Search results for "Viscosity."

Acoustic methods for measuring the porosities of porous materials incorporating dead-end pores

2013

International audience; The acoustic properties of porous materials containing dead-end (DE) pores have been proposed by Dupont et al. [J. Appl. Phys. 110, 094903 (2011)]. In the theoretical description, two physical parameters were defined (the dead-end porosity and the average length of the dead-end pores). With the knowledge of the open porosity (measured with non-acoustic methods), and the measurement of kinematic porosity (also called the Biot porosity in this article), it is possible to deduce the dead-end porosity. Two acoustic methods for measuring the Biot porosity for a wide range of porosities are proposed. These methods are based on acoustic transmission and on the low and high …

Micromechanics of “raspberry” morphology in PPE/SAN polymer blends compatibilized with linear ABC triblock terpolymers

2015

Abstract The effect of compatibilization with a symmetrical polystyrene- block -polybutadiene- block -poly(methyl methacrylate) (SBM) triblock terpolymer on the morphological and mechanical properties (specifically toughness) of immiscible poly(2,6-dimethyl-1,4-phenylene ether)/poly(styrene- co -acrylonitrile) (PPE/SAN) blends with different blend (w/w) ratios is investigated. We study the effect of blend viscosity on the localization of the compatibilizer at the blend interface, influencing the mechanical properties of the macroscopic material. The impact of the specific morphology of the blends, known as “raspberry morphology”, on the final material will be explained using thermomechanica…

Translational diffusion coefficients of volatile compounds in various aqueous solutions at low and subzero temperatures.

2005

International audience; Translational diffusion coefficients (D(12)) of volatile compounds were measured in model media with the profile concentration method. The influence of sample temperature (from 25 to -10 degrees C) was studied on translational diffusion in sucrose or maltodextrin solutions at various concentrations. Results show that diffusivity of volatile compounds in sucrose solutions is controlled by temperature, molecule size, and the viscosity of the liquid phase as expected with the Stokes-Einstein equation; moreover, physicochemical interactions between volatile compounds and the medium are determinant for diffusion estimation. At negative temperature, the winding path induce…

A comparative study on Kθ evaluation from [η]-M data in single and mixed solvents through various excluded volume theories

1991

Abstract By allowing for the dependence of B on molecular weight, through its relationship with A2, modified Flory-Fox-Schaefgen, Kurata-Stockmayer-Roig, Berry and Inagaki-Suzuki-Kurata equations are obtained, relating [η] to A2 and to Kθ. Through these equations, Kθ can be determined from data sets for [η]-A2. Because of the scarcity of these data sets, A2 values have been calculated from experimental data for [η] and trial Kθ values through two parameter theories, namely, through the Flory-Krigbaum-Orofino theory for Ψ. Iterative processes were followed until coincidence was obtained between trial Kθ values and those evaluated from the modified excluded volume equations. The method has be…

Decay estimates in the supremum norm for the solutions to a nonlinear evolution equation

2014

We study the asymptotic behaviour, as t → ∞, of the solutions to the nonlinear evolution equationwhere ΔpNu = Δu + (p−2) (D2u(Du/∣Du∣)) · (Du/∣Du∣) is the normalized p-Laplace equation and p ≥ 2. We show that if u(x,t) is a viscosity solution to the above equation in a cylinder Ω × (0, ∞) with time-independent lateral boundary values, then it converges to the unique stationary solution h as t → ∞. Moreover, we provide an estimate for the decay rate of maxx∈Ω∣u(x,t) − h(x)∣.

Unsteady Separation for High Reynolds Numbers Navier-Stokes Solutions

2010

In this paper we compute the numerical solutions of Navier-Stokes equations in the case of the two dimensional disk impulsively started in a uniform back- ground flow. We shall solve the Navier-Stokes equations (for different Reynolds numbers ranging from 1.5 · 10^3 up to 10^5 ) with a fully spectral numerical scheme. We shall give a description of unsteady separation process in terms of large and small scale interactions acting over the flow. The beginning of these interactions will be linked to the topological change of the streamwise pressure gradient on the disk. Moreover we shall see how these stages of separation are related to the complex singularities of the solution. Infact the ana…

1993

In a new theoretical approach the separation of a pair of chain molecules (measured thermodynamically by the second osmotic virial coefficient A2) is treated as a two-step process: In the first step the molecules are detached from each other by the addition of solvent—keeping their dimensions constant—and in the second step the now isolated coils are allowed to relax into their equilibrium dimensions. For the description of the second step, in which only segments belonging to one molecule take part, an intra-molecular interaction parameter is introduced on the basis of the intrinsic viscosity. The present two-parameter approach yields A2 = A + σ M−(1−a) for the dependence of A2 on the molec…

A Viscosity Equation for Minimizers of a Class of Very Degenerate Elliptic Functionals

2013

We consider the functional $$J(v) = \int_\varOmega\bigl[f\bigl(|\nabla v|\bigr) - v\bigr] dx, $$ where Ω is a bounded domain and f:[0,+∞)→ℝ is a convex function vanishing for s∈[0,σ], with σ>0. We prove that a minimizer u of J satisfies an equation of the form $$\min\bigl(F\bigl(\nabla u, D^2 u\bigr), |\nabla u|-\sigma\bigr)=0 $$ in the viscosity sense.

Darstellung, eigenschaften und umsetzungen von polyvinylsulfofluoriden

1960

Vinylsulfofluorid wurde mit Azo-bis-isobutyronitril polymerisiert. Es wurden Polymerisationsgrade bis 390 erreicht. Die Molekulargewichte wurden durch Viskositatsmessungen an den durch Verseifung der Polyvinylsulfofluoride gewonnenen Natriumsalzen der Polyvinylsulfonsaure ermittelt. Die Polyvinylsulfofluoride wurden mit Ammoniak, aliphatischen und aromatischen Aminen umgesetzt. Dabei wurden Umsatze bis zu 80 Mol% erreicht. Vinylsulfofluoride was polymerized with azo-bis-isobutyronitrile. The degree of polymerisation was up to 390. The molecular-weights were determined by measuring the viscosity of the sodium-salts of polyvinylsulfonic acids obtained by saponification of polyvinylsulfofluori…

Testing of a constitutive equation with free volume dependent relaxation spectrum

1979

A model of non-linear viscoelasticity with relaxation times dependent upon free volume is here proposed. The free volume is related to the isotropic part of the stress tensor by means of a simple differential equation. The model predictions are compared with a large amount of experimental results taken on polymeric melts or concentrated solutions and reported in the literature. The single parameter of the model is determined, within each set of data, by fitting of the viscosity curve. A satisfactory agreement is obtained with data taken under both elongation and shear for which also the relaxation behavior after single and double strain steps is considered.