Basic Principles of Dispersions

Tharwat F. Tadros

• Publisher: De Gruyter
• Year: 2017
• eBook ISBN: 9783110540192
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Industrial & Technical Chemistry

Volume 2 of the Handbook of Colloid and Interface Science is a survey into the theory of dispersions in a variety of fields, as well as characterization by rheology. It is an ideal reference work for research scientists, universities, and industry practitioners looking for a complete understanding of how colloids and interfaces behave in the areas of materials science, chemical engineering, and colloidal science.

1Flow characteristics (rheology) of colloidal dispersions

1.1Introduction

Investigations on the flow characteristics, or rheology, of colloidal dispersions are of considerable importance in a number of aspects. For example, the rheology of colloidal dispersions can be applied for evaluation of the stability/instability of the dispersion without any dilution (which can cause significant changes in the structure of the system) and this requires carefully designed techniques that should cause as little disturbance to the structure as possible [1–7]. These measurements provide accurate information on the state of the system such as its flocculation, coalescence (with emulsions) and creaming. These measurements are also applied for the prediction of the long-term physical stability of the dispersion.

In this chapter, I will start with descriptions of the various rheological techniques that can be applied to study the state of the dispersion. This is followed by an analysis of the rheological behaviour of the different colloidal dispersions. Four main types of systems will be considered, namely hard-sphere dispersions (where both repulsion and attraction are screened), electrostatically stabilized dispersions (where the rheology is mainly determined by double layer repulsion), sterically stabilized dispersions (where the rheology is determined by steric repulsion) and flocculated dispersions. In the latter case a distinction will be made between weakly and strongly flocculated systems.

1.2Rheological techniques

Four different types of rheological techniques can be applied and these are summarized below.

1.2.1Steady state shear stress σ–shear rate γ measurements

In this case, the dispersion is placed in the gap between two concentric cylinders (Fig. 1.1), two parallel plates or a cone and plate geometry (Fig. 1.2). In the latter geometry, the cone is truncated to avoid damage to the tip of the cone and to have a sufficient gap in order to avoid grinding of the dis...

Table of contents

• Cover
• Title Page
• Copyright
• Preface
• Contents
• 1 Flow characteristics (rheology) of colloidal dispersions
• 2 Wetting and spreading
• 3 Solid/liquid dispersions (suspensions)
• 4 Liquid/liquid dispersions (emulsions)
• 5 Multiple emulsions
• 6 Gas (air)/liquid dispersions (foams)
• 7 Liquid/solid dispersions (gels)
• 8 Polymer colloids (latexes)
• 9 Microemulsions
• 10 Liposomes and vesicles
• 11 Deposition of particles at interfaces and their adhesion
• 12 Characterization, assessment and prediction of stability of colloidal dispersions
• Index