Knowledge

Zincdialkyldithiophosphates (ZDDPs) form protective antiwear tribofilms but the growth mechanism and their contribution to friction on non-ferrous alloys are not well understood. Using a recently developed in situ AFM technique, we monitor the growth of ZDDP based tribofilms, friction, and wear, over Al matrix and Si phase of ADC12, sliding against a nonferrous alumina probe. Sliding tests performed at elevated temperature (110 °C), simultaneously over Al and Si phase, reveal tribofilm growth on both Al and Si regions without noticeable wear. However, the tribofilm thickness, density, and coefficient of friction on the Si phase are higher than on the Al matrix. Significant wear and increase in the coefficient of friction was observed when sliding within the Al matrix region alone.

Gels and oil-in-water emulsions are widely used in food, pharmaceutical, and personal care applications. In the case of emulsions, they can be either stabilized by an amphiphilic molecule, forming classical emulsions, or by colloidal particles, forming a Pickering emulsion. These systems exhibit rich rheological and frictional characteristics and factors such as component concentration and/or interactions can affect their final properties. Thus, their characterization is fundamental to understanding their performance from product development to final use. This dissertation provides insights on how to manipulate properties of multicomponent gels and emulsions based on their components, guiding the formulation of products with desired rheological and lubrication properties. For that, we focus on two groups of systems: 1) classical oil-in-water emulsions containing microgel-forming polymers and phospholipids as well as several simplified versions of these systems, and 2) Pickering emulsions stabilized by nanodiamond particles.

The layered, lamellar phase of lyotropic liquid crystals display promising tribological properties possessing low shear strength between layers, solid like elasticity and high load carrying capacity perpendicular to their layered structure. Being able to visualise and study the behaviour of LLC in high pressure contacts at a range of speed, slide-roll ratio (SRR) and temperature conditions can facilitate the understanding of the mechanism of action behind their low friction properties.

A microscope setup has been developed that is capable of collecting real time, high contrast videos of film formation, bulk alignment, and flow of liquid crystal containing lubricants in an EHD ultra-thin film tribometer. This project aims to describe an economic set of methods to evaluate qualitatively the behaviour of liquid crystals in and around tribological contacts.

This is demonstrated with two types of liquid crystals; lamellar lyotropic Oleic Acid/Triethanolamine and smectic thermotropic 8CB.

This study sought to examine the effects of moderate intensity exercise on lubrication performance of saliva. We hypothesized that exercise would result in enhanced salivary lubricity by direct sympathetic stimulation of the salivary proteins…
In total, 11 healthy young pre-menopausal female participants (mean age: 24.4 ± 1.8 years, BMI: 22.1 ± 1.9 kg/m2) were included in a within-subjects repeated measures experimental design. Unstimulated whole saliva was collected at rest (S0), immediately after 45 min of moderate intensity cycling at ∼70 % maximum heart rate (mean: 133.4 ± 0.8 bpm) or time-match quiet rest (S1), and after a 60 min of recovery period (S2). Ex vivo salivary lubricity were measured using soft tribology. Total protein content, mucin (MUC5B) concentration, and α-amylase activity were determined.

The present invention relates to a lubricating composition containing (a) an oil of lubricating viscosity; and (b) a compound selected from the group consisting of: (i) an ester-containing heterocycle; (ii) an amide-containing heterocycle; and (iii) a pyrimidine, wherein the ester-containing heterocycle and the amide-containing heterocycle have a hydrocarbyl group containing 6 to 40 carbon atoms. The invention further provides for a method of supplying an internal combustion engine with the lubricating composition.

The present disclosure relates to lubricant additives such as dispersants and dispersant viscosity modifiers including acyl peptide grafted polymers and lubricating oil compositions comprising such additives. The disclosure also relates to the use of lubricant compositions comprising the additives herein for improving the soot or sludge handling characteristics of an engine lubricant composition and while minimizing the deterioration of engine's elastomer compatibility.

This report describes the results of a study in response to the FY2014 Vehicle Technologies program DE-FOA-0000991 solicitation for fuel economy improvement of cars and trucks (Area of interest 11: powertrain friction and wear reduction). It stated, “parasitic losses within vehicle engines and drivetrains are responsible for approximately two million barrels of oil consumption per day in the US. These losses are caused by friction between components, movement of components through fluids, and movement of fluids through components”. The objective of the study is to develop and demonstrate friction and wear reduction technologies for light duty vehicles that improve fuel efficiency of legacy vehicles by at least 2%, without adverse impacts on vehicle performance or durability.

A novel test is reported which allows the measurement of the friction of molten chocolate in a model tongue–palate rubbing contact. Friction was measured over a rubbing period of 150 s for a range of commercial samples with different cocoa content (85–5% w/w). Most of the friction curves had a characteristic pattern: initially a rapid increase occurs as the high-viscosity chocolate melt is sheared in the contact region followed by friction drop as the film breaks down. The exceptions were the very high (85%) and very low (~ 5%) cocoa content samples which gave fairly constant friction traces over the test time. Differences were observed in the initial maximum and final friction coefficients depending on chocolate composition. Generally, the initial maximum friction increased with increasing cocoa content. At the end of the test, the rubbed films on the lower slide were examined by optical microscopy and infrared micro-reflection spectroscopy. In the rubbed track, the chocolate structure was severely degraded and predominately composed of lipid droplets, which was confirmed by the IR spectra. The new test provides a method to distinguish between the friction behaviour of different chocolate formulations in a rubbing low-pressure contact. It also allows us to identify changes in the degraded chocolate film that can be linked to the friction profile. Further development of the test method is required to improve simulation of the tongue–palate contact including the effect of saliva and this will be the next stage of the research.

This work is about the use of two ionic liquids obtained from fatty acids (FAILs) as an additive at 0.5 and 2 wt% to a polyol ester (POE) base oil. Tribological tests under two different configurations (reciprocating and sliding/rolling “ball-on-disc”) were performed at different temperatures and loads. Worn surface was measured and analyzed after reciprocating experiments by confocal and scanning electron microscopies and by X-ray photoelectron spectroscopy (XPS). Main results showed that these FAILs at low concentration did not change the viscosity of the POE and hence the tribological behaviors of the mixtures and the POE under elastohydrodynamic lubrication (EHL) in rolling/sliding tests were similar, but using mixtures resulted in lower friction regarding the POE under mixed lubrication regime; the friction behavior in reciprocating tests was similar with the use of all mixtures and the POE at 25 °C for the two loads used, while the mixtures outperformed the antiwear behavior of the POE; the antifriction behavior of the mixtures under both loads at 100 °C was slightly worse than that of the POE and all mixtures had better antiwear performance than the POE.