摘要:

Variations of apparent viscosity with pore size in both the Newtonian and shear‐thinning regimes have been studied in noninertial flow of a rodlike polymer solution through well‐calibrated cylindrical pores, small glass bead beds, sharp‐edged particle packs, and a sandstone under conditions where flow properties are not influenced by polymer adsorption or retention. The bulk shear viscosities of microgel‐free xanthan solutions were accurately measured over a wide range of shear rates and polymer concentrations in order to determine macromolecular dimensions, confirm rodlike behavior, and know the effects of shear rate on intermolecular interactions. In fine pores, both the Newtonian apparent viscosity and the shear‐thinning index were found to decrease with pore size as long as pore diameters were larger than rod length. Such behavior is interpreted by the existence near the wall of a depleted layer in which steric hindrances decrease monomer concentration and thus viscosity near the wall. The proposed two‐fluid flow model satisfactorily predicts the experimental results in both cylindrical pores and stochastic porous media, confirming the dimensional origin of this depleted layer which is insensitive to both pore shape and the chemical nature of the wall.

ISSN:0148-6055    

DOI:10.1122/1.549660

出版商:The Society of Rheology    

年代:1982

数据来源: AIP

摘要:

The rheological properties of 0.25‐1.0 wt % solutions of the hydroxyethyl cellulose, Natrosol 250HHR, obtained with various viscometers are presented. At sufficiently high shear rates, power law behavior is observed with Couette viscometers. The nature of the viscosity data at low shear rates calculated from measurements of a variety of falling spheres is described. The variation of apparent viscosity with concentration and temperature is illustrated. These solutions are widely used in several oil production operations.

ISSN:0148-6055    

DOI:10.1122/1.549661

出版商:The Society of Rheology    

年代:1982

数据来源: AIP

摘要:

The rheological and morphological properties were examined on solutions of a styrene‐butadiene (SB) diblock copolymer in so‐called selective solvents, which dissolve only one block but precipitate the other. In such solvents the block copolymer molecules aggregate and form micelles with the precipitated blocks as the cores and the dissolved blocks as the cilia. Above a certain critical concentration and below a certain critical temperature, the solutions exhibit nonlinear behavior even under small‐amplitude oscillation and also plastic flow with a true yield stress. A simple constitutive model incorporating the plasticity as well as the viscoelasticity describes these plastic and nonlinear behavior, at least, semiquantitatively. Small‐angle x‐ray scattering studies on these solutions indicate that the block copolymer micelles are regularly arranged into a simple cubic “macrolattice.” The micellar solutions undergo a transition from plastic, nonlinear behavior to linear viscoelastic behavior, either with increasing temperature or decreasing concentration, accompanied by a transition from the ordered macrolattice structure to a disordered structure in which the micellles are dispersed randomly. These results suggest that the stability of the macrolattice is the main cause of the plasticity of the solutions. The nature of the plasticity is discussed in terms of density fluctuation of the ciliary block chains within the macrolattice space.

ISSN:0148-6055    

DOI:10.1122/1.549662

出版商:The Society of Rheology    

年代:1982

数据来源: AIP

摘要:

Commercial polymer processing operations like fiber spinning and film blowing involve extremely large spatial temperature gradients, and it is not uncommon for the rate of change of temperature, following a material element, to exceed104 K/s.Nevertheless, it has been quite usual to neglect this rapidly changing thermal history and to account for temperature variations through the use of a time‐temperature superposition alone. Recent experimental data show that this simplified approach is inadequate and that a more general theory is needed. In this work, the flexible dumbbell molecular model of dilute solution rheology is extended to include the dependence of the stress upon the temperature history as well as upon the deformation rate history. The resulting equation properly reduces to the upper convected Maxwell model under isothermal conditions, but under nonisothermal conditions it contains a new parameter which, at least for polymer solutions, can be determined entirely from a knowledge of molecular variables. The application of this equation to the nonisothermal uniaxial extension of polymer melts shows encouraging agreement with available experimental data.

ISSN:0148-6055    

DOI:10.1122/1.549663

出版商:The Society of Rheology    

年代:1982

数据来源: AIP

摘要:

The topography of flow of liquids in a Couette‐type apparatus and its variation with the rate of shear was investigated by light scattering measurements on highly dilute aqueous dispersions of rodlike β‐FeOOH crystals of colloidal size. The method proved to be a very sensitive tool for detecting centrifugal particle migration and especially for analyzing the detailed topography of flow on vortex formation. Very significant particle orientation was found to persist even at shear rates exceeding by far the onset of turbulence.

ISSN:0148-6055    

DOI:10.1122/1.549683

出版商:The Society of Rheology    

年代:1982

数据来源: AIP

摘要:

The viscosity of suspensions of nearly uniform rigid rods has been shown to exhibit transient non‐Newtonian behavior. Damped oscillations of frequency approximately twice that of the rotation of the suspended particles occur. The attenuation of the oscillations is shown to be mainly due to polydispersity and particle interactions. Rotary Brownian motion which can also contribute to the damping was considered theoretically but shown to be negligible in our experiments. Effects of the axis ratio of the particles and the rate of shear on the damping were studied in detail, and the results were found to be in general agreement with earlier theoretical predictions.

ISSN:0148-6055    

DOI:10.1122/1.549664

出版商:The Society of Rheology    

年代:1982

数据来源: AIP

摘要:

The transient non‐Newtonian viscosity of suspensions with a (slightly polydisperse) bimodal particle size distribution and of rather highly polydisperse suspensions has been studied. For bimodal systems the dominant frequencies can be determined from the frequency spectra of the oscillations. They correspond to the rotational frequencies of the two species constituting the bimodal suspension. For polydisperse suspensions, the damping in viscosity is very rapid and the dominant frequency is shifted toward values corresponding to the period of rotation of the larger particles present.

ISSN:0148-6055    

DOI:10.1122/1.549665

出版商:The Society of Rheology    

年代:1982

数据来源: AIP