Complex Fluids at Interfaces: Some Open-Ended Problems in Colloidal Systems

Many chemical products that we use everyday are highly complex fluids that contain dispersed solids, flow modifiers, surface active agents, fillers, polymers, colorants, solvents etc. This concoction of materials leads to a complex flow behavior under various environmental, shipping, storage and usage conditions, many of which are not well understood. Some examples of these products include shampoos, detergents, adhesives, cement pastes and oil dispersions. Flow & interfacial behavior of these complex fluids can be a key factor in the application performance and consumer satisfaction with these products.

In this talk, we will use practical examples of these ubiquitous products to describe some of these complex flows. We will outline some of our efforts in using a scientific and statistical approach in understanding this behavior as well as strategies used to modify flow properties to meet those needs. We will describe the use of rheology, imaging as powerful tools to characterize these systems under various time, temperature and storage conditions. However, rheological characterization of these systems is also fraught with complications of high normal stresses, high inertia and slip behavior. We will endeavor to outline few of the open-ended problems that remain important but not well understood.