Rheological Properties of Colloidal Solutions, Pigment Suspensions, and Oil Mixtures

Abstract

The law of Arrhenius which correlates the viscosity of a colloidal solution logarithmically to the volume percent concentration of solid matter has previously been tested only for dilute suspensions which appeared to the investigators to behave like true Newtonians. Similar suspensions have been tested at higher concentrations of solid matter and the authors found that although Arrhenius' law could not be checked, a similar exponential law evolved, which, however, is correct only within the tested region of viscosity. The authors realized that with the increase of solid matter the suspension can become plastic or pseudo-plastic and may also show thixotropic behavior. Therefore it was considered as a major part of this investigation to determine the validity of Arrhenius' law in that region of concentration, where plasticity occurs. Although Arrhenius' law was not found to be applicable for plastic materials, two exponential laws, similar to Arrhenius' law, have been established between the plastic viscosity and the volume percent of pigment content of a plastic suspension on the one hand, and between the yield value and the volume percent of pigment content of a plastic suspension on the other hand. The two constants in the exponents of the two equations have been shown to be logarithmically related to the average diameter, d3, of the pigment particles contained in the suspension. Oil mixtures with the same and with different type constituents have been tested below a certain rate of shear, called ``the limiting rate of shear,'' where they are Newtonian liquids, and also above this limiting rate of shear where they behave like thixotropic plastics. Their Newtonian viscosities, obtained at rates of shear below the limiting rate of shear, have been found to increase logarithmically with the volume percent of one of the oils contained in the mixture, which is in agreement with Arrhenius' exponential law. However, above the limiting rate of shear, oil mixtures deviate from the exponential law, which is logically expected, since their limiting rate of shear depends on the Newtonian viscosity and therefore is different for each oil mixture.

Predicting Viscosity of Limestone–Water Slurry

“…Irrespective of the solids concentration, the specific surface area of the particles increases due to presence of more finer particles in sample S-1 that leads to the production of new surfaces and the total number of particles increases promoting a decreasing of inter-particle distance. For 3 sample S-2 with larger median particle size and with less proportion of finer particles, the interaction between particles is weak. Hence the relative viscosity indicates higher values for S-1 than S-2 at a specific solids concentration and shear rate.…”

“…The density of the sample has been determined with 50 ml standard specific gravity bottle. The density of the sample is 2.743g/cm 3 . The chemical analysis of the sample was done by standard methods and is given in Table 1.…”

“…A number of theoretical and empirical equations have been developed to predict the viscosity of concentrated suspensions [3,4]. Each equation has achieved some agreement between prediction and measurement, but with limits to factors such as solids concentration and powder characteristics, in a variety of suspension systems.…”

The Role of Binder Adsorption for High Solid Loading Nano‐Zirconia Extrusion Pastes

“…The fact that the extrapolation to 0% solid loading deviates from the viscosity of the medium (η r ≠ 1) was already observed by Weltmann et al . who introduced the correction factor A for this reason.…”

“…With these constant conditions the torque can be considered to be proportional to the viscosity of the feedstock and viscosity equations as given in can be directly applied to the torque M . In this study, the viscosity equation of Weltmann is used:where Φ is the volume fraction of the solid, and A and B are constants. A is a correction factor and the B is found to be proportional to ‐log d .…”