This report covers the first year of the 1FPRI Suspension Rheology Project 1985-88 at the K,U.Leuven. It deals with the prediction and manipulation of the rheological properties of colloidal suspensions. Both colloidally stable and weakly flocculated systems are considered.
With respect to the stable systems, a procedure is described to predict viscosities over a wide range of conditions using a limited number of experiments. Suitable equations for shear rate and concentration dependency are given. The average error is shown to be less than 10% in most cases.
Data on concentrated systems are compared with recent theoretical predictions. The correlation is quite promising and might lead to a more scientific basis for predicting rheological properties. The present results suggest a method to derive the interparticle potential, which governs the physical behaviour of colloidal suspensions, from the modulus- concentration relation.
New samples are being prepared to study the transition from hard to soft particles. They will also be used to extend the previous results on monodisperse suspensions to systems with a particle size distribution. Making suitable materials is an even more important problem for the weakly flocculated systems. Various suspensions of silica and bentonite particles have been screened. It is being attempted to detect changes in structure with shear rate and time using rheological and dielectrical and/or neutron scattering methods. Preliminary results with these three techniques are shown.