Rheology of suspensions
Written by: Steve Carrington
Understanding rheological properties of suspensions and how particle characteristics are controlling factors
Given the complementary range of materials characterization techniques we have here at Malvern, the measurement of dispersed systems – from suspensions, emulsions and foams, to pastes and gels – is something that we are very familiar with. Our technologies are widely applied at at all stages of the product lifecycle – from particle and molecular characterization of constituent components, to formulation development and stability, to assessment of processing, application and end-use product performance with rheology.
Suspensions or dispersions of particles in a liquid medium are encountered in a variety of industries and find use in a diverse range of applications. These include adhesives, agrochemicals, building and construction, paints, inks and coatings, food and drink, and cosmetics, personal care and pharmaceutical formulations.
We all know from everyday experience of common suspensions that properties of the mixture change dramatically with the concentration of particulates added – think of adding cornflour or cement to water for example. There is a significant increase in viscosity – with the system starting as a free-flowing liquid at low particle concentrations, and evolving through to a paste and eventually a self-supporting soft solid at higher concentrations. It’s not only the concentration of the dispersed phase that impacts on rheological properties though – other important physical properties are the average particle size and particle size distribution; the zeta potential or charge for colloidal particles; and even the shape of the particles (see graphic below).
To review these important aspects, we are going to be running a Suspension Properties Masterclass – which comprises a series of five webinars that will discuss key properties of the dispersed phase, and their impact on (bulk) suspension rheology and ultimately the system stability. See full details of all webinars, and sign up to attend or view here.
Presenters for the series are Dr. John Duffy and Dr. Adrian Hill, who are both Product Technical Specialists for Malvern’s rheology products. John has industrial experience in the Personal Care sector, and Adrian in the Inks and Coatings sector. Working closely with Malvern’s complementary particle characterization technologies, both John and Adrian have extensive experience in helping customers understand and characterize the rheological properties of dispersed systems.
If you have any specific questions about characterizing dispersed systems – contact us here – and we’ll try to help.