Influence of temperature on mechanical stability of lubricating greases

Krasnokutskaya, M. E.; Nakonechnaya, M. B.; Синицын, В. В.; Prokopchuk, V. A.; Mnishchenko, G. G.

doi:10.1007/bf00727266

Cited by 8 publications

(5 citation statements)

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“…Thus, the grease consistency will become lower after a certain shear time which is reflected in a decrease of the complex shear modulus, whilst the thickening effect will be reduced. The degree of irreversible structural breakdown is governed, among other factors, by temperature, the elapsed time and the strain/stress values applied on the sample [18]. Figure 6 shows the complex modulus decay when a shear stress outside the linear viscoelasticity range is applied on the lubricating grease sample, at different temperatures (25, 100 and 160°C), and the subsequent recovery when a shear stress inside the linear region is again restored.…”

Section: Thermo-mechanical Reversibilitymentioning

confidence: 97%

Thermorheological behaviour of a lithium lubricating grease

et al. 2006

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Thermal-induced changes in the viscous and viscoelastic responses of lubricating greases have been investigated through different rheological techniques in a temperature range of 0-175°C. Small-amplitude oscillatory shear and viscous flow measurements were carried out on a model conventional lithium lubricating grease prepared by inducing the in situ saponification reaction between 12-hydroxystearic acid and hydrated lithium hydroxide. The linear viscoelasticity functions dramatically decrease above 110°C, but not below this critical temperature, which determines the maximum recommended operating temperature in relation to its durability and resistance under working conditions. Two different regions, below and above this critical temperature, in the plateau modulus versus temperature plot have been detected. From this thermal dependence, a much larger thermal susceptibility of the lubricating grease at temperatures above 110°C is apparent. The thermo-mechanical reversibility of this material has been studied by applying different combined stress-temperature protocols. Regarding the viscous flow, a minimum in the shear stress versus shear rate plots appeared at temperatures above 60°C, more pronounced as temperature increases, resulting from material instabilities. The experimental results obtained have been explained on the basis of the thermo-mechanical degradation of the lubricating grease microstructure.

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Section: Thermo-mechanical Reversibilitymentioning

confidence: 97%

Thermorheological behaviour of a lithium lubricating grease

et al. 2006

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“…Consequently, grease non-linear viscoelastic and viscous functions, at constant shear strain/ rate, will decrease with shear time. The degree of irreversible structural breakdown is governed, among other factors, by temperature, elapsed time and shear strain/stress applied on the sample [21,22]. Figure 7 shows results obtained from triple-step-shear stress tests in oscillatory shear carried out on selected lubricating grease samples.…”

Section: Rheo-destruction and Recovery Testsmentioning

confidence: 98%

Atomic Force Microscopy and Thermo-Rheological Characterisation of Lubricating Greases

et al. 2010

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In this work, non-perturbed microstructures of several commercial and model lubricating greases, differing in nature and concentration of the thickener agent, were examined using the atomic force microscopy (AFM) technique. Grease microstructure mainly depends on the nature of the thickener employed and, also, on thickener concentration and viscosity of the base oil. Thermal-induced changes in the viscoelastic response of lubricating greases have been investigated by using different rheological techniques in a temperature range of 0-175°C. Small-amplitude oscillatory shear (SAOS) measurements were carried out to determine the mechanical spectra of the different samples studied. Lubricating grease rheological thermal susceptibility was analysed by following the evolution of the plateau modulus with temperature. SAOS functions dramatically decrease, in most cases, above a characteristic temperature, which depends on nature and/or concentration of the thickener used and therefore on grease microstructure. The thermo-mechanical reversibility of grease microstructure has been studied by carrying out triple-step-shear stress tests (shear stresses inside and outside of the linear viscoelasticity range), at different temperatures. The degree of lubricating grease non-reversible structural breakdown, which increases with temperature, depends on the shear stress applied above the linear viscoelasticity limits.

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“…Thus, its microstructure may be permanently destroyed after submitting the sample to severe operating conditions, such as high temperatures or high shear rates, by not only breaking the weakest bonds but eventually degrading the thickener as well. The degree of irreversible structural breakdown is governed, among other factors, by temperature, the elapsed time, and the strain/stress values applied on the sample [23]. Figure 8 shows the evolution of the complex modulus, which unifies both elastic ( G ′) and viscous ( G ″) contributions of the material, with the elapsed time, for a grease modified with recycled PPr‐2, submitted at different temperatures and stress cycles.…”

Section: Resultsmentioning

confidence: 99%

The effect of recycled polymer addition on the thermorheological behavior of modified lubricating greases

Martín‐Alfonso¹,

Valencia²,

Sánchez³

et al. 2012

Polymer Engineering & Sci

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This article deals with the influence of temperature on the rheological behavior of lithium lubricating greases modified with three different types of recycled polymers, high-density polyethylene (HDPE), low-density polyethylene, and polypropylene (PP), all deriving from waste plastic recycling plants. Grease formulations containing diverse polymers were manufactured and rheologically characterized. Small-amplitude oscillatory shear and viscous flow measurements over a temperature range of 25-1758C were carried out. The experimental results obtained suggest that a blend of HDPE and PP could be considered a suitable potential viscosity modifier for lithium lubricating greases in a wide range of in-service temperature. Thus, the lubricating greases studied modified by HDPE or PP show quite promising results at low or high temperature, respectively. In addition, thermomechanical reversibility has been studied by applying different combined stresstemperature protocols. Lubricating greases containing any of the recycled polymers studied show a significant irreversible structural breakdown when the sample is submitted to temperatures and stresses higher than 758C and 200 Pa, respectively. Regarding lubricating grease viscous flow behavior, a minimum in the shear stress versus shear rate plots appeared at temperatures above 508C

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Influence of temperature on mechanical stability of lubricating greases

Cited by 8 publications

References 0 publications

Thermorheological behaviour of a lithium lubricating grease

Thermorheological behaviour of a lithium lubricating grease

Atomic Force Microscopy and Thermo-Rheological Characterisation of Lubricating Greases

The effect of recycled polymer addition on the thermorheological behavior of modified lubricating greases

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