Exploring the impact of particle characteristics on suspension rheology

How particle size, shape and zeta potential influence suspension rheology

Introduction

Many products are suspensions or dispersions of particles in a liquid medium. Examples range from adhesives, ceramics, paints and inks through to foods, drinks, personal care products and medicines. The physical properties of the dispersed particles in such systems, including particle size, particle size distribution, concentration, electric charge (zeta potential), and even particle shape, can all strongly influence the overall (bulk) rheological properties of a suspension, thereby defining product behavior and functionality. Understanding these interactions is crucial when it comes to achieving desirable product performance, whether it be a stable paint or medicine, workable cement, or a visually appealing shower gel or drink.

This white paper examines the impact of particle properties on suspension viscosity, and more broadly on rheological behavior. It looks in some detail at how particle size, shape and zeta potential influence critical aspects of suspension performance such as viscosity and stability and how these properties can be manipulated to tailor this behavior.

Understanding the effect of particle concentration

At the start of his career Albert Einstein studied and described the flow field around a single hard sphere in a liquid [1, 2]. He concluded that single particles increased the viscosity of a liquid as a simple function of their phase volume, according to the formula.

η – viscosity of the suspension
ηmedium – viscosity of the medium
ɸ – volume fraction of solids in the suspension