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A dominant extensional flow mixing device (Reactor/Elongational Flow MiXer; RMX) was used to prepare styrene-butadiene rubber (SBR)/silica nanocomposites with high physical performances. First, the processing parameters such as the temperature, number of mixing cycles, and sequenced mixing protocol have been optimized. Thereafter, the morphological structure of different compounds was probed using scanning and transmission electron microscopy. The prediction of the flow properties during processing of uncured materials were modeled using the dynamic and capillary rheometry. The thermo-mechanical sweep behavior of the as-prepared silica-filled SBR specimens was also investigated. By comparing with SBR/silica compounds prepared by the internal mixer, it was proven that elongational flow mixing process can not only reduce mixing energy consumption but also make the manufactured parts to have high state of dispersion, excellent viscoelastic properties, high extensional and yield stresses, and high elastic and rubbery moduli. This study highlights the potential of the elongational flow mixing as an innovative processing approach which is compatible with the industrial expectations for the fast manufacturing of high-performance silica and carbon black filled rubber compounds.

During processing and bubble growth processes, the melt viscosity changes with temperature, pressure, and blowing agent concentration. Therefore, measurement and prediction methods for viscosity characterization in terms of temperature, pressure, and blowing agent dependency are needed. This study demonstrates the applicability of in-line viscosity measurements during the foam injection molding process and a model for viscosity superposition and prediction. In the present study, polystyrene and a modified polylactide for foaming applications with nitrogen as blowing agent are investigated. By changing the injection speed, temperature, and blowing agent concentration, the process conditions are varied, and thus the resulting pressure drops within the in-line measurement die. The calculated shear rates and viscosities are shifted to a master curve by the application of superposition principles. The viscosity dependency on temperature is described by the Arrhenius equation, the pressure by the Barus equation, and for the blowing agent concentration, a novel Barus-like equation was derived and applied. The prediction of the master curve viscosity function was achieved by the power-law model in combination with the superposition principles and showed good agreement with the shifted in-line data. Finally, the in-line measurements and viscosity predictions are validated by comparing them to rotational and capillary rheometer measurements.

The rheology of cement paste under vibration follows the transformation from Bingham model to Hershel-Bulkly model to Power-Law model. Most of the existing research is obtained through a large number of experiments in the data fitting process, and cannot express the time-varying characteristics of viscosity. Furthermore, thixotropy of cement paste is based on static experiment and cannot be applied under vibration. In this paper a shear-vibration equivalent theory is proposed, which consider the effect of vibration is the same as the shear effect on the viscosity change of cement paste. Combining vibrational shear equivalent theory and HI theory, the rheological changes of cement paste under vibration are obtained through numerical simulation. This theory has been verified by a series of experiments with numerical simulations, and can be used to study the rheology of concrete under vibration.

This paper is devoted to the analysis of the rheological properties of polysulfone solutions in N-methylpyrrolidone, which are an intermediate stage in preparing lithium-ionic batteries. The viscosity of the solutions has been measured in wide ranges of shear rate, temperature, and concentration. The crucial role of water in measuring the rheological properties of solutions has been observed and avoided. The solutions under study are Newtonian liquids, but they demonstrate the elasticity at moderately high concentrations. The concentration dependence of viscosity is very strong, and the threshold was found where the viscosity grows unlimitedly due to the transition of the solution to the gel-like state. Temperature dependences of viscosity are described by the Arrhenius-type equation with the activation energy increasing along with an increase in the polymer concentration in solutions.

Predicting drilling fluids rheology is crucial to control/optimize the drilling process and the gas extraction from drilling fluids in logging systems. A Couette viscometer measured the apparent viscosity of a bentonite mud at various shear rates and temperatures. The bentonite mud behaved as a yield-pseudoplastic fluid, and a modified Herschel-Bulkley model predicted the shear rate and temperature effects upon the shear stress. A pipe viscometer was built to seek a correlation between the mud flow rate and the pressure drop and thereby determine refined Herschel-Bulkley parameters. Coupling a rheological model to a pipe viscometer enables the continuous acquisition of apparent viscosities of Newtonian or non-Newtonian fluids at a rig-site surface.

Rheological parameters being of great importance for sludge process management, they are increasingly studied. However, experimental procedures may strongly impact their determination. Sample volume, measuring device depth and roughness but also mechanical history, have to be well-controlled to ensure reproducible results. Indeed, even if shear history can be erased with a sufficient preshear for diluted sludge, this paper clearly established that no steady state can be achieved for concentrated sludge. The longer the shear history, the lower the rheological characteristics: Reproducible results are hardly obtained.

Xanthan gum is a biopolymer used in several different industries for a variety of applications. In the Petroleum Industry, xanthan gum has been applied in Enhanced Oil Recovery (EOR) methods for mobility control due to its Non-Newtonian rheological behavior, relative insensitivity to salinity and temperature compared to other conventional synthetic polymers, as well as its environmentally-friendly characteristics. As challenging reservoir conditions arise, candidate polymers should meet the screening factors for high salinity, high temperatures and heterogeneous reservoirs. This paper aims to evaluate the effects of temperature and monovalent salts on the rheological behavior of xanthan gum for Enhanced Oil Recovery purposes. We tested polymer solutions with brine salinities of 20,000/110,000/220,000 ppm of Sodium Chloride in a rheometer at temperatures of 23, 50, and 77°C. The results acquired showed that temperature plays a key role in viscosity and salinity protected the solution viscosity against negative thermal effects, unusually a turning point is observed where the increase in the monovalent salt content enhanced the polymeric solution viscosity. Such investigations coupled with a detailed discussion presented in the paper contribute to understand critical aspects of xanthan gum and its capability to provide basic requirements that fit desired screening factors for EOR.

The time dependent rheological behavior of a concentrated CaCO3 particle suspension is studied. The particles are suspended in a mixture of three industrial products: two resins, composed of styrene monomer, a styrene-butadiene-styrene block copolymer, and an unsaturated polyester oligomer, and one surfactant, acting as a dispersing agent for the particles. For the measurements, a MCR 301 rheometer from Anton Paar is used in the rotational mode, with a Couette geometry. An unusual behavior is observed, in which the low shear-rate viscosity of the suspension depends in a non-monotonous way on the shear rate applied during a previous shear history. The viscosity of the suspension at low shear rate depends both on the value of the prior shear rate, and the time during which it is applied. We found that the phenomenon is more pronounced when the particles volume fraction is increased. We propose an interpretation of the observed phenomenon in which links of different strengths can be formed between the particles and only the weakest links are destroyed by moderate shear rates.

Visco-plasticity characterized by yield stress is an important rheological property of composite propellant suspensions. The yield stress along with viscosity affects various unit operations in propellant processing as well as the quality of final product. The characterization of yield stress of propellant suspensions using direct measurement techniques, such as forced falling ball and slump test is described. The slump test is a simple and quick measurement tool with applicability at processing site whereas forced ball drop is useful for measurement of very high yield stress. The yield stress measurement of propellant suspension of four different compositions with varying particle size and volume fraction using above methods is reported and results are compared with vane geometry of rotational rheometer. Further, the yield stress behavior was studied for the propellant compositions with increasing solid loading. The dependence of yield stress of the studied propellant compositions on the reduced packing fraction f/fm of solids is established and expressed by a mathematical correlation. In addition, effect of vibration on yield stress was also studied using slump test.

Shortenings are examples of soft viscoelastic materials with important mechanical functions in baking applications. To fully understand their mechanical functionality, it is essential to correlate material microstructure with rheological behavior. We investigated commercial shortenings designed for various applications, with emphasis on those intended for use in laminated doughs. The microstructure of laminating shortenings was characterized by well-defined crystallites arranged in a layer-like fashion, whereas all-purpose and cake shortenings exhibited more distorted crystallites packed in a more heterogeneous manner. Oscillatory and creep shear behavior demonstrated that all shortenings acted as viscoelastic solids, but laminating shortenings had higher viscosities at “rest” in the linear regime. Recovery in the nonlinear regime showed that laminating shortenings had lower fractional recovery associated with pronounced plastic irreversible deformations. Extrusion tests also in dicated higher viscous dissipation for laminating shortenings. It is argued that the unique layered microstructure is partly responsible for the increased viscous and plastic flow of laminating shortenings, aspects that dictate the ability of these products to endure mechanically demanding processes without apparent catastrophic failure.

Graphene/polymer nanocomposites are the latest trends in materials science in the recent years, but the technology of their preparation plays a crucial role in obtaining reliable materials with repeatable and enhanced properties. Up to now, there are many unresolved problems in controlling the dispersion of the graphene filler and the corresponding influence on the properties of the final nanocomposite materials. In the present study, we apply rheological methods for controlling the quality of the graphene dispersion. We prepare and characterize epoxy/graphene nanodispersions with graphene contents varying from 0.05 to 1 wt% and explore the effect of different mixing regimes on the dynamic moduli and viscosity, thus assessing the degree of the dispersion. The rheological percolation threshold and relaxation time spectra are determined, in order to evaluate the internal structure of the nanodispersions. The relaxation spectrum is highly efficient to probe the effects of interfaces and interconnections on the relaxation dynamics of molecules in nanodispersions. Rheological results combined with transmission electron microscopy (TEM) observations confirm that the low frequency dynamic viscosity and moduli strongly increase, with increasing the degree of dispersion due to the exfoliation of graphene sheets. The rheological percolation threshold was found at very low concentration depending from the processing conditions. The weight of the relaxation spectra is strongly shifted to higher values, compared to the neat epoxy resin and this effect is much stronger around and above the rheological percolation threshold.

Limited information exists in literature regarding the effect of styrene-butadiene rubber (SBR) latexes on rheology and stability of lightweight self-consolidating concrete (LWSCC) intended for repair and precast works. Four series of LWSCC mixtures prepared with various lightweight aggregate (LWA) and SBR concentrations were considered in this project: The free water was adjusted to secure compressive strength of 40 ± 3.5 MPa. The slump flow remained fixed at 700 ± 25 mm, while unit weight varied from 1790 to 2280 kg/m3. Test results have shown that SBR additions lead to reduced concrete flow rate and passing ability. However, improved static stability such as bleeding, segregation, and floating of LWA. The rheological properties including yield stress and plastic viscosity increased for higher SBR additions, reflecting increased cohesiveness resulting from coalescence of water-soluble latexes and binding of cementitious matrix. Three categories of LWSCC classes specified in the European Guidelines were proposed with respect to rheological properties. A Ψ-factor was developed along with series of regression models to predict the combined effect of free water, viscosity-modifier, LWA, and SBR on rheology and stability of polymermodified LWSCC

This paper investigates the influence of limestone crushed sand dust (LCSD) on rheological properties of cement mortar based on crushed sand (CS) with different mineralogical nature (limestone and siliceous). A LCSD with a specific surface BET of 1470 m2/kg was used at different content replacement by mass of sand (0, 5, 10, 15, and 20 %). The water-cement ratio (W/C) and the cement content were kept constant for all mixes. The results show that the slump decreased as well as the flow time, the yield stress and the viscosity of mortar increased with the increase in LCSD content. Thus, the mortar based on limestone crushed sand (LS) has a low loss of rheological properties compared with a mortar based on siliceous crushed sand (SS). Yet, for 0 % of LCSD, it was found that the rheological properties are nearly equal for both CSs. The use of superplasticizer (Sp) significantly improves the workability and rheological properties. However, the rheological behavior of mortar has been strongly affected by increasing the volume concentration of CS whereas the effect of CS on fresh mortar presents significantly greater disadvantages compared with rolled sand (RS).

Linear low density polyethylene (LLDPE)/poly lactic acid (PLA) blends were prepared via different melt mixing methods. The effects of various blend compositions and two mixing methods on morphological and rheological behavior of the blends were studied. Scanning electron microscope (SEM) was used to investigate morphology behavior of the blends. The rheological studies illustrated that all samples presented shear thinning behavior and the PLA-rich blends exhibited a Newtonian region. It was found from the rheological measurements that the LLDPE/PLA (75/25 w/w) prepared by batch mixer exhibited higher values of storage modulus and complex viscosity, which is in agreement with the morphology results. In addition, using the different mixing methods, significant differences in the morphological results for the LLDPE/PLA (50/50 w/w) blend were observed. Finally, the results showed that the blends prepared by batch mixer exhibited better morphology, higher storage modulus, and complex viscosity.

This paper represents the rheology of screen printing pastes based on BaTiO3 nanopowder. It is found that the pastes are shear thickened fluids with subsequent shear thinning under high shear rates. Different concentrations of plasticizer in organic binder lead to various conformations of ethyl cellulose molecules that influence the type of adsorption between polymer molecules and nanoparticles. The flow loop shows intervals of shear rate corresponding to rheopexy, pseudoplasticity and thixo - tropy. The appearance of rheopexy indicates that the added amount of plasticizer may be insufficient to bind the majority of free functional groups of the polymer and the remaining groups are bound with BaTiO3 nanoparticles forming a strong structural network. But in the case of pseudoplastic structures, the polymer molecule exists in the conformation where almost all free functional groups are bound with the nanoparticle surfaces. The pseudoplastic properties of the system are caused by the structural polymer-polymer links. SEM and optical profilometry of the obtained films shows that plasticization lead to the formation of thin (less than 1 μm) smooth (Ra is equal to the size of individual BaTiO3 nanoparticle) prints

Natural rubber latex concentrate (NRLC) is an important material used in manufacturing dipped products, yet thorough analysis of their colloidal and rheological properties are still lacking in these areas. In this work, the colloidal and rheological behaviour of the NRLC was studied. The NRLC particle size was in the range of 0.3 to 2 μm with narrow particle size distribution. The response of NRLC to an applied deformation was assessed through rheological experiments which include dynamic oscillation and steady state measurements. A change from liquid-like to solid-like behavior was observed as the volume fraction of the NRLC was increased above 0.48. The plastic viscosity and yield stress of the NRLC increased with increasing volume fraction according to the Bingham equation. The maximum packing volume fraction of the NRLC was found to be 0.75 with a diffused double layer thickness of 14 nm at ϕ =0.61.

This study is a contribution to the understanding of how rheological properties of a fluid influences swallowing, especially people suffering from swallowing disorders (dysphagia). Our hypothesis was that fluid elasticity contributes to safe and pleasant swallowing. In the present study three food grade model fluids with specific rheological properties were developed and used: a Newtonian fluid with constant shear viscosity, an elastic Boger fluid with constant shear viscosity and a shear-thinning fluid which was elastic and had rate dependent shear viscosity. By comparing the swallowing of these model fluids the specific rheological effects could be distinguished. Sensory analysis of the perceived ease of swallowing was performed by a panel of healthy individuals, and by a group of dysphagic patients. The swallowing of the latter group was also characterized by videoflouroscopy and the transit times in the mouth and pharynx were determined. The hypothesis was confirmed by dysphagic patients who perceived swallowing easier for the elastic model fluids. A sensory panel of healthy individuals could not distinguish differences in swallowing, likely because their swallowing functions well and is an involuntary process. Quantitative videofluoroscopic measurements of swallowing transit times for the dysphagic patients suggested that fluid elasticity contributed to easy and safe swallowing, but the effect was not statistically significant due to the large spread of type of swallowing disorder.

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.

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.

The temperature has a significant influence on the character of flow of polymer suspensions filled with BaTiO3 nanoparticles, changing its viscosity and rheology. The viscous flow of suspensions at lower temperature from 5 to 25°C began at higher activation energy ΔEa1 and the systems were thixotropic, characterized with shear thickening at the initial stage of shearing after breaking of structural bonds between the polymer molecules. Herewith, increased shear stresses caused the enlargement of structural elements through additional flocculation by polymer bridging because of adsorption-desorption of EthCell molecule on BaTiO3 nanoparticles surface. At higher temperatures of 30 – 45 °C the viscous flow of suspensions began at the lower values of ΔEa2 indicating decreasing of leisure EthCell chains sufficient to form transient polymer network. Elevation of the temperature stipulated the predominant contribution of thermal Brownian motion to the character of flow. The mobility of macromolecules segments increased, BaTiO3 nanoparticles became to rotate, making impossible the additional structuring. Hence, the effective hydrodynamic radii of floccules remained constant. Moreover, being thixotropic at lower temperatures, the suspensions were characterized by the increasing of effective radii of floccules throughout the shear thickening region. In turn, rheopexic-thixotropic type of flow was characterized by the constant size of floccules along up-flow curves due to the dominant contribution of rotational Brownian motion. Thus, it is very important to control the temperature regime of processing method when exploitation of polymer suspensions.

A triple pressure-stage capillary rheometer was individually developed for providing an insight of pressure effect on polymeric melts viscosity during steady and continuous flow. Three capillary dies with identical/varied diameters and aspect ratio were assembled in series along the flow direction, relying on which the flow was divided into three zones with varied pressures under the same flow rate. Several polymeric melts, such as low density polyethylene (LDPE), polystyrene (PS), polypropylene (PP) as well as its nanocomposites of PP/CaCO3, PP/Mg(OH)2, and PP/halloysite nanotubes (PP/HNTs) were taken as the experimental samples. The principles for calculating the pressure sensitivity of shear viscosity in capillary flow were discussed, including methods based on constant shear rate (CSR), constant shear stress (CSS), and curve superposition (CSP). For the several polymer melts adopted in this work, a sequence of pressure dependence of viscosity was revealed as PS > PP > LDPE, which is typically acknowledged.

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.

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.

This study aims to prepare optimal feedstock for fabrication of Al/SiC nanocomposites by the low-pressure injection molding technique. For this purpose, micron-sized aluminum and nanosized SiC powders were mixed with different amounts of the binder consisting of 89 wt% paraffin wax, 9 wt% bees wax, and 2 wt% stearic acid. Rheometry analyses as well as the Weir model were utilized to determine the optimal feedstock with the desired rheological properties and high homogeneity. Considering powder to binder ratios, shear sensitivity, flow activation energy, and homogeneity within the rheometry analyses, the feedstock of 78 wt% powder loading is selected as the optimal sample for injection molding. Investigation of optimal feedstock by the scanning electron microscopy technique also verified the high homogeneity of this feedstock. In addition, it was observed that all of the feedstocks had thixotrop behavior.

As a fundamental rheological property, shear yield stress is used to assess the flowability of suspensions. Slump test is a cheap and quick experiment which is commonly used to estimate shear yield stress on-site. It has been generally believed that, cylinder height to diameter ratio and lifting velocity has no effect on the slump test results. In this work, the sensitivity of the slump test to the height to diameter ratio and lifting velocity of cylinder was investigated. Projections on the top surface of suspension column after the slump test were also analyzed. Results indicated that, the effect of cylinder height to diameter ratio is negligible in the low range of shear yield stress, while it is remarkable in the high range. It was deduced that, using a cylinder with dimension ratio in the range of 0.83 to 1.15 is more reliable. Furthermore, it is shown that the lifting velocity of cylinder has a significant effect on the results. A high lifting velocity could introduce a great error in estimation particularly in a large height to diameter ratio.

The core of activated sludge monitoring lies in the biological analyses. Anyway, the knowledge of sludge physical characteristics is crucial for a proper management of WWTPs (Waste Water Treatment Plants). One of these physical features is viscosity that, notwithstanding its valuable role has not yet become a routine analysis. This study examined the evolution of rheological properties of two sludges alongside the “purification route” (from the biological reactor up to the sludge treatments). It could been shown that sludges behaved like non-Newtonian fluids and dry solids content strongly affected viscosity values, which reached relatively high values. Microscopic observation of flocs was carried out. Both the sludges revealed similar features, in particular an over-proliferation of filamentous bacteria. This work showed how rheological measurements can be a tool to obtain information on microbiological composition of activated sludge and how it could be related to settleability properties.

The rheological behavior of oilfield surfactants (Aromox® APA-T and APA-TW) at various concentrations was studied using steady shear and dynamic testing. The results showed that the solutions exhibit non-Newtonian behavior at all concentrations, with their rheological character influenced by the temperature and ionic content of the base fluid. Temperature was observed to have a significant effect on viscosity and dynamic data. The apparent viscosity at different temperatures could be reduced to a single master curve using horizontal and vertical shift factors. However, satisfactory scaling could not be attained for the dynamic or viscoelastic data. Molecular scaling using characteristic time for data at different concentrations proved unsuccessful due to the strong non-Newtonian character of surfactant solutions. Scaling relations between rheological parameters and concentration indicated the presence of long micelles in APA-T solutions. APA-TW solutions, on the other hand, contained branched micelles.

Fruit juices concentrated by osmotic distillation are characterized by higher organoleptic and sensorial properties than those of juices concentrated by thermal evaporation as confirmed by several research studies. On the other hand, no literature is readily available about the rheological characterization of juices concentrated by osmotic distillation. This work aimed at investigate the rheological behavior of the concentrated blood orange juice prepared from the clarified juice by using thermal evaporation and osmotic distillation processes as a function of solids concentration in the range 115 - 614 g/kg of total soluble solids (TSS) within a range of 20 - 70 °C. The effect of the temperature and concentration on the juice viscosity was studied. Arrhenius- type correlation equations for viscosity were used to represent the temperature dependence of viscosity. Values of the Arrhenius equation parameters (flow activation energy) were calculated for the measured viscosities of juices as a function of concentration. Results indicated no significant differences in the rheological behavior for orange juices concentrated with both methods. The juices exhibited a Newtonian behavior regardless of the concentration method.

Electrorheological measurements represent a key approach in characterizing the efficiency of electrorheological fluids. The rotational rheometers, the Physica MCR 501 (Anton Paar) equipped with an electrorheological cell and the Bohlin Gemini CVOR 150 (Malvern Instruments) modified for electrorheological experiments generate an electric field in two completely different ways. Each of the two generations has a specific influence on electrorheological measurements. The experimental data were obtained and compared for a suspension of polyaniline powders mixed (10 wt%) in silicone oil. For a concentric-cylinders arrangement, it was shown that the data are fully comparable for both rheometers. However, for a parallel-plate arrangement, the data using the Physica MCR 501 provide higher values in comparison with both the corresponding plate-plate data obtained with the Bohlin Gemini CVOR 150 and with the mutually comparable concentric cylinders data.

Starch-based adhesives play a relevant role in paperboard production and are becoming more and more interesting, for different uses, because they are based on renewable biopolymers. Starch modifications or additive addition are becoming frequent to obtain the macroscopic properties desired for specific uses. In this paper the effects of the addition of four different tannins on a typical adhesive, adopted for corrugated paperboard production, were investigated by using fundamental rheological techniques, both in dynamic and steady conditions. It was found that tannins increase the onset of starch gelatinisation, estimated as the knee point of the storage modulus in a dynamic temperature ramp test, and decrease the steady shear viscosity. This is due to the interactions between tannin and starch that affect the gelatinisation and retrogradation reactions weakening the starch network. Even though a partial reinforcement effect was also observed, owing to the polymeric nature of tannin components, a lower consistency, with respect to the neat adhesive, was found for all modified samples. Tannin has shown itself able to modify technological properties such as gelatinization temperature and viscosity, since the specific results are determined by the nature and amount of tannin; therefore it could be used to adapt adhesive characteristics to specific applications, potentially improving starch-based adhesive competitiveness with respect to different adhesives.

Incorporation of liposome into gel is the most common approach for the preparation of topical and transdermal liposomal formulation, due to the ability of liposome to improve the drug deposition and permeation rate within the skin. In this study, the liposomal gel consisted of iota-carrageenan, carboxymethyl cellulose, and chitosan-coated-oleic acid liposome were prepared. The effect of liposomes on the rheological properties of the iota-carrageenan-carboxymethyl cellulose mix gel was evaluated. The rheological result indicated that the presence of the chitosan-coated-oleic acid liposomes in the gel had modified the viscoelastic and flow characteristics of the gel. The input energy from the oscillatory test could be stored more effectively in the elastic component of the liposomal gels, as compared to the original gel itself. This result showed that the liposomal gels exhibited greater elasticity and were more solid-like when compared with the original gel system. The complex viscosity of the liposomal gels was slightly higher than the original gel. The complex viscosity of the liposomal gels was also found to decrease with increasing frequency, indicating the shear thinning behavior of the liposomal gels. The lower Power Law Index PLI of the liposomal gels indicated a greater shear thinning behavior and better spreadability.

Rheological and electrical properties of polymeric nanoparticle solutions and their influence on the rheological and electrical properties of red blood cell (RBC) suspensions have been studied. Poly(acrylic acid) macromolecules of different architecture and molecular weight were used: (i) a new core-shell type star polymer whose interior forms hyperbranched polystyrene bearing arms of poly(acrylic acid) with molecular weight Mn = 56 920 Da and (ii) linear polyacrylic chains with average molecular weights Mn= 6000, 20000, and 225000 Da. The polymers dissolved in physiological solution with weight concentrations 1 mg/ml and 0.2 mg/ml were used for the experiments. Under physiological conditions the star-shaped macromolecules present spherical nanoparticles while the linear poly(acrylic acid)s adopt an extended chain conformation close to rod-like particles. The apparent viscosity of the nanoparticle solutions and RBC suspensions in the presence and absence (the control) of nanoparticles were measured using a rotational viscometer Contraves Low Shear 30 (LS 30) at a steady flow at shear rates from 0.0237 to 94.5 s-1and temperature 37º C. A method, based on the measurement of dielectric properties of dispersed systems in Couette viscometric blood flow was applied. A concurrent measurement system and data acquisition system implied into the Contraves LS 30 were used to quantify the electrical conductivity. The main advantage of this technique is that blood is subjected to a uniform shearing field in a Couette rheometric cell as well as the information about the mechanical and electrical properties of the fluid is obtained in parallel. The results show that rheological and electrical properties of the nanoparticle solutions and RBC suspensions, namely their electrical conductivity and apparent viscosity, are dependent on the shear rates, shape, concentration and molecular weight of the polymers.

This paper presents the development of a vane rheometer to estimate mortar plastic viscosity and yield stress. The rheological parameters were developed from measurements using a procedure to convert the vane torque and rotational velocity data into shear stress versus shear rate relationships. The used procedure considered the locally sheared material as a Bingham fluid and computed the characteristic shear rate from Couette analogy. The apparatus was tested with three experimental programs in which many rheological parameters of mortar compositions were calculated. The obtained results validated the rheometer test procedure and confirmed that the test results are reproducible.

We present a study of the structural and thermomechanical properties of lyotropic phase in the quasi ternary system made of Cetylpyridinium chloride (CPCl)/hexanol/salt water (0.9 % by mass) with and without cobalt microparticles. Phase transition temperatures of the structural sequence isotropic L 1/nematic calamitic Nc,/hexagonal H have been determined by differential scanning microcalorimetry. Temperature induced developable domains in hexagonal phase H and disclinations in calamitic nematic phase Nc were observed in crossed polar optical microscopy in confined geometry. A rheological study of calamitic nematic phase Nc highlighted structuring effect of cobalt microparticles from a concentration of 2 % to be demonstrated by an increase in viscosity and viscoelastic moduli. This could be explained by a stabilization of disclinations.

The effect of viscoelasticity on multilayer polymer extrusion is discussed. In these coextrusion processes predetermined patterns are created with a remarkable breadth of complexity even in geometrically simple dies via elastic rearrangements caused by the second-normal stress differences. A computational method is offered, based on the mapping method, which quantitatively describes the flow-induced patterns. Besides that the results are esthetically beautiful, they are also relevant for practice, since process and die design optimization is now possible. Not only to minimize interface distortion, but potentially also to deliberately create new processes and products based on this flow-induced patterning of polymers.

Blends of 30-phr silica filled elastomeric chlorinated polyethylene (CPE) and natural rubber (NR) at the blend composition ratio of 80/20 CPE/NR were prepared with various mixing time from 120 to 600 s. Viscoelastic behaviours of cured and uncured blends were determined using two rheometers with different shear modes, i.e., the oscillatory rheometer (Rubber Process Analyser, RPA2000) and the rate-controlled capillary rheometer (Goettfert Rheotester 2000). Results obtained reveal that the viscoelastic behaviour of blends is influenced by the formation of silica transient network, particularly in cured blends. Mixing time affects viscoelastic properties of vulcanised blends to some extent which is due probably to the high extent of thermal degradation, but plays no significant role in viscoelastic properties of unvulcanised blends. The superimposition of oscillatory and steady shear results is possible when the elastic component is eliminated from the results.

The rheological behaviour of PVC plastisols composed of a blend of suspension and micro-suspension resins in different proportions was investigated. The present work was mainly focused on the variation of the zero shear viscosity versus the concentration of the extender resin. Hence, the packing fraction Fm was evaluated using the Krieger-Dougherty equation. These experiments confirmed the major influence of particle size distribution concerning the decrease of viscosity for concentrated suspensions. In addition, a model based on the porosity model developed by Ouchiyama et al. (Ouchiyama N, Tanaka T: Porosity estimation for random packings of spherical particle”, Ind. Eng. Chem. Fundam. 23 (1984) 490-493) to predict the packing fraction in the case of multimodal lattices was successfully applied to our PVC plastisols formulations.

The purpose of this paper was to re-evaluate the novel rheological method of Crosby et al. [J. Rheol. 46 (2002) 401] to characterise long chain branching (LCB) in polyethylenes (PE) using the rheology of concentrated solutions. The feasibility of this dilution method centred on knowing the class of branched material and the molecular tube theory-based technique for the determination of two topological parameters (n, bU), where n is the number of entanglements between branch points while bU is the probability of meeting a branch point when tracing along the molecule from a random monomer against the direction of polymerisation. This paper proposes new possible approaches to calculate the two topological parameters (n, bU) set for metallocene polyethylenes (mPE), and their ambiguity discussed, as the results are dependent on the approach taken, though the previous authors mentioned only one. In addition, their approach requires an input value of LCB/1000C obtained from the standard analytical solution (SEC-V or SEC-LALLS) methods, hence, until now, without proper demonstration of the potential advantage of the dilution rheology method for LCB characterisation, as the main premise of their published article was to characterise the degree of LCB via rheological measurements without recourse to other methods of LCB characterisation.

Rheological properties of food fluids are useful for quality control, texture evaluation, and food structure determination. The rheological behavior is dependent on the size, form and concentration of solids in suspension and the system structure. Star fruit (Averrhoa carambola L.) pulp was obtained from the crude fruit and treated enzymatically, pasteurized and homogenized at 11000 rpm for 2 min and 22000 rpm for 5 min. The pulp presented Newtonian characteristics with R2 values greater than 0.98. Enzymatic treatment under 55˚C for 1 h reduced the crude pulp viscosity from 1.84 to 1.22 mPa·s. Pasteurization under 100˚C for 10 min increased the viscosity at around 26% in relation to the crude pulp, resulting in a turbid and homogeneous product. To evaluate the influence of the insoluble solids, filtration or concentration to 50% from the initial volume were carried out using laboratory procedures. Filtration of the pasteurized pulp promoted a viscosity decrease of 60% while concentration increased the viscosity from 2.28 to 7.98 mPa·s.

The behaviour of reverse micellar solution and reverse hexagonal and lamellar liquid crystal phases in pluronic L64/water/p-xylene ternary system was investigated by rheological techniques. Samples with an increasing water content along the amphiphilic copolymer-lean side of the ternary phase diagram were analysed at different temperatures and a different behaviour was evidenced by both dynamic and steady tests for each considered phase, depending on the morphology of structure (micellar, lamellar, hexagonal phases). It was observed that the reverse micelles size increases with increasing water concentration and decreases with increasing temperature, without any phase transition. On the contrary the normal micelles become anisometric on temperature, showing a transition to a liquid crystalline phase. The observed mechanical spectra of the liquid crystalline phases are typical of hexagonal and lamellar phases according to the literature [1, 2]. A phase transition with temperature was found for both liquid crystalline phase (lamellar and hexagonal) by rheological tests and was confirmed by ocular inspection.

The term |G*|/(1-(1/tanδ sinδ)) has been suggested as one of the best candidates for the replacement of the Super-pave specification parameter |G*|/sinδ, which has been found to be inadequate in rating polymer-modified binders for high temperature performance grading. This refinement of the Superpave specification parameter evolved through a theoretical derivation based on fundamental concepts. It was shown to be more sensitive to the variations in the phase angle δ than the original Superpave specification parameter. It thus described the unrecovered strain in the asphalt binders more accurately, and hence related to actual field performance data. This article provides a comprehensive treatise of the parameter |G*|/(1-(1/tanδ sinδ)) giving details of its derivation, salient features that are attributed to its success, comparison with actual field performance data for validation and a one-on-one comparison with the existing parameter |G*|/sinδ. It is shown that for all available field data, the parameter |G*|/(1-(1/tanδ sinδ)) does a better job in correlating with the rutting behavior than the parameter |G*|/sinδ for unmodified as well as modified asphalts. Since it is obtained in the same manner as the parameter |G*|/sinδ through the determination of |G*| and δ from a stress-controlled or strain-controlled dynamic shear rheometer, it means that no retraining of technicians and staff is required and implementation for the use of this parameter is immediate, thereby saving enormous amount of time and money. This parameter has the further advantage of being in a form easily adaptable to modeling, and thereby directly applicable for pavement design purposes.

The determination of flow curves and the apparent viscosity curves at 28°C of creams containing human leukocyte alpha interferon as active principle is presented in this paper. These creams are used for the treatment of papiloma virus and herpes simplex. It is demonstrated that their behaviour corresponds to a thixotropic fluid. The Herschel-Bulkley model parameters are presented and discussed as an indicator of the grade of thixotropy. Apparent viscosity plotted as a function of shear rate and storage time allows defining the time period in which the samples recover their initial structure. Additionally it was concluded that for determining the quality of the product, the acceptance limit of the viscosity should be specified for a given shear rate.

The effects of composition and resulting morphology on the rheology of thermoplastics filled with different talc platelets were studied in the 0-22% range of volume fraction, Φ. The sufficiently filled polymer composites exhibit a rheological behavior which significantly differs from the pure polymers used in this work, a linear low density polyethylene, a low density polyethylene and a polyamide 12. The changes in the rheological behavior are influenced by the size, the concentration and the surface treatment of plate-like talc particles. They also depend on the chemical nature and viscous and elastic characteristics of the polymer matrix. In particular, the effect of platelet orientation on the viscoelastic properties of reinforced composites was pointed out. For sufficiently filled systems, a low frequency response indicative of a pseudo solid-like behavior is obtained only during the first frequency sweep. In fact, the low frequency storage modulus, G’, is constant. With repeated frequency sweeps, more platelets were aligned in the flow direction, thus the low frequency storage modulus gradually decreases and becomes dependent on frequency, ω. The low frequency complex viscosity η* also progressively decreases with repeated frequency sweeps. In addition, for these systems, the low shear viscosity η build up in an unbounded manner because of the existence of particle-particle interactions. There are stresses below which there is no flow indicating the existence of yield values. Steady shear elastic properties are also studied, especially in the case of systems showing an apparent yield stress.

Previous studies involving rheological measurement of semi-solid foods have reported a large amount of data variability, but have focused little on understanding the cause of such variability. This project examined whether differences in normal force have an effect on the variability of rheological measurements. Experimental methods focused on error introduced during sample loading; specifically whether normal force application during loading influenced the storage (G’) and loss (G”) moduli of semi-solid and liquid foods. Samples were loaded to 5 or 20 N between the parallel plates of a TA-1000N rheometer and tested immediately. For all semi-solid products tested, normal force application during sample loading did significantly affect oscillatory parameters, with G’ and G” measurements increasing up to 50 % with greater normal force. However, loading normal force did not significantly influence the parameters measured for the liquid sample. This suggests that differences in normal force during loading could be a significant source of data variability during rheological measurement of semi-solid products.

New compounds, called inhibitors, provide anti-yellowing effect for mechanical pulps and papers, when added to the coating formulation. The rheology of coating mixtures, which contain clay, ground calcium carbonate, starch, latex, inhibitors and other minor additives, affects to a certain extent the final quality of the coated paper. The purpose of this work is to investigate the effect of the total weight charge of inhibitors, when present between coating color ingredients, on the thixotropy and visco-elasticity of the mixture and other rheological properties. We also study the degree of interaction between inhibitor and coating ingredients using Transmission Electron Microscope (TEM) and water retention measurements.