Thixotropy of complex calcium greases

Krasnokutskaya, M. E.; Nakonechnaya, M. B.; Dugina, L. N.

doi:10.1007/bf00725294

Cited by 2 publications

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“…They assumed that as the shear rate increases and then decreases, the free energy of the soap particles, which directly depends on their strain energy, changes. Krasnokutskaya et al 26 examined the effect of the long storage of complex lime greases at different temperatures on their mechanical stability during shearing and on the kinetics of thickener microstructure reconstruction after shearing. The phenomena were investigated in the standard way, i.e.…”

Section: Effect Of Thickener Microstructure On Lithium Grease Flow Resistance In Lubrication Systemsmentioning

confidence: 99%

Assessment of the effect of temperature, shear rate and thickener content on the thixotropy of lithium lubricating greases

Paszkowski

2012

Proceedings of the Institution of Mechanical Engineers, Part J:

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As part of this research the thixotropy of lubricating greases based on mineral oil ORLEN OIL SN-400, thickened with lithium 12-hydroxystearate has been investigated. The investigations consisted in shearing grease samples in the rotational rheometer head for 1 h, followed by 24- h relaxation and again 1-h shearing, at a constant shear rate gradient. The increase in the structural viscosity of the grease, caused by the partial reconstruction of the lithium thickener microstructure between the two shearing stages, after 24- h relaxation, was studied. The studies have shown that there is a non-unique dependence between grease temperature T, shear rate gradient [Formula: see text], thickener percentage Sc and the intensity of grease microstructure reconstruction. In the adopted ranges of the input quantities: T (from −20 °C to + 80 °C), [Formula: see text] (from 8.1 to 48.6 s−1) and Sc (from 4% to 9%), the largest increment in structural viscosity was observed for the grease with thickener percentage Sc = 7.5%, sheared at shear rate gradient [Formula: see text] = 8.1 s−1 at temperature T = 28 °C. On the basis of the experimental studies, a mathematical relation for predicting the increment in the structural viscosity of lithium greases in different shearing conditions has been developed. The relation can find wide application in engineering practice in the design of machine lubrication systems and in the selection of lubricating media thickened with lithium soap.

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Section: Effect Of Thickener Microstructure On Lithium Grease Flow Resistance In Lubrication Systemsmentioning

confidence: 99%

Assessment of the effect of temperature, shear rate and thickener content on the thixotropy of lithium lubricating greases

Paszkowski

2012

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…Thickener forms network structure and base oil is held in the structure [4]. Because of this network structure, lubricating greases show complex rheological behavior such as yield stress and thixotropy [5,6]. These complicated rheological properties of lubricating greases are caused by deformation, destruction and reconstruction of the network structure, and also related to the interaction between thickener and base oil.…”

Section: Introductionmentioning

confidence: 99%

Relation between Dielectric Relaxation and Rheological Properties of Lubricating Greases

et al. 2012

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The dielectric spectroscopy method was applied to the investigation of the dynamics of base oil and thickener of lubricating grease. In order to observe the dielectric relaxations both of base oil and thickener, the lubricating grease formed from polyol ester base oil and lithium 12-hydroxy stearate thickener was prepared. Apparent viscosity, dynamic viscoelasticity and creep properties were measured, and the temperature characteristics of these rheological properties were compared to that of dielectric relaxation time. Prepared lubricating grease showed two dielectric relaxation processes. The dielectric relaxation observed in low-frequency and high-frequency regions were attributed to thickener and polyol ester base oil, respectively. The dielectric relaxation time of the high-frequency relaxation exhibited non-Arrhenius-type temperature dependence. This temperature characteristic is similar to that of viscoelastic relaxation time, shift factor obtained from superposition of creep compliance data, and viscosity of polyol ester base oil. On the other hand, the dielectric relaxation time of the low-frequency relaxation showed Arrhenius-type temperature dependence. However, no clear relation was observed between the dielectric relaxation in low-frequency region and the rheological properties measured in this study.

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Thixotropy of complex calcium greases

Cited by 2 publications

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Assessment of the effect of temperature, shear rate and thickener content on the thixotropy of lithium lubricating greases

Assessment of the effect of temperature, shear rate and thickener content on the thixotropy of lithium lubricating greases

Relation between Dielectric Relaxation and Rheological Properties of Lubricating Greases

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