T11 of anionic polystyrenes from zero shear melt viscosity

Zero shear melt viscosity data, n_o, as a function of temperature on anionic polystyrenes (PS), as measured by Pierson and by Ueno et al., have been analysed using both a first derivative program and computerized regression analysis. Such data at each $\text{M}{}_{\mathrm{n}}$ fall on three straight lines when plotted as log n_o vs 1000/T, usually connected by curvature, with intersections corresponding to the liquid-liquid intermolecular transition, T₁ and an intramolecular liquid-liquid transition, T₁₁ lying about 40 K above T₁₁T₁₁ and T′₁₁, are given in tabular and graphical form as a function of $\text{M}{}_{\mathrm{n}}$ We conclude that zero shear conditions were attained and that quasi-equilibrium values of T₁₁ and T′₁₁, have resulted. Analysis of a third body of n_o data on anionic PS's by Suzuki reveals additional evidence for T₁₁. These new results on T₁₁ and T′₁₁ are discussed in terms of other literature data on melt viscosity of PS by other techniques for analysing such data.     

Alternative view of self-diffusion and shear viscosity

By performing an elementary transformation, the conventional velocity autocorrelation function expression for the temperature and density dependent self-diffusion constant D(T,rho) has been reformulated to emphasize how initial particle momentum biases final mean displacement. Using collective flow variables, an analogous expression has been derived for 1/eta(T,rho), the inverse of shear viscosity. The Stokes-Einstein relation for liquids declares that D and T/eta should have a fixed ratio as T and rho vary, but experiment reveals substantial violations for deeply supercooled liquids. Upon analyzing the self-diffusion and viscous flow processes in terms of configuration space inherent structures and kinetic transitions between their basins, one possible mechanism for this violation emerges. This stems from the fact that interbasin transitions become increasingly Markovian as T declines, and though self-diffusion is possible in a purely Markovian regime, shear viscosity in the present formulation intrinsically relies on successive correlated transitions.     

Study on the shear viscosity behavior of keratin/PEO blends for nanofibre electrospinning

Graessley's theory has been applied to keratin/PEO concentrated aqueous solutions giving qualitative insight to the rheology of these polymer blends in electrospinning. The shear rate dependent viscosity of different blends was compared with that of pure polymer solutions. The characteristic time τ_η was calculated by the minimum value of at the beginning of the non‐Newtonian viscosity behavior. Flow curves of PEO (at concentration from 1.0 to 7.0 wt %) reduce to a single curve by plotting η/η₀ against . Moreover, PEO solutions exhibit a linear proportionality between zero‐shear viscosity and the characteristic time η₀ ∝ τ_η. Keratin/PEO blend solutions follow the same proportionality at very high and low keratin content, whereas linearity drops when the keratin content range from 50 to 70%. The departure from the theory has been interpreted as a sign of some interaction between the macromolecules of keratin and PEO. It was supposed that keratin displaces solvent molecules and expands the PEO chain coils increasing the relaxation time of the polymer solution. This behavior was correlated with changes in the morphology of the nanofibres produced by electrospinning from these polymer blends. Finally, additive rules to zero‐shear viscosity were applied to keratin and PEO solutions, indicating that the experimental η₀ values were higher than the theoretical ones for all the proportions of the blends, especially for high keratin amount. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1193–1201, 2008     

Rotational viscosity of nematic liquid crystals and their shear viscosity under flow alignment

The influence of molecular properties on the rotational viscosity, γ₁, of nematic liquid crystals is studied. The shear viscosity under flow alignment, η_s, is determined for the same liquid crystals. A significant correlation between both quantities is found. An equation is presented which allows the calculation of γ₁ from η_s with an error of about 20 per cent for the liquid crystals studied.     

A correlation of foam stability with surface shear viscosity and area per molecule in mixed surfactant systems

Summary Aqueous solutions of sodium dodecyl sulfate yield very unstable foam with a very high rate of drainage because they exhibit a relatively low surface shear viscosity. When a solubilizate, such as dodecanol is present in the system, the rate of drainage and thus foam stability prove to be a function of surface shear viscosity. In itself surface shear viscosity appears to be a function of the state of the film as well as the relative amount of the surfactants that is adsorbed at the surface. Systems of fatty acid — fatty alcohol (decanoic acid — decanol, octanoid acid — octanol) exhibit maximum foam stability at molar ratios of 1:3 and 9:1, respectively. At the same molar ratios in these systems, the rate of drainage is minimum and surface shear viscosity is maximum. Studies on mixed monolayers of stearic acid — stearyl alcohol showed minima in the average area per molecule at the 9:1 and 1:3 molar ratios.It is proposed that the molecular interaction which causes the reduction in the average area per molecule in the mixed monolayer also causes the maximum in surface shear viscosity, the minimum in the rate of drainage, and the maximum in foam stability.

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Zusammenfassung Wäßrige Lösungen von Natriumdodecylsulfat haben sehr instabile Schäume mit einer hohen Draingeschwindigkeit, die mit der relativ niedrigen Oberflächengeschwindigkeit zusammenhängt. Bei Gegenwart eines Solubilisators, wie z. B. Dodecanol, wird die Draingeschwindigkeit und die Schaumstabilität eine Funktion der Oberflächenscherviskosität. Die Oberflächenscherviskosität selbst scheint eine Funktion des Filmzustandes und der relativen Tensidmenge zu sein, die an der Oberfläche adsorbiert ist. In den Systemen Fettsäure-Fettalkohol treten Maxima der Schaumstabilität bei Molverhältnissen 1:3 bzw. 9:1 auf. Bei den gleichen Molverhältnissen hat die Draingeschwindigkeit ein Minimum und die. Oberflächenscherviskosität ein Maximum. In Monoschichten von Stearinsäure und Stearylalkohol erreicht der Platzbedarf pro Molekül Minima bei Molverhältnissen von 9:1 und 1:3.Es wird angenommen, daß die gleichen Wechselwirkungen, welche zur Reduktion des Platzbedarfs in den gemischten Monoschichten führen, auch die Maxima in der Oberflächenscherviskosität und die Minima in der Draingeschwindigkeit und damit die Maxima in der Schaumstabilität bedingen.

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With 7 figures     

Nature of the kinematic shear viscosity of water

Nature of the kinematic shear viscosity of water ν is discussed in the work. Dependences of ν on temperature t, reduced volume $ \tilde \upsilon Nature of the kinematic shear viscosity of water ν is discussed in the work. Dependences of ν on temperature t, reduced volume , and the average number of hydrogen bonds per one molecule n _H (t = T/T _c, =υ/υ_c, T _c and υ_c are critical values of temperature and reduced volume) are analyzed in detail on a liquid-vapor coexistence curve. It is shown that at T < T _H (T _H ≈ 310 K is the characteristic temperature of water) the formation of the kinematic shear viscosity is induced by activation. At T > T _H, the shear viscosity of water is the sum of two contributions. One of them is of the same nature as in simple liquids, and another is caused by effects of hydrogen bonds. The temperature dependence of ν in this temperature region has nothing in common with exponential formulas of activation theory. The explicit form of the functional dependence of the kinematic shear viscosity on t, , and n _H is found and substantiated. It is shown that the value and temperature dependence of n _H resulting in the experimental values of the kinematic shear viscosity of water agree well with the values corresponding to density and evaporation heat data. __________ Translated From Zhurnal Strukturnoi Khimii, Vol. 49, No. 6, pp. 1092–1100, November–December, 2008. Original Russian Text Copyright ? 2008 by N. P. Malomuzh and A. V. Oleinik     

Remarks on the shear viscosity of surfaces stabilised with soluble surfactants

A survey is made of previously reported values of the surface shear viscosity of sodium dodecyl sulphate solution which reveals inconsistencies. The origin of these inconsistencies is thought to be due to the fact that, because SDS is a soluble surfactant, the surface deformation rate is governed by a three-dimensional sublayer adjacent to the surface and is therefore inherently experiment-dependent. Because of this, only an apparent surface shear viscosity that is specific to a particular experiment can be measured. However, for an insoluble surfactant, an intrinsic two-dimensional surface viscosity can be clearly defined. Some methods of measuring an apparent surface shear viscosity assume that the surface shear viscosity is the only surface property that determines the drainage rate from foam or individual Plateau borders but there is experimental evidence to show that other surface properties may be significant.     

Determination of nanocellulose fibril length by shear viscosity measurement

The lengths of ten types of cellulose nanofibrils were evaluated by shear viscosity measurement of their dilute dispersions. Aqueous dispersions of surface-carboxylated cellulose nanofibrils with a uniform width of ~3 nm were prepared from wood cellulose by 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated oxidation and successive mechanical treatment. Cellulose nanofibril samples with different average lengths were prepared by controlling the conditions of the oxidation or mechanical treatment. The viscosity-average lengths, L _visc, of the nanofibrils were calculated by applying the shear viscosities of the dilute dispersions to an equation for the dilute region flow behavior of rod-like polymer molecules. The obtained L _visc values ranged from 1,100 to 2,500 nm and showed a linear relationship to the length-weighted average length, L _w, measured by microscopic observation; the relation was described as L _visc = 1.764 × L _w + 764. The influences of the electric double-layer of the nanofibrils and surface-carboxylate content on the value of L _visc were also investigated.     

The nonlinear shear gradient effect on the shear viscosity of a ternary system near a plait point

We have studied the shear viscosity of a ternary liquid mixture (water-ethanol-chloroform) near a plait point by the capillary method and found an apparently strong levelling-off as we approach the critical point. This levelling-off cannot be explained simply in terms of a strong cusp. It is found that the nonlinear shear gradient effect suggested by Oxtoby can be used to explain this behavior.     

Theoretical scheme for the shear viscosity of Lennard-Jones fluids

We use the shear viscosity expression from the Enskog theory of dense gases in a perturbative scheme for the Lennard-Jones (LJ) fluid. This perturbative scheme is formulated by combining the analytic rational function approximation method of Bravo Yuste and Santos [Phys. Rev. A 43, 5418 (1991)] for the radial distribution function of hard-sphere fluids and the well known Mansoori-Canfield/Rasaiah-Stell perturbation theory to determine an effective diameter for the LJ fluid. The scheme is reliable on a wide range of temperatures and densities, and is very accurate around the critical point. Using this information, we build an accurate empirical formula for the shear viscosity in the liquid phase, which fits the recent data [K. Meier et al., J. Chem. Phys. 121, 3671 (2004)] in the whole simulation range.     

The viscosity and structure of dispersed systems

The concepts and basic flow models of structured dispersed systems, namely, suspensions and solutions of polymers in Newtonian dispersive medium, are considered. The disadvantages of the existing rheological models and possibilities of the application of structural models of viscosity to describe both nonlinear plastic and pseudoplastic flows are shown.     

The shear viscosity of supercritical oxygen at high pressure

Shear viscosities of supercritical oxygen have been measured up to a pressure of 5.7 GPa at 294 K. A modified free-volume expression fits the data within 6% between the limits of the tenuous gas and 4.8 times the critical density. Nitrogen viscosities were found to correspond to those of oxygen through a simple scaling by critical constants. Viscosities were measured in the high-pressure diamond-anvil cell with a rolling-ball technique. The dynamics of a sphere rolling on an inclined plane were investigated in the context of these experiments. The effect of a second surface, situated above the sphere, was experimentally determined.     

Prediction of the non-Newtonian viscosity and shear stability of polymer solutions

The structure-property relationships derived here permit the prediction of both the zero-shear viscosity ₀, as well as the shear rate dependent viscosity . Using this molecular modeling it is now possible to predict over the whole concentration range, independently of the molecular weight, polymer concentration and imposed shear rate. However, the widely accepted concept: dilute — concentrated, is insufficient. Moreover it is necessary to take five distinct states of solution into account if the viscous behavior of polymeric liquids is to be described satisfactorily. For non-homogeneous, semi-dilute (moderately concentrated) solutions the slope in the linear region of the flow curve (= must be standardized against the overlap parameterc · []. As with the ₀-M-c-relationship, a-M -c- relationship can now be formulated for the complete range of concentration and molecular weight. Furthermore, it is possible to predict the onset of shear induced degradation of polymeric liquids subjected to a laminar velocity field on the basis of molecular modeling. These theoretically obtained results lead to the previously made ad hoc conclusion (Kulicke, Porter [32]) that, experimentally, it is not possible to detect the second Newtonian region.Roman and Italian symbols a exponent of the Mark-Houwink relationship - b exponent of the third term of the ₀-M -c relationship - c concentration /g · cm^–3 - E number of entanglements per molecule - F(r) connector tension - f function - G _i ^A shear modulus; A indicates that it /Pa has been evaluated by a transient shear flow experiment; i is the shear rate to whichG ^A refers to - G storage modulus /Pa - G _p plateau modulus /Pa - H() relaxation spectrum /Pa - h shift factor (₀/_r) - K _H Huggins constant - K _b third constant of the ₀-M -c relationship - K constant of the Mark-Houwink relationship - M molecular weight /g · mol^–1 - M _e molecular weight between two /g · mol^–1 entanglement couplings - N number of segments per molecule - n slope in the power-law region of the flow curve - p p-th mode of the relaxation time spectrum - R gas constant /8.314 J·K^–1·mol^–1 - r direction vector - T temperature /K Greek symbols ß reduced shear rate - shear rate /s^–1 - shear viscosity /Pa·s - _s solvent viscosity /Pa·s - _sp specific viscosity - ₀ zero-shear viscosity /Pa·s - apparent viscosity at shear rate - reduced viscosity - viscosity of polymeric liquid in /Pa·s the second Newtonian region - [] intrinsic viscosity/cm³·g^–1 - screening length/m - /g·cm ^–3 density - relaxation time/s - ₀ experimentally derived relaxation time/s - angular frequency of oscillation Indices conc concentrated - corr slope corrected - cr critical - deg degradation - e entanglement - exp experimental - mod moderately concentrated/semi-dilute - n number average - p polymer - R Rouse - rep reptation - s solvent - sp specific - theo theoretical - weight average - relaxation time - o experimental or steady state - * critical - ** transition moderately conc. — conc. - + transition dilute — moderately cone. Paper presented at the 2nd bilateral U.S.-West German Polymer Symposium, Yountville, the 7th–11th September 1987.     

Scaling law of shear viscosity in atomic liquid and liquid mixtures

A scaling law relating the shear viscosity of one and two component liquid mixtures to their excess thermodynamic entropies defined through pair correlation functions is derived by approximating the mode coupling theory expressions of frictions and then combining with the Stokes-Einstein relation. Molecular dynamics simulation has been performed to generate the data of shear viscosity for one and two component liquid mixtures to test the derived scaling law. The derived scaling laws yield numerical results of shear viscosity for one component and two component liquid mixtures, which are in excellent agreement with the molecular dynamics simulation results for a wide range of density and interaction potential.     

Effect of internal viscosity on Brownian dynamics of DNA molecules in shear flow

The results of Brownian dynamics simulations of a single DNA molecule in shear flow are presented taking into account the effect of internal viscosity. The dissipative mechanism of internal viscosity is proved necessary in the research of DNA dynamics. A stochastic model is derived on the basis of the balance equation for forces acting on the chain. The Euler method is applied to the solution of the model. The extensions of DNA molecules for different Weissenberg numbers are analyzed. Comparison with the experimental results available in the literature is carried out to estimate the contribution of the effect of internal viscosity.     

Back propagation modeling of shear stress and viscosity of aqueous Ionic-MXene nanofluids

Journal of Thermal Analysis and Calorimetry - Back-propagation modeling of viscosity and shear stress of Ionic-MXene nanofluid is carried out in this work. The data for Ionic-MXene nanofluid of...     

Intrinsic viscosity of solutions of rigid particles at high shear rates

The results of a numerical calculation which extends Scheraga's calculation on the non-Newtonian behavior of the viscosity factor v of rigid ellipsoid solutions are given here and compared to experimental data obtained on different poly(γ-benzyl L -glutamate) samples in helical configuration, over a wide range of molecular weight, up to 980,000. Relations for the axial ratio p, the rotary diffusion constant D, and a test of the deformability of the polymer under shear, are given as functions of the shear-rate dependence of the intrinsic viscosity. The experimental behavior under shear shows that PBLG becomes somewhat flexible in dichloroethane, but not in m-cresol. The dimensions calculated from the viscometric results suggest discrete changes in the length per monomeric unit of the helix at different well defined molecular weights.     

A rheological study of latex polystyrene-based model systems

Latex two-phased polystyrene blends have been produced by three different mixing routes. Polystyrene (PS) and lightly crosslinked polystyrene (XPS) latices were either mixed, or else used as seeds in two-stage polymerizations. This resulted in different microstructures by each of the procedures, leading to different rheological behaviors. Latex PS/XPS systems flow at every composition studied. Activation energies are independent of XPS content, and of the same order of magnitude as PS. Power-law relaxation has been observed for the physically blended system in the terminal region. This has been attributed to the formation of a “continuous” XPS network in the range 60–100% XPS.