Viscosity Of Aqueous Solutions Research Articles

Volumetric and viscometric studies of molecular interactions in systems containing tartaric acid in water/aqueous-L-arginine solutions at 303.15 K

The densities and viscosities of aqueous solutions containing tartaric acid and L-Arginine were measured at 303.15 K. The densities were used to calculate the apparent molar volume of tartaric acid in water and aqueous-L-Arginine solutions. The apparent molar volumes were fitted to the linear fit Masson relation and relative viscosities were fitted to the Jones-Dole equation. From Masson relation, the partial molar volumes were determined and from Jones-Dole equation, the viscosity B-coefficients were determined. Strong solute-solvent interactions in aqueous solutions of tartaric acid solutions were observed from the transfer volumes and viscosity B-coefficient. The pH of these systems was also measured to understand the transfer of a proton from solute to cosolute. A weakening of solute-solvent interactions and loosening of the hydration sphere of tartaric acid on the addition of cosolute has been observed.

Dynamics of formation of poly(vinyl alcohol) filaments with an energetically efficient micro-mixing mechanism

We present a pneumatic approach for massive production of poly(vinyl alcohol) (PVA) filaments based on a mixing mechanism at the micrometer scale using so-called Flow Blurring (FB) atomizers. This micro-mixing is triggered by a turbulent, bubbly motion generated by implosion of a gas current into a liquid feeding tube. The energy of the gas, the liquid viscosity, and the geometry of the atomizer play an active role in the size and shape of the ejecta. The shear viscosity of aqueous solutions of PVA of various molecular weights was investigated to assess their rheological nature using a dimensionless parameter based on the solutions’ concentration and the polymer’s molecular weight and its entanglement molecular weight. The solutions exhibited a shear thinning behavior at low shear rates and a Newtonian behavior at moderate rates. PVA solution with viscosity above the threshold value is prone to forming filaments during atomization with FB devices. Analyses of the dynamics of the atomization revealed two main types of ejections depending on the liquid flow rate and viscosity: either a bundle of filaments formed from within the atomizer or a more continuous single structure developed in the vicinity of the atomizer exit. Furthermore, based on Kolmogorov’s energy cascade, we propose a scaling law for the mean filament diameter as a function of liquid properties, atomizer geometry, and imposed pressure. The present work may have significant implications in the large-scale processing of liquids leading to useful materials.

Prediction of the properties of food biopolymer gels at the molecular-atomic level

The analysis of the main regularities, conditions and factors influencing the mechanism of structural changes in food biopolymer molecules during gelation using the laws of thermodynamics is carried out. A computational method for predicting the properties of gel-like food systems is considered. It makes it possible to establish the dependence of the characteristic viscosity of aqueous solutions of hydrocolloids and the hydrodynamic radius of biopolymer molecules on the charge of its molecular structures and the pH of the active acidity of the medium. On the example of gelatin, calculations are presented and it is shown that, in comparison with a neutral medium, the hydrodynamic radius of protein molecules increases approximately to (120–123) % both at high and low pH values, which makes it possible to predict the water-binding capacity of protein molecules and determine the optimal modes of technological processes.

Viscosity of Aqueous Polysaccharide Solutions and Selected Homogeneous Binary Mixtures

The viscosity (η) of dextran (Dex), methyl cellulose (MC), hydroxypropylmethyl cellulose (HPMC), κ-carrageenan (KC), alginate (Alg), and carboxymethyl cellulose (CMC) was measured as a function of the shear rate (γ̇) over a broad range of concentrations both in salt-free water and in 0.1 M NaCl. The concentration (C) dependence of the Newtonian viscosity (η0) was found to be universal for neutral polysaccharides and anionic polysaccharides in 0.1 M NaCl when C was multiplied with the intrinsic viscosity. The dependence was compared with theoretical predictions assuming dominant hydrodynamic or dominant topological interactions. The effect of electrostatic interactions was observed for anionic polysaccharides in salt-free water but not at higher concentrations. Master curves of the shear thinning behavior at different concentrations were obtained when η/η0 was plotted versus τ. γ̇, with τ being a concentration-dependent time that characterizes the onset of shear thinning. Binary mixtures of two neutral polysaccharides (MC and HPMC), two anionic polysaccharides (Alg and CMC), and a neutral (Dex) and anionic polysaccharide (KC) were investigated as a function of the composition and the total polysaccharide concentration. The behavior of the first two mixtures was similar to that of a single polysaccharide with an intermediate intrinsic viscosity. Significant synergy was observed for the third type of mixtures in salt-free water demonstrating the important effect of electrostatic interactions between charged polysaccharides at low concentrations even in concentrated solutions of neutral polysaccharides.

Impact of polymer type, ASD loading and polymer-drug ratio on ASD tablet disintegration and drug release

Amorphous solid dispersion (ASD) has become an attractive strategy to enhance solubility and bioavailability of poorly water-soluble drugs. To facilitate oral administration, ASDs are commonly incorporated into tablets. Disintegration and drug release from ASD tablets are thus critical for achieving the inherent solubility advantage of amorphous drugs. In this work, the impact of polymer type, ASD loading in tablet and polymer-drug ratio in ASD on disintegration and drug release of ASD tablets was systematically studied. Two hydrophilic polymers PVPVA and HPMC and one relatively hydrophobic polymer HPMCAS were evaluated. Dissolution testing was performed, and disintegration time was recorded during dissolution testing. As ASD loading increased, tablet disintegration time increased for all three polymer-based ASD tablets, and this effect was more pronounced for hydrophilic polymer-based ASD tablets. As polymer-drug ratio increased, tablet disintegration time increased for hydrophilic polymer-based ASD tablets, however, it remained short and largely unchanged for HPMCAS-based ASD tablets. Consequently, at high ASD loadings or high polymer-drug ratios, HPMCAS-based ASD tablets showed faster drug release than PVPVA- or HPMC-based ASD tablets. These results were attributed to the differences between polymer hydrophilicities and viscosities of polymer aqueous solutions. This work is valuable for understanding the disintegration and drug release of ASD tablets and provides insight to ASD composition selection from downstream tablet formulation perspective.

Stability, flocculation, and rheological behavior of silica suspension-augmented polyacrylamide and the possibility to improve polymer flooding functionality

In this study, the characterization and rheological behavior of silica suspensions in aqueous/polymeric media are investigated. The variation of silica nanoparticles size and concentration, polymer molecular weight and concentration, pH, valency, and concentration of electrolytes are considered for this purpose. The findings show that bridging flocculation of dispersed silica nanoparticle-augmented polymer solution increases with nanoparticle concentration, nanoparticle diameter, the charge of electrolyte, and electrolyte concentration. In contrast, it decreases with an increase in pH and polymer concentration. Also, the intrinsic shear viscosity of aqueous polymer solution increases with molecular weight, unlike the behavior of polymer solution in the presence of silica nanoparticles. The shear viscosity and the rate of bridging flocculation of the silica nanoparticle-augmented polymer solution primarily increase until it reaches a maximum and finally decreases with further increasing polymer molecular weight. In polymer high molecular weight and high concentration, the repulsion due to steric stabilization overcomes the interaction between two adsorbed polymer chains resulting in a stable form of suspension. By utilizing the proper conditions, core flooding experiments are designed and implemented to enhance the hydrolyzed polyacrylamide polymer flooding efficiency. Around 20–52% higher recovery was obtained for the silica nanoparticle-augmented polymer solutions with respect to the polymer flooding.

Modeling of the density, viscosity and electrical conductivity of aqueous solutions saturated in boric acid in presence of lithium sulfate or sodium sulfate at 293.15 to 313.15 K

The modeling of the density, viscosity and electrical conductivity of aqueous solutions saturated with boric acid, in the presence of sodium sulfate or lithium sulfate, are presented. The salt concentrations range studied were from (0 to 3.3242) mol·kg−1 for sodium sulfate and from (0 to 2.9336) mol·kg−1 for lithium sulfate at temperatures from (293.15 to 313.15) K and at 1 atm pressure. A model for the density was derived using the Pitzer model. The Eyring's absolute rate theory and the Pitzer model were combined to represent the viscosity. The Casteel-Amis equation was modified to describe the electrical conductivity with temperature and boric acid effects where necessary. The results showed that the models successfully represented the properties studied and are robust for estimation purposes within and beyond the experimental range studied. Also, it was found that short range interactions of boric acid, sulfate, sodium and lithium ions with water molecules are relevant to determine the volumetric and transport properties of these solutions and that the electrical conductivity is determined by charged species (Na+, SO42−, NaSO4−, HSO4− and Li+, SO42−, LiSO4−) and the solution viscosity; that is mainly influenced by these salts concentrations, boric acid solubility behavior with these salts and temperature. This is valuable information to improve the processes of boric acid production.

Prediction of viscosity and surface tension properties of aqueous solution of ionic liquids EMIES

1-Ethyl-3-methylimidazolium ethyl sulfate (EMIES) was synthesized by using N-methylimidazole and diethyl sulfate as raw materials, the density, viscosity and surface tension of aqueous EMIES with various concentrations were measured in the temperature range from 288.15 to 328.15 K. According to the Jones-Dole empirical equation, the viscosity B-coefficients were calculated. Using the empirical equation of the relationship between Δμ2≠0 and T, the activation entropy (ΔS2≠0) and activation enthalpy (ΔH2≠0) were further obtained, the viscosity values of aqueous EMIES were predicted by using the Eyring semiempirical equation, which were highly consistent with experimental values of the viscosity. Furthermore, on the basis of the traditional Eӧtvӧs empirical equation, the new Eӧtvӧs equation was further derived by using the linear relationship between the molar surface Gibbs energy (gs) and temperature, each parameter has the definite physical meaning and a new unit of energy in new Eӧtvӧs equation. The predicted values of the surface tension of aqueous EMIES were obtained by the definition of the molar surface Gibbs energy, which were highly consistent with the experimental values of the surface tension.

Experimental measurements and modelling of viscosity and density of calcium and potassium chlorides ternary solutions

Measured viscosity and density data for ternary aqueous solutions of CaCl2 and KCl are presented at temperatures between 293 and 323 K with 5 K increment. A modified Jones–Dole was introduced by adding extra terms and proved to be suitable for modelling of the viscosity data. Goldsack and Franchetto, Hu and Exponential models are used to correlate the viscosity data, too. Al models are correlated as a function of temperature and concentration. All models had successfully predicted the viscosity with high precision reaching a maximum average absolute deviation (AAD) of less than 2.3%. The modified Jones–Dole showed the best results among other models. Viscosity of the ternary solution is higher than the viscosity of water by about 15% at low concentrations and reaches about 270% at the highest concentrations. The amount of CaCl2 has more significant effect on the ternary mixture viscosity compared to KCl. This has created difficulty in measuring the viscosity and consequently the challenge in finding the different models parameters. Ternary solution densities were successfully correlate with Kumar’s model with AAD of less than 0.4%. Comparison of the ternary solution density and viscosity with the few available data literature showed a good agreement.

Influence of the composition of cement systems on the activity of modifying additives

Modifiers of cement systems with different compositions of functional groups of polymers were studied: carboxymethylcellulose, methylcellulose, polyvinyl alcohol, polyacrylamide. The results of studies of the influence of active ions on the viscosity of aqueous solutions of water-soluble polymers using viscometry methods are presented. The influence of the type and composition of functional groups of polymer additives on the resistance to calcium, sodium and potassium ions is analyzed. It is shown that in the presence of calcium, sodium or potassium ions in the liquid phase of cement solutions, it is possible to reduce the effectiveness of polymers as stabilizers of binding systems. The most resistant to electrolytes are polymers with dominated hydroxyl groups. The composition of functional groups of water-soluble polymers and the possibility of their interaction with various ions contained in cement, aggregate, filler, in the closing water, in the composition of soils have a decisive influence on the compatibility of the polymer and the binder, the properties of cement-polymer compositions. The principles of regulating the rheological and technological properties of cement-polymer compositions, deformations of dispersed systems by selecting the rational composition of the dispersed mixture, mineral and chemical additives are given. The regularities of compatibility of components of cement systems, mineral and chemical additives in order to increase the adhesion and strength characteristics of materials based on them in the development of compositions of masonry solutions, injection and other compositions for chemical fixing of soils, in individual housing construction, in order to carry out repair and restoration work to strengthen soil bases and stone structures are presented.

Development of dark-field dynamic light scattering microscopy and its application: Tracking dynamics of particles in condensed slurries spreading on planar/nonplanar substrates

HypothesisWhile dynamics of particles in slurries is usually evaluated by dynamic light scattering measurements, this technique had only been applicable to particles in the bulk slurries. Because this limitation is mainly owing to strong reflection of light, the dynamics of particles in slurries spreading/drying on solid substrates is to be obtained by spatially separating the reflection light from scattering (signal) light. This may allow us to track the particles in practical samples such as cosmetics or inks spreading on solid surfaces. ExperimentWe developed novel “dark-field dynamic light scattering microscopy”. The system was evaluated with test samples of polystyrene beads dispersed in several viscosities of bulk glycerol aqueous solutions. This setup was then applied to slurries spreading/drying on planar and nonplanar substrates. FindingsThe results for planar surface indicate that origin of coffee-ring are the particles flowing into the edge of the droplet just before complete drying. On a skin-modelled nonplanar substrate, the slurry on bumps was found to maintain semi-dry condition longer than that at dents. This suggests that the dispersive medium was supplied to bumps from dents. This unique flow was explained as effective drying from the bumps increased surface tension at the bumps to pull up the liquid around.

Thermo-associating polymers based on cross-linked 2-acrylamido-methylpropane sulfonic acid, part B: Effect of co-solutes on solution behavior

Thermo-thickening copolymers have gained prominence in technological advancements due to its attractive properties and great potential to overcome the deficiency of viscosity of conventional copolymer upon increasing temperature and salinity. The work in this paper was devoted to examine the aqueous solution viscosity behavior of a new class thermo-thickening copolymer, poly(sodium 2-acrylamido-2-methylpropanesulfonic acid-co-N,N’-methylenebisacrylamide)-g-poly(acrylamide-co-N, N’-diethylacrylamide) denoted as CGBA in the presence of co-solutes. CGBA, which were reported in our previous work manifested notable viscosity enhancement macroscopically above the threshold temperature. However, the effect of small molecules on thermo-associative behavior was still unsettled. Based on structure/properties dependence of CGBA, this work aimed to explore the effect of small molecules and the role of molecular structure on aqueous solution viscosity behavior. The contributions of various added co-solutes such as anionic surfactant, acidic specie, monovalent and divalent salts were considered. For that purpose, three copolymers having distinctive composition of side-arms and length of side-arms were selected and their thermo-associating behaviors were followed by viscosity measurement. Results from rheological tests showed that these co-solutes induced notable modifications in the characteristic of thermo-thickening behavior. For all the co-solutes used, it was observed a strong dependence between the side-arms/water/co-solutes ternary system and the macroscopic property upon heating. Spectrofluorimetric and environmental scanning electron microscope (ESEM) tests were used to gain a deeper insight into the precise mechanism of phase transition process. Results from spectrofluorimetric experiment indicated that, only when the fraction of DEAm in CGBA was higher enough, it would appear strong abrupt macroscopic property above the threshold temperature, which could delay the offset of hydrophobic association phenomenon in the presence of anionic surfactant. Similar effect was also observed in the presence of added acidic specie. Conversely, the addition of monovalent and divalent salts showed dissimilar effects. ESEM revealed that, in comparison with monovalent salt, divalent salt favored the formation of larger and more condensed CGBA skeleton above the threshold temperature which led to an improved macroscopic response. This work demonstrates for the first time the micro-structure changes of copolymer, which was probably the main reason for the changes in magnitude of thermo-thickening effect in different divalent salt dosages.

Viscosity of potassium carbonate solutions promoted by new amines

"The objective of this paper is presenting the experimental results of the viscosity measuring for the aqueous solutions of potassium carbonate with new amines as promoters. In this work, ethylenediamine (EDA) and triethylenetetramine (TETA) were chosen as rate promoter candidates. The viscosity of the ternary aqueous solutions (K2CO3-Amine-H2O) has been measured for a blending 25 wt % potassium carbonate, amine concentrations between 1 to 7 wt % for EDA and 1 to 3 % for TETA, at atmospheric pressure and temperatures from 298 K to 343 K."

Rheological Behavior of a Quaternary Ammonium Copolymer in the Presence of Inorganic Salts

Quaternary ammonium random copolymers poly(methacryloyloxyethyl trimethyl ammonium chloride-co-acrylamide) P(DMC-AM) with either varied cationicities or intrinsic viscosities were synthesized and their structure was analyzed by FTIR and NMR; the results verified the structure of the P(DMC-AM). The rheological behavior of the P(DMC-AM) resulting from its polymer structure (cationicity and intrinsic viscosity) in NaCl aqueous solutions was studied. The results showed that increasing the polymer cationicity could enhance its salt resistance, especially at low cationicity, and the apparent viscosity was in direct proportion to the intrinsic viscosity of the P(DMC-AM) in salt solutions. Furthermore, salt effects (ionic radius, cationic valence, and anion valence) on the apparent viscosity were characterized. They clearly showed that the apparent viscosity was decreased with the increase of ion radius and ion valence. In particular, a difference in polymer aggregation was found when multivalent cations or anions containing solvents were added; two schematic models describing the rheological behavior of the P(DMC-AM) molecules in multivalent salt solutions are proposed.

Surprising peculiarities of the shear viscosity for water and alcohols

This work is devoted to the discussion of surprising behavior of the kinematic shear viscosities for water, methanol and ethanol properties ethanol – one of monohydric alcohols of methanol series. We will show that the application of the standard activation approach to them is conjugated with insuperable difficulties. In order to describe the behavior of the shear viscosity in them the approach, developed for low-molecular argon-like liquids is used. The non-spherical shape of alcohol molecules is taken into account. The special attention is focused to the shear viscosity of aqueous solutions of ethanol, demonstrating a strong dependence on alcohol concentration. A new approach, generalizing that for one-component liquids, is proposed. The careful comparison with experimental data supports our main assumptions.

Universal viscosifying behavior of acrylamide-based polymers used in enhanced oil recovery

Conventional polymers used in enhanced oil recovery (EOR) are acrylamide-based copolymers of very high molecular weight. Their viscosity in aqueous solution depends on various physicochemical parameters such as monomer composition, concentration, average molecular weight, polydispersity, salinity level and ionic composition, temperature, etc. Moreover, solutions are non-Newtonian; they exhibit low-shear Newtonian plateau viscosity at a low-shear rate followed by a shear thinning region at a higher shear rate. In the absence of a predictive model, for any new polymer grade or lot, any new or slightly varying field condition, it is necessary to perform a whole set of viscosity measurements at varying concentrations, which is tedious, time-consuming, and not valuable. Flow curves (viscosity vs shear rate) were measured on a great number of polymer solutions in various physicochemical conditions (variation of the polymer microstructure, monomer composition, molecular weight, brine salinity, and temperature). The flow curves in dilute nonentangled, semidilute nonentangled, and semidilute entangled regimes were modeled by only two adjustable parameters: the intrinsic viscosity [η] and the relaxation time in the dilute regime λd. The zero-shear viscosity η0 (more specifically, the specific viscosity ηsp) and the power law index n obey master curves that are solely functions of the overlap parameter C[η]. The relaxation time λ depends on C[η] and the relaxation time in the dilute regime λd. All these results are consistent with predictions for a neutral polymer in a good solvent. By using these master curves, intrinsic viscosity of any polymer/brine system can be easily obtained at various temperatures from a single measurement in the semidilute regime in which viscosity is higher than water, and classic rheometers are very sensitive. The whole flow curve η(γ˙) can be predicted at any concentration, temperature, and molecular weight. For any unknown polymer/brine system, the determination of λd enables us to determine the viscosimetric average molecular weight M of the polymer. Finally, by using the additive property of the intrinsic viscosity of binary solutions, a method is proposed to evaluate the molecular weight of field samples. Polymer physics is today considered well described and well known. However, the beauty and the usefulness of this physics have been partly ignored by the EOR community up to now. This study gives a methodology to predict the viscosifying behavior and the molecular weight of any acrylamide-based copolymer/brine system. By attributing the molecular weight rather than a viscosity value, on-site and lab quality control will be greatly improved.

Physicochemical and rheological properties of aqueous Tara gum solutions

Commercial Tara gum from three sources was purified by precipitation with isopropanol and evaluated on the structural, physicochemical and rheological properties. FT–IR and NMR techniques were used to determine the molecule structure and monosaccharide composition of Tara gum. The physicochemical properties were determined by intrinsic viscosity measurement using capillary viscosimetry and the rheological properties were determined by rotational viscosimetry. The monosaccharide composition of Tara gum galactomannans showed strong influence of their origin, with a mannose/galactose (Man/Gal) ratio varying between 1.54 and 1.85. Intrinsic viscosity of Tara gum in aqueous solution was influenced by its origin and temperature, and it was well correlated to the sigmoidal model. Hydrochloric acid was found to influence intrinsic viscosity below pH 2, however, combined with temperature treatment (80 ∘C), this limit was increased to pH 4. The rheological behavior at diluted concentrations resulted in shear thickening fluid, with an exponential increase of the consistency coefficient with concentration. Apparent viscosity of semi-diluted and concentrated Tara gum aqueous solutions were modeled by the Cross equation, where zero shear viscosity was influenced by gum concentration and temperature, with different activation energies.

Concentration Dependences of Macromolecular Sizes in Aqueous Solutions of Albumins

On the basis of experimental data for the shear viscosity in the aqueous solutions of ovine serum albumin and using the cellular model describing the viscosity in aqueous solutions, the concentration dependences of the effective radius of ovine serum albumin macromolecules in the aqueous solutions within a concentration interval of 3.65–25.8 wt% and a temperature interval of 278–318 K at the constant pH = 7.05 are calculated. The concentration and temperature dependences of the effective radii of ovine, bovine, and human serum albumin macromolecules are compared. It is shown that they are partially similar for the solutions of ovine and human serum albumins within concentration intervals of 0.12–0.49 vol% and 0.18–0.48 vol%, respectively, provided an identical acid-base balance (pH) in those solutions. The following conclusions are drawn: (i) the concentration dependences of the effective radii of structurally similar macromolecules of various albumins are similar, but provided an identical pH, and (ii) the dependence of the volume concentration of aqueous albumin solutions on the temperature at the constant radius of a macromolecule confirms the hypothesis about the existence of a dynamic phase transition in aqueous solutions at a temperature of 42 ∘C, at which the thermal motion of water molecules significantly changes.

Nonlinear friction dynamics in the cognitive process of food textures: Thickness of polysaccharide solution.

"Thickness" is one of the descriptors of texture in liquid and semisolid foods. In this study, friction in thickener aqueous solutions was evaluated, using a biomimetic friction evaluation system, to show the correlation between friction data and sensory thickness and the recognition mechanism of this sensation during the process of eating. This system can measure friction forces under sinusoidal movement on fractal agar gel, which mimics the morphology and physical properties of the tongue. We found that an increase in the viscosity of the thickener aqueous solution was responsible for both the sensory score of thickness and the asymmetric profile of the friction coefficient in a reciprocating motion. In the case of low viscosity liquids such as water, many of the subjects did not feel thickness, and the friction profile "stable pattern I," that is, a static friction coefficient larger than kinetic friction and a similar profile in the outward and inward processes were observed. However, in the case of solutions containing 3 or 5 wt% of food thickener, the friction profile "unstable pattern I," that is, different friction behaviors in the outward and inward processes, was observed, and many of the subjects experienced strong thickness. In addition, the static friction coefficient at the first cycle was small, and the changes of friction coefficient by the reciprocating motion being repeated was large. These friction phenomena can occur in the mouth and are expected to induce sensory thickness.

Effect of including a hydrophobic comonomer on the rheology of an acrylamide‐acrylic acid based copolymer

AbstractSynthesis and design of polymer systems based on acrylamide for enhanced oil recovery (EOR) is essential for reservoirs with high salinity and high temperature conditions. The use of associative monomers or the modification of the polymers with hydrophobic functional groups represents a promising alternative that extends the use of chemical EOR. In this study, terpolymers based on acrylamide, acrylic acid and butyl methacrylate were synthesized and the rheological properties of aqueous solutions of the obtained polymers at different pH values, and salt concentrations were evaluated. The results show that at alkaline conditions the viscosity of aqueous solutions of a polymer synthesized with 68.6 wt% of acrylamide, 22.9 wt% of acrylic acid and 8.6 wt% of butyl methacrylate increases by a factor of more than 1,000 at a 3 wt% concentration. Also, all polymers with the hydrophobic modification showed higher viscosity in saline solutions compared to their acrylamide‐acrylic acid analogue.