Rheological Properties of Disperse Systems of Solid Particles

Abstract

Experimental studies by the author and his co?workers on rheological properties of disperse systems were reviewed. These investigations were carried out from the standpoint of comparison with the rheological properties of polymeric liquids such as polymer solutions and melts. Samples investigated are many kinds of disperse systems employing some Newtonian and non-Newtonian liquids as disperse media.
Some rheological peculiarities of the disperse system have been found. In the present review, following problems were discussed. One is a characteristic relaxation mechanism at the time scale longer than the maximum relaxation time of the medium, that is, a long-time relaxation process, and the other is the nonlinear viscoelasticity. They were discussed in relation to the degree of aggregation of dispersing particles and to the diffusional motion of the aggregate. The theoretical relationships by Sadron and Brenner for the rotational diffusion coefficients of the ellipsoid of revolution were applied to low-angle light scattering data for the aggregate particles. Then the characteristic relaxation time of the long-time relaxation process and the rotational relaxation time of an aggregate were related to the degree of aggregation. In the nonlinear region, the characteristic relaxation time was independent of the dynamic strain amplitude. These experimental results strongly suggest that the aggregate of dispersing particles behaves individually as a relaxation or a flow unit having a characteristic relaxation time.