Suspension Rheology

August 2 and 3, 2008 (Saturday and Sunday)

Instructors

Instructor Biosketch

With over 50 years of academic and industrial research experience in the colloid rheology laboratory, including over 100 publications and patents on the topic, Professors Mewis and Wagner have prepared a short course designed for introducing a beginning colloid rheologist to the field. This course is based on a text currently in progress. Both have lectured extensively on the topic and have taught short courses at both the beginner and more advanced levels, including courses for The Society of Rheology in the US and the European Rheology Society in Europe.

For additional information, visit the web pages of Prof. Mewis and Prof.Wagner.

Course Description

The course is designed to be an introduction to the rheology of colloidal dispersions with emphasis on practical measurement and interpretation of rheological measurements on colloidal dispersions. The object is to provide the participants with:

1. Qualitative understanding of the various phenomena that contribute to the rheology of suspensions;
    
2. Scaling relations and quantitative laws to predict the basic rheology of such systems;
    
3. Strategies to measure, characterize and design suspensions with well defined processing or application properties.

This course is of interest to students and practitioners of colloid rheology in industry as well as academia. A basic understanding of physical chemistry is necessary with some familiarity with colloidal science and basic rheology helpful but not required.

The course is structured so as to build systematically upon the fundamental understanding of how various properties of colloids and their interactions lead to the observed rheological behaviour. This starts with systems where only purely hydrodynamic effects are present (i.e. suspensions with non-colloidal particles). Next, colloidal particles are introduced; with Brownian motion but without any particle interaction force. After that systems with additionally repulse interparticle forces are dealt with: i.e. colloidally stable systems. Finally attractive forces are added which can lead to flocculated suspensions and colloidal gels.  The methods of rheological measurement design and execution are discussed, treating the special difficulties that arise in the case of suspensions. Case studies will be analyzed to illustrate the basic concepts of the course. Finally, special advanced topics are to be included depending on the interest of the students. Time is available for a question and answer session based on problems and issued submitted by students prior to the course.

Course Outline

1. Rheological Concepts and Rheological Phenomena in Colloidal Dispersions (1.5 hrs)
   1. Basic rheological concepts
   2. Overview of rheological phenomena in suspensions (based on case studies)
       
2. Hydrodynamic Effects (Suspensions of Large Particles) (1 hrs)
   1. Dilute systems: Relative viscosity and Einstein relation
   2. Semi-dilute systems: Batchelor relation
   3. Concentrated systems (maximum packing, viscosity-concentration relations, effect of particle size distribution)
       
3. Suspensions of Brownian Particles (1.5 hrs)
   1. Mechanism of Brownian motion
   2. Contribution of Brownian motion to the viscosity
   3. Viscoelasticity in suspensions of Brownian Hard Spheres (scaling relations)
       
4. Colloidally Stable Suspensions (2 hrs)
   1. Electrostatic and Steric stabilization, resulting suspension structure
   2. Effect of interparticle repulsion on dilute suspensions
   3. Viscosity of concentrated stable suspensions, scaling relations
   4. Viscoelastic effects, link to interparticle potential, scaling relations
   5. Shear thickening
       
5. Flocculated Suspensions (2 hrs)
   1. Mechanisms of flocculation (electrostatic, depletion, bridging…)
   2. Structure of flocculated systems (flocs, agglomerates, particle gels; their description in RDF, fractals, percolation theory, stat diagrams).
   3. Viscosity of dilute, flocculated systems
   4. Gels and glasses
   5. Thixotropy (reversible time effects)
       
6. Rheological Measurements of Suspensions (1.5 hrs)
   1. Special requirements and problems (based on case studies)
   2. Measurement strategies
       
7. Formulation of suspensions for controlled rheology (1.5 hrs)
   1. Design rules for formulation suspensions with a given rheology (based on case studies)
       
8. Advanced Topics in Colloidal Suspension Rheology (depending on student preferences) (2-3 hrs)
   1. Suspension in viscoelastic media (filled polymers, nanocomposites)
   2. Suspensions containing non-spherical particles (fibers, rods, ...)
   3. Microrheology