37 results found
Puhan D, Wong JSS, 2019, Properties of Polyetheretherketone (PEEK) transferred materials in a PEEK-steel contact, Tribology International, Vol: 135, Pages: 189-199, ISSN: 0301-679X
© 2019 Elsevier Ltd Polyetheretherketone (PEEK) is a high performance polymer that can be an alternative to metal for some moving components in unlubricated conditions. During rubbing, PEEK is transferred to the counterface. The formation and properties of PEEK transfer films on steel and sapphire are studied by in-situ observations of PEEK wear process, contact temperatures and triboemission, as well as FTIR and Raman spectroscopies ex-situ. Our results suggest that frictional heating alone may not be sufficient to generate PEEK degradation observed in the transfer materials. Triboplasma observed during rubbing, together with mechanical shear, may promote generations of radicals and degradation of PEEK, which subsequently influence the properties of PEEK transfer film and performance of polymer-metal tribopair.
Puhan D, Nevshupa R, Wong JSS, et al., 2019, Transient aspects of plasma luminescence induced by triboelectrification of polymers, TRIBOLOGY INTERNATIONAL, Vol: 130, Pages: 366-377, ISSN: 0301-679X
Jeffreys S, di Mare L, Liu X, et al., 2019, Elastohydrodynamic lubricant flow with nanoparticle tracking, RSC ADVANCES, Vol: 9, Pages: 1441-1450, ISSN: 2046-2069
Jean-Fulcrand A, Masen MA, Bremner T, et al., 2019, Effect of temperature on tribological performance of polyetheretherketone-polybenzimidazole blend, Tribology International, Vol: 129, Pages: 5-15, ISSN: 0301-679X
© 2018 The Authors Polyetheretherketone (PEEK) is one of the most commonly used High Performance Polymers (HPP) although its high temperature performance is poor. In this study, polybenzimidazole (PBI), a HPP with one of the highest glass transition temperatures currently available, is blended to PEEK to form a 50:50 blend (TU60). Tribological performance of the blend (TU60) was investigated by rubbing it against steel at temperatures up to 280 °C. Results obtained are compared to those from neat PEEK and neat PBI. All three polymers were thermally stable during the duration of tests. However chemical analyses on polymeric transfer layers on steel surfaces and polymer debris suggest polymer degradation. The degradation observed is shear-assisted, possibly promoted by shear heating. Indeed the estimated interfacial temperature based on Jaeger model was above the melting point of PEEK in some cases. TU60 outperforms PEEK in all test conditions and PBI at 280 °C. TU60 formed transfer layers on steel similar to that of PEEK. When contact temperature is closed to the melting point of PEEK, PEEK in the TU60 creates a low strength transfer layer which acts as an interfacial lubricant. This reduces friction which in turn reduces PBI degradation in TU60 at high temperature. This work provides a strategy for creating interfacial layers to improve polymer tribological performance while maintaining the integrity of the polymer.
Dench J, di Mare L, Morgan N, et al., 2018, Comparing the molecular and global rheology of a fluid under high pressures, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 20, Pages: 30267-30280, ISSN: 1463-9076
Campen S, Smith B, Wong J, 2018, Deposition of Asphaltene from Destabilized Dispersions in Heptane-Toluene, ENERGY & FUELS, Vol: 32, Pages: 9159-9171, ISSN: 0887-0624
Yang S, Wong J, Cai M, et al., 2018, Tribological Properties of In-situ Ionic Liquid Additives for Mixed and Hydrodynamic Lubrication, Mocaxue Xuebao/Tribology, Vol: 38, Pages: 342-348, ISSN: 1004-0595
© 2018, Science Press. All right reserved. This work focused on studying the tribological performance of IL additives in the mixed and hydradynamic lubrication regimes. Polyethylene glycol (PEG-400) was used as the base fluid, ILs were synthesized in situ by dissolving lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) in PEG. Mini Traction Machine was used to measure the friction coefficients with entrainment speeds at room temperature, 60 ℃ and 80 ℃ and at various slide-roll ratios for confirming the effect of IL additives on the tribological properties, and the rheological behavior of PEG was also investigated. This work would provide a new research method for further study of the lubrication mechanism of ionic liquids, which is of great significance for guiding the design of new ionic liquid lubricating materials.
Yang S, Wong JSS, Zhou F, 2018, Ionic Liquid Additives for Mixed and Elastohydrodynamic Lubrication, TRIBOLOGY TRANSACTIONS, Vol: 61, Pages: 816-826, ISSN: 1040-2004
Jean-Fulcrand A, Masen MA, Bremner T, et al., 2017, High temperature tribological properties of polybenzimidazole (PBI), POLYMER, Vol: 128, Pages: 159-168, ISSN: 0032-3861
Campen S, di Mare L, Smith B, et al., 2017, Determining the Kinetics of Asphaltene Adsorption from Toluene: A New Reaction-Diffusion Model, ENERGY & FUELS, Vol: 31, Pages: 9101-9116, ISSN: 0887-0624
Guo Y, di Mare L, Li RKY, et al., 2017, Structure of Amphiphilic Terpolymer Raspberry Vesicles, POLYMERS, Vol: 9, ISSN: 2073-4360
Dench J, Morgan N, Wong JSS, 2017, Quantitative Viscosity Mapping Using Fluorescence Lifetime Measurements, TRIBOLOGY LETTERS, Vol: 65, ISSN: 1023-8883
Laux KA, Jean-Fulcrand A, Sue HJ, et al., 2016, The influence of surface properties on sliding contact temperature and friction for polyetheretherketone (PEEK), POLYMER, Vol: 103, Pages: 397-404, ISSN: 0032-3861
Galmiche B, Ponjavic A, Wong JSS, 2016, Flow measurements of a polyphenyl ether oil in an elastohydrodynamic contact, JOURNAL OF PHYSICS-CONDENSED MATTER, Vol: 28, ISSN: 0953-8984
Tysoe W, Spencer N, 2016, Looking at lube in a new light, Publisher: Society of Tribologists and Lubrication Engineers
Parkes M, Myant C, Cann PM, et al., 2015, Synovial Fluid Lubrication: The Effect of Protein Interactions on Adsorbed and Lubricating Films, Biotribology, Vol: 1-2, Pages: 51-60
© 2015 Elsevier Ltd. All rights reserved. Synovial fluid lubrication is dependent on protective protein films that form between joint surfaces. Under static conditions surface film formation occurs through adsorption, while under dynamic conditions protein aggregation under shear and load becomes the dominant mechanism. This work examines how the protein content of six model synovial fluids affects film formation under static and rolling conditions and if the changes in properties can be correlated. With an increase in the statically adsorbed mass and the rate of adsorption the film thickness under rolling increased. These increases did not correlate with the total protein content of the fluid, but were dependent on the type of protein. An increase in pH reduced the adsorbed mass, rate of adsorption and film thickness, but was of secondary importance to the type of protein. The rolling film thickness was also correlated with the viscoelastic properties of the films formed under static conditions. In this case thinner rolling films corresponded to the more hydrated, viscoelastic adsorbed films. The strong correlations found between the properties of the adsorbed films and those formed under rolling indicate that the same protein-protein and protein-surface interactions may govern both mechanisms of film formation despite the differences in the film structures.
Wong JSP, Hu M, Shi D, et al., 2015, In-situ monitoring on dynamics of solute transport in polymer films, Polymer, Vol: 58, Pages: 67-75, ISSN: 0032-3861
© 2015 Elsevier Ltd. All rights reserved. A new and non-invasive technique based on confocal laser scanning microscopy (CLSM) that allows the visualization of penetrant diffusion in-situ has been developed and was applied to quantify local solute dynamics in polymeric films. The effectiveness of the proposed technique was demonstrated using a model penetrant, rhodamine-6G (Rh-6G), and a system of polyvinyl alcohol (PVA) films with different degree of cross-linking, and different content of montmorillonite (MMT) clay. The penetrant's transport across PVA films were monitored by measuring the time evolutions of through thickness fluorescence intensity profiles. These profiles were then converted to concentration profiles, which allow local diffusion coefficients of the model solute (i.e. Rh-6G) to be determined. The developed methodology was applied to both single layer and bilayers films and local diffusion heterogeneity was detected. Hence the technique developed can be applied to multi-layer films, and can be beneficial to film developments for packaging and filtration technology.
Liu X, Spikes H, Wong JSS, 2014, In situ pH responsive fluorescent probing of localized iron corrosion, CORROSION SCIENCE, Vol: 87, Pages: 118-126, ISSN: 0010-938X
Ponjavic A, di Mare L, Wong JSS, 2014, Effect of Pressure on the Flow Behavior of Polybutene, JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS, Vol: 52, Pages: 708-715, ISSN: 0887-6266
Parkes M, Myant C, Cann PM, et al., 2014, The effect of buffer solution choice on protein adsorption and lubrication, TRIBOLOGY INTERNATIONAL, Vol: 72, Pages: 108-117, ISSN: 0301-679X
Ponjavic A, Wong JSS, 2014, The effect of boundary slip on elastohydrodynamic lubrication, RSC Advances, Vol: 4, Pages: 20821-20829
The effect of interfacial slip on the friction and film thickness in an elastohydrodynamic (EHD) contact was directly evaluated. Experiments showed that the film thickness and friction decrease upon the application of an oleophobic coating given a sufficient pressure, as opposed to bare glass. Direct measurements of the slip velocity enabled the determination of a power law relationship between pressure and slip length. This implied the existence of spatial heterogeneity of the flow in the tribological contact due to the pressure distribution, which was confirmed by experiments. The power law relationship could also be used to predict the film thickness and friction based on conservation of mass and by using a rheological model for the lubricant. The film thickness and friction predictions were compared to experimental results. The former matched experimental observations. The latter however, underestimated the reduction in friction due to slip by a factor of two, suggesting the necessity of further work to elucidate the interplay between lubricant flow, rheology and friction. This journal is © the Partner Organisations 2014.
Wong JSS, Ponjavic A, 2013, Through-thickness velocity profile of sheared sub-micron thick polymer melt
The through-thickness velocity profile of a sub-micron thick polymer melt, under - elastohydrodynamic (EHL) conditions, has been recently obtained for the first time by the authors using photobleached imaging technique. In this work, the developed technique is applied to investigate the effect of shear rate on the evolution of velocity profile in polybutene (PB). The velocity profile of PB in an EHL contact severely deviates from the common linear assumption and exhibits shear localization. Depending on the average shear rate experienced by the polymer melt, interfacial slips and localized shear banding were observed.
Ponjavic A, Chennaoui M, Wong JSS, 2013, Through-Thickness Velocity Profile Measurements in an Elastohydrodynamic Contact, TRIBOLOGY LETTERS, Vol: 50, Pages: 261-277, ISSN: 1023-8883
Wong J, Ponjavic A, 2013, Flow-profile mapping in elastohydrodynamic lubrication region
Chennaoui M, Wong JSS, 2012, Corrosion of Aluminum in Oil-Based Nanoemulsion
While metal components immersed in oil-based lubricants suffer from corrosion, very few studies investigate such phenomenon. As water-in-oil nanoemulsions can be formed intentionally and accidently in oil lubricants, they were used as model systems in this corrosion study to investigate the effect of surface topography on corrosion of Aluminium. The initiation sites of corrosion were identified using fluorescence imaging with a resolution of 1 micrometer. It shows for the first time metal corrodes in oil-based nanoemulsion. It was found that corrosion preferentially occurred at regions with surface irregularity. The corrosion mechanisms are discussed using percolation theory and charge transfer in surfactant networks of semi-dilute micelle solutions.
Wong JSS, Hong L, Bae SC, et al., 2010, Fluorescence Recovery after Photobleaching Measurements of Polymers in a Surface Forces Apparatus, JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS, Vol: 48, Pages: 2582-2588, ISSN: 0887-6266
Bae SC, Wong JS, Kim M, et al., 2008, Using light to study boundary lubrication: spectroscopic study of confined fluids, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 366, Pages: 1443-1454, ISSN: 1364-503X
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