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

Polyalkylene Glycol (PAG) Based Lubricant for Light & Medium Duty Axles

The axle lubricant (SAE 75W‐140) widely used in the market place over the last few years is primarily formulated from …

The axle lubricant (SAE 75W‐140) widely used in the market place over the last few years is primarily formulated from polyalpha olefin (PAO) basestock.  This investigation focused on polyalkylene glycol (PAG) base stocks which are significantly different chemically from PAO and because of their polar nature it is hypothesized that they can adsorb relatively easily on contacting surfaces resulting in significant friction reduction and improved fuel economy. Axle efficiency is generally quite high at high torque range but it could be quite low at low torque  range representative of EPA drive cycles. Therefore, this project primarily focuses on improving  axle efficiency and thus fuel economy in the low torque range while maintining all durability attributes.

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Paper

Synergisms and Antagonisms Between MoS2 Nanotubes and Representative Oil Additives under Various Contact Conditions

MoS2 nanotubes are known to enhance the tribological properties of lubricants thanks to support friction-reducing and anti-wear properties. However, in fully-formulated lubricants particularly for steel elements, …

MoS2 nanotubes are known to enhance the tribological properties of lubricants thanks to support friction-reducing and anti-wear properties. However, in fully-formulated lubricants particularly for steel elements, other properties such as oxidation and corrosion protection are also necessary to provide a comprehensive lubricating performance and protection against oil degradation. As a consequence, the coexistence of MoS2 nanotubes with other oil additives is unavoidable in immediate future lubrication technologies. This study investigates the influence of representative oil additives such as anti-wear (AW), extreme pressure (EP), detergents and dispersants on the rheological and tribological performance of lubricant mixtures containing MoS2 nanotubes (NTs). The results obtained provide a wide overview on which of the current commonly used oil additives have a place in future nanolubricant formulations and which additives need to be reconsidered. In general, the synergy between the oil additives and the MoS2 nanotubes strongly depends on the contact conditions. The reason lies in the interaction mechanisms between the MoS2 nanotubes and the lubricated surfaces under the presence of the supplementary additive. MoS2 have an excellent synergy with AW additives under mixed rolling/sliding conditions due to the exfoliation of MoS2 platelets on top of the AW tribofilm. Under reciprocating sliding, the interaction between the MoS2 nanotubes and dispersant leads to higher antagonisms. Under extreme pressure unidirectional sliding, their synergy is better with S containing EP additives.

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Paper

Oral Lubrication Matters: Effects on Satiety

As overeating, overweight and obesity remain public health concerns, it is crucial to design satiety-enhancing foods that suppress appetite and …

As overeating, overweight and obesity remain public health concerns, it is crucial to design satiety-enhancing foods that suppress appetite and lower snack intake. Existing research identifies oro-sensory targets to promote satiation and satiety within the “satiety cascade”, yet it remains unclear as to whether it is ‘chewing’ or ‘oral lubrication’ that might amplify satiation signals. Here we have combined techniques from experimental psychology, food material science and mechanical engineering to measure the role of chewing and lubrication using novel, model foods as preloads on subjective appetite and intake of a salty snack. Three mint flavoured hydrogels were engineered to vary in their texture (fracture stress) and lubrication (inverse of friction coefficient) properties, and a control group received a mint tea. Results showed that snack intake was suppressed by 32% after eating the low chewing/high lubricating preload as compared to the high chewing/low lubricating preload (p<0.05). No other significant effects were found for snack intake. Hunger ratings decreased from t1 to t3 (p<0.05), however differences between conditions were subtle and not significant. Thus, this proof-of-concept study demonstrates that manipulating oral lubrication is a promising new construct to reduce snack intake that merits future research in the oro-sensory satiety domain.

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Paper

Method for Lubricating Surfaces

A method of lubricating the contact between a first surface coated with a hydrogenous carbon film or coating of type …

A method of lubricating the contact between a first surface coated with a hydrogenous carbon film or coating of type a-C:H, ta-C:H, a-C:H:Me or a-C:H:X, as classified by VDI Standard VDI 2840 and a second ferrous, preferably steel surface. The method comprises supplying to said contact a lubricating oil composition comprising a major amount of an oil of lubricating viscosity and (a) an oil-soluble or oil dispersible molybdenum compound in an amount such as to provide between 150 and 1000 ppm by weight of molybdenum to the lubricating oil composition, and (b) between 0.1 and 5% by weight with respect to the weight of the lubricating oil composition of a polymeric organic friction modifier, the organic friction modifier being the reaction product of (i) a functionalised polyolefin, (ii) a polyether, (iii) a polyol and (iv) a monocarboxylic acid chain terminating group.

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Paper

Marine Lubricating Oils and Method of Making and use Thereof

Provided are marine lubricating oils including from 15 to 95 wt % of a Group III base stock having a …

Provided are marine lubricating oils including from 15 to 95 wt % of a Group III base stock having a kinematic viscosity at 100 deg. C of 4 to 12 cSt, 0.5 to 55 wt % of cobase stock having a kinematic viscosity at 100 deg. C of 29 to 1000 cSt, 0.1 to 2.0 wt % of a molydithiocarbamate friction modifier, 0.1 to 2.0 wt % of a zinc dithiocarbamate anti-wear additive, and 2 to 30 wt % of other lubricating oil additives. The cobase stock is selected from the group consisting of a Group I, a Group IV, a Group V and combinations thereof Also provided are methods of making and using the marine lubricating oils.

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Paper

The Development and Application of a Scuffing Test Based on Contra-rotation

Scuffing is a surface failure mode that occurs in sliding–rolling contacts subjected to high loads and high sliding speeds, such …

Scuffing is a surface failure mode that occurs in sliding–rolling contacts subjected to high loads and high sliding speeds, such as those in gears and cam-followers. Owing to its sudden onset, rapid progression and dependence on both fluid and boundary lubricant films, scuffing is difficult to study in a repeatable manner. This paper describes further development of a recently proposed scuffing test method based on contra-rotation, its extension to higher loads using a new experimental set-up and its application to study the onset of scuffing with a selection of model and fully-formulated oils. The method employs two surfaces moving in opposite directions under rolling–sliding conditions, with a fixed load and step-wise increasing sliding speed. By decoupling the entrainment and sliding speeds, the method allows the effects of lubricant formulation on scuffing performance to be isolated from the influence of viscosity. The approach achieves high sliding speeds in parallel with low entrainment speeds, while minimising the undesirable effects of surface wear and frictional heating. The proposed test is relatively fast and economical, with total test time of about 30 min including specimen cleaning and set-up. Results show that the newly implemented modifications have improved the repeatability of the test method, so that the number of repeat tests required for reliable oil ranking results is minimal. Tests with model and fully-formulated oils show that the onset of scuffing is characterised by a sharp and unrecoverable increase in friction and accompanied by the destruction of any boundary films. All tests show that the relationship load × speedn = constant holds at scuffing, with the exact value of the exponent n being dependent on the oil formulation. Additivised oils were shown to have enhanced scuffing resistance, which arises from their ability to postpone the uncontrollable rise in friction to higher sliding speeds. Finally, the critical maximum contact temperature scuffing criterion was shown to predict the onset of scuffing in our tests better than the frictional power intensity criterion.

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Paper

Lubrication Performance of Graphene-containing Oil on Steel and DLC-coated Surfaces

Several studies have successfully demonstrated the friction-reduction and anti-wear properties of graphene on the nano- and micro-scales, but our understanding …

Several studies have successfully demonstrated the friction-reduction and anti-wear properties of graphene on the nano- and micro-scales, but our understanding of the tribological behaviour of graphene on the macro-scale remains very limited. Accordingly, this study presents the macro-tribological behaviour of a graphene-containing oil in the lubrication of steel/steel contacts and DLC/DLC contacts. We show that graphene platelets, as additives to the base oil, can, especially in the boundary-lubrication regime, decrease the friction in the DLC/DLC contacts by up to 50%, as well as in the steel/steel contacts by up to 44%. The predominant lubrication mechanism of the graphene platelets was shown to be the formation of a protective tribofilm for both types of surfaces. The effects of the concentration of graphene (0–5 wt.%) and the lubrication regimes on the formation of the tribofilm are also investigated and explained with a schematic 2-D contact model.

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Paper

Responsive Polysaccharide-grafted Surfaces for Biotribological Applications

The elucidation of biolubrication mechanisms and the design of artificial biotribological contacts requires the development of model surfaces that can …

The elucidation of biolubrication mechanisms and the design of artificial biotribological contacts requires the development of model surfaces that can help to tease out the cues that govern friction in biological systems. Polysaccharides provide an interesting option as a biotribological mimic due to their similarity with the glycosylated molecules present at biointerfaces. Here, pectin was successfully covalently grafted at its reducing end to a polydimethylsiloxane (PDMS) surface via a reductive amination reaction. This method enabled the formation of a wear resistant pectin layer that provided enhanced boundary lubrication compared to adsorbed pectin. Pectins with different degrees of methylesterification and blockiness were exposed to salt solutions of varying ionic strength and displayed responsiveness to solvent conditions. Exposure of the grafted pectin layers to solutions of between 1 and 200 mM NaCl resulted in a decrease in boundary friction and an increase in the hydration and swelling of the pectin layer to varying degrees depending on the charge density of the pectin, showing the potential to tune the conformation and friction of the layer using the pectin architecture and environmental cues. The robust and responsive nature of these new pectin grafted surfaces makes them an effective mimic of biotribological interfaces and provides a powerful tool to study the intricate mechanisms involved in the biolubrication phenomenon.

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Paper

Driveline Fluids Comprising API Group II Base Oil

Described herein is a process, comprising: a) selecting an API Group II base stock with selected viscosity index and pour …

Described herein is a process, comprising: a) selecting an API Group II base stock with selected viscosity index and pour point; b) blending a base oil with the base stock, and c) adding to the base oil: i) a liquid ethylene propylene copolymer viscosity modifier that reduces a traction coefficient, and ii) an additive package, to make a driveline fluid that has a defined viscosity index and excellent shear stability. Also provided is a driveline fluid composition having the high viscosity index and excellent shear stability, comprising: a) a base oil comprising from 50 wt % to 100 wt % API Group II base stock; b) a liquid ethylene propylene copolymer viscosity modifier that reduces a traction coefficient; and c) an additive package. Further provided is a method for lubricating an axle or manual transmission by supplying the driveline fluid composition.

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