Rheological properties of concentrated suspensions

Abstract

Publisher Summary This chapter discusses various aspects related to the rheological behavior of concentrated suspensions. Concentrated colloidal suspensions are characterized by yield stresses, shear thinning and thixotropic behavior, and for small amplitude shear flow, the elastic moduli could be significantly larger than the loss moduli. The rheological behavior of a concentrated suspension is the result of various contributions that are very difficult to measure and accurately describe. When dealing with industrial suspensions, other complications may arise from uncontrollable parameters, such as purity and technical specifications of the various components. The continuum concept is no longer valid for highly concentrated suspensions. Hence, in modeling the rheological properties of such materials, the assumption of affine deformation embedded needs to be relaxed. This can be done empirically using the Gordon- Schowalter derivative with a slip parameter instead of the usual upper convected derivative. A better and probably more successful route is to use computer (direct) simulations of the dynamics of particles injected in a suspending fluid. Such (2-D) computer simulations are carried out for a few hundred long rigid fibers and the qualitative results are shown.