The Non-Newtonian Characteristics of Lubricating Oils

Selby, Theodore W.

doi:10.1080/05698195808972315

Cited by 109 publications

(54 citation statements)

References 4 publications

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“…The widely reported mechanism of how polymers improve VI is that polymers raise the viscosity of the fluid proportionately more at higher temperatures than at lower temperatures due to expansion of the polymer coil with increasing temperature (Figure 1) [4]. Surprisingly, given the extensive commercial applications in engine oils and other lubricating fluids there are only scattered reports on the solution properties of VMs and the effects of temperature.…”

Section: Introductionmentioning

confidence: 98%

“…Although we have shown that the polymer coil expansion model of Selby [4] is not a required mechanism to explain how polymers increase the viscosity index of lubricating oils, it can enhance the effect.…”

Section: Effect Of Coil Expansion On VI Calculation (Pma Case)mentioning

confidence: 99%

“…Surprisingly, given the extensive commercial applications in engine oils and other lubricating fluids there are only scattered reports on the solution properties of VMs and the effects of temperature. The proposed mechanism originates from a paper by Selby in 1958 [4]. However, the paper is lacking in any physical data that supports the proposed mechanism, but it refers to the work by Flory who stated that the radius of gyration, R g , of polymer molecules depends on the interactions between polymer chain segments and solvent molecules [5].…”

Section: Introductionmentioning

confidence: 99%

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How Polymers Behave as Viscosity Index Improvers in Lubricating Oils

Covitch¹,

Trickett²

2015

ACES

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One of the requirements of engine lubricating oil is that it must have a low enough viscosity at low temperatures to assist in cold starting and a high enough viscosity at high temperatures to maintain its load-bearing characteristics. Viscosity Index (VI) is one approach used widely in the lubricating field to assess the variation of viscosity with temperature. The VI of both mineral and synthetic base oils can be improved by the addition of polymeric viscosity modifiers (VMs). VI improvement by VMs is widely attributed to the polymer coil size expanding with increasing temperature. However, there is very little physical data supporting this generally accepted mechanism. To address this issue, intrinsic viscosity measurements and Small-Angle Neutron Scattering (SANS) have been used to study the variation of polymer coil size with changing temperature and concentration in a selection of solvents. The results will show that coil size expansion with temperature is not necessary to achieve significant elevation of viscosity index.

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Section: Introductionmentioning

confidence: 98%

Section: Effect Of Coil Expansion On VI Calculation (Pma Case)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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How Polymers Behave as Viscosity Index Improvers in Lubricating Oils

Covitch¹,

Trickett²

2015

ACES

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“…These, in turn, relate in a complex fashion to other basic physical chemical parameters. It was hypothesized that the mode of action focused on the hydrodynamic volume of the molecule as a function of temperature [49], where the molecular size in solution was highly contracted at low temperature, thus contributing little to viscosity. But at high temperature, it was greatly expanded, thus making a large contribution.…”

Section: Mechanism Of Functionmentioning

confidence: 99%

Viscosity Index Improvers and Thickeners

Stambaugh

Kinker

2009

Chemistry and Technology of Lubricants

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The viscosity index of an oil or an oil formulation is an important physical parameter. Viscosity index improvers, VIIs, are comprised of five main classes of polymers: polymethylmethacrylates (PMAs), olefin copolymers (OCPs), hydrogenated poly(styrene-co-butadiene or isoprene) (HSD/SIP/HRIs), esterified polystyrene-co-maleic anhydride (SPEs) and a combination of PMA/OCP systems. The chemistry, manufacture, dispersancy and utility of each class are described. The comparative functions, properties, thickening ability, dispersancy and degradation of VIIs are discussed. Permanent and temporary shear thinning of VII-thickened formulations are described and compared. The end-use performance and choice of VI improvers is discussed in terms of low-and high-temperature viscosities, journal bearing oil film thickness, fuel economy, oil consumption, high-temperature pumping efficiency and deposit control. Discussion of future developments concludes that VI improvers will evolve to meet new challenges of increased thermaloxidative degradation from increased engine operating temperatures, different base stocks of either synthetic base oils or vegetable oil-based, together with alcohol-or vegetable oil-based fuels. VI improvers must also evolve to deal with higher levels of fuel dilution and new types of sludge and also enhanced low-temperature requirements. IntroductionThe 'viscosity index', VI, was an important measure of quality early in the history of the lubricants industry, indicating an oil's potential applications over a wide range of temperatures, described in Section 1.3.2. Pennsylvania grade oils,~100 VI, were the standard against which all others were measured. Hydrogenation and solvent extraction processes were developed to upgrade lubricants from poorer quality crude oils, but the practical VI ceiling for 1930s refinery technology was~110-115.Early workers found that small amounts of rubber dissolved into mineral oil substantially raised VI; however, high levels of unsaturation in the polymer led to oxidation and sludge formation. This was overcome by using a synthetic polymer prepared from gasoline light ends [1], and similar behaviour was later described for 153 R.M. Mortier et al. (eds.), Chemistry and Technology of Lubricants, 3rd edn.,

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“…High viscosity indices are desirable as they indicate minor influence of temperature on the lubricant viscosity [4]. So far, most commercial lubricants contain polymer-based additives in order to improve the viscosity-temperature profile.…”

Section: Introductionmentioning

confidence: 99%

Practical Application of CO₂ as a Viscosity Index Improver for Lubricants

et al. 2016

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In terms of reducing power losses and ensuring optimal lubrication, a high viscosity index is crucial for lubricants exposed to changing load or temperature conditions. Several studies suggest that an enormous improvement of the viscosity-temperature characteristics could be achieved by the application of dissolved CO 2 on various base oils. The direct link between the applied pressure and the lubricant viscosity offers the possibility of adjustable and thus tunable lubricants. The practical implementation of dissolved CO 2 as a viscosity index improver is investigated on a roller bearing test rig. The results indicate a significant reduction of power losses and show that it is possible to influence the friction condition in the rolling contact through viscosity adaptation.

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The Non-Newtonian Characteristics of Lubricating Oils

Cited by 109 publications

References 4 publications

How Polymers Behave as Viscosity Index Improvers in Lubricating Oils

How Polymers Behave as Viscosity Index Improvers in Lubricating Oils

Viscosity Index Improvers and Thickeners

Practical Application of CO₂ as a Viscosity Index Improver for Lubricants

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The Non-Newtonian Characteristics of Lubricating Oils

Cited by 109 publications

References 4 publications

How Polymers Behave as Viscosity Index Improvers in Lubricating Oils

How Polymers Behave as Viscosity Index Improvers in Lubricating Oils

Viscosity Index Improvers and Thickeners

Practical Application of CO2 as a Viscosity Index Improver for Lubricants

Contact Info

Product

Resources

About

Practical Application of CO₂ as a Viscosity Index Improver for Lubricants