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.

Spotlight Paper

Study of Permanent Shear Thinning of VM Polymer Solutions

Using the unique features of the USV, researchers were able to clearly quantify the permanent shear thinning of high molecular …

Using the unique features of the USV, researchers were able to clearly quantify the permanent shear thinning of high molecular weight polymer solutions.  Further investigations using a standard GPC process (gel permeation chromatography) revealed that the polymer breakdown process is very different at low and high polymer concentrations. The paper finally put to rest the argument whether it is the applied shear rate or shear stress which determines shear thinning (spoiler alert: it’s the shear stress).

Open Access Link:
https://link.springer.com/content/pdf/10.1007/s11249-017-0888-7.pdf

PCS review

Spotlight Paper

Cooperativity Between Zirconium Dioxide Nanoparticles and Extreme Pressure Additives in Forming Protective Triboflms: Toward Enabling Low Viscosity Lubricants

Cutting edge MTM nanoparticle research carried out at the highly respected Carpick laboratory. The paper showed how relatively large nanoparticle …

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Cutting edge MTM nanoparticle research carried out at the highly respected Carpick laboratory. The paper showed how relatively large nanoparticle of Zirconium dioxide (ZrO2), combined with organic capping ligands can form robust tribofilms under a wide range of contact conditions. Impressively significant   wear reduction was also reported when the nanoparticles were blended in commercial formulations.

Open Access Link:
https://link.springer.com/article/10.1007%2Fs11249-020-01346-1

PCS review

Paper

Tribology – Novel Oral Processing Tool for Sensory Evaluation of Food

Food oral processing is a study of mastication that involves food-saliva interaction. Instrumental approaches have improved sensorial attributes like texture …

Food oral processing is a study of mastication that involves food-saliva interaction. Instrumental approaches have improved sensorial attributes like texture by stimulating the oral environment for the past years. However, a thorough estimation of oral food processing is still an open research topic with persisting challenges. This review summarizes the role of tribology as a novel oral processing tool for the sensory evaluation of foods. The paper further covered state of the art on instrumentation, working principles, the efficiency of the tribometer, and its application in dairy and non-dairy foods. Moreover, sincere attempts have been made to classify the research gap and challenges in oral food processing using tribometer.

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Paper

Substituent Control of Tribofilm Growth under Mechanochemical Conditions

Lubricant additives that reduce wear by forming protective tribofilms on sliding surfaces are crucial to maintaining the efficient and reliable …

Lubricant additives that reduce wear by forming protective tribofilms on sliding surfaces are crucial to maintaining the efficient and reliable operation of many engineering systems. The most important of these additives, zinc dialkyldithiophosphate (ZDDP), has been in use for almost a century; however, several aspects of the physicochemical mechanisms through which it reduces wear remain unclear. While changes to the molecular structure of ZDDP are known to affect tribofilm formation and antiwear performance, the underlying mechanisms are not well understood. Here, we show using macroscale tribometer experiments under well-defined temperature and stress conditions, how the ZDDP tribofilm formation rate on steel from nonpolar base oils can be controlled by tailoring the additive’s alkyl substituents. Our results suggest that the chain-length, branching and presence of cycloaliphatic groups can affect the packing density, steric hindrance, and stress transmission, leading to large differences in the temperature- and stress-dependencies of the tribofilm formation rate.

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Paper

In-Situ Observation of the Effect of the Tribofilm Growth on Scuffing in Rolling-Sliding Contact

General reductions in lubricant viscosities in many machine components mean that the role of lubricant additives in forming tribofilms has …

General reductions in lubricant viscosities in many machine components mean that the role of lubricant additives in forming tribofilms has become increasingly important to provide adequate surface protection against scuffing. However, the relationship between scuffing and the formation and removal of tribofilms has not been systematically demonstrated. In this study a step-sliding speed scuffing test based on contra-rotation using MTM-SLIM and ETM-SLIM has been employed to observe concurrently tribofilm thickness and the onset of scuffing. The initial sliding speed used was found to significantly affect scuffing performance since it determines the extent to which a tribofilm can form before critical sliding speed conditions are reached. Generally, additives that formed thicker tribofilms, especially ZDDPs and triphenyl phosphate, gave effective protection against scuffing, though their protective tribofilms were progressively removed at higher sliding speeds, eventually resulting in scuffing.

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Paper

The Use of the MTM Rig for Wear Testing

The wear rate of any lubricated contact is dependent on many factors, including, surface roughness, lubricant composition, environment, operating conditions, …

The wear rate of any lubricated contact is dependent on many factors, including, surface roughness, lubricant composition, environment, operating conditions, temperatures, etc. There are also many different wear mechanisms, often operating in parallel. Since wear in itself is not an intrinsic property of a system, different wear tests can give very different results.
Despite their popularity and widespread use, all wear bench test methods all have some shortcomings when used to investigate complex lubricant additive combinations. However sophisticated the test method, they are inevitably unable to directly mimic real lubricated contacts conditions of machine elements. Interpretation of different bench test results can be difficult and misleading conclusions can sometimes be drawn.
A new pure sliding wear test is described which can produce measurable wear within a reasonable period of time. The repeatability and merits of the test method is discussed.

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Paper

Rheological Properties of Lubricants and Their Correlation With Fuel Economy Performance

One of the least expensive pathways to achieving improvements in vehicle fuel economy is through changes to engine lubricant viscosity …

One of the least expensive pathways to achieving improvements in vehicle fuel economy is through changes to engine lubricant viscosity and composition. Driven by ever more stringent emissions regulations, OEMs are therefore requiring engine oils to continue protecting engines at lower viscosities and reduced friction.
Different engine operating conditions represent a range of lubrication conditions, and to better understand the full impact of engine lubrication process, one must understand how oils perform in these conditions. In general, additives in lubricants help to provide the right balance of fuel economy while maintaining durability protection. The focus of the present study is on the hydrodynamic lubrication regime, and the rheological properties of oils were investigated and correlated to their fuel economy performance in different engines, Mercedes Benz OM 501 LA and Detroit Diesel DD13, and driving cycles, WHTC (World-Harmonized Transient Cycle) and modal.

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Paper

Biomimetic Water-Based Lubricant Development: Nanoencapsulation with Liposomes

The replacement of traditional mineral oil lubricants with water-based bio-compatible fluids has long been a desirable, if unrealised, ambition in …

The replacement of traditional mineral oil lubricants with water-based bio-compatible fluids has long been a desirable, if unrealised, ambition in many applications. This is particularly relevant in marine-based energy generation systems, where oil-based lubricants create a high risk of environmental pollution. The use of bio-lubricants has been explored in several previous studies, however no significant technological advances have been achieved. Most of the work has focused on traditional lubrication mechanisms, with bio-molecules being employed to form an adsorbed surface film which reduces friction. However, due to their inherent biological, thermal and/or oxidative instability, bio-molecules are unsuited to long-term industrial applications. The alternative approach is to use stable, bio-friendly molecules, designed to exploit the lubrication mechanisms found in nature. These mechanisms have evolved to be far more diverse than those found in traditional “mineral oil” tribology and are, as yet, poorly understood.

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