[Complex suspension rheological behavior in the range of flow geometry]

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Table of Contents

ABSTRACT5

INTRODUCTION6

LITERATURE REVIEW13

Importance of Rheology13

Colloidal Systems13

Definition and Classification13

Suspensions14

Foam14

Emulsions15

Forces acting on colloidal systems15

Rheological Properties of Kaolin Suspensions15

Factors affecting Kaolin Suspension Rheology15

Surface Charges and Structure of Kaolin Suspension16

Classifications of Fluid Behavior19

Newtonian Fluid20

Non-Newtonian Fluid20

Times-Independent Behaviour of Fluid21

Shear thinning fluids22

Shear-thickening fluid behavior23

Viscoplastic fluid behavior23

Time-dependent Behaviour of Fluid24

Thixotropy25

Rheopexy26

The DLVO Forces27

The Van der Waals Attractive Force27

The Electrostatic Force28

The Non-DLVO Forces28

Bridging Interactions28

Steric Repulsions29

Rheological Instruments30

Concentric Cylinder Rheometer30

Four-bladed Vane Rheometer32

Problems encountered on Concentric Cylinder Rheometer34

Viscous Heating34

Slip or Wall effects34

Cavitation35

Secondary Flow36

EXPERIMENTAL METHOD37

Rheological properties of a fluid38

Constitutive38

Main types of behaviour40

Fluid threshold41

Macroscopic properties and rheological Suspension42

Newtonian Suspensions42

Methodology of homogenization42

The representation of VER step43

The location step43

The homogenization step43

Method Estimation44

Elastic modulus vs. yield stress45

Yield stress46

Simplified modelling of the liquid-solid transition46

Micromechanical modelling of the transition in liquids and solids50

Experimental study of the structure and destructing of a thixotropic material54

RESULTS AND DISCUSSION56

CONCLUSION AND FUTURE WORK65

Scope of the Studies72

APPENDIX77

Abstract

It has been reviewed in this study that fluid mechanics and rheology of dense suspensions, emphasizing investigations of microstructure and total stress. “Dense” or “highly concentrated” suspensions are those in which the average particle separation distance is less than the particle radius. For these suspensions, multiple-body interactions as well as two-body lubrication play a significant role and the rheology is non-Newtonian. We also include investigations of multimodal suspensions, but not those of suspensions with dominant non-hydrodynamic interactions. It was considered results from both physical experiments and computer simulations and explore scaling theories and the development of constitutive equations. The study has also developed an approach for scaling to study the behaviour of a macroscopic particle composite material. To this end, we presented the main characteristics of homogenization methods to obtain a characterization of the equivalent homogeneous behaviour of a heterogeneous material. We also noted the main results obtained by the homogenization approach for nonlinear isotropic particle suspensions in non-deformable fluid-Hershel Bulkley. We then studied the effect of particle poly-dispersity on the values rheological parameters of a bi-disperse suspension. These results also show that the structure to assess and disintegration of a suspension of colloidal particles in a non- thixotropic colloidal fluid, it suffices to study the properties of the suspending fluid. From this result, it is necessary to perform further experiments not only on the carrier fluid, but also in the presence of non-colloidal particles order to have accurate results. Our preliminary results show that this line of study is very promising.

Introduction

Kaolin is said to be an industrial mineral that possesses many distinct physical and chemical properties making it very useful in different industrial applications such as in paper industry. Kaolin is used in adding rigidity and strength to rubber products as well. It is also added to plastics, ceramics and paints wherein it gives smoother surface, chemical resistance and desirable flow properties (Murray and Kogel, 2005). All this variety of properties is achieved at low cost of kaolin.

This study aims to come-up with useful results of rheological behaviour specifically of non-Newtonian flow, since there is an insufficient data available to predict the flow behaviour of these ...