Viscosity divalent effects

Divalent Effect In the brine of low to medium sahnities (monovalent content), the viscosity of polyacrylamide solution increases as hydrolysis proceeds (increases). However, in the presence of divalents, the viscosity behavior will be determined largely by the divalent metal ion concentrations. As hydrolysis increases, more acrylic acid exists in the solution. Hydrolyzed polyacrylamides (negative carboxyl groups) interact strongly with divalent metal cations such as Csi and Mg ". This phenomenon is commonly associated with reduction in solution viscosity, formation of gels or precipitates. 

The effects of ion valence and polyelectrolyte charge density showed that at very low ionic strength found that when the counterion valence of added salt changes from monovalent (NaCl) to divalent (MgS04), the reduced viscosity decreases by a factor of about 4.5. If La(N03)3 is used, the reduced viscosity will be further decreased although not drastically. As for polyelectrolyte charge density, the intrinsic viscosity was found to increase with it because of an enhanced intrachain electrostatic repulsion (Antonietti et al. 1997). 

The major mode of polyacrylamide decomposition at elevated temperature (in the absence of oxygen) is hydrolysis (319,320). Thus, the concentration of divalent metal ions has an effect on viscosity retention at high temperature. Chelating and sequestering agents have been used to reduce the adverse effect of... 

The effect of divalent ions such as SO4 " has been studied either by electric permittivity techniques, or by viscosimetry. It was experimentally observed that the dielectric increment is larger than in the presence of monovalent ions. In the presence of the bivalent counterions there are two opposite effects. From one hand, the bivalent ions tend to increase the dielectric increment through a charge effect, while from the other hand the observed reduction of the viscosity proves that in the presence of SO4 - the polyions contract76). 

The addition of NaCl to the aqueous phase is mainly for organoleptic reasons but its effect on caseinate must not be overlooked. Increasing the concentration of NaCl increases the ionic strength without the complications of the strong binding phenomena found with divalent cations. Large changes in the concentration of the univalent cations and their associated anion have a number of important effects on the viscosity of the aqueous phase (Table 9.3) and the stability of the emulsion. The observed small decrease in pH and the increased viscosity of the aqueous system may be related directly. 

Molecular viscosity, which is measured in centistokes, is a nonlinear function of molecular weight and of concentration. Thus, a 2% solution of polymer in water usually does not have twice the viscosity of a 1% solution. Each batch of a commercial polymer therefore must be measured for viscosity at the appropriate concentration. The addition of salts can affect the final viscosity of some polymers. Divalent anions and cations can have a major effect on the conformation of polymers in solution, occasionally causing incompatibilities when formulations are mixed together in the eye. 

Consistency. Lecithins are available in both fluid and plastic (solid) forms. Fluid lecithins generally follow Newtonian flow characteristics. The viscosity profile of lecithins is a complex function of acetone-insoluble content, moisture, mineral content, acid value, and the combined effects of assorted additives such as vegetable oils and surfactants. Generally, higher AI and/or moisture content yields higher viscosity, whereas an increased AV often decreases viscosity. Certain divalent minerals, such as calcium and others, can also adjust the viscosity level. 

The intrinsic viscosity of a homogeneous PAM solution increases when NaCl is added to the solution. When CaCh is added, the viscosity increase is even more obvious. However, HPAM viscosity decreases when a monovalent salt (e.g., NaCl) is added. The reason is that the added salt neutralizes the charge in HPAM side chains. When HPAM is dissolved in water, Na dissipates in the water. -COO in the high molecular chains repel each other, which makes them stretch, hydrodynamic volume increase, and viscosity increase. When the salt is added, -COO is surrounded by some Na, which shields the charge. Then -COO repulsion is reduced, the hydrodynamic volume becomes smaller, and the viscosity decreases. When divalent salts—CaCb, MgCla, and/or BaCla—are added in an HPAM solution, their effect is complex. At low hydrolysis, the solution viscosity increases after it reaches the minimum. At high hydrolysis, the solution viscosity decreases sharply until precipitation occurs. 

The melt viscosity is regarded as still too high for injection molding of these materials. However, an additional option for adjusting their processing conditions is their plastification. An effective means for attenuating ionic association within the clusters is the incorporation of various metal acetates, particularly Zn acetate, which supposedly breaks-up divalent sulfonate linkages ... 

The viscosity of a glass depends on its particular composition. Indeed, the glass composition is chosen, in part, to ensure it has the appropriate viscosity for the various processes it must undergo during its production and use. For example, univalent and divalent ions are often used to decrease the viscosity, as these network modifiers tend to break up the silica network. The effect of various ions on the structural modification depends on the field strength and polarizabil-... 

Polyacrylamide El, with the lowest electrochemical degradation factor of 11.2 in Table 3, experiences the smallest reduction of resistance factor in the presence of univalent and divalent electrolytes, from 55.9 in river water to 49.5 in an 80/20 mixture of river and formation waters. These unusually large resistance factors probably resulted from the hydrodynamic resistance of the long linear polymer chain which is a unique characteristic of its gamma radiation manufacturing process. There appears to be some correspondence between the effect of electrolytes on viscosity and screen factor since polymers C and D1 with the lowest electrochemical degradation exhibit the greatest reduction in screen factor on... 

The relative viscosity of both hydrolysed HPAM, a polyelectrolyte, and unhydrolysed PAM, a neutral molecule, are shown in Figure 3.11 as a function of salt concentration (Martin and Sherwood, 1975). As expected, the salt only affects the charged molecules. The repulsion between the backbone charges is screened by the local double layer formed by the small electrolyte species. At higher salt concentrations, the screening effect is more marked, and consequently the viscosity is lower. The effect of divalent ions. 

Divalent ions (Ca+ +, Mg + + ) bond readily to the negatively charged macro-ion in preference to a monovalent ion, such as sodium. The effect of divalent-ion concentration on relative viscosity is more pronounced than sodium-ion concentration because the divalent ions locate themselves in such a way as to screen the negative charges on the backbone more effectively. 

Relative viscosity values follow the concentration of the polymer in the effluent (fig. 9). However they are lower than the viscosities expected from the injected brine (fig. 10). Actually, the low viscosities are due to a higher concentration of divalent cations in the produced brine compared to the amount of divalent cations in the Chateaurenard field brine. The effect is... 

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