Knowledge

Welcome to our knowledge centre. Here you can find a selection of resources and articles on our products and industries we are involved with.

Paper

Compositions Containing Diesel and Fatty Acid Methyl Ester/Maleic Anhydride/Esters (FAME/MA/Esters) and the Use of FAME/MA/Esters to Improve the Lubricity of Diesel

A composition containing diesel (e.g., containing less than about 15 ppm sulfur) and fatty acid methyl ester/maleic anhydride/esters (FAME/MA/esters), wherein …

A composition containing diesel (e.g., containing less than about 15 ppm sulfur) and fatty acid methyl ester/maleic anhydride/esters (FAME/MA/esters), wherein the FAME/MA/esters are prepared by a method involving reacting FAME with MA to form FAME/MA and reacting FAME/MA with alkyl alcohol to form FAME/MA/esters; wherein the FAME is conjugated. The FAME/MA/esters are produced from tung oil or from plant oils in which the unsaturated fatty acids have been converted to conjugated fatty acids. Also a method of improving the lubricity of diesel, involving combining diesel and FAME/MA/esters, wherein the FAME/MA/esters are prepared by a method involving reacting FAME with MA to form FAME/MA and reacting FAME/MA with alkyl alcohol to form FAME/MA/esters; wherein the FAME is conjugated.

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Paper

Low Viscosity Lubricating Oils With Improved Oxidative Stability And Traction Performance

Provided is lubricating oil composition including from 10 to 90 wt % of a base stock comprising a C28-C32 hydrocarbon …

Provided is lubricating oil composition including from 10 to 90 wt % of a base stock comprising a C28-C32 hydrocarbon fraction (“dimers”) and optionally a C42-C48 hydrocarbon fraction (“trimers”) produced by oligomerization of a linear C14 mono-olefin, a linear C16 mono-olefin, or a mixture thereof, in the presence of a Lewis acid catalyst, and the remainder of the composition including one or more lubricating oil additives. The lubricating oil composition provides an oxidative stability of greater than 100 hours (time to 200% KV@40 deg. C. increase) and a mini traction machine (MTM) average traction coefficient at 100 deg. C. of less than 0.0081.

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Paper

Thermal Behaviour of Synovene and Oleamide in Oil Adsorbed on Steel

Oleamide and Synovene lubricant additives when mixed together show a clear co-operative efect leading to friction and wear reduction. Sum …

Oleamide and Synovene lubricant additives when mixed together show a clear co-operative efect leading to friction and wear reduction. Sum Frequency Generation vibrational spectroscopy has been used to record in situ spectra of these additives with the aim of understanding the behaviour of these molecules when adsorbed on steel immersed in a model base oil at pre-selected temperatures. The spectra of the individual components and of mixtures have been recorded up to 130 °C. Individual spectra from both molecules have been distinguished using per-deuterated oleamide. The temperature at which maximum ordered adsorption of pure Synovene molecules occurs drops from ~130 to~70 °C in the mixture with oleamide. Our results show that co-adsorption occurs, which causes a change in net polar orientation of the oleamide component suggesting the hydrocarbon chains of the oleamide molecules reverse their polar orientation when Synovene is present. The net effect of co-adsorption and change in orientation as well as conformation of the two molecules could explain the reduction of friction and wear observed at the metal–metal interface.

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Paper

Correlation of high frequency QCM sphere-plate stiffness measurements with macroscopic frictional contacts in thin film and bulk stainless steel materials

We compare friction coefficient values μ for stainless steel contacts, obtained directly using a ball on disk tribometer and/or a …

We compare friction coefficient values μ for stainless steel contacts, obtained directly using a ball on disk tribometer and/or a basic “da Vinci” method, with values inferred from two microscale analysis methods reported in the literature that treat the response of a Quartz Crystal Microbalance (QCM) to rubbing contacts with one or more ball bearings. The microscale analysis methods both employ a Cattaneo-Mindlin slip scenario to relate contact stiffness to QCM response. Analysis Method 1 involves sweeps of the QCM amplitude of vibration while ball bearings are held in continuous contact with the oscillating electrode. It obtains μ from the slope of the associated frequency or bandwidth shift trace. We find that this method yields values for μ that compare favorably with macroscale values when the bandwidth dependence on vibrational amplitude is utilized. Method 2 obtains μ by analyzing the shifts in frequency and bandwidth that occur when ball bearings are brought in and out of contact with a QCM’s oscillating electrode at a fixed vibrational amplitude. We find that this method yields values for μ that compare favorably with macroscale values when the measurements are performed with a contact comprised of 3 close-packed ball bearings situated symmetrically about the center of the QCM electrode. Overall, the results validate the combination of assumptions employed in the analysis methods, and support the methods as a viable means for linkage of macro and nanoscale tribological measurements.

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Paper

Rheological and Tribological Behavior of Gels and Emulsions Containing Polymer and Phospholipid

Oil-in-water (O/W) emulsions are widely used in food, pharmaceutical, and personal care applications. These types of systems often contain hydrophobically …

Oil-in-water (O/W) emulsions are widely used in food, pharmaceutical, and personal care applications. These types of systems often contain hydrophobically modified polymers and phospholipids, where the polymer acts as a rheology modifier or emulsifier, while the phospholipid acts as a functional performance surfactant. However, the underlying mechanism through which the different components affect rheological and tribological characteristics is not well understood. To this end, we take a hierarchical approach, evaluating first the hydrophobically modified polymer alone, followed by polymer and phospholipid and then an O/W emulsion stabilized with the polymer or the phospholipid and polymer combined. We characterize the tribological behavior using a soft model contact consisting of polydimethylsiloxane (PDMS), which has elastic modulus similar to human skin. Bulk rheology results show that the studied systems are shear thinning and have gel-like behavior with elastic modulus increasing substantially upon phospholipids addition. Friction coefficients increase in the elastohydrodynamic regime with increasing sample viscosity. However, systems containing the hydrophobically modified polymer and phospholipids show a lower friction coefficient at the boundary regime. Adsorption studies with a quartz crystal microbalance with dissipation (QCM-D) measurements show that phospholipids are being adsorbed onto the PDMS surface. Confocal laser scanning microscopy of the PDMS surfaces before and after immersion in a hydrophobically modified polymeric suspension containing rhodamine B shows the presence of the polymer on the PDMS surface even after DI water rinse, indicating polymer adsorption, thus resulting in lower friction coefficients at low speeds.

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Paper

Industrial Gear Oils: Influence of Bulk Oil Temperature and Contact Pressure on Tribological Performance and Subsurface Changes

This study was designed to investigate the influence of oil temperature and contact pressure on the tribological performance of three …

This study was designed to investigate the influence of oil temperature and contact pressure on the tribological performance of three industrial gear oils but also on the corresponding changes taking place beneath the metal surfaces in contact. The result shows that increase in the oil temperature and contact pressure increases surface–additive interaction, promoting the formation of low-friction tribofilms. Subsurface characterisation of the worn surfaces shows that higher oil temperature and contact pressure promotes surface hardening of spheroidised AISI 52100 steel, degradation of the near-surface (< 0.8 µm) microstructural integrity and corresponds to an increase in wear. This study clearly shows that the gear oil formulations and the tribofilms they form uniquely influence the extent of subsurface deformation and wear.

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Paper

Measurement of EHD Friction at Very High Contact Pressures

EHD friction curves have been measured up to very high pressure (pmean = 5 GPa, pmax = 7.5 GPa) using a newly developed, rolling-sliding, …

EHD friction curves have been measured up to very high pressure (pmean = 5 GPa, pmax = 7.5 GPa) using a newly developed, rolling-sliding, ball on disc machine, the ETM. Six base fluids have been studied, spanning the API base oil categories Group I to Group V. At high pressures, thermal effects become substantial even at quite modest slide-roll ratios, and these must be considered when analysing friction measurements in terms of the underlying rheological properties of the oils. By comparing measurements from steel/steel and WC/WC ball and disc combinations with very different thermal conductivities, the use of thermal correction to derive isothermal friction curves has been validated. At relatively low pressures (mean pressure = 1 GPa), there are substantial differences between the EHD friction properties of the various API Group base oils, but as pressure is raised these diminish and the EHD friction coefficients of all the Groups approach a similar maximum value at a given temperature. EHD friction continues to be quite strongly temperature dependent even at very high pressure. As pressure is increased, EHD friction curves become progressively steeper, so that friction coefficients at very low slide-roll ratios (1 to 2% SRR) become several times greater at high than at low pressure. This has important practical implications for the efficiency of rolling element bearings at high pressures since these components normally operate in this SRR range. There is no evidence of any of the base oils reaching a limiting shear stress over the whole pressure and temperature range studied. Instead, shear stress continues to increase with log(strain rate) in accord with the Eyring-activated flow model up to very high pressures.

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Paper

Rheological and Wetting Properties of Environmentally Acceptable Lubricants (EALs) for Application in Stern Tube Seals

The use of Environmentally Acceptable Lubricants (EALs) for stern tube lubrication is increasing. Although the machine components of a sailing …

The use of Environmentally Acceptable Lubricants (EALs) for stern tube lubrication is increasing. Although the machine components of a sailing vessel are designed to operate together with mineral oil-based lubricants, these are being replaced by the less environmentally harmful EALs. Little is known about the rheological performance of EALs in particular at the high shear rates that occur in stern tube seals. In this study, the viscosity and wetting properties of a set of different EALs is analysed and compared to traditional mineral oil-based lubricants using a set of experimental techniques. Some of the EALs present Newtonian behavior whereas other show shear thinning. No significant difference in surface tension was observed between the different lubricants.

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Paper

Polymer-Thickened Oil Rheology When There is No Second Newtonian

The recent development of quantitative elastohydrodynamics makes the accurate description of the temperature, pressure, and shear dependence of viscosity extremely …

The recent development of quantitative elastohydrodynamics makes the accurate description of the temperature, pressure, and shear dependence of viscosity extremely important. It has been customary for tribologists to expect a second Newtonian plateau to appear in any flow curve for a polymer-blended lubricant and, since viscometers at ambient pressure cannot reach such a plateau, procedures have been suggested to extrapolate to a second Newtonian from commercial high-shear viscometer data. Two examples of oils, characterized in pressurized thin-film Couette viscometers, are presented for which there is no second Newtonian. Extrapolation from ambient-pressure high-shear viscometer data, by fixing the second Newtonian viscosity at the viscosity of the base oil, is not useful. Apparently, the second Newtonian will not appear when the base oil begins to shear thin at the shear stress for which the second Newtonian inflection might appear.

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