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The purpose of this paper is to measure the apparent and complex viscosities of the zinc‐rich coatings derived from sodium silicate solution modified with aluminium chloride (AlCl₃), and then theoretically analyse the relation between viscosity behaviour and physiochemical mechanisms.

According to the different dosages of AlCl₃, five coatings were prepared. The apparent viscosities as functions of shear rate, time and temperature, complex viscosity with variations of temperature and heating rate of these coatings were measured using an AR500 rheometer.

Results showed that the zinc‐rich coatings possessed the typical shear thinning behaviour and the apparent viscosity increased with time until solidification. Complex results showed that the complex viscosity depended strongly on heating rate. Both apparent and complex viscosities initially decreased to minimum and then started to increase, while temperature was ramped from 0 to 70°C.

It is believed that there is no published literature about the apparent and complex viscosities of the zinc‐rich coatings from sodium silicate solution modified with AlCl₃. This paper presents the first attempt to obtain the rheological data of these zinc‐rich coatings.

The purpose of this paper is to present a novel method to investigate the microscopic mechanism of the oil film under the pure squeeze elastohydrodynamic lubrication (EHL) motion. An optical EHL squeeze tester is used to explore the effects of squeeze velocity, load, temperature, and lubricant viscosity on the dimple film thickness that occurs when a ball approaches a flat plate covered by a thin layer of oil.

The grayscale interferometric technique was used to study the thickness of the lubricating film in an EHL point contact. The light source was a He‐Ne laser. Through the transparent optical glass and by means of optical interference, the interference fringe patterns of the contact region were observed by a charge‐coupled device camera recording. The two elastic bodies were a sapphire disk and a steel ball. The contact was lubricated with paraffin‐based oil.

Results show that increasing the squeeze speed, load, viscosity, and decreasing the temperature, make the dimple deeper, and the contact area increases. Moreover, as the squeeze speed and load decrease and temperature increases, the fluidity of the lubricant increases and less time is needed to extrude. The maximum thickness of the dimple increases with increasing squeeze speed, load, lubricant viscosity, and decreasing temperature. The greatest effect of pure squeeze EHL motion is found with squeeze velocity, followed by load, and then temperature for the same lubricant viscosity.

The paper usefully describes the use of a self‐development optical EHL squeeze tester to explore the effects of temperature, squeeze velocity, load, and lubricant viscosity on the dimple film thickness which occurs between two components approaching each other.

The purpose of this paper is to reveal the characteristics of hydrodynamic load capacity and torque transferred by oil film with variable viscosity, and the effect of groove number, width and depth on the hydrodynamic load capacity and torque transfer.

The radial temperature of friction pair and viscosity of YLA‐N32 hydraulic oil were measured through experiments, and a viscosity‐diameter expression was deduced using polynomial fitting method. Analytical expressions for hydrodynamic load capacity and torque of the oil film were deduced based on hydrodynamic lubrication theory.

The investigation shows the hydrodynamic load capacity and transferred torque with variable viscosity are much less than that with constant viscosity. Load capacity increases with the increase of groove depth which is the most significant influence factor, while it has the least influence on torque. Groove width has great influence on load capacity and torque. The load capacity increases with the increase of groove width; contrarily, torque decreases with the increase of groove width. Groove number has little influence on load capacity, while it has great influence on torque. The torque decreases with the increase of groove number.

In this paper, analytical solutions for hydrodynamic load capacity and torque of the oil film with variable viscosity are deduced. The paper reveals the relationship between hydrodynamic load capacity, torque transfer and groove number, width and depth.

The purpose of this paper was to examine the rheological characterisation of thickened water under different temperature and pH conditions and thickened milk with different fat contents.

Beverages thickened with powdered thickeners are used in the medical management of individuals who suffer swallowing difficulties (dysphagia). Each individual requires a specific level of thickness to best meet the needs of their dysphagia. Although the level of thickness is defined, obtaining the correct consistency of thickened fluids is difficult. This is due to fluctuations associated with temperature and type of fluids to be thickened. Rheological characterisation of commercially available xanthan gum-based thickener was performed under different conditions of temperature, pH and fat contents.

The viscosity and the yield stress of thickened water was found to be unaffected by pH. Similarly, temperature did not affect the viscosity at a high thickener concentration, although it did at lower concentration levels. Conversely, viscosity and yield stress increased as fat levels increased in thickened milk. Furthermore, thickened water took less than 2 minutes to reach equilibrium viscosity, while thickened milk required approximately 15 minutes to reach equilibrium viscosity.

These findings have implications for the standing time required for different beverages before they are thickened to a consistency that has been deemed safe for the patient’s physiological needs. Additionally, it highlights that different liquid base substances required different amounts of thickener to achieve the same level of thickness.

Findings from this study confirms and explores the variability of thickened fluids under different conditions of temperature, pH and fat content for the medical management of dysphagia.

Previous work has suggested that the adhesion between oil and metallic surfaces of an engine could be an important factor in determining crankcase cleanliness. It can be shown that it is only necessary to measure the spreading pressure of an oil on metal in order to get a direct measure of the work of adhesion, Surface tensions of lubrictaing oils vary very little and it can be assumed that the critical film pressure (C.F.P.) obtained with a given apparatus is an acceptable measure of the work of adhesion as well as of the spreading pressure. Oils of similar properties may vary tenfold in their C.F.P's. The addition of additives influences the spreading pressure, the largest increments in C.F.P. being given by dispersant and detergent additives.

The purpose of this work is to investigate the static performance characteristics of thermohydrodynamic journal bearing operating under nanolubricants (lubricants containing per cent weight concentration of nanoparticles).

Addition of nanoparticles in the lubricant increases lubricant viscosity. To study the effect of this variation on journal bearing, analytical models are developed for the relationship between viscosity, 0-0.5 per cent weight concentration of nanoparticles and temperature range of 300-900°C. To obtain pressure and temperature distribution, modified Reynolds and energy equations are solved by using the finite element method. The viscosity field (varies with temperature and per cent weight concentration of nanoparticles) is updated in these two equations by using the developed analytical model. The steady-state performance characteristics are computed for various values of eccentricity ratios for non-thermoviscous (viscosity of lubricant varies with per cent weight concentration of nanoparticles) and thermoviscous (viscosity of lubricant varies with per cent weight concentration of nanoparticles and temperature) cases. The lubricant and the nanoparticles used for the present work are SAE15W40, copper oxide (CuO), cerium oxide (CeO₂) and aluminum oxide (Al₂O₃).

The pressure and temperature distribution across the lubricant film in the clearance space of journal bearing and static performance characteristics are calculated.

The computed results show that addition of nanoparticles in the lubricant influences the performance characteristics considerable in thermoviscous case than non-thermoviscous case.

Refers to how the mechanical properties of polymer‐based composite objects produced via rapid layered fabrication methods can be improved significantly using short discontinuous fibres as reinforcements. Notes in this context, that the viscosity of the uncured fibre‐photopolymer composite liquids affects the raw‐material handling, the layer formation and the draining operations. Assesses the effects of aspect ratio, surface coating and volume fraction of short glass fibres on the viscosity of the fibre‐photopolymer composite liquids. Based on extensive experimentation and analysis, concludes that the shear viscosity of the composite liquids increases with increasing fibre‐volume fraction, showing that this effect is more pronounced at low shear rates than at high shear rates. Reveals, similarly, that the aspect ratio of the dispersed fibres has a stronger effect on the increase of viscosity at low shear rates and that the surface coating of the dispersed fibres also affects the viscosity of the composite liquids.

In part I of this study a new dry coating analysis was developed relating pigment cluster voids and pigment particle distribution to the pigment cluster dispersion coefficient, C_q, and the critical pigment volume concentration (CPVC). Part II of this study has addressed a wet coating analysis to relate pigment particle size distribution and viscosity in a coating formulation to the pigment cluster dispersion coefficient.

This study introduced the relationships for the wet coating by building on the dry coating evaluations introduced in part I of this study. Part II of this study showed that the CPVC for a solvent based coating can be significantly influenced by a change in the viscosity measured interaction coefficient, σ, as influenced by a change in an additive such as the surfactant concentration in the matrix or polymer phase of the coating. The CPVC was also shown to be strongly influenced by a separate analysis of the pigment particle size distribution to modify the coating viscosity.

It was pointed out recently that an increase in flow additive increased the CPVC but decreased viscosity. Consequently, it was shown theoretically in this study that viscosities compared at the same relative viscosity, η/η₀, and at the same filler composition, f_i, using the generalized viscosity model would require decrease in the interaction coefficient, σ, to increase the global volume fraction of filler or pigment, Φ_F. This implied that a measurement of the interaction coefficient, σ, should be a direct measure of the ability of the CPVC to be modified. A minimum viscosity from the generalised viscosity model also resulted at the maximum packing fraction, which in turn was found to increase the CPVC of the coating. Consequently, part II of this study has yielded a useful relationship between the cluster dispersion coefficient, C_q, and the interaction coefficient, σ, from the generalised viscosity model.

While the experimental measurement of the parameters to isolate the clustering concepts introduced in this study may be difficult, it is expected that better quantitative measurement of clustering concepts will eventually prove to be very beneficial to providing improved suspension applications including coatings. The close relationship introduced in this study between clustering concepts and viscosity should provide an improved ability to measure the parameters to isolate clustering in coatings and other suspension applications.

The theoretical relationship developed in this study between the pigment cluster dispersion coefficient, C_q, and CPVC and the theoretical and experimental relationship between CPVC and the viscosity interaction coefficient, σ, inferred a direct relationship between C_q and the viscosity interaction coefficient, σ. Consequently, it was shown that the theoretical pigment cluster model developed in this study could be directly related to the experimental matrix additive composition controlling viscosity in a coating formulation. The practical implication is that the measurement tools introduced in this study should significantly influence future suspension formulations to provide better measurement and control of clustering and viscosity in coatings and other suspension applications.

Part II of this study has shown how a useful relationship can be generated between the interaction coefficient, σ, from the generalised viscosity model and the pigment cluster dispersion coefficient, C_q, developed in part I of this study. In addition, this study also showed that effective control of the CPVC of a coating can be modified by judicious control of the interaction coefficient using pigment particle size distribution and/or viscosity control additives in a wet coating analysis.

This study aims to introduce a new theoretical approach to blend spherical and non‐spherical particles in a coating to improve its viscosity characteristics.

Theoretical analysis has been used to modify an existing model developed by this author to apply to a broad range of particle configurations.

Non‐spherical particles like fibres or discs in a suspension or coating have been found to have three different viscosity response regions. Consequently, the viscosity of suspensions or coatings with these types of particles appears to have two apparent maximums as a function of concentration. Improved viscosity control of coatings have been found to be directly achievable by blending particles with different shapes based on the concentration relative to this first maximum. This optimisation process has been found to be better understood using a new variable which has been described as the “sphericity”, s. The “sphericity”, s, as described in this study has been defined as the relative ratio of the surface to volume fraction for a non‐spherical particle to that of a sphere of equivalent volume.

Experimental data involving monodisperse particles of different configurations is often extremely difficult to obtain. However, the theoretical general concepts can still be applicable.

The model presented in this paper provides practical guidelines to blending pigments with different particle shapes to control the viscosity of coatings and suspensions.

The model presented in this paper provides the first apparent guidelines to control the blending of pigments in coatings and composites with different particle shapes using the “sphericity” of the pigment particle.

The purpose of this study is to investigate thermal conductivity and dynamic viscosity of graphene nanoplatelet-based (GNP) nanolubricant.

Nanolubricants in concentrations of 0.025, 0.05, 0.1 and 0.5 Wt% were prepared by means of two-step method. The stability of nanolubricants was monitored by visual inspection and dynamic light scattering tests. Thermal conductivity and dynamic viscosity of nanolubricants in various temperatures between 25°C–70°C were measured with KD2-Pro analyser device and a rotational viscometer MRC VIS-8, respectively. A comparison between experimentally achieved results and those obtained from existing models was performed. New correlations were proposed and artificial neural network (ANN) model was used for predicting thermal conductivity and dynamic viscosity.

The designed nanolubricant showed good stability after at least 21 days. Thermal conductivity and dynamic viscosity increased with particles concentration. In addition, as the temperature increased, thermal conductivity increased but dynamic viscosity decreased. Compared to the base oil, maximum enhancements were achieved at 70°C with the concentration of 0.5 Wt.% for dynamic viscosity and at 55°C with the same concentration for thermal conductivity. Besides, ANN results showed better performance than proposed correlations.

This study outcomes will contribute to enhance thermophysical properties of conventional lubricating oils.

To the best of our knowledge, there is no paper related to experimental study, new correlations and modelling with ANN of thermal conductivity and dynamic viscosity of GNPs/SAE 5W40 nanolubricant in the available literature.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2020-0088/