Studies on viscosity behaviour of alkali halides in aqueous N,N′ dimethyl urea solution

The viscosity behaviour of ternary systems comprising alkali halides (concentration range 0.125–3 M) in aqueous N,N′ dimethyl urea (0.6 M) solution, over the temperature range 25–40°C has been investigated. It has been found that Moulik's equation (ν/ν_$\text{0}$)² = M + KC² holds good for these systems for the concentrated region. From the relative viscosity data, the “effective” rigid molar volume, V_e and apparent B coefficient have been computed employing the Breslau-Miller procedure at temperatures 25, 30, 35 and 40°C. These data have been used to explain the structuring effect in N,N′ dimethyl urea solution.     

Studies on viscosity behaviour of concentrated alkali halides in aqueous urea solution

The relative viscosity data of sodium and potassium halides (concentration range 0.125–3 M) in aqueous urea (1.0 M) solution at the temperature 25°, 30°, 35° and 40°C have been determined. The data have been found to satisfy Moulik's equation, for concentrated solution of the alkali halides beyond the Einstein's region. Furthermore the “effective” rigid molar volume V_e and the apparent B coefficient have been computed employing Breslau and Miller treatment from the relative viscosity data. On the basis of apparent B coefficient values obtained for different temperatures, it has been observed that both sodium and potassium halides in aqueous (1.0 M) urea solution show structure breaking trend.     

Viscosity variation of N-cetyl pyridinium chloride—high concentration range

N-cetyl pyridinium chloride in aqueous solution is found to obey the equation of fluidity, lnη_rel = (kN)/[N₀(N₀ ? N)] up to a high concentration, almost saturation. Despite micellar association the plot of ln η_relvsN/(N₀ ? N) was found to be linear for N₀ = 5.0, the hypothetical concentration at which glass transition would occur. The linearity of the plot is maintained in the presence of an added electrolyte, sodium chloride producing lower values for N₀ as the concentration of sodium chloride is increased.     

Viscocity of tetraethylammonium bromide and tetrabutylammonium bromide: High concentration range

The viscocity tetraethylammonium bromide and of tetrabutylammonium bromide in aqueous solutions have been measured in the concentration range 0.6–2.3 M and 0.5–1.56 M respectively at 35.0°c. The results of viscocity are satisfactorily represented by the equation ln η_rel = k′N/N_o)(N_o)?N). While the value of N₀ = 11 is of reasonable magnitude for tetraethylammonium bromide, it is unusually large for tetrabutylammonium bromide. It is seen that the equation in the dilute solution range leads to the Jones-Dole form minus the Falkenhagen term involving the square root of concentration. The Jones-Dole B-coefficient is identified withk′/N²₀ and the latter found to be in good agreement with the B-coefficients derived from the Jones-Dole equation.     

A structure rheological study of cellulose trinitrate in ethyl acetate

A structure rheological analysis was undertaken with cellulose trinitrates dissolved in ethyl acetate. Empirical scaling laws with molecular mass and concentration were found for the zero shear viscosity η_o and the critical shear rate $ \dot \gamma _C $ at the onset of shear thinning. Values for the apparent chain element A' were calculated from the concentration dependent network strand M_e and extrapolated to zero concentration. They were compared with dilute solution data. From the concentration dependence of the mass of network strand M_e a network with hindered penetration was inferred.     

Concentration dependence on viscosity of oligourethane diols

To obtain viscosity suitable for application, relatively low molecular weight polymers, i.e., oligomers, are used in the formulation of high solids coatings. To support this requirement, the concentration dependence of the viscosity of synthesized oligourethane diols in different solvents was analyzed using Erickson's models. By regression analysis, it was found that the correlation coefficients are fairly good and the plots of the residuals are more random. The weight intrinsic viscosity, [η_o], composed of the oligomer component, O_5[η]o, and the oligomer-solvent interaction component, I_[η]o, was calculated from the intercept of the plot of 1/ln η_r vs. 1/o₀. The parameter I_[η]o, related to the solvent molar volume and the distance between the oligomer and solvent partial cohesion parameter coordinates, indicates the degree of interaction between the oligomer and solvent. The partial cohesion parameters of the oligomers obtained by the group-contribution method were used for calculating the interaction component of oligourethane diols. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1343–1351, 1997     

Viscosity of polypropylene oxide solutions over the entire concentration range

An empirical equation is presented which describes polymer solution viscosity, η, over the entire concentration range from a knowledge of intrinsic viscosity, [η], Huggins constant, k′, and bulk flow viscosity of polymer, η₀. The equation is: \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{\eta _{sp}}}{{C[\eta]}} = \exp \left\{{\frac{{{\rm k'[}\eta {\rm]C}}}{{1 - bC}}} \right\} $\end{document} where solution viscosity, η, is contained in η_sp. No arbitrary parameters are invoked since b can be evaluated at bulk polymer (C = polymer density) where everything else is known. The equation accurately portrays the viscosity of polypropylene oxide (PPG 2025) from infinite dilution to bulk polymer in a very good solvent (benzene) and in a somewhat poorer (～ θ) solvent (methylcyclohexane). The hydrodynamic consequences of the thermodynamic interactions between polymer and solvent are reflected in the constants. This equation should be applicable to other polymer/solvent systems, and thus be immediately useful to those working with concentrated polymer solutions.     

Radiation chemical studies of protein reactions: Effect of protectors against radiation

Sodium glutamate and sodium benzoate were found to protect protein reactions from radiation damage. The behavior of the viscosity changes was determined. The experimental equation for the protective effect is given by η_red(∞) = a(log X)² + b(log X) + c, where η_red(∞) is the reduced viscosity of the solution at infinite time X is the concentration of the radiation protectors, and a, b, and c are adjustable constants.     

Effect of concentration on apparent viscosity of a globular protein solution

The viscosity of a globular protein solution as a function of concentration was studied with a cone and plate viscometef (Ferranti-Shirley Viscometer System) using, β-lactoglobulin as a model. An aqueous buffer solution (pH 7, ionic strength 0.04) containing up to 40 percent protein was subjected to rates of shear between 800 and 17,000 sec^?1. Specific viscosity of β-lactoglobulin up to 10 weight percent was proportional to the weight concentration of protein in solution such that: η_s = η₀ [ 1+0.8 (weight percent concentration)] where η₀ and η_s are viscosity coefficients for the pure solvent and the solution, respectively. For 3-40 weight percent, a linear relation of shear rate and shear stress was observed at high shear rates. Linearity began at 3500, 4300, 6800, and 7000 see^?1 for 10, 20, 30 and 40 weight percent concentrations respectively. The apparent viscosity was lower below these critical shear rates.     

Rheological behavior of compatible polymer blends. I. Blends of poly(styrene-Co-acrylonitrile) and poly(ε-caprolactone)

The rheological behavior of blends of poly(styrene-co-acrylonitrile) (SAN) and poly(ε-caprolactone) (PCL) was investigated, using a cone-and-plate rheometer. For the study, blends of various compositions were prepared by melt blending using a twin-screw compounding machine. The rheological properties measured were shear stress (σ₁₂), viscosity (η), and first normal stress difference (N₁) as functions of shear rate (γ) in steady shearing flow, and dynamic storage modulus (G′) and loss modulus (G″) as functions of angular frequency (ω) in oscillatory shearing flow, at various temperatures. It has been found that logarithmic plots of N₁ versus σ₁₂, and logarithmic plots of G′ versus G″, become virtually independent of temperature but vary regularly with blend composition, and that the zero-shear viscosity of the blends, (η_o)_blend, follows the relationship, 1/log(η_o)_blend = w_A/log η_0A + w_B/log η_0B, where η_0A and η_0B are the zero-shear viscosities of components A and B, respectively, and w_A and w_B are the weight fractions of components A and B, respectively. The physical implications of the relationship found are discussed.     

Solution properties of hydrophobically modified polyelectrolytes synthesized via solution and micellar copolymerization

Hydrophobically modified polyelectrolytes (HMPEs) were synthesized using sodium 2‐acrylamido‐2‐methyl‐propanesulfonate and N‐n‐dodecylacrylamide as monomers with the same feeding ratio via micellar and solution copolymerization. The effects of hydrophobic association and electrostatic interaction on the solution properties of the HMPEs were studied. Compared with HMPE obtained via solution copolymerization (s‐PAD), the hydrophobic interaction of HMPE obtained via micellar copolymerization (m‐PAD) is more obvious due to the micro‐blocky distribution of hydrophobic groups. The viscosity properties of m‐PAD in deionized water or brine follow well the scaling theory of polyelectrolytes. However, for s‐PAD, the concentration where zero‐shear viscosity (η₀) and solvent viscosity (η_s) follow η₀ ≈ 2η_s is more likely to be critical entanglement concentration (c_e) rather than critical overlap concentration (c*). It is suggested that modifying of the transition region from c* to c_e is valid and reasonable for s‐PAD. It is believed that the different solution properties of s‐PAD and m‐PAD should be attributed to the distributions of hydrophobic groups in the chains. Copyright © 2010 Society of Chemical Industry     

Rheological characterization of concentrated cellulose solutions in 1‐allyl‐3‐methylimidazolium chloride

The rheological properties of high concentrated wood pulp cellulose 1‐allyl‐3‐methy‐limidazolium Chloride ([Amim]Cl) solutions were investigated by using steady shear and dynamic viscoelastic measurement in a large range of concentrations (10–25 wt %). The measurement reveals that cellulose may slightly degrade at 110°C in [Amim]Cl and the Cox–Merz rule is valid for 10 wt % cellulose solution. All of the cellulose solutions showed a shear thinning behavior over the shear rate at temperature from 80 to 120°C. The zero shear viscosity (η_o) was obtained by using the simplified Cross model to fit experimental data. The η_o values were used for detailed viscosity‐concentration and activation energy analysis. The exponent in the viscosity‐concentration power law was found to be 3.63 at 80°C, which is comparable with cellulose dissolved in other solvents, and to be 5.14 at 120°C. The activation energy of the cellulose solution dropped from 70.41 to 30.54 kJ/mol with an increase of concentration from 10 to 25 wt %. The effects of temperature and concentration on the storage modulus (G′), the loss modulus (G″) and the first normal stress difference (N₁) were also analyzed in this study. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Study of viscosity abnormality of PS/toluene solution in extremely dilute concentration regime

The concentration dependence of the reduced viscosity η_sp/c and the translational diffusion coefficient D as well as the radius of gyration R_g of polystyrene in toluene were studied by viscometry and laser light scattering (LLS), respectively. The influence of the experimental error on the determination of the η_sp/c was investigated and a quantitative relation was given out. Viscometric experiment found that the η_sp/c–c curve is clearly divided into two parts by dynamic contact concentration c_s. When c > c_s, it shows normal linearity as predicted by Huggins equation. But when c < c_s, i.e., in the extremely dilute regime, the η_sp/c–c curve is no longer linear and levels off considering the experimental uncertainty. This new finding was confirmed by the following LLS experiment, which indicates that the size of the polymer chains no longer varies with concentration when c < c_s. As a result, we, for the first time, using the method of combination of viscometry and LLS, prove an important conclusion that in the extremely dilute concentration regime, the reduced viscosity of polymer solution, at least for PS/toluene, conforming to the Einstein viscosity equation is just the intrinsic viscosity and independent of the concentration. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4440–4446, 2006     

A model for the zero shear viscosity

An empirical equation for the number of entanglements per molecule has been proposed, which applies over all the molecular weight range. On this ground a simple equation for the zero shear viscosity of monodisperse polymer melts, η₀, has been worked out that appears able to properly take into account the sharp transition of viscosity between the monomeric and the entanglement regimes. The molecular parameters appearing in the new viscosity equation are: the monomeric molecular weight m₀, the monomeric friction factor ζ₀, the molecular weight M, the average molecular weight between entanglements M_e, and the entanglement friction factor ζ_e^3.4. This last parameter was evaluated for a number of monodisperse polymers.     

The influence of the tunnel probability on the anodic oxygen evolution and other redox reactions at oxide covered platinum electrodes

Potentiostatic and galvanostatic pulse measurements were carried out to investigate the anodic oxygen evolution at platinum electrodes in 1N H₂SO₄ in dependence on the oxide layer thickness d and the electrode potential ε. The thickness d (1·5–10 Å) was obtained from cathodic charging curves. Further, the temperature dependence (0°–81°C) was evaluated from Bowden's measurements. Summarizing, the current i_o2 follows the relation, log i = A - (E⁰_a - αFη)/2·3 RT - d/d_o. The experimental activation energy E_o = E^o_a = αFη decreases linearly with increasing overvoltage η. The linear decrease of log i with increasing d, which is given by the term d/d_o, is correlated to the probability of the quantum mechanical tunnel transition of the electron from adsorbed ions, OH^?_ad or O^2?_ad respectively, through the oxide layer to the metal. Similar effects of the oxide layer thickness on the current density were observed in the case of the oxygen evolution at iridium, the CO-oxidation on platinum, and the reduction of Cl^? and Ce⁴⁺ at platinum. In these cases a rate determining electron transfer through the oxide layer is also assumed.     

Radiation chemical studies of protein reactions: Effect of protectors on the breaking of secondary bonding in protein

Radiation protective effect of the breaking of secondary bonding in protein was examined with sodium benzoate, monosodium 1-glutamate, 1-arginine, and thiourea, and the behavior of viscosity against the protector was obtained. An experimental equation for the viscosity change is given by ηred = b ? a log X, where ηred is the reduced viscosity of the solution, X is the protector concentration, and a and b are adjustable constants.     

Synthesis and Structural Characterization of Metal Compounds Incorporating the Ortho-Quinone Manganese Tricarbonyl Complex as an Organometalloligand

Three π-quinonoid compounds incorporating the organometalloligand ortho-quinone manganese tricarbonyl ([(C₆H₄O₂)Mn(CO)₃]^?, o-QMTC) have been synthesized and characterized by IR and X-ray crystallography: [Pd(o-QMTC)(PPh₃)₂]BF₄·CH₂Cl₂ (1), (o-QMTC)Rh(1,5-cyclooctadiene) (2), and Cu(o-QMTC)₂ (3). The formally anionic o-QMTC ligand features Mn-arene bonding that is best described as η⁴-bound. Nevertheless, o-QMTC interplanar angular data and ν_co data suggest significant contribution from η⁵ and η⁶ forms. In each of the compounds, the o-QMTC organometalloligand(s) contribute to a square planar geometry about the Pd(II), Rh(I), or Cu(II) metal center.     

Long-range hydrodynamic response of particulate liquids and liquid-laden solids

In viscous particulate liquids, such as suspensions and polymer solutions, the large-distance steady-state flow due to a local disturbance is commonly described in terms of hydrodynamic screening—beyond a correlation length ξ the response drops from that of the pure solvent, characterized by its viscosity η₀, to that of the macroscopic liquid with viscosity η > η₀ For cases where η >> η₀ we show, based on general conservation arguments, that this screening picture, while being asymptotically correct, should be refined in an essential way. The crossover between the microscopic and macroscopic behaviors occurs gradually over a wide range of distances, ξ < r < (η / η₀)^1/2 ξ In liquid-laden solids, such as colloidal glasses, gels, and liquid-filled porous media, where η → ∞, this intermediate behavior takes over the entire large-distance response. The intermediate flow field, arising from the effect of mass displacement rather than momentum diffusion, has several unique characteristics: (i) It has a dipolar shape with l/r ³ spatial decay, negative transverse components, and vanishing angular average. (ii) Its amplitude depends on the liquid properties through η₀ and ξ alone; thus, in cases where ξ is fixed by geometry (e.g., for particulate liquids tightly confined in solid matrices), the large-distance response is independent of particle concentration. (iii) The intermediate field builds up non-diffusively, with a distance-independent relaxation rate, making it dominant at large distances before steady state has been reached. We demonstrate these general properties in three model systems.     

Flow behavior of well characterized polyethylene melts

A careful characterization and rheological study of low density polyethylene (LDPE) reveals that long-chain branching (LCB) plays a decisive role. At constant molecular weight (M?_w) higher LCB reduces the Newtonian viscosity η_o and the shear sensitivity, increases the activation energy E_o, and finally delays transition to pseudoplastic flow to higher shear rates and the onset of melt fracture to higher shear stresses (τ_d). The flow parameters η_o, \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma _{cr} $\end{document}_cr, τ_d, and the derived flow relaxation times are uniquely correlatable by means of a modified molecular weight (gM?_w) incorporating the LCB effect. High density polyethylene are less shear sensitive than their low-density counterparts, have a lower activation energy, fracture at higher shear stress levels and cannot be regarded as branchless LDPE's.     

The complete identity of the isotherm equations of dubinin and john for determination of the volume and degree of microporosity of carbon

Complete identity of adsorption isotherms of Dubinin and John is proved by showing that the slope D of Dubinin equation is equal to slope D₀ of Dubinin type equation derived from John's isotherm and also showing that the terms involved in D and D₀ are fundamentally the same. It is shown that the degree of microporosity is proportional to n the slope of John's isotherm. B the measure of microporosity in Dubinin equation is inversely proportional to n. The advantages of John's isotherm are also given.