscopy (LIBS) technique. LIBS spectra of fresh, partially used and fully used grease samples are recorded using time-gated ICCD spectrometer for verification of compositional degradation of [...] Read more.
The elemental composition of lubricating soft grease used in rail engines are studied using laser induced breakdown spectroscopy (LIBS) technique. LIBS spectra of fresh, partially used and fully used grease samples are recorded using time-gated ICCD spectrometer for verification of compositional degradation of the used grease. LIBS spectra of grease samples are analyzed by comparing with emission spectra of elements published by NIST standard database. Many spectral lines of impurity elements like Fe, Cu, Ba, Mg, Mn, Ni, S, Zn, Si, Pb, Ti, Ca and Al present in the grease in ppm or ppb level in trace level concentrations are observed in excess in the used grease mainly due to wear and tear. On the other hand in fresh grease, spectral lines of Ca, Al and Na are observed predominantly. Full article
(This article belongs to the Special Issue Lubricating Greases)
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