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Author index ►Jingqing Li, Lei Wang, Donghong Yu, Jesper de Claville Christiansen, Shichun Jiang

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Wall Slip of Polyolefin Plastomers under Oscillatory Shear

Appl. Rheol.28:3 (2018) 33226 (14 pages) ►

The oscillatory shear rheological behaviors of a polyolefin plastomer (POP) at various temperatures were examined within its linear viscoelastic (LVE) regime. The apparent storage modulus, loss modulus, complex modulus, complex viscosity, and phase angle of POP at various temperatures are all found gap dependent, revealing that wall slip occurred under the applied oscillatory shear with the shear stress amplitude controlled constant. All Han plots and van Gurp-Palmen (vGP) plots of POP samples overlapped each other at various gaps at a certain temperature, suggesting that a time-gap-superposition (TGS) is valid with all the apparent angular frequency dependent storage modulus and loss modulus of POP at various gaps shifted to their master curves at a selected reference gap. This indicates that the wall slip can be understood as adding a dashpot in series to POP sample only with the apparent relaxation time multiplied by a shift factor. By TGS, a method to determine the wall slip length b and the actual oscillatory shear rheology of the fluids was consequently established. The results showed that the obtained b is dependent on temperature and wall slip made it possible to extend the experimental angular frequency range to lower frequencies. Further analysis revealed that wall slip did not influence the Arrhenius viscosity dependence of POP on temperature, while the viscous flow activation energy decreased.► Cite this publication as follows:

Li J, Wang L, Yu D, Christiansen JdC, Jiang S: Wall Slip of Polyolefin Plastomers under Oscillatory Shear, Appl. Rheol. 28 (2018) 33226.

Rheological properties of KCl/polymer type drilling fluids containing particulate loss prevention material (LPM) were characterized by an integrated inverse model-experimental approach. Rheological measurements for LPM-laden KCl/polymer type drilling fluids were carried out on a 6-speed rotational viscometer. The algorithm based on Tikhonov regularization was validated to be applicable and reliable to compute the shear rate in a rotational viscometer equipped with a widened annular gap. With the validated algorithm, the dial readings versus rotational speed data were transformed into shear stress vs. shear rate form. The results indicate that the rheological diagrams of the KCl/polymer type drilling fluids resemble those of a yield stress fluid and can be well represented by the Hershel-Bulkley model. The observed variation shows that rheological parameters were affected significantly by the addition of particulate LPM. The amount and the particle size of particulate LPM have a combined effect on the rheological properties of LPM-laden KCl/polymer type drilling fluids.► Cite this publication as follows:

Wang G, Du H: Rheological Properties of Kcl/Polymer Type Drilling Fluids Containing Particulate Loss Prevention Material, Appl. Rheol. 28 (2018) 35727.Heather M. Shewan

9th Australian-Korean Rheology Conference

Appl. Rheol.28:2 (2018) 55-56 ►

► Cite this publication as follows:

Shewan HM: 9th Australian-Korean Rheology Conference, Appl. Rheol. 28 (2018) 55.

Concentrated suspensions are very complex in nature and exhibit non-Newtonian flow properties although the suspending fluid might behave as a Newtonian fluid. Among the interesting properties, wall slip will be the main focus of this study. The formation of wall slip layer adjacent to the solid boundary may lead to inaccurate measurement of rheological properties. So, the measured viscosity can be lower than the actual viscosity and thus a basic understanding on wall slip is critical. Concentration, particle size, and temperature are the factors affecting the wall slip mechanism. Therefore, this research study tends to study the relationship between the parameters (concentration, particle size, and temperature) and wall slip. The result shows that the slip velocity increases with shear stress under the conditions where (i) concentration decreases, (ii) particle size increases, and (iii) temperature increases. Two regression models considering the three parameters are proposed and can be used respectively as an alternative to predict slip velocity and true shear rate.► Cite this publication as follows:

Chin RJ, Lai SH, Ibrahim S, WanJaafar WZ: Factors affect wall slip: particle size, concentration and temperature, Appl. Rheol. 28 (2018) 15775.

The hydration kinetics of four CEM I 52.5 N cements in the presence of two different superplasticizers was studied. The kinetics was characterized by monitoring the evolution of the dynamic modulus at constant frequency on a rotational rheometer. The method consists of predicting the time dependence of the elastic modulus by a kinetic equation of the self-acceleration type and fitting the equation to the experimental data. The model defines two main characteristic constants i.e. the characteristic time which defines the initial rate of hydration and the self-acceleration coefficient. It is shown that the model can accurately predict the initial hydration of cement paste with and without superplasticizer. The effect of the different cement properties and their interaction with superplasticizers can be observed in the kinetics of hydration.► Cite this publication as follows:

Masalova I, Mbasha W, Haldenwang R, Malkin AY: Rheokinetics of cement paste hydration during the dormant phase, Appl. Rheol. 28 (2018) 15452.

► Cite this publication as follows:

Haldenwang R: Southern African Society of Rheology Meeting (SASOR 2015), Appl. Rheol. 26 (2016) 62.

► Cite this publication as follows:

Cheneler D: Viscoelasticity of Polymers: Theory and Numerical Algorithms (Kwang Soo Cho), Appl. Rheol. 26 (2016) 10.

The addition of certain ingredients in conventional concrete is essential for improving rheological properties of this construction material. The effect of limestone and superplasticisers on the hydration kinetics of self-compacting concrete (SCC) was investigated on cement paste scale. These additives interact mostly with cement paste, since aggregates are considered to be inert materials. The understanding of the effect of these mineral and chemical additives on the hydration kinetics of cement paste is the key to design a self-compacting concrete with great properties. Four CEM I 52.5 N Portland Cements, limestone (LS) and one type of superplasticiser (SP) were used in this research. The hydration kinetics were evaluated by monitoring the storage modulus growth and different coefficients of a self-acceleration kinetics equation were used to depict the effect of different concentrations of SP with and without the optimum concentration of limestone (30 %) on the hydration kinetics of cement pastes. It was observed that the rate of hydration increased with the increase in SP concentration depending on the cement used. The addition of limestone in the superplasticised cement paste significantly retarded the hydration kinetics for all four cements. The rheological behavior of self-compacting cement paste was found to be very sensitive to the chemical and physical properties of the cements used.► Cite this publication as follows:

Elmakki R, Masalova I, Haldenwang R, Malkin A, Mbasha W: Effect of limestone on the cement paste hydration in the presence of polycarboxylate superplasticiser, Appl. Rheol. 26 (2016) 25122.

Different rheological methods for yield stress estimation of cement pastes during initial hydration were used and results were compared. These methods include measuring of the hysteresis loop, flow curves (recalculated to the same time of hydration) and large amplitude oscillating strain (LAOS). Experiments were performed with four Ordinary Portland Cements from one manufacturer, produced at different factories and one polycarboxylate acid based superplasticiser (SP). The yield stress values obtained by constructing flow curves is the only method which gives information about the evolution of the rheological properties, reflecting structure evolution of cements pastes. It was shown that the yield stress values established by the LAOS method and that calculated from the flow curves are similar while the values found from the downward part of the hysteresis loops are much lower. Differences in the yield stress values obtained by various methods are related to the different states of the material corresponding to the kinetics of hydration. The hysteresis loops provide information about thixotropic characteristics of the material including characteristic times of rebuilding and the rate of yield stress evolution of cements. The rheological properties are very sensitive to the chemical and physical differences of the cements and could be used for their characterization.► Cite this publication as follows:

Mbasha W, Masalova I, Haldenwang R, Malkin A: The yield stress of cement pastes as obtained by different rheological approaches, Appl. Rheol. 25 (2015) 53517.

We provide methodologies to characterise the rheology of ultra-low volumes of polymer solutions and biological fluids (10 - 100 μL) on a rotational rheometer. The technique utilises a parallel plate geometry with narrow gaps of 20 - 100 micrometers, which is an order of magnitude less than conventional methods. Despite the complications these gaps present, the use of appropriate protocols ensures reliable and accurate rheological characterisation of fluids, including shear-dependent viscosity, normal stresses and linear viscoelasticity. This rheological technique.s usefulness is further demonstrated by showing how the rheology of hyaluronan solutions evolve during fermentation. The intrinsic viscosity of the hyaluronan macromolecule is determined using less than 100 μL of solution extracted directly from the bioreactor, and this is used to provide a reasonable indicator of its molecular weight as it develops during the fermentation process. The ability to measure rheology of ultra-low volumes has applications in the characterisation of biological fluids and high value macromolecules, as well as generally in biotechnology and nanotechnology research fields.► Cite this publication as follows:

Boehm MW, Shewan HM, Steen JA, Stokes JR: Illustrating ultra-low-volume rheology on a conventional rheometer: Charting the development of hyaluronan during fermentation, Appl. Rheol. 25 (2015) 55609.

► Cite this publication as follows:

Haldenwang R: 5th Southern African Society of Rheology Conference (SASOR 2014), Appl. Rheol. 25 (2015) 53.

This paper is concerned with the numerical solution of polymer melt flows of both extrudate-swell and tube-tooling dieextrusion coatings, using a hybrid finite element/finite volume discretisationfe/fv. Extrudate-swell presents a single dynamic free-surface, whilst the complex polymer melt coating flow exhibit two separate free-surface draw-down sections to model, an inner and outer conduit surface of the melt. The interest lies in determining efficient windows for process control over variation in material properties, stressing levels generated and pressure drop. In this respect, major rheological influences are evaluated on the numerical predictions generated of the extensional viscosity and Trouton ratio, when comparing solution response for an exponential Phan-Thien Tanner (EPTT, network-based) model to that for a single extended Pom-Pom (SXPP, kinematic-based) model. The impact of shear-thinning is also considered. Attention is paid to the influence and variation in Weissenberg numberWe, solvent-fraction β (polymeric concentration), and second normal stress difference N_{2}(ξ parameter for both EPTT, and α anisotropy parameter for SXPP). The influence of model choice and parameters upon field response is described in situ through, pressure, shear and strain-rates and stress. The numerical scheme solves the momentum- continuity-surface equations by a semi-implicit time-stepping incremental Taylor-Galerkin/pressure-correction finite element method, whilst invoking a cell-vertex fluctuation distribution/median-dual-cell finite volume approximation for the first-order space-time hyperbolic-type stress evolution equation.► Cite this publication as follows:

Al-Muslimawi A, Tamaddon-Jahromi H, Webster MF: Numerical computation of extrusion and draw-extrusion cable-coating flows with polymer melts, Appl. Rheol. 24 (2014) 34188.

This study addresses the Taylor-Galerkin/pressure-correction solution of industrial high-speed reverse roller coating flow associated with thin-film paint-coatings of strip-steel. Novel aspects lie in the inclusion of the dynamic wetting line and flow analysis due to surface tension and inelastic rheology effects, via shear-thinning and lowering high shear viscosity levels. The main aim of the study is to predict the zonal flow influences by examining viscous flow structures around the meniscus, nip and wetting line regions, conveyed via streamline and shear rate patterns, surface distributional lift and localised nip-pressures. The majority of this study focuses on the secondary nip-vortex and its influences on the contact point and dynamic wetting line. This aspect of the flow provides the driving mechanism for the onset of instabilities, which governs the entire process and tends to determine the consistency of the film thickness at the outflow. Positive peak-pressures tend to increase with decrease in nip-gap size. At low nip-gap size, negative peak pressures are observed around the substrate-wetting line contact region. At higher speed-ratios, positive peak pressures are seen to increase with less recirculation apparent around the contact zone. Significantly and upon surface tension increase, the dynamic wetting line is sucked further inwards towards the nip-gap, stimulating a localised wetting line-foil third vortex structure, which causes an apparent reduction in film-leakage thickness.► Cite this publication as follows:

Echendu S, Tamaddon-Jahromi H, Webster M: Modelling Reverse Roll Coating flow with dynamic wetting lines and inelastic shear thinning fluids, Appl. Rheol. 23 (2013) 62388.

Ultrasonic Velocity Profiling (UVP) is a powerful technique for velocity profile measurements in research and engineering applications as it is the only available method that is cost-effective, relatively easy to implement and applicable to opaque fluid suspensions, which are frequently found in industry. UVP can also be combined with Pressure Drop (PD) measurements in order to obtain rheological parameters of non-Newtonian fluids by fitting theoretical rheological models to a single velocity profile measurement. The flow properties of complex fluids are almost exclusively obtained today using commercially available instruments, such as conventional rotational rheometers or tube (capillary) viscometers. Since these methods are time-consuming and unsuitable for real-time process monitoring, the UVP+PD methodology becomes a very attractive alternative for in-line flow behavior monitoring as well as quality control in industrial applications. However, the accuracy of the UVP+PD methodology is highly dependent on the shape and magnitude of the measured velocity profiles and there are still a few problems remaining with current instrumentation and methods in order to achieve the robustness and accuracy required in industrial applications. The main objective of this research work was to optimize an UVP+PD system by implementing new transducer technology and signal processing techniques for more accurate velocity profile measurements as well as rheological characterization of complex fluids under industrial/realistic conditions. The new methodology was evaluated in two different pipe diameters (22.5 and 52.8 mm) and tested with three different non-Newtonian fluids in order to obtain a wide range of rheological parameters. Results were also compared to conventional rotational rheometry and tube viscometry. It was found that rheological parameters obtained from accurate velocity data across the pipe radius, especially close to pipe walls where the velocity gradient is high, showed better agreement to conventional rheometry than when compared to results obtained using profiles measured with conventional UVP instrumentation and commercial software (Met- Flow SA Version 3.0). The UVP+PD method is now more robust and accurate. The main challenge remaining is to successfully implement a complete non-invasive system in industrial processes that is able to achieve real-time and accurate complex flow monitoring of non-Newtonian fluid suspensions.► Cite this publication as follows:

Kotze R, Wiklund J, Haldenwang R: Optimization of the UVP+PD rheometric method for flow behavior monitoring of industrial fluid suspensions, Appl. Rheol. 22 (2012) 42760.

A new conceptual non-contact method for liquid viscosity measurement in capillary tube using mobile phone as the data acquisition facility is proposed. The video and image for the capillary force driven flow of the test liquid was recorded by the phone camera. After the imaging reconstruction of the flow velocity in the horizontal capillary and the capillary head in the vertical direction, a digital image processing software was developed to calculate the liquid viscosity in MATLAB 2007b environment, recurring to the established theoretical correlation for flow mechanics. To demonstrate the feasibility and accuracy of the method, 10 groups of liquid were measured and the results were compared with the data obtained from a standard rotating viscometer. The relative error was found falling in the range of 0 ~ 20 %. This study establishes a pervasive low cost way for viscosity measurement of various solutions.► Cite this publication as follows:

Yang Y, Wang H, Liu J: Mobile Phone Enabled Pervasive Measurement of Liquid Viscosity, Appl. Rheol. 21 (2011) 63890.

The rheological behaviour of non-Newtonian, highly concentrated and non-transparent fluids used in industry have so far been analysed using commercially available instruments, such as conventional rotational rheometers and tube viscometers. When dealing with the prediction of non-Newtonian flows in pipes, pipe fittings and open channels, most of the models used are empirical in nature. The fact that the fluids or slurries that are used normally are opaque, effectively narrows down the variety of applicable in-line rheometers even further, as these instruments are normally based on laser or visible light techniques, such as Laser Doppler Anemometry. In this research, an Ultrasonic Velocity Profiling technique (UVP), in combination with a pressure difference (PD) measurement, was tested to provide in-line measurement of rheological parameters. The main objective of this research was to evaluate the capabilities of the UVP-PD technique for rheological characterisation of different concentrations of non-transparent non-Newtonian slurries. Kaolin, bentonite, Carboxymethyl Cellulose (CMC) and water solutions were used as model non-Newtonian mining slurries. Results determined by the UVP-PD method were compared with results obtained by off-line rheometry and in-line tube viscometry. The agreement between the UVP-PD method, tube viscometry and conventional rheometry was found to be within 15 % for all of the highly concentrated mineral suspensions investigated over a given range of shear rates.This method, if used in combination with a pressure difference technique (PD), has been found to have a significant potential in the development process of new in-line rheometers for process control within the mining industry.► Cite this publication as follows:

Kotze R, Haldenwang R, Slatter P: Rheological characterisation of highly concentrated mineral suspensions using an Ultrasonic Velocity Profiling with combined Pressure Difference method, Appl. Rheol. 18 (2008) 62114.

Oxide ceramic masses are used for catalysts and catalyst carriers. For a reliable processing hydrocolloids (e. g. cellulose) are usually added in order to decelerate demixing phenomena. Oxide ceramic masses react to simple shearing with hardening (peptisation: increase of the shear stress with the shear deformation) [1]. The present study analyses, if an ultrasonic treatment has also an impact on the structure, the shelf-life (in the green state), the correlated flow behaviour of oxide ceramic masses and presumably (not tested) the mechanical properties in the hardened, sintered state. The idea of using ultrasonic treatment is to change the microstructure (see below) and, therefore, to minimise or even give up the standard addition of stabilizers to minimize demixing in aqueous oxide ceramic suspensions. Besides the additional costs of an extra process unit, stabilisers cause often deteriorated mechanical properties (porosity, crack behaviour) of the ceramics in the hardened state after the sintering. Therefore, pump experiments (apparent viscosity), oscillatory (G´ and G´´) and steady shear experiments (h), particle-size analysis (particle-size distribution, agglomerate strength), light microscopy, decanting experiments and pH-determinations have been performed. The obtained results show, that the hardening of the apparent viscosity (derived from the flow) during pump experiments with simultaneous ultrasonic treatment in a flow cell is combined with an increase of the fine fraction, the formation of enlarged, but smoother agglomerates, the change of the pH-value and the evolution of a three-dimensional network (gelling). All these processes increase both the amount of bound/immobilised (chemically or physically bound by or onto the solidsurfaces) and of retained water (interior of agglomerates and/or the pores of the floWand ultrasonic-induced network). This means that the volume fraction of the rheologically "free" water decreases and simultaneously the effective solid volume fraction increases. With respect to the concept of the rheologically effective solid fraction this is combined with an increasing viscosity. At the same time the tendency of demixing decreases significantly. Thus, by an appropriate combination of shear flow and ultrasonic treatment, the aqueous oxide ceramic suspensions are stabilised and a reliable processing of the initially problematic solid/fluid mixtures can be realised without stabilisers (eluding their negative consequences with respect to the quality of the sintered state).► Cite this publication as follows:

Gotz J, Rewese L, Walch M, Geissler A: Influence of an Ultrasonic Treatment on the Structure and Flow Behaviour of Oxide Ceramic Masses, Appl. Rheol. 15 (2005) 204.Thomas Schweizer

Polymer Viscoelasticity (Yn-Hwang Lin)

Appl. Rheol.15:4 (2005) 202-203 ►

► Cite this publication as follows:

Schweizer T: Polymer Viscoelasticity (Yn-Hwang Lin), Appl. Rheol. 15 (2005) 202.

► Cite this publication as follows:

Rheological Societies, Petrie CJS, Mielke W, Coussot P, Kissi NE, Fischer P, Mavrantzas VG, Grizzuti N, Jarvela P, Wanger MH: Society's Site Mar 2005 - Aug 2005 , Appl. Rheol. 15 (2005) 59.

The structural development undergoing during the cure of a latex polymer is accompanied by viscoelastic changes, so that this process can be investigated using a rheological approach. We present in this paper the results of a study carried out on one of the most widely used chemical binders in the field of textile nonwovens: acrylic latexes. The rheological measurements have been performed on the latex films in a rectangular torsion and dynamic oscillatory mode, and the observations are discussed in terms of crosslinking. The results obtained show that the zone where crosslinking occurs in the polymer can be clearly identified by the investigation method used.► Cite this publication as follows:

Lewandowski M, Rochery M, Bellayer S, Fourdrin S: Rheology of the Curing Process of Acrylic Latexes Used as Chemical Binders, Appl. Rheol. 12 (2002) 174.

The viscoelasticity of reduced-fat Cheddar and Mozzarella cheeses was characterized in small (parallel disk rheometer, go = 0.01) and large (sliding plate rheometer, 0.2< go <7) amplitude oscillatory shear at 40 and 60 C. We deduced the linear relaxation spectrum from the small strain measurements. At large strain amplitudes, we found sinusoidal stress responses whose amplitudes are well below those predicted from the linear relaxation spectrum, and yet remarkably linear with strain amplitude. We call this the large strain linear regime. We discovered that the Lodge rubberlike liquid can quantitatively explain the large strain linear regime if we scale down the relaxation moduli in the linear spectrum by a constant. This large strain linear regime persists to much higher strain amplitudes for Cheddar (go <= 4) than for Mozzarella (go <= 1). This is perhaps due to oriented structure of the protein matrix in the Mozzarella cheese.► Cite this publication as follows:

Wand YC, Gunasekaran S, Giacomin AJ: The Lodge Rubberlike Liquid Behavior for Cheese in Large Amplitude Oscillatory Shear, Appl. Rheol. 11 (2001) 312.

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Hugelshofer D, Windhab EJ, Wang J: Rheological and Structural Changes During The Mixing of Suspensions and Emulsions, Appl. Rheol. 10 (2000) 22.

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