Viscosity Concentration Curves Research Articles

Experimental evaluation of polymer performance for tertiary oil recovery in oil field

Polymer flooding is an important technology for enhancing the recovery of underground crude oil, and it is currently the most widely used technology for enhancing recovery in China. The main principle of polymer flooding is to increase the viscosity of injected water through a water-soluble polymer, thereby improving the mobility ratio, expanding the swept volume, and increasing the oil recovery rate and crude oil recovery factor. The viscosity-increasing performance of the polymer solution is the most important parameter of its oil displacement characteristics. The main factors that affect the viscosity of the polymer are the molecular structure, molecular weight, concentration, the salinity of formation water or injected water, temperature, and formation shear. Therefore, the viscosity-increasing performance, salt resistance, and shear resistance of the polymer are evaluated. Through indoor experiments under target reservoir conditions, the viscosity-concentration curves of four polymers A, B, C, and D are measured, and the viscosity data before and after shearing of the polymer as well as the viscosity of the polymer at different salinities are obtained. The results show that, considering the viscosity-increasing performance, shear resistance, salt resistance and quality control of the polymer, under the experimental conditions, the recommended sequence of the 4 polymers is: A, C, D, and B.

Do Clustering Monoclonal Antibody Solutions Really Have a Concentration Dependence of Viscosity?

Protein solution rheology data in the biophysics literature have incompletely identified factors that govern hydrodynamics. Whereas spontaneous protein adsorption at the air/water (A/W) interface increases the apparent viscosity of surfactant-free globular protein solutions, it is demonstrated here that irreversible clusters also increase system viscosity in the zero shear limit. Solution rheology measured with double gap geometry in a stress-controlled rheometer on a surfactant-free Immunoglobulin solution demonstrated that both irreversible clusters and the A/W interface increased the apparent low shear rate viscosity. Interfacial shear rheology data showed that the A/W interface yields, i.e., shows solid-like behavior. The A/W interface contribution was smaller, yet nonnegligible, in double gap compared to cone-plate geometry. Apparent nonmonotonic composition dependence of viscosity at low shear rates due to irreversible (nonequilibrium) clusters was resolved by filtration to recover a monotonically increasing viscosity-concentration curve, as expected. Although smaller equilibrium clusters also existed, their size and effective volume fraction were unaffected by filtration, rendering their contribution to viscosity invariant. Surfactant-free antibody systems containing clusters have complex hydrodynamic response, reflecting distinct bulk and interface-adsorbed protein as well as irreversible cluster contributions. Literature models for solution viscosity lack the appropriate physics to describe the bulk shear viscosity of unstable surfactant-free antibody solutions.

The Behavior of Polyacrylonitrile Solutions in Dimethylformamide at Very Low Concentrations

The viscometric behavior of polyacrylonitrile solutions in dimethylformamide at 25°C has been examined at high dilutions. The reduced viscosity—concentration curves are strongly dependent on the flow conditions, being influenced by the viscometer capillary size. The observed viscosity abnormality in the extremely dilute concentration regime is also due to the adsorption phenomena on the viscometer wall surface and to conformational changes of macromolecules in solution.

Influence of solvent and polymer sort on anomalous rheological behavior of polymer solution at high dilution

The rheological behavior of polyvinyl acetate (PVAc) in N,N′=dimethylformamide (DMF), methyl ethyl ketone (MEK), 1,2-dichloroethane (DCE), tetrahydrofuran (THF) and toluene (TOL), polystyrene (PS) in DMF, MEK, DCE, THF and cyclohexane (CYH), and random ethylene-vinyl acetate (EVA) copolymer in DCE, TOL, CYH with and without surfactant of Span80 and in the DCE/CYH solvent mixtures with surfactant of Span80 was examined at high dilution. It was shown that the extent and type of the upsweep or downsweep (anomalous rheological behavior) of the reduced viscosity-concentration curves of these different polymers at high dilution are markedly dependent on the dielectric constant of the solvent and the polarity of the polymer used. The experimental results indicated that the anomalous rheological behavior of EVA copolymer, widely used as a flow improver, is related to its efficiency in reducing viscosity and depressing pour point of crude oil and waxy solvents.

Properties of in situ Composites Based on Semiflexible Thermotropic Liquid Crystalline Copolyesteramide and Polyamide 66 Blends

Liquid crystalline polymer—polyamide 66 (LCP/PA 66) blends were compounded using a Brabender mixing followed by compression moulding. The LCP employed was a semi-flexible liquid crystalline copolyesteramide based on 30 mol% of p-amino benzoic acid (ABA) and 70 mol% of poly(ethylene terephthalate) (PET). The in situ composites were investigated in terms of thermal, dynamic mechanical, morphological and rheological properties. The differential scanning calorimetry (DSC) results showed that the inclusion of the semi-flexible LCP into LCP/PA 66 blends retards the crystallization rate of PA 66. Furthermore, the melting temperature, the crystallization temperature and the degree of crystallinity of PA 66 were reduced considerably due to LCP addition. On the basis of DSC and dynamic mechanical analyses (DMA), PA 66 and LCP components of the blends were miscible in the melting state, but is partially miscible in the solid state. Hot-stage optical microscopy examination reveals that the LCP microfibrils with random orientation are formed in the PA 66 matrix of compression moulded LCP/PA 66 blends. In addition, the LCP domains within the PA 66 matrix deformed microfibrils, and oriented along the flow direction under the application of shearing force. The formation of microfibrils resulted in an increase in the storage modulus. Finally, the viscosity-concentration curves of the LCP/PA 66 blends exhibited an apparent maximum at 2.5 wt% LCP content, thereafter, the viscosity fell dramatically with increasing LCP concentrations.

Lyotropic behaviour of liquid crystalline poly(ester amide) containing diamide links

The lyotropic behaviour of a poly(ester amide) (PEA), poly[bis (terephthalate butyramide) hexane] (PBTBH) containing aliphatic diamide links prepared through the amido diol route was studied by isothermal viscosity measurements at different shear rates and cross polarized light microscopic measurements in m-cresol, N-methyl pyrollidone (NMP) and concentrated sulphuric acid. The effects of polarity of solvent, shear rate and polydispersity on the threshold concentration were investigated. The viscosity values of the liquid crystalline (l.c.) PEA were found to increase with increase in concentration, reach a maximum and then decrease sharply. The critical concentration at which the viscosity–concentration curve shows a maximum and the threshold concentration where maximum anisotropy was observed did not coincide. The threshold concentrations in the viscosity-concentration curve obtained for the PEA are 56, 54 and 50 wt%, respectively, in m-cresol, NMP and concentrated sulphuric acid. The present experiments show that the threshold concentration depends on the polarity of the solvent, shear rate and polydispersity of the polymer. A narrow molecular weight distribution gives a sharper peak with a lower threshold concentration. PBTBH exhibited the typical shear thinning region under low shear rate peculiar to l.c. polymer solutions. The Newtonian plateau and the second shear thinning region under higher shear rate were also observed. Region I behaviour was confirmed by a number of observations, namely (a) the lack of scaling of transient viscosities during startup with strain and (b) the strong dependence of D 0 on concentration. In Region I, the viscosity showed a mild dependence on shear rate. This corresponds to a decrease of texture size with shear rate approximately as D −1/2, as in the Wissbrun model. The formation of the l.c. phase was confirmed by polarized light microscopy. Appearance of anisotropic inclusions in an isotropic phase started appearing prior to the occurrence of the critical concentration. As the concentration of anisotropic phase increased, the well known ‘phase inversion’ took place and isotropic inclusions in anisotropic phase started appearing as the system approached the threshold concentration. A fully anisotropic phase above the threshold concentration gave the typical nematic threaded texture under the polarized light microscope. A polydomain microstructure was observed in the shear thinning region under low shear rate, which tumbled down to a monodomain structure on application of higher stress.

Rheological Properties of Aqueous Suspensions of Chitin Crystallites

Rheologically, suspensions of chitin crystallites are found to behave as other molecular liquid crystalline polymers (LCPs). The average hydrodynamic diameter of the crystallites in the suspension at pH 4 is determined to be approximately 80 nm using dynamic light scattering. Conductimetric and pH titration results show that the pKaof the crystallites is 6.3, which is the same as that reported for chitosan. In combination with phase diagrams, flow properties of isotropic, biphasic, and anisotropic chitin suspensions were investigated. For isotropic suspensions, a classical shear thinning behavior of rodlike particles is observed. In the case of biphasic suspensions, a two-regime curve is observed where tactoids first orient, deform, and then break up under a shearing force. Similar to other LCPs, a three-regime flow curve is found for the anisotropic suspensions. The viscosity–concentration curve exhibits a maximum at the phase separation concentration, and this maximum is less distinct with a decrease of the ionic strength. Secondary electroviscous effects due to strong particle–particle interactions influence the viscosity of the suspensions at higher concentrations.

The effect of inorganic salts on the viscosity behavior of sodium dodecyl benzenesulfonate solution with high concentration

Abstract The relative viscosity-concentration curves of sodium dodecyl benzenesulfonate (SDBS), 1 2 MgCl2, LiCl, NaCl, 1 2 Na2SO4, and NaI solutions vs water and of 1 2 MgCl2, LiCl, NaCl, 1 2 Na2SO4, and NaI in SDBS solutions with concentrations of 0.298, 0.454 and 0.617 mol dm−3 vs the surfactant solution, and the maximum relative viscosity values and corresponding concentrations of 1 2 BaCl2, 1 3 AlCl3 and 1 3 LaCl3 in SDBS solutions with concentrations of 0.298, 0.454 and 0.617 mol dm−3 vs the surfactant solution have been determined respectively at 298.2 ± 0.2 K. The thickening efficiency of inorganic salts is remarkable for concentrated SDBS solutions. When the salt concentrations are lower, the thickening efficiencies of various salts are in the following orders: 1 2 MgCl2 > NaCl > LiCl and NaI > NaCl > 1 2 Na2SO4. However, when the salt concentration reaches a certain value, SDBS forms a precipitate with the salt and the thickening ability of the salt reaches its limit. The maximum relative viscosity values of the SDBS solutions in the presence of various salts are markedly different, the orders being LiCl > 1 2 MgCl2 > NaCl and 1 2 Na2SO4 > NaCl > NaI. The differences diminish as the SDBS concentration increases. These results are interpreted in terms of the structure of the micelle solution, electrostatic interactions between ions and micelles, ionic hydratability, changes in the water structure and an activity product effect.

Rheology of solutions of rodlike polymers: theory and comparison with experiments

The Doi theory (J. Polym. Sci., Polym. Phys. Ed. 1981,19, 229) of concentrated solutions of rodlike particles is compared with the recent treatment of Bahar and Erman (J. Polym. Sci., Polym. Phys. Ed. 1986,24,1361) of the lattice theory of rods in a potential flow field. The Doi theory is modified by introducing a flow term to its effective mean-field potential, similar to that of the lattice treatment. Results of calculations based on the modified Doi theory are in agreement with existing viscosity concentration data on a-helical poly(benzylg1utamate) in m-cresol. At relatively low shear rates, the experimentally observed sharp maximum in viscosity is found to be located in the biphasic region. In this region the orientational order parameter and viscosity are double-valued. The characteristic features of the biphasic regime predicted by the theory are discussed. The viscosity-concentration curves exhibit smoother maxima at higher shear rates, although no phase separation is predicted by the theory. As the flow rate is further increased, the maximum gradually disappears in agreement with experiments. Also, the experimentally observed Newtonian plateau in the plots of viscosity against shear rates is obtained by the theory. Quantitative agreement between theory and experiment fails at high shear rates.

Poly(alkylvinylpyridine 1-oxides) and corresponding alkylpyridine oxides: electronic spectra and interaction with silicic acid

Poly-(2-vinylpyridine 1-oxide) is chemotherapeutically active against pathogenic effects of silica in animals and it has been suggested that the activity is related to structure and interaction with silicic acid. Alkyl derivatives of this polymer have been synthesised. As compared with the corresponding ethylpyridine 1-oxides, the electronic spectra of these polymers all show bathochromic shifts and there is a large reduction in the extinction coefficients. No interaction of the monomeric analogues of the polymers with silicic acid can be demonstrated by spectral changes, but interaction of the polymers with 0·01M-monosilicic acid and with polymerised silicic acid produces shifts in the electronic spectra of the polymers and changes in viscosity. An attempt has been made to relate the form of the viscosity–concentration curves with the structure of each polymer on the assumption that there is bonding between N-oxide and an adjacent alkyl group. No interaction between silicic acid and poly(2-methyl-6-vinylpyridine 1-oxide), in which there are alkyl groups on either side of the N-oxide, can be demonstrated, and this polymer is inactive against the pathogenic effects of silica.

The viscosity of suspensions of straight, rigid rods

A study was made of the effect of concentration on the relative viscosity of suspensions of straight, rigid nylon fibers with axis ratio of about 20 in a concentric-cylinder viscometer. At volume concentrations below 0.0042, relative viscosities obtained experimentally were within 2% of those predicted by Burgers' theory provided measured values of the orientations of the particles were used in the calculations. As the concentration increased above 0.0042, which was close to the “critical concentration” predicted by Mason, there was a rapid increase in viscosity followed by a slight decrease and a second increase. The rise and dip in the viscosity-concentration curve were due partially to changes in the orientations of the rods and partially to fiber-fiber interactions. Data for the higher concentration range were correlated semiempirically. It was also found that there was no measurable wall effect even at fiber diameter and fiber length to annulus width ratios of 0.0176 and 0.358, respectively. Measurements on suspensions of curved fibers showed that a very slight curvature had a pronounced effect on the viscosity.

Minima in the surface viscosity concentration curves of electrolyte solutions

Minima in the surface viscosity concentration curves of electrolyte solutions

Studies on pharmaceutical suspensions. IV. Viscosities of dilute solutions of CMC's and MC's and sedimentation of barium sulfate particles in their solutions

It was proved that the nature of the dilute solutions of carboxymethylcellulose and methylcellulose differed markedly in concentrations above and below the minimum point which appears in the reduced viscosity-concentration curves of these solutions. The fact was proved through the examination of temperature dependency of viscosity and of sedimentation rate of barium sulfate granules in these solutions. A equation with better approximation was obtained for carboxymethylcellulose by the addition of the first order term of the concentration to Fuoss' equation As a result of measuring the sedimentation rate of barium sulfate in these solutions, it was learned that sedimentation occurred in three steps periodically, and parameters corresponding to its initial and median periods were calculated. Effect of carboxymethylcellulose and methylcellulose on the sedimentation rate was found to be qualitatively as well as quantitatively different.

Semiquantitative aspect of short branch detection by using polyelectrolyte expansive effects

AbstractLinear and branched dextran polyelectrolyte reduced viscosity–concentration curves, obtained by employing a solvent which contained a low concentration of simple electrolyte, were characterized by means of a set of relative expansion ratios, \documentclass{article}\pagestyle{empty}\begin{document}$ R_{nc_m } $\end {document} . The sets of \documentclass{article}\pagestyle{empty}\begin{document}$ R_{nc_m } $\end {document} for branched and linear dextran polyelectrolyte samples of identical degree of substitution, whose reduced viscosity–concentration curves were determined in the same solvent, did not differ. This is interpreted as indicating that the same expansive mechanism operated in the linear and branched polyelectrolyte systems when they were diluted. Plots of \documentclass{article}\pagestyle{empty}\begin{document}$ R_{nc_m } $\end {document} versus absolute concentration for linear and branched polyelectrolyte samples (of identical degrees of substitution, of different degrees of substitution and whose reduced viscosities were determined in solvents of different simple electrolyte concentrations) gave straight lines with a common intercept on the ordinate axis but with different slopes. It is suggested that the slope factor or p values of these lines might be employed as a means of detecting and measuring short branching in polymers convertible to polyelectrolytes.

Viscosity behavior of branched and linear potassium carboxymethyl dextrans

AbstractSamples of branched and linear dextran of near identical intrinsic viscosities have been carboxymethylated to varying degrees and converted to the potassium salts. The reduced viscosity–concentration curves of the branched and linear carboxymethyl dextran polyelectrolytes of identical degree of substitution in aqueous potassium chloride solutions (0.001N and 0.0005N) were compared. Significant differences were observed to exist. At low degrees of substitution (0.06–0.20 carboxymethyl group per anhydroglucose unit) the branched macroion possessed larger reduced viscosities than did its linear counterpart. At a higher degree of substitution (ca. 1.0 carboxymethyl group per anhydroglucose unit) the reduced viscosity curves of the branched and linear macroions crossed. These differences were shown to be independent of shear rate, molecular weight and molecular weight distribution. It is concluded that branching is responsible for the differences in the reduced viscosity–concentration behavior of the branched and linear potassium carboxymethyl dextran samples because of the higher charge density in the branched macroion.

Studies on biocolloids and polyelectrolytes—the plant—gums viscosity of azrechtic acid

AbstractAzrechtic acid (ARA) has been obtained by the electrodialysis of an aqueous solution of the gum of Azadirechta indica in an acidic medium. The viscosity of this gum acid has been investigated under different experimental conditions, i.e., with dilution in aqueous and in isoionic concentration of added electrolyte (HCl), and with change in pH. It is observed that the reduced viscosity of the aqueous solutions increases rapidly with dilution and the reduced viscosity—concentration curve is concave upwards instead of being linear as in the case of linear polymers. The viscosity of aqueous ARS solutions follows the equation, ηsp/C = A/(1 + B√C) where A, B, and D are constants (A = 0.03, B = 0.1845, and D = 0.05), as well as the equation ηsp/C = aCb, in which a and b are constants and equal to 0.2113 and −0.4375, respectively. It is observed that in isoionic concentrations of added electrolyte (HCl, 2.20 × 10−4 g.‐equiv./l.), the sharp rise in the ηsp/C versus C curve vanishes, and the curves show well defined maxima which shift to higher concentrations of the gum acid as the electrolyte concentration increases and ultimately vanish at sufficiently high concentration of the added electrolyte (HCl, 2.20 × 10−3 g.‐equiv./l.), and the ηsp/C versus C curves become linear. The viscosity of azrechtic acid at constant solute concentration increases rapidly when the pH is increased by the addition of NaOH, becomes maximum at a pH of about 6, after which it falls rapidly and becomes constant after a pH of 12. The viscosity also decreases when the pH is decreased on addition of HCl and becomes constant after a pH of 2.0. All these phenomena have been explained on the basis that azrechtic acid behaves as a polyelectrolyte.

The viscosity behavior of linear and branched dextran sulfates

AbstractLinear and branched samples of potassium dextran sulfate have been prepared without significant degradation from samples of linear and branched dextran having similar intrinsic viscosities. The dilute solution viscosity behavior of these polyelectrolytes has been studied with particular reference to the effect of branching and degree of sulfation. A comparison of the reduced viscosity—concentration curves, in aqueous 0.001N and 0.0005N KCl, of linear and branched potassium dextran sulfate with the same degree of sulfation revealed a significant difference in their viscosity behavior. This difference is attributed to a greater charge density in the nonlinear sample resulting from its branched structure.

Effect of water-soluble and water-insoluble long-chain polar additives on micellar solutions of sodium dodecylbenzene sulfonate

Additions of long-chain polar compounds to aqueous solutions of sodium dodecylbenzene sulfonate resulted in the separation of a liquid-crystalline phase. This was first observed after the addition of 0.2 to 0.25 mole of water-insoluble polar compound per mole of anionic surfactant. It was found necessary to add 0.6 to 2 moles of watersoluble long-chain polar compound per mole of anionic surfactant before a separate liquid-crystalline phase could be observed. At concentrations below that required for liquid-crystal formation, additions of PEG 400 monostearate to aqueous solutions of sodium dodecylbenzene sulfonate resulted in a steady decrease in the Krafft temperature, a viscosity minimum, and a surface-tension minimum. With sucrose monotallowate, similar results were obtained, except that a minimum was not obtained in the viscosity-concentration curve.

Characterization and properties of the phosphomannan from Hansenula hostii NRRL Y-2448

The phosphorylated mannan produced in good yield from glucose by the bisexual diploid yeast, Hansenula holstii NRRL Y-2448, appears to be the first significantly phosphorylated polysaccharide to be obtained from a yeast or a nonpathogen. Isolated as the potassium salt, this water-soluble polysaccharide derivative has constituents in the proportion, d-mannose:phosphorus:potassium::5:1:1. The product has [ α] D 25 + 103 ° (in 0.1 M potassium chloride), M N (reducing power) 103,000 ± 10,000, M W (light scattering) of the order of 16 × 10 6, S 20, w = 44, and an unusually homogeneous molecular distribution for an unfractionated, native polymer. The single titration equivalence-point of the polyacid at pH 7.2 indicates a phosphodiester structure. Weak acid liberates secondary hydrogen ions and causes molecular degradation; dilute alkali appears to cause no structural change. Aqueous solutions show exceptional resistance to microbial attack. The brilliantly clear aqueous solutions have properties characteristic of a plastic, thixotropic, polyelectrolyte. The viscosity-concentration curve shows a viscosity maximum of 2500 cp. at 1.5% polysaccharide concentration and a minimum of 1700 cp. at 3%. At suitable concentrations of phosphomannan and borax, complexing and cross-linking occur; the presence of potassium chloride augments these effects.

A viscosity study of polyelectrolytes in the presence of added salts

AbstractThe effect of various added simple electrolytes upon the solution viscosity of polymethacrylic acid and hydrolyzed polyacrylonitrile was studied. The viscosity behavior of these polymers in water and in the presence of added NaCl was typical of that of polyelectrolytes. The addition of multivalent anions (sulfate, diacid phosphate, oxalate, and succinate) to solutions of polymethacrylic acid decreasesd the viscosity at low added salt concentrations, but a reversal in the reduced viscosity–concentration curve was obtained as the ionic strength was increased. This increase in viscosity can be partly explained on the basis of increased ionization originating from the behavior of the added multivalent anions. However, this is not the complete explanation since the relative efficiency of these anions in increasing the viscosity is not consistent with the values of the dissociation constants. A possible alternative explanation involves the formation of associated complexes of the polyions. It is further demonstrated that the limiting intrinsic viscosities at infinite ionic strength is dependent upon the initial polymer charge.