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Salaheldin Elkatatny, Muhammad Shahzad Kamal, Fahd Alakbari, Mohamed Mahmoud
Optimizing the Rheological Properties of Water-based Drilling Fluid Using Clays and Nanoparticles for Drilling Horizontal and Multi-Lateral Wells

Appl. Rheol. 28:4 (2018) 43606 (8 pages)

Drilling fluid constitutes an important part of the drilling operations. Gel strength property of drilling fluids plays a key role in drilling multilateral and long horizontal reservoir sections. Losing the gel strength will accumulate drilled cuttings and as a result, sticking of the drill string. Solving this issue takes a long time and increase the total cost of the drilling operations. The objectives of this paper are to (1) determine the rheological properties of calcium carbonate water-based drilling fluid over a wide range of temperature, (2) assess the effect of adding nanoclay, Bentonite, and nanosilica on the gel strength problem associated with the current field formulation of calcium carbonate water-based drilling fluids, and (3) optimize the concentration of Bentonite, nanosilica, and nanoclay in the drilling fluid. The concentration of Bentonite, nanoclay, and nanosilica was varied from 1 wt% to 10 wt%. Rheological properties results confirmed that the gel strength of the calcium carbonate water-based drilling fluid reached zero lb/100ft2 by increasing the temperature to 200 °F (93.33 °C). This issue was solved by adding different concentrations of Bentonite, nanoclay, and nanosilica. At low Bentonite concentrations (3.33 wt%), the gel strength still reduced with time. At high Bentonite concentrations (10 wt%), the gel strength increased with time. The optimum concentration of Bentonite was 6.66 wt%, which yielded a flat rheology profile of the gel strength. These results confirmed that the rheological properties of the water-based drilling fluid were optimized by using Bentonite. Similarly, 7.5 wt% nanosilica showed the optimum performance. Nanoclay was not effective in improving the rheological properties of the calcium carbonate drilling fluid.

Cite this publication as follows:
Elkatatny S, Kamal MS, Alakbari F, Mahmoud M: Optimizing the Rheological Properties of Water-based Drilling Fluid Using Clays and Nanoparticles for Drilling Horizontal and Multi-Lateral Wells, Appl. Rheol. 28 (2018) 43606.

Theau Conte, Rachid Bennacer, Mohend Chaouche
Thixotropic behavior of cement paste under large amplitude oscillatory shear

Appl. Rheol. 27:5 (2017) 53914 (9 pages)

Cement-based materials exhibit highly complex rheological properties, in particular yielding and thixotropy. These two properties can be characterized by considering rebuilding under a constant stress (creep) after shear at high rate. The rebuilding kinetics can be considered through the time evolution of the viscoelastic properties. However at the beginning of the rebuilding process the oscillatory behavior may be non-linear since the microstructure is destroyed by the shear flow. In the present investigation the rebuilding kinetics of cement pastes under oscillatory stress is considered through the transition from large amplitude oscillatory shear (LAOS) regime to small amplitude oscillatory shear (SAOS) regime. Three different cement paste mixes are considered: plain cement, nano-clay blended cement paste and cellulose ether blended cement paste. These three mixes are selected in order to deal with qualitatively different rheological properties.

Cite this publication as follows:
Conte T, Bennacer R, Chaouche M: Thixotropic behavior of cement paste under large amplitude oscillatory shear, Appl. Rheol. 27 (2017) 53914.

Esteban F. Medina-Banuelos, Benjamin M. Marin-Santibanez, Jose Perez-Gonzales, Francisco Rodriguez-Gonzalez
Couette flow of a yield-stress fluid with slip as studied by Rheo-PIV

Appl. Rheol. 27:5 (2017) 53893 (11 pages)

The Couette flow of a model yield-stress fluid with slip at the walls, a 0.12% Carbopol® 940 microgel, was analyzed in this work by simultaneous rheometrical and particle image velocimetry measurements (Rheo-PIV). The Rheo-PIV technique was first tested in the analysis of the Couette flow of a Newtonian fluid and then used to determine the velocity and shear rate distributions of the microgel across gap. A reliable and full description of the different flow regimes occurring in the steady Couette flow of yield-stress fluids with slip at the rheometer walls was obtained, which includes rigid body-like motion at stresses below the yield one, rigid body-like motion and shear flow at stresses above the yield one, as well as pure shear flow once the shear stress at the outer cylinder overcomes the yield value. Slip occurred at both cylinders, which were made up of hydrophobic (inner) and hydrophilic (outer) materials, respectively. The slip velocity values measured at both walls increased along with the shear stress and the trends of these dependencies deviated from the predictions of the hydrodynamic and elastohydrodynamic lubrication mechanisms of slip in the flow of soft deformable particle dispersions [1]. Besides, the yield stress was determined with good accuracy from the velocity profiles, as well as the location of the yielded and non-yielded regions for each flow condition. Finally, the consistency of the obtained velocity profiles was tested by comparison with a theoretical prediction for the Couette flow problem of a Herschel-Bulkley fluid without slip.

Cite this publication as follows:
Medina-Banuelos EF, Marin-Santibanez BM, Perez-Gonzalez J, Rodriguez-Gonzales F: Couette flow of a yield-stress fluid with slip as studied by Rheo-PIV, Appl. Rheol. 27 (2017) 53893.

Katja A. Fröhlich, Eleni Mitrentsis, Frank Clemens, Botho Hoffmann, Véronique Michaud, Thomas Graule
Assessment of the Dispersion Quality of refractive index-matched nanodispersions

Appl. Rheol. 26:6 (2016) 65050 (10 pages)

Dispersion quality has a large influence on the resulting properties of filled polymers, hybrids and nanocomposites in general. Reducing the van der Waals forces and therefore, matching the refractive index between the filler and the matrix should improve dispersion in hybrid materials. However, in this case the usual light-based techniques cannot be used to assess dispersion quality. In this work, dispersions containing silica nanoparticles and a solvent mixture of 1-butanol and Benzyl alcohol were analysed by rheological methods. The refractive index of the solvent was changed by varying the mixing ratio, and thus the effect of index difference on the filler-matrix interaction was investigated. In agreement with theory, a stronger gel network was observed when the refractive index of filler and solvent were matched. If the difference in refractive index of the two materials became too large, particles and solvent interaction was reduced, and agglomerates were formed. This resulted in a weaker gel network.

Cite this publication as follows:
Frohlich KA, Mitrentsis E, Clemens F, Hoffmann B, Michaud V, Graule T: Assessment of the Dispersion Quality of refractive index-matched nanodispersions, Appl. Rheol. 26 (2016) 65050.

Tom C. B. McLeish (Ed.)
Obituary Alexei Likhtman (1971-2015)

Appl. Rheol. 25:6 (2015) 53-54

Alexei Likhtman, a leading scientist in Theoretical Soft Matter Physics, has died aged 44

Born in 1971 into a family with strong scientific tradition, Alexei was educated in Moscow. He was awarded a Diploma in Physics with honours from the Physics Department of Moscow State University (MGU) in 1994. He remained at MGU for his PhD research, supervised by Professor Alexander Semenov. The topic, his first foray into polymer physics, was the calculation of the extraordinary ordered nanoscale patterns of chemical separation that are spontaneously generated within polymer melts whose molecules contain extended regions of different chemistry but joined together. These systems maintained a lifelong fascination for Alexei, as did the collaboration with the experimental group in Crete that the Russians worked with closely. The relationship with Crete remained strong and close until the end of Alexei's life. A more important lifelong partnership also began in Moscow - it was as students there that Alexei and Katrina met and married in December 1990. The family grew after their daughters Sonya and Asya were born while Alexei was working on his PhD thesis. Helping to look after two little girls however did not stop him from producing a high quality piece of work. Till the end of his days Alexei remained a loving, committed, hands on dad, always reliable and extremely loyal to his family. The family stayed in Moscow for two more years, with Alexei as a Scientific Fellow at Moscow State University, before moving to the U.K, in 1998, where he took up a position as a Research Assistant in the Department of Applied Mathematics at Leeds University, where Semenov, now his colleague, had also moved. That initial one year position marked the beginning of family's long life in the UK

Alexei stayed at Leeds from 1998 until 2007: in 1999 he moved to the Department of Physics and Astronomy, where he worked on theories of fast flow of entangled polymer melts, including theory and simulations of the convective constraint release model, supervised by Professor Tom McLeish, and working collaboratively with Prof. Scott Milner at an ex tended international workshop at the Kavli Institute of Theoretical Physics in Santa Barbara. In 2002, Alexei’s research had developed to the point where he was awarded an Advanced EPSRC Fellowship, which he held from 2002-2005 in the School of Physics and Astronomy. In this period, Alexei worked on developing new models of polymer dynamics, simultaneous description of rheology, neutron spin-echo, neutron scattering, diffusion, dielectric spectroscopy and NMR experiments, the theory of chemical reactions in polymers and computer simulations. This work has been recognized in many ways, including the best paper award of the Journal of Rheology (2006). From 2005-2007 Alexei held his Fellowship in the Department of Applied Mathematics, also as University Fellow, supervising a team of three postdoctoral researchers working on molecular simulations of polymer melts, slip-links model of entanglements and experimental rheology. Although a theoretician, he worked with experimental colleagues in different laboratories and performed experiments himself, learning and questioning every single detail. As a result, he personally developed the most reliable experimental protocol for measuring the flow properties of polymer melts yet found by the Leeds lab. For an experimentalist, it was a treat to interact with Alexei in this context, a unique experience that led to improved experiments. Co-supervising a PhD student, Richard Graham, the two formulated a now-celebrated non-linear but easily-computable mathematical model for the flow of linear polymers of well-defined length (the ROLiE-Poly model).

He worked hard not only on brilliant new theoretical science, but on making this accessible to others. For example, his foresight and energy led to the creation, with long-time colleague Jorge Ramirez, of a free software tool (called REPTATE) that enabled experimental scientists in universities and industry to sort their polymer flow data and compare it quickly and efficiently to theoretical models, greatly accelerating fundamental research and its application.

In May 2007, Alexei moved to the Department of Mathematics and Statistics at the University of Reading, as Professor of Mathematical Physics. There, together with Prof. Mark Matsen, he created a new group of theoretical polymer physics and within a few years had put Reading ‘on the map’. The group focused on the microscopic foundations of the tube theory and using a blend of theory and multi-scale simulation to dig deeper, and with more care, into the underlying physics than any other group in the world. A testimony of Alexei’s brilliance is his unique ability to bridge concepts and methodologies from different fields. He did so in his recent simulation work by using concatenated ring polymers to study polymer entanglements.

Alexei achieved enormous academic distinction, and his achievements came remarkably quickly – testament to his brilliance as a scientist. Several theoretical works on the linear and non-linear viscoelasticity of entangled polymers carry his name, including the famous Likhtman-McLeish model (2002) for slow flows (which was 90% Likhtman) and the GLaMM model (2003) for fast flows (with Graham and Milner). His Advanced EPSRC Fellowship came at the age of 31, and he was appointed Professor of Mathematical Physics in Reading at the age of just 35. Yet while undoubtedly successful himself, Alexei was equally proud of the many achievements of the group he developed. For example, in September this year he spoke glowingly of how two poster prizes out of three available at the Institute of Physics Polymer Physics Biennial Conference were won by post-doctoral researchers from his team. In the same month, he was appointed as the first Mercator Fellow of the Freiburg-Strasbourg-Basel-Mulhouse International Research Training Group on 'Soft Matter Science'. He enjoyed a productive visit to Strasbourg, during which he described himself as "feeling like a PhD student again" (possibly partly due to the position that his former PhD supervisor, Semenov, now holds there!). This is typical of his modesty and enthusiasm.

Alexei was one of those wonderful scientists who remind us that just because something is obvious, doesn't make it true. Alexei would challenge every idea that we had at Leeds – including the ones that we thought were obviously true. But the way in which he demolished your ideas was so kind and so surgically precise that it always felt good somehow. He was a particularly vociferous critic of the bad habit that much of the polymer rheology community had got into, of presenting theory together with data from just one technique, then subtly altering the parameters when data from a different technique was brought into comparison. A wonderful paper from 2005 compared his remarkable ‘slip-link model’ to data on rheology, NMR and diffusion measurements simultaneously. He leaves us a permanent reminder that you learn more from theory when it disagrees with experiment and that an experimentalist should have a good grasp of theory and vice versa.

Alexei was a wonderful colleague, and all those who were lucky enough to work with him Benefitted immensely from his enthusiasm, support and wisdom. Alexei was an intellectual powerhouse, a truly curious mind, a wonderfully creative thinker, a brilliant teacher at undergraduate and graduate levels, with academic gravitas way beyond his years, yet completely ap proachable, modest and always friendly in a natural way that charmed anybody who met him. The superb group he built in Reading and the quality of people he brought in reflect his vision and sense of commitment.

He was hugely supportive of those for whom he felt he had a responsibility. His dedication to his PhD students and his research team went well beyond professional duty. He sought to provide a family-like environment for the group, especially supportive for those who were far from home. He presented himself as an exemplary reference figure for all the young people in his group, full of energy and full of life. In this continuous work of hospitality and welcome he was supported by his family, to whom he was utterly devoted as husband and father.

Alexei was so much more than an academic and an intellectual. He truly enjoyed life and always managed to combine professional activities with hobbies and family activities. He did so last summer when he visited friends with his family following a workshop and seminar. He had a passion for so many things ranging from sports (especially swimming and hiking) to photography. A truly happy, free spirited man, full of energy and passion for things he did, he had as infectious a love of life as a tireless desire to find scientific truth. He was a great admirer of nature and outdoors with real care about the world and people around him. He was a great friend, a funny, spirited, yet always serious person, and his daily passionate presence, his enthusiasm for science, his warm friendship, will be sorely missed.

Alexei died on 11 October 2015 following a fall while hiking in Maryland, USA. He is survived by his wife Katrina, and their two daughters, Sonya and Asya.

Cite this publication as follows:
McLeish TCB: Obituary Alexei Likhtman (1971-2015), Appl. Rheol. 25 (2015) 53.

Tommi Borg, Esko J. Paakkonen
Linear viscoelastic model for different flows based on control theory

Appl. Rheol. 25:6 (2015) 64304 (10 pages)

Traditional Maxwell-type models have limitations when applied to the flows of real polymers containing macromolecules and complex microstructures. The main weakness of Maxwell models is the use of relaxation-time spectra that conducts to ill-posed problems in integral functions, and shear-induced relaxation spectrum transformations may lead to non-linearity. In contrast, control theory, which has apparently not been applied in rheology so far, enables modelling without knowledge of relaxation times. This study used viscoelastic constitutive equations derived from control theory and a new polymer fingerprint, which we call the rheologically effective distribution (RED). The study shows that a relaxation-time scheme is not essential to describe viscoelasticity, and applying the RED to computational modelling provides many theoretical and practical Benefits, including giving higher accuracy. The proposed model is versatile and presents viscoelastic formulas for shear viscosity and other types of flow. Furthermore, the new model provides explanations for the empirical Cox-Merz rule and a power law behavior, the origin of which is frequently disputed in rheology.

Cite this publication as follows:
Borg T, Paakkonen EJ: Linear viscoelastic model for different flows based on control theory, Appl. Rheol. 25 (2015) 64304.

Rudolf Hampl, Otakar Vacin, Martin Jasso, Jiri Stastna, Ludo Zanzotto
Modeling of tensile creep and recovery of polymer modified asphalt binders at low temperatures

Appl. Rheol. 25:3 (2015) 34675 (8 pages)

The creep and recovery of asphalt modified with Elvaloy 4170 and polyphosphoric acid were studied at low temperatures, by inductive phenomenological methods. Two models of the tensile compliance function were investigated. Both models were derived from the linear viscoelastic retardation spectra and successfully used for the description of the creep and recovery tests in the studied asphalt binders. Large effects due to oxidative aging in a rolling thin film oven were found from the recovered compliance function recorded in a Bending beam rheometer at a temperature of - 20 C. The studied compliance function models worked well at higher and lower temperatures in creep and recovery experiments on conventional and modified asphalt binders for both shear and tensile creep.

Cite this publication as follows:
Hampl R, Vacin O, Jasso M, Stastna J, Zanzotto L: Modeling of tensile creep and recovery of polymer modified asphalt binders at low temperatures, Appl. Rheol. 25 (2015) 34675.

Umme Amina Mannan, Md Islam, Mekdim Weldegiorgis, Rafiqul Tarefder
Experimental investigation on rheological properties of recycled asphalt pavement mastics

Appl. Rheol. 25:2 (2015) 22753 (9 pages)

Studies have shown that rheology of asphalt mastic plays an important role in pavement performance, specifically for the case of recycled asphalt pavement (RAP) mastics which contains mostly aged binder. This study determines the rheological properties of RAP mastics and a comparison is conducted with the no-RAP binder. Influence of RAP fines on rutting and cracking performances is also studied. A performance grade PG 70-22 binder is mixed with varying percentages (10, 20, and 40%) of crushed stone (no-RAP) and RAP fines to prepare mastics. Dynamic Shear Rheometer testing is conducted to measure the complex shear modulus G*, and phase angle δ of these mastics at high and intermediate temperatures through frequency sweep. Bending Beam Rheometer test is conducted at low temperatures (-10 C, -16 C, and -22 C) to measure the stiffness S and relaxation (m-value). Direct Tension Test is conducted to compute the failure strain at -22 C. Results show an improvement in rutting with the addition of RAP fines (increase in G*/sinδ), a decline in low-temperature cracking resistance (increase in S). Addition of RAP fines up to 20% does not affect the fatigue resistance of the mastics adversely. However, fatigue cracking of 40% RAP mastic is shown to be high (increase in G*sinδ). 40% RAP mastic shows a smaller failure strain than the virgin binder and 40% no-RAP mastic, which indicates that mastics containing RAP are more susceptible to low-temperature cracking. To characterize the viscoelastic properties of the RAP mastics, the G* master curve is constructed at 22 C reference temperature. RAP mastics. master curves follow the sigmoidal function irrespective of %RAP in mastics. However master curves do not show any significant difference between RAP mastics and no-RAP mastics.

Cite this publication as follows:
Mannan UA, Islam M, Weldegiorgis M, Tarefder R: Experimental investigation on rheological properties of recycled asphalt pavement mastics, Appl. Rheol. 25 (2015) 22753.

Dominique Dupuis, Karim Bekkour, Kaouther Ben Azouz
On the modeling of the rheological behaviour of bentonite dispersions in polymer solutions

Appl. Rheol. 24:2 (2014) 24283 (9 pages)

Bentonite dispersions in polymer solutions may behave as gel like materials. Under stress, the structure formed at rest is progressively destroyed and a solid-liquid transition occurs. The rheological characterization of such kind of systems is often done by applying stress ramps of the sample. A simple Herschel-Bulkley equation is not convenient to fit the answer of the material to the ramp since it does not take in account the effect of time. The models for yield stress fluids involving two viscosity levels are not convenient too since they don.t take in account the elastic behavior at low stresses. We propose in this paper two equations in order to determine some parameters characterizing the rheological behavior of such systems. The results obtained both in oscillatory and permanent shear are compared according to Winter.s representation and a rescaling of the complex modulus is proposed to superimposed the data in the solid/liquid transition region.

Cite this publication as follows:
Dupuis D, Bekkour K, BenAzouz K: On the modeling of the rheological behaviour of bentonite dispersions in polymer solutions, Appl. Rheol. 24 (2014) 24283.

Martin Boisly, Markus Kästner, Jörg Brummund, Volker Ulbricht
General aspects of yield stress fluids - Terminology and definition of viscosity

Appl. Rheol. 24:1 (2014) 14578 (11 pages)

This work contributes to general theoretical aspects of yield stress fluids with significance for practical phenomenological material modeling. It introduces a terminology so that the material class .yield stress fluid. is defined and can be distinguished from the terms .solid. and .liquid.. This new material classification is based on two criteria, the equilibrium relation and the flow function. In line with this terminology, an experimental procedure for classifying the material behavior is presented. The second key aspect of this paper is a discussion on the proper definition of the term .viscosity.. The Benefit of the differential viscosity over the dynamic viscosity in case of non-Newtonian fluids in general is worked out. This is shown by the most elementary yield stress fluid, the friction element, because it is the basis of the yield stress concept. Its constitutive equations are given for positive as well as negative strain rates and are also able to represent the preyield behavior. The theory presented in this article is also applied to the Maxwell, Kelvin-Voigt, and Bingham element to demonstrate the working principle.

Supplementary Information is contained as an attachment to the reprint-pdf.

Cite this publication as follows:
Boisly M, Kastner M, Brummund J, Ulbricht V: General aspects of yield stress fluids - Terminology and definition of viscosity, Appl. Rheol. 24 (2014) 14578.

Meral Akkoyun, Christian Carrot, Benoit Blottiere
On the use of an internal mixer to study the impregnation of carbon fillers by organic liquids

Appl. Rheol. 24:1 (2014) 13487 (8 pages)

Impregnation of organic liquid electrolytes in conductive powders is of major importance in the field of energy storage devices such as batteries or super-capacitors. Impregnation during mixing and processing operations becomes usual for practical reasons and requires a better understanding of the changes of the rheological behavior of the mix. In this paper, the impregnation of propylene carbonate (PC) and dimethyl sulfoxide (DMSO) in activated carbon (AC) and carbon black (CB) was studied by using an internal mixer. Monitoring of the torque of the filler/liquid blend as a function of the amount of liquid fed in the mixing chamber, enables to detect the transition from the solid friction of the dry powder to the lubricated liquid (or viscous) behaviour of the concentrated paste of wetted powder. The results were compared with data obtained by conventional nitrogen adsorption porosimetry combined with the knowledge of the molecular diameter of the liquids. A characteristic change was observed as soon as the liquid completely fills the porosity of the filler. Both tested liquids (DMSO and PC) impregnate more carbon black and the take-up rate is slightly higher for DMSO in comparison to PC because, as a polar liquid, DMSO has a better interaction with both fillers.

Cite this publication as follows:
Akkoyun M, Carrot C, Blottiere B: On the use of an internal mixer to study the impregnation of carbon fillers by organic liquids, Appl. Rheol. 24 (2014) 13487.

M. Guettari, I. Ben Naceur, G. Kassab, A. Ponton, T. Tajouri
Temperature and concentration induced complex behavior in ternary microemulsion

Appl. Rheol. 23:4 (2013) 44966 (7 pages)

Viscosity measurements were performed in water/AOT (sodium bis(2-ethylhexyl) sulfoccinate)/isooctane microemulsions as a function of temperature between 25 C and 55 C, molar ratio Wo = water/AOT ranging from 3 to 45 and three values of AOT/isooctane volume fractions (Φm = 0.1, 0.15, and 0.2). It was shown that microemulsions behaved as Newtonian fluids in the studied range of shear rate. For a critical molar ratio, Woc, the corresponding viscosity, ηoc, was shown to be constant with temperature but dependent on the micellar concentration. For Wo < Woc, the solutions behaved as simple fluids and the temperature dependence of viscosity was described by an Arrhenius law. The total activation energy was found to be dependent on W with a maximum for Wo = 5. A correlation between the microscopic structure of the reverse micelles and the total activation energy was proposed. However, a complex fluid behavior was observed for Wo > Woc, where the viscosity increased with temperature. For some values of Wo, the viscosity reached a maximum, which could be explained by attractive interdroplet interactions and formation of droplet clusters.

Cite this publication as follows:
Guettari M, BenNaceur I, Kassab G, Ponton A, Tajouri T: Temperature and concentration induced complex behavior in ternary microemulsion, Appl. Rheol. 23 (2013) 44966.

Abdelhakim Benslimane, Karim Bekkour, Pierre Francois
Effect of addition of Carboxymethylcellulose (CMC) on the rheology and flow properties of bentonite suspensions

Appl. Rheol. 23:1 (2013) 13475 (10 pages)

In this work, Bentonite suspension and mixtures containing 5 wt% of Bentonite and 0.1 and 0.5 wt% of carboxymethyl cellulose (CMC) were investigated in terms of their rheology and hydrodynamic behaviour in pipe flow. All fluids exhibited non- Newtonian rheological behaviour that can be well described by the three parameters Herschel-Bulkley model. The axial velocity distribution was determined using ultrasonic pulsed Doppler velocimetry technique. In the laminar regime the flow parameters were predicted by integration of the constitutive rheological model used. In the turbulent flow, the Dodge and Metzner model was applied to fit the experimental data. The measurements of the friction factor showed a small amount of drag reduction for the pure Bentonite suspension, whereas for the polymer.clay blend the drag reduction was more important.

Cite this publication as follows:
Benslimane A, Bekkour K, Francois P: Effect of addition of Carboxymethylcellulose (CMC) on the rheology and flow properties of bentonite suspensions, Appl. Rheol. 23 (2013) 13475.

Mohamed Ilies Bahlouli, Karim Bekkour, Adel Benchabane, Yacine Hemar, Ali Nemdili
The effect of temperature on the rheological behavior of polyethylene oxide (PEO) solutions

Appl. Rheol. 23:1 (2013) 13435 (15 pages)

The rheological properties of polyethylene oxide (PEO) solutions were investigated, at different temperatures, using small and large deformation rheological methods. Steady-state flow measurements showed that the flow behavior of the PEO solutions is well described by the Cross model, which yields the critical concentrations c* (from the dilute regime to semidilute regime) and c** (from the semi-dilute regime to the concentrated regime). In the range of the temperatures investigated here, the apparent viscosity is found to obey the Arrhenius equation below a critical temperature we believe corresponds to the cloud point temperature. Above the cloud point temperature, the viscosity increased with temperature. Similarly below the cloud point, both transient and dynamic tests showed that PEO solutions exhibit viscoelastic behavior, where both the elastic G' and viscous G'' modules increased with the increase in concentration and with the decrease in temperature. The Cox-Merz rule was found to apply to the PEO solutions at temperatures lower than the cloud point temperature, whilst divergence was reported after phase separation. The frequencies at which G' = G'', i.e. the reciprocal of the relaxation times of the temporary polymer network, was found to increase (the relaxation times decline) with decreasing polymer concentration, in agreement with the relaxation times, derived from the Cross model. In essence, this study demonstrates that it is possible to monitor accurately the cloud point temperature of PEO solutions by viscometric analysis.

Cite this publication as follows:
Bahlouli MI, Bekkour K, Benchabane A, Hemar Y, Nemdili A: The effect of temperature on the rheological behavior of polyethylene oxide (PEO) solutions, Appl. Rheol. 23 (2013) 13435.

Stephan Laske, Andreas Witschnigg, Hannelore Mattausch, Milan Kracalik, Gerald Pinter, Michael Feuchter, Guenther Maier, Clemens Holzer
Determining the ageing of polypropylene nanocomposites using rheological measurements

Appl. Rheol. 22:2 (2012) 24590 (9 pages)

The principle of silicate layer reinforcement in a polymer matrix is known as the formation of a 3D network of single layers. Nevertheless there is still a lack of knowledge about the physical ageing of nanocomposites respectively the stability of this network over time. As most of the nanocomposite applications have a more or less long-term shelf life respectively storage time, the investigation of the storage-time dependent behavior of the layered 3D structure in a polymer matrix is of major interest. In this study, the rheological (shear and elongational) properties of different polypropylene nanocomposites were measured using a cone-plate rheometer and a Rheotens apparatus. To evaluate the structural stability over time, the samples were measured immediately after processing and after defined periods (18 and 36 months) stored under constant conditions. Furthermore the network structure was determined using XRD and TEM measurements. The results show, that, depending on the clay rate and especially the degree of exfoliation, the rheological properties are changing significantly. Thereby chain splitting caused by photo-oxidative degradation, leading to a loss in molecular weight, as well as a weakened 3D network by reverse diffusion of the polymer chains out of the clay gallery and/or reagglomeration of the nanoparticles are the two main factors.

Cite this publication as follows:
Laske S, Witschnigg A, Mattausch H, Kracalik M, Pinter G, Feuchter M, Maier G, Holzer C: Determining the ageing of polypropylene nanocomposites using rheological measurements, Appl. Rheol. 22 (2012) 24590.

Victor Chernov, Benveniste Natan
A simplified model for the evaluation of the rheological properties of a suspension of solids in a power-law fluid

Appl. Rheol. 22:1 (2012) 15163 (10 pages)

An effort is made to determine theoretically the new rheological properties of a rheologically defined non-Newtonian fluid as a result of the addition of particles in the original fluid. A theoretical model is proposed to determine the rheological properties of a dilute suspension of infinite-length round particles for a Power-Law fluid, which is treated as a homogeneous fluid with new rheological properties. The equations of a two-dimensional, dilatational, creeping, steady-state flow of a near-Newtonian fluid around a solid circular particle are developed and solved. The solution is obtained by computation of the dissipation relation and is based on the change of the shear rate in a shear flow of the suspension. The model is solved numerically. The resulting from the particle addition fluid is found to be more shear-thinning in comparison to the original. Experimental evidence from the literature supports the soundness of the present findings.

Cite this publication as follows:
Chernov V, Natan B: A simplified model for the evaluation of the rheological properties of a suspension of solids in a power-law fluid, Appl. Rheol. 22 (2012) 15163.

Yan Meng, Joshua Otaigbe
Mechanism of unexpected viscosity decrease of polymer melts by low-Tg inorganic phosphate glass during processing

Appl. Rheol. 21:4 (2011) 42654 (11 pages)

We report unprecedented non-Einstein-like viscosity decrease of polymer melts by special low glass transition, Tg, inorganic tin fluorophosphate glass (Pglass) that is remarkably counter to widely accepted dispersions, suspensions, and composites theories. The well dispersed low-Tg Pglass dramatically decrease the polymer melt viscosity while increasing its Young's modulus in the solid state at low loading (<2%) however decreasing with high loading (>2%), making the hybrid Pglass/polymer solid material stronger yet easier to process in the liquid state. Disruption of the Nylon 6 melt dynamics, strong physicochemical interactions, and submicrometer nanophase separation (proved by rheometry, FTIR, DSC, SEM, NMR and XRD) are thought to be responsible for this experimental fact. This finding should Beneficially impact our ability to prepare lower viscosity, very highly filled Nylon 6 melts from already existing materials and polymer processing methods such as injection molding and extrusion, making the simple strategy potentially widely applicable in a number of applications such as thinner barrier resistant thin films, composites, and membranes for heterogeneous catalysis.

Cite this publication as follows:
Meng Y, Otaigbe J: Mechanism of unexpected viscosity decrease of polymer melts by low-Tg inorganic phosphate glass during processing, Appl. Rheol. 21 (2011) 42654.

Vassilios C. Kelessidis, Vasiliki Hatzistamou, Roberto Maglione
Wall slip phenomenon assessment of yield stress pseudoplastic fluids in Couette geometry

Appl. Rheol. 20:5 (2010) 52656 (8 pages)

Results are presented aiming to determine whether wall slip occurs while performing rheological measurements of Carbopol solutions and Bentonite dispersions at different concentrations using a standard oil-field Couette-type viscometer with two gap sizes. Yield stresses using a vane rheometer were also determined and compared to those obtained by extension of the experimentally-derived rheological curves at the Couette viscometer.The results show that, if preparation procedures are followed as suggested for Carbopol solutions and by API standard for drilling fluids, simulating either the pre-shearing in the rig mud pumps or in the bit nozzles during drilling operations, wall slip does not occur, with a good agreement of the rheograms and of the yield stresses determined for both gap sizes of the Couette viscometer and by the vane rheometer. No slip occurs also for CMC solutions which exhibited pseudoplastic power-law behavior.

Cite this publication as follows:
Kelessidis VC, Hatzistamou V, Maglione R: Wall slip phenomenon assessment of yield stress pseudoplastic fluids in Couette geometry, Appl. Rheol. 20 (2010) 52656.

Benhamou Mabrouk
2nd International Workshop on Soft Condensed Matter Physics and Biological Systems (SMPPMM 2010)

Appl. Rheol. 20:3 (2010) 176-176

Cite this publication as follows:
Mabrouk B: 2nd International Workshop on Soft Condensed Matter Physics and Biological Systems (SMPPMM 2010), Appl. Rheol. 20 (2010) 176.

D.C. Venerus, J. Buongiorno, R. Christianson, J. Townsend, I.C. Bang, G. Chen, S.J. Chung, M. Chyu, H. Chen, Y. Ding, F. Dubois, G. Dzido, D. Funfschilling, Q. Galand, J. Gao, H. Hong, M. Horton, Lin-wen Hu, C.S. Iorio, A.B. Jarzebski, Y. Jiang, S. Kabelac, M.A Kedzierski, C. Kim, Ji-Hyun Kim, S. Kim, T. McKrell, R. Ni, J. Philip, N. Prabhat, P. Song, S. Van Vaerenbergh, D. Wen, S. Witharana, Xiao-Zheng Zhao, Sheng-Qi Zhou
Viscosity measurements on colloidal dispersions (nanofluids) for heat transfer applications

Appl. Rheol. 20:4 (2010) 44582 (7 pages)

This article reports viscosity data on a series of colloidal dispersions collected as part of the International Nanofluid Property Benchmark Exercise (INPBE). Data are reported for seven different fluids that include dispersions of metal-oxide nanoparticles in water, and in synthetic oil. These fluids, which are also referred to as 'nanofluids,' are currently being researched for their potential to function as heat transfer fluids. In a recently published paper from the INPBE study, thermal conductivity data from more than 30 laboratories around the world were reported and analyzed. Here, we examine the influence of particle shape and concentration on the viscosity of these same nanofluids and compare data to predictions from classical theories on suspension rheology.

Cite this publication as follows:
Venerus DC, Buongiorno J, Christianson R, Townsend J, Bang I, Chen G, Chung S, Chyu M, Chen H, Ding Y, Dubois F, Dzido G, Funfschilling D, Galand Q, Gao J, Hong H, Horton M, Hu L-W, Iorio CS, Jarzebski AB, Jiang Y, Kabelac S, Kedzierski MA, Kim C, Kim J-H, Kim S, McKrell T, Ni R, Philip J, Prabhat N, Song P, VanVaerenbergh S, Wen D, Witharana S, Zhao X-Z, Zhou S-Q: Viscosity measurements on colloidal dispersions (nanofluids) for heat transfer applications, Appl. Rheol. 20 (2010) 44582.

Leonard Sagis
Rheology of complex fluid-fluid interfaces: a unified approach based on nonequilibrium thermodynamics

Appl. Rheol. 20:2 (2010) 24380 (8 pages)

Surface rheological properties affect the dynamics of vesicles, nanoparticles, emulsion droplets, foam bubbles, polymer microcapsules, liquid jets, living cells, lung avioli, thin liquid films, and many other multiphase systems. Surface rheology is therefore relevant for a wide range of disciplines in the areas of physics, chemistry, engineering, biology, and medicine. Currently used descriptions of surface rheology have a number of limitations, and in particular are hard to generalize to the large deformation regime. Data are often analyzed with constitutive equations based on straightforward generalizations of models developed for describing bulk phase rheology. Since the latter are in general designed to describe incompressible materials, they are not guaranteed to describe highly compressible interfaces correctly. Here we discuss a unified approach to surface rheology based on nonequilibrium thermodynamics (NET) that provides a consistent set of balance and constitutive equations for the unambiguous determination of surface rheological parameters, both near and far beyond equilibrium. A closer integration of experimental surface rheology and multiphase nonequilibrium thermodynamics would clearly be Beneficial for both disciplines.

Cite this publication as follows:
Sagis L: Rheology of complex fluid-fluid interfaces: a unified approach based on nonequilibrium thermodynamics, Appl. Rheol. 20 (2010) 24380.

Kaouther Ben Azouz, Dominique Dupuis, Karim Bekkour
Rheological characterizations of dispersions of clay particles

Appl. Rheol. 20:1 (2010) 13041 (9 pages)

In this work,we consider model fluids which are dispersions of clay particles in aqueous solutions of carboxymethyl cellulose. Their rheological properties are measured in both steady and oscillatory shear flows.We present the experimental results obtained for different polymer concentrations and for three different molecular weights of the polymer. The clay is a Bentonite sample and the particle concentration is fixed to a value of 5 %. The mechanical properties of these materials is the result of a competition between different mechanisms: association-dissociation of aggregates of particles, adsorption of polymer on the particles and desorption of solvent molecules from the particles, bridging of the particles by long polymer chains.

Cite this publication as follows:
BenAzouz K, Dupuis D, Bekkour K: Rheological characterizations of dispersions of clay particles , Appl. Rheol. 20 (2010) 13041.

Stefan Kubens
The Nordic Rheology Society Conference 2009

Appl. Rheol. 19:6 (2009) 364-365

Cite this publication as follows:
Kubens S: The Nordic Rheology Society Conference 2009, Appl. Rheol. 19 (2009) 364.

Nour el Hou Belkham, Abdelaziz Mehamha, Djafer Benachour
Rheological behavior of alumina ceramic pastes

Appl. Rheol. 19:6 (2009) 64969 (5 pages)

The rheological behavior of ceramic oxide hydroxide alumina pastes with high solid loading is investigated. In order to enable an adequate and experimentally rheological characterization, the measurements are carried out with a Rheostress viscometer under isothermal conditions. Various compositions of a commercial AlOOH powder and binder mixture are investigated. We discuss the variation of loss modulus G', storage modulus G'', apparent and complex viscosities h, h* as function of frequency and shear rate.The solid phase used here is the boehmite; the most important precursor for the g-Al2O3 phase for several applications such as catalysts or functional layers of ceramics. Solid phase compositions used are justified by the applications of boehmite in the manufacturing of catalytic materials. A transition zone that appears at a concentration of 55 %wt of the solid phase (Pural) and at which the rheological behavior changes from viscoelastic to elastic is observed. This transition is of a importance as far as ceramic manufacturing is concerned.

Cite this publication as follows:
Belkham NeH, Mehamha A, Benachour D: Rheological behavior of alumina ceramic pastes, Appl. Rheol. 19 (2009) 64969.

Sandrine Paumier, Anne Pantet, Philippe Monnet, Nathalie Touze-Foltz
Evaluation of the viscoelastic properties of a clay material using a flow curve

Appl. Rheol. 19:2 (2009) 23824 (11 pages)

The specific properties of Bentonite such as hydration, swelling,water absorption, viscosity, yield stress and thixotropy make it a valuable material in the form of mineral powder for a wide range of uses in agronomy, cosmetics and civil engineering. A flow curve is a quick test used to evaluate the rheological basic properties of a viscous fluid. However, many Bentonite dispersions exhibit a complex flow curve, with yield stress and thixotropy area, especially at high concentration. In this study, flow curves from raw and activated Bentonites dispersed in water were acquired at 6, 8 and 10% mass concentrations. Five stages along the flow curve were identified.To explain each stage, rheograms obtained from a dispersion made with a model material were studied in depth. The model material was a smectite extracted from a raw Bentonite then saturated with calcium or sodium. Many homoionic and bi-ionic dispersions were prepared at various concentrations. The analysis and the modelling of some creep-recovery tests by a Zener model showed the relationship between the initial stage in the flow curve, named AB stage, and the viscoelastic properties of the fluid. The AB stage corresponds to the deformation of the material in the solid state. The τB point corresponds to an intermediate yield stress between the solid state and the start of the heterogeneous fracturation. The study of many bi-ionic dispersions allowed drawing the evolution of the yield stress as a function of concentration and saturation. The composition of the raw Bentonites was expressed as an equivalent bi-ionic dispersion by calculating an active smectite percentage. A good correlation was obtained at the highest concentrations between τB from the bi-ionic model dispersions and the raw Bentonites dispersions

Cite this publication as follows:
Paumier S, Pantet A, Monnet P, Touze-Foltz N: Evaluation of the viscoelastic properties of a clay material using a flow curve, Appl. Rheol. 19 (2009) 23824.

Francesca Lionetto, Alfonso Maffezzoli
Rheological characterization of concentrarted nanoclay dispersions in an organic solvent

Appl. Rheol. 19:2 (2009) 23423 (8 pages)

Nanoclay dispersions in organic solvents are widely used in cosmetics for a variety of gels and creams, whose properties depend on the powder content and the processing method. The control of the shear applied during processing is therefore essential for achieving the required properties.This study demonstrates the utility of applying rheological measurements for characterizing cosmetic products based on nanoclays and relating their viscoelastic properties to end-use performances. In particular, a rheological characterization of Bentonite dispersions in isododecane at different clay content and shear history is presented. For each inorganic content, both mixed samples and samples subjected to several calendering runs were studied. The effect of shear and clay content on the viscoelastic properties was investigated by a combination of oscillatory shear experiments under small-deformation conditions and by X-Ray diffraction. The tested samples showed a gel-like behaviour with a final structure depending on the applied shear stress. By increasing the inorganic content in the dispersion, a reduction in the gel stability to a further shear application was observed. Two models, developed for colloidal gels,were used to fit the rheological results enabling to evaluate the microstructure and the degree of dispersion of the tested samples and to relate the colloidal structure to the elastic properties.

Cite this publication as follows:
Lionetto F, Maffezzoli A: Rheological characterization of concentrarted nanoclay dispersions in an organic solvent, Appl. Rheol. 19 (2009) 23423.

Primoz Ternik, Jure Marn
Numerical study of blood flow in stenotic artery

Appl. Rheol. 19:1 (2009) 13060 (11 pages)

In the present study,we investigate the behaviour of the human blood in a stenosed blood vessel. The human blood is studied as a Newtonian as well as non-Newtonian fluid. We consider three rheological models of the shear-thinning non- Newtonian models and compare them with the Newtonian model. The blood flow through a stenosed blood vessel is studied numerically by solving the three dimensional Navier-Stokes equation along with the continuity equation and particular rheological model. Distribution of velocity, pressure,wall shear stresses and flow recirculation characteristics are determined for two time steps of the cardiac cycle. Present results indicate a significant influence of the shear-thinning viscous behaviour of a human blood on the most important hemodynamic parameters that play a key role in formation of atherosclerotic plaques. Last but not least, a systematic grid refinement analysis as well as numerical accuracy study IS performed and present numerical results may be treated as the Benchmark.

Cite this publication as follows:
Ternik P, Marn J: Numerical study of blood flow in stenotic artery, Appl. Rheol. 19 (2009) 13060.

Reinhardt Kotze, Rainer Haldenwang, Paul Slatter
Rheological characterisation of highly concentrated mineral suspensions using an Ultrasonic Velocity Profiling with combined Pressure Difference method

Appl. Rheol. 18:6 (2008) 62114 (10 pages)

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.

Zoran Susteric, Tomaz Kos
Rheological Idiosyncrasies of Elastomer/Clay Nanocomposites

Appl. Rheol. 18:5 (2008) 54894 (10 pages)

Rheological properties of elastomeric nanocomposites with organically modified Montmorillonite clays, as possible replacements or supplements to classical active fillers, such as carbon black or silica, have been intensively studied in recent years. Possessing large specific surface areas acquired through the melt-mixing processes of elastomeric intercalation and subsequent filler exfoliation, the clay particles have indeed proved to be highly eligible reinforcing and thermally stabilizing ingredients for application in elastomers. In fact, their performance has shown to be in many respects superior to that of classical fillers, particularly owing to some unusual, though Beneficial, exhibited properties. Namely, apart from uncommonly high surface activity, manifested by creation of a host of van der Waals type secondary linkages with elastomer molecules, the main curiosity of clay filler is its dissipative action. Using dynamic mechanical functions under different deformational and temperature conditions, as means for rheological characterization of nanocomposites, the foregoing nano-scale traits are clearly reflected in substantial stiffness at low strains and, unexpectedly, dwindling energy loss with increasig filler content and/or decreasing temperature. Besides, rheological analysis of this kind, together with appropriate theoretical grounds, has enabled elucidation of peculiar conduct, as well as macroscopic insight into the very nature of secondary interactions in elastomers.

Cite this publication as follows:
Susteric Z, Kos T: Rheological Idiosyncrasies of Elastomer/Clay Nanocomposites, Appl. Rheol. 18 (2008) 54894.

Nicolas Benard, Sebastien Jarny, Damien Coisne
Definition of an experimental blood like fluid for laser measurements in cardiovascular studies.

Appl. Rheol. 17:4 (2007) 44251 (9 pages)

Nowadays it is necessary to perform experimental measurements to compare with numerical calculations. In this study we focus on different aqueous solutions which are tested to obtain in the same time a rheological blood like fluid and particular optical properties for laser measurements (particle image velocimetry (PIV) or laser Doppler velocimetry (LDV)). Using viscometric tests we show that the non Newtonian behavior of blood is reached by adding xanthan gum in aqueous glycerol and aqueous potassium thiocyanate solutions. Optical properties are directly achieved by modifying glycerol or thiocyanate potassium concentrations. Indeed we proove using refractometric measurements that the addition of xanthan gum does not affect the value of the refractive indexes. Finally,we can prepare an optical blood like fluid adapted to cardiovascular studies by adjusting the proportion of the different components.

Cite this publication as follows:
Benard N, Jarny S, Coisne D: Definition of an experimental blood like fluid for laser measurements in cardiovascular studies., Appl. Rheol. 17 (2007) 44251.

Markus Gahleitner
Austrian Rheologists meet in Leoben, Sep 19, 2005

Appl. Rheol. 15:5 (2005) 344

Cite this publication as follows:
Gahleitner M: Austrian Rheologists meet in Leoben, Sep 19, 2005, Appl. Rheol. 15 (2005) 344.

Ben Hanson, Martin Levesley, John Fisher
Using Self-Sensing Techniques to Produce a Small, Robust, Inexpensive Rheometer

Appl. Rheol. 13:5 (2003) 242-250

Self-sensing is the technique of using a transducer to both actuate and sense concurrently, therefore eliminating the need for separate sensors. A sensorless rheometer could be much smaller, simpler and more robust than traditional designs. One application where such a rheometer would be desired is the in-situ measurement of curing bone cement in orthopaedic surgery. A set of equations was developed that models the relationship between force, motion and back-e.m.f. generation for a class of electromagnetic actuators. This enables velocity, displacement and force to be self-sensed from voltage measurements only. This self-sensing was validated on a conventional linear electromagnetic actuator, and a small rotary moving magnet device, which was designed to be a small self-sensing rheometer. The accuracy of the estimation was assessed and shown to compare favourably with measured data. The actuators were then used to construct simple rheometers to measure bone cement. Rheological models were used to calculate storage and loss moduli and dynamic viscosity from the self-sensed values of displacement, velocity and torque. The accuracy of these self-sensing rheometers was verified against a traditional rheometer using a silicone fluid and a polyethylene oxide solution. The self-sensing rheometers were used to characterise acrylic bone cements during curing, reinforcing and extending upon previous results. The elimination of sensors meant that it was possible to produce a small, inexpensive rheometer with a very simple structure. This indicates there is potential to develop small rheo-transducers for certain applications.

Cite this publication as follows:
Hanson B, Levesley M, Fisher J: Using Self-Sensing Techniques to Produce a Small, Robust, Inexpensive Rheometer, Appl. Rheol. 13 (2003) 242.

Waheed Uddin
Viscoelastic Characterization of Polymer-Modified Asphalt Binders of Pavement Applications

Appl. Rheol. 13:4 (2003) 191-199

Rutting is a primary reason of premature deterioration of asphalt highway pavements. Pavements constructed with polymer and other modifiers are showing improved performance. The virgin asphalt and modified asphalt binders and mixes used on several test sections of the I-55 highway rehabilitation project in northern Mississippi are compared. The laboratory creep compliance data for these binders were measured at low temperatures using a modified test procedure adapted for the Bending Beam Rheometer device. Dynamic Shear Rheometer was used at high service temperatures. The creep compliance data of the binder was used as an input to simulate creep compliance behavior of the mix using a micromechanical model. The field evaluation confirms the relatively poor performance of the virgin asphalt section with respect to rutting, compared to modified binder sections.

Cite this publication as follows:
Uddin W: Viscoelastic Characterization of Polymer-Modified Asphalt Binders of Pavement Applications, Appl. Rheol. 13 (2003) 191.

Giovanni Polacco, Otakar Josef Vacin, Dario Biondi, Jiri Stastna, Ludovit Zanzotto
Dynamic Master Curves of Polymer Modified Asphalt from Three Different Geometries

Appl. Rheol. 13:3 (2003) 118-124

Polymer modified asphalt is an highly temperature sensitive material. To obtain the master curves of dynamic material functions, for this material, it is necessary to perform the testing over the temperature interval from - 30.C to at least 90.C. Since in this temperature range the polymer modified asphalt undergoes the transition from a glass-like to a Newtonian-like material, the Benefit of using three testing geometries is studied here. The geometries used were: torsion bar (for the low temperatures), plate-plate (for the mid range temperatures) and bob and cup (for the high temperatures). The advantage of the combination of these three geometries is discussed. Stress and strain controlled rheometers were used to conduct all dynamic experiments. Master curves obtained by these geometries cover up to 20 decades of the reduced frequency.

Cite this publication as follows:
Polacco G, Vacin OJ, Biondi D, Stastna J, Zanzotto L: Dynamic Master Curves of Polymer Modified Asphalt from Three Different Geometries, Appl. Rheol. 13 (2003) 118.

Sabine Beckmann, Jürgen Niemeyer
Flow Patterns of Polymer Solutions Injected into Dispersions of Bentonite

Appl. Rheol. 13:1 (2003) 14-18

The flow behaviour of colloidal dispersions is largely influenced by the interactions between the dispersed particles. We studied the influence of either natural or synthetic polyelectrolytes solutions on flow patterns within colloidal clay dispersion. For this purpose, highly diluted aqueous polymer solutions were intruded into a radial Hele-Shaw cell filled with montmorillonite dispersions. The developing flow patterns were recorded with a high resolution digital camera. The morphological parameters: fractal dimension, total number of branching, branching density of the patterns, compactness and form were obtained by digital image analysis. The results show that the patterns are largely affected by the different polymers.

Cite this publication as follows:
Beckmann S, Niemeyer J: Flow Patterns of Polymer Solutions Injected into Dispersions of Bentonite, Appl. Rheol. 13 (2003) 14.

Karim Bekkour, Nadja Kherfellah
Linear Viscoelastic Behavior of Bentonite-Water Suspensions

Appl. Rheol. 12:5 (2002) 234-240

Bentonite are extensively used materials in a wide range of applications. Creep and oscillatory shear experiments in the linear viscoelastic domain were carried out on Bentonite-water suspensions at different solid fractions. It was found that Bentonite dispersions exhibit important viscoelastic behavior which could be represented by the generalized Kelvin-Voigt mechanical model. It is well known that an exhaustive study of colloidal dispersions may require the determination of its viscoelastic properties over a wide frequency scale. Unfortunately, due to microstructure changes, the experiments are limited in time. In order to avoid such limitation, oscillatory data were deduced from creep curves - without actually vibrating the clay dispersions - because a periodic experiment at frequency w is qualitatively equivalent to a creep test at time 1/w. That is, it was possible to complete the dynamic response in the low-frequency range using data obtained from the transient response in creep.

Cite this publication as follows:
Bekkour K, Kherfellah N: Linear Viscoelastic Behavior of Bentonite-Water Suspensions, Appl. Rheol. 12 (2002) 234.

Christophe Baravian, Audrey Lalante, Alan Parker
Vane rheometry with a large, finite gap

Appl. Rheol. 12:2 (2002) 81-87

The vane geometry with a large gap is used to determine the Newtonian, non-Newtonian and viscoelastic properties of complex fluids. We show that when this geometry is carefully characterized, it can be used for precise rheometry. A novel effective cylinder approximation is used to obtain the shear rate and shear stress factors. The effective radius is found to be close to the height of the triangle formed by joining the tips of adjacent blades. This result differs significantly from that of previous work. Flow visualization has been used to confirm that the stream lines Bend towards the centre between the blades. These factors can be used to determine the flow curves of non-Newtonian liquids, using Krieger.s power law expansion. The standard procedure for using the vane to determine the yield stress is also carefully investigated and alternative procedures are suggested.

Cite this publication as follows:
Baravian C, Lalante A, Parker A: Vane rheometry with a large, finite gap, Appl. Rheol. 12 (2002) 81.

K. Bekkour, H. Ern, O. Scrivener
Rheological Characterization of Bentonite Suspensions and Oil-In-Water Emulsions Loaded with Bentonite

Appl. Rheol. 11:4 (2001) 178-187

With stress controlled rheometer we investigate the behavior for different concentrations, of paraffin oil-inwater emulsions, Bentonite suspensions as well as charged Bentonite emulsions. We were particularly interested in how aging affects the rheological properties. Using a structural model, we correlate the macroscopic experimental results to the fluid microstructure characteristic parameters and we calculate the emulsions and suspensions mean characteristic unit size. The comparison of these mean particle diameters with those obtained by microscopy and light-scattering measurements confirms the soundness of such procedure to estimate the structural characteristics, the effective concentrations and the effective mean particle diameter of oil-in-water emulsions and Bentonite suspensions.

Cite this publication as follows:
Bekkour K, Ern H, Scrivener O: Rheological Characterization of Bentonite Suspensions and Oil-In-Water Emulsions Loaded with Bentonite, Appl. Rheol. 11 (2001) 178.

Alain Goubert, Jan Vermant, Paula Moldenaers, Axel Göttfert, Benoit Ernst
Comparison of measurement techniques for evaluating the pressure dependence of the viscosity

Appl. Rheol. 11:1 (2001) 26-37

The different methods that can be used for measuring the effect of a hydrostatic pressure on the viscosity of polymer melts are evaluated. A linear low-density polyethylene is chosen as test material, as it can be expected to have a small pressure dependency. Special attention is given to methods employing capillary rheometry, as these methods yield a range of shear rates and pressures that are typically encountered under polymer processing conditions. The accuracy of the different techniques is evaluated considering also the complexity of the experimental devices. First it is investigated to which extent standard capillary rheometry can be used to extract information about the pressure dependency of the viscosity. Secondly, it is shown how the accuracy can be greatly increased by the simple addition of a pressure chamber below the exit of the capillary, with a needle valve to regulate the back pressure. The results from this device are compared with those from a more robust method using a pressurized double piston rheometer and with literature data. The experimental values for the pressure coefficient of the viscosity will also be compared with those predicted from PVT data using Utracki's method.

Cite this publication as follows:
Goubert A, Vermant J, Moldenaers P, Gö, ttfert A, Ernst B: Comparison of measurement techniques for evaluating the pressure dependence of the viscosity, Appl. Rheol. 11 (2001) 26.

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