Mechanics of Dispersions Part 1: Identification of Parameters in Structural Hysteresis

Abstract

By reference to a study of the viscoelastic and thixotropic properties of carbon black in mineral oil, Mewis et al.1 have reported on the phenomenon of structural hysteresis. This work is of interest because of the experimental proof that characterization of the structure of thixotropic systems by one parameter is inadequate, a subject about which there has been some controversy.2 r There are many reported examples of two phase systems of monodisperse and of heterodisperse dispersions of particulate solids in a liquid phase showing viscoelasticity, or thixotropy, or both.3 The size of the particles has ranged from the lower limit to just above the upper limit of what is called the colloidal subdivision of matter.4 Whether the elastic response in such viscoelastic systems is entropic or potential in origin has not been established. It is, therefore, of some importance to examine the basic theory of two phase dispersions so as to determine the number of parameters required to describe behaviour observed in the usual kind of rheological experiment, and to investigate how the theory could further our understanding of such dispersions and of related scientific problems. We choose a statistical thermodynamic method.