Investigation of Tribological Behavior of Lubricating Greases Composed of Different Bio-Based Polymer Thickeners

Vafaei, Seyedmohammad; Fischer, Dennis; Jopen, Max; Jacobs, Georg; König, Florian; Weberskirch, Ralf

doi:10.3390/lubricants9080080

Cited by 17 publications

(9 citation statements)

References 31 publications

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“…In addition, the results indicate that these amorphous crosslinking points increase in importance with increasing thickener concentration. Compared to aliphatic polyurea thickener in castor oil, the PT system has a comparatively lower flow limit of 5.0–6.0% [ 10 ]. However, since the overall flow limit is dependent on the chain mobility [ 10 ], and since this is limited by the higher crystallinity of the PT system [ 11 ], it may be possible to increase the flow limit by using shorter aliphatic dicarboxylic acids.…”

Section: Resultsmentioning

confidence: 99%

Comparative Studies on the Organogel Formation of a Polyester in Three Different Base Oils by X-ray Analysis, Rheology and Infrared Spectroscopy

Jopen,

Paulus,

Sternemann

et al. 2023

Gels

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High-performance greases typically consist of a base oil and polyurea as a thickener material. To date, few alternatives to polyureas have been investigated. Polyesters could be one such alternative; however, little is known about the gelation of such polyesters because, unlike polyureas, they cannot form hydrogen bonds between the polymer chains. Here, we present studies on the gel formation of a polyester based thickener poly(hexane dodecanoate) with 1-octanol endgroups in three different base oils, i.e., a mineral oil (Brightstock 150), a synthetic Polyalphaolefin (Spectrasyn 40) and castor oil (85 to 90 wt.% ricinoleic acid triglyceride). Small- and wide-angle X-ray scattering measurements indicate a strong interaction of the polyester with castor oil and an increase in the crystalline fraction, with an increasing polymer amount from 5 to 40 wt.%. Moreover, infrared analysis of the polyester in castor oil showed gel formation at a minimum concentration of 20 wt.%. The strong interaction of the polyester with castor oil compared to the other two base oils led to an increase in the yield point γF as a measure of the mechanical stability of the gel, which was determined to be 5.9% compared to 0.8% and 1.0% in Brightstock and Spectrasyn, respectively.

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Section: Resultsmentioning

confidence: 99%

Comparative Studies on the Organogel Formation of a Polyester in Three Different Base Oils by X-ray Analysis, Rheology and Infrared Spectroscopy

Jopen,

Paulus,

Sternemann

et al. 2023

Gels

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“…In a previous publication [46], we have already shown oscillation rheology measurements of bio-based polyurea greases and the influence of the chemical thickener structure on the flow limit. The oscillation measurements were carried out to determine the yield point and the flow limit of the different greases at 25 • C. The yield point here indicates the end of the linear viscoelastic range (LVE) [47].…”

Section: Rheologymentioning

confidence: 88%

“…Further, the determined relative flow limit γ F of the 18 grease systems under investigation were plotted against the previously determined degree of polymerization (DP) (Figure 4). The degree of polymerization was chosen for the correlation, since it represents a measure of the mobility of the polymer chains [46] and thus allows a better comparison of the structurally different systems. All three system series reveal a linear increase of γ F with increasing DP, however, they differ in their slope.…”

Section: Rheologymentioning

confidence: 99%

Polyurea Thickened Lubricating Grease—The Effect of Degree of Polymerization on Rheological and Tribological Properties

Jopen

Degen²,

Henzler³

et al. 2022

Polymers

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Lubricating greases based on urea thickeners are frequently used in high-performance applications since their invention in 1954. One property that has so far been neglected in the further development of these systems due to their low solubility and the resulting difficulty of analysis, is to better understand how the degree of polymerization affect such polyurea lubricating systems. In this work, we prepared three different oligo- or polyurea systemswith different degrees of polymerization (DP) and investigated the influence of DP on rheological and tribological properties. The results showed that the DP has an influence on the flow limit in rheology as well as on the extreme pressure (EP) and anti-wear (AW) properties as examined by tribology measurements. By optimizing the DP for a thickener system, comparable EP and AW properties can be achieved through the use of additives. The DP showed an increasing influence on the flow limit. This could reduce damage to rolling bearings due to lateral loading at rest. Therefore, modifying the DP of the polyurea systems shows similar effects as the addition of external additives. Overall, this would reduce the use of additives in industrial applications.

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“…Grease is a common lubricant in rolling bearings, and comprises base oil, thickener, and small amounts of additives. Commercial greases are mostly produced from petrochemical base oils and thickeners [32]. A semi-solid grease can provide the benefits of liquid lubricants without needing a reservoir, and also the advantages of solid lubricants by maintaining body structure.…”

Section: Biodegradable Greasementioning

confidence: 99%

Current Status and Future Prospects of Biolubricants: Properties and Applications

Sarma

Vinu

2022

Lubricants

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Biolubricants generated from biomass and other wastes can reduce the carbon footprint of manufacturing processes and power generation. In this paper, the properties and uses of biolubricants have been compared thoroughly with conventional mineral-based lubricants. The biolubricants, which are currently based on vegetable oils, are discussed in terms of their physicochemical and thermophysical properties, stability, and biodegradability. This mini-review points out the main features of the existing biolubricants, and puts forward the case of using sustainable biolubricants, which can be generated from agro-residues via thermochemical processes. The properties, applications, and limitations of non-edible oils and waste-derived oils, such as bio-oil from pyrolysis and bio-crude from hydrothermal liquefaction, are discussed in the context of biolubricants. While the existing studies on biolubricants have mostly focused on the use of vegetable oils and some non-edible oils, there is a need to shift to waste-derived oils, which is highlighted in this paper. This perspective compares the key properties of conventional oils with different oils derived from renewable resources and wastes. In the authors’ opinion, the use of waste-derived oils is a potential future option to address the problem of the waste management and supply of biolubricant for various applications including machining, milling applications, biological applications, engine oils, and compressor oils. In order to achieve this, significant research needs to be conducted to evaluate salient properties such as viscosity, flash point, biodegradability, thermo-oxidative and storage stability of the oils, technoeconomics, and sustainability, which are highlighted in this review.

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Investigation of Tribological Behavior of Lubricating Greases Composed of Different Bio-Based Polymer Thickeners

Cited by 17 publications

References 31 publications

Comparative Studies on the Organogel Formation of a Polyester in Three Different Base Oils by X-ray Analysis, Rheology and Infrared Spectroscopy

Comparative Studies on the Organogel Formation of a Polyester in Three Different Base Oils by X-ray Analysis, Rheology and Infrared Spectroscopy

Polyurea Thickened Lubricating Grease—The Effect of Degree of Polymerization on Rheological and Tribological Properties

Current Status and Future Prospects of Biolubricants: Properties and Applications

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