Knowledge

In order to tackle the new challenges towards the reduction of carbon emissions in transport industry, the present work aims to understand the effect of the friction modifier (FM) molybdenum dithiocarbamate (MoDTC) on the performance of an automobile engine. A petrol engine has undergone motored test trials, measuring the friction torque reduction when the FM additive is blended into a fully formulated SAE 5W30 oil. Moreover, the engine has been dismantled after the test, investigating the tribochemistry of MoDTC at different key engine components undergoing boundary lubrication, using Raman microscopy. This work demonstrates that materials and contact pressure play a crucial role in MoDTC tribochemistry to form a low friction tribofilm, contributing to global engine friction reduction.

Wine creates a group of oral-tactile stimulations not related to taste or aroma, such as astringency or fullness; better known as mouthfeel. During wine consumption, mouthfeel is affected by ethanol content, phenolic compounds and their interactions with the oral components. Mouthfeel arises through changes in the salivary film when wine is consumed. In order to understand the role of each wine component, eight different model wines with/without ethanol (8%), glycerol (10 g/L) and commercial tannins (1 g/L) were described using a trained panel. Descriptive analysis techniques were used to train the panel and measure the intensity of the mouthfeel attributes. Alongside, the suitability of different instrumental techniques (rheology, particle size, tribology and microstructure, using Transmission Electron Microscopy (TEM)) to measure wine mouthfeel sensation was investigated. Panelists discriminated samples based on their tactile-related components (ethanol, glycerol and tannins) at the levels found naturally in wine. Higher scores were found for all sensory attributes in the samples containing ethanol. Sensory astringency was associated mainly with the addition of tannins to the wine model and glycerol did not seem to play a discriminating role at the levels found in red wines. Visual viscosity was correlated with instrumental viscosity (R =0.815, p=0.014). Hydrodynamic diameter of saliva showed an increase in presence of tannins (almost 2.5–3-folds). However, presence of ethanol or glycerol decreased hydrodynamic diameter. These results were related with the sensory astringency and earthiness as well as with the formation of nano-complexes as observed by TEM. Rheologically, the most viscous samples were those containing glycerol or tannins. Tribology results showed that at a boundary lubrication regime, differences in traction coefficient lubrication were due by the presence of glycerol. However, no differences in traction coefficients were observed in presence/absence of tannins. It is therefore necessary to use an integrative approach that combines complementary instrumental techniques for mouthfeel perception characterization.

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.

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.

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.

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.

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.

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.

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.