(39b) Complex Fluid Flows in Chemical Product Development

Many Chemical Products that we use everyday are prepared,
sold or used as highly complex formulations which may
contain liquids and dissolved or dispersed solids. These are typically a
complex medley of flow modifiers, surface active
agents, fillers, polymers, colorants and solvents. This concoction of materials
leads to a complex flow behavior under various conditions, many of which are
not well understood. Some examples of these products include paints &
coatings, adhesives, slurries and pastes, thermosetting or film forming
polymers and consumer products such as laundry detergents, skin lotions and
shampoos. Flow behavior can be a key determining factor
of the product characteristics such as particle size and distribution in
dispersed polymer systems or other emulsion products. Flow properties can also
be critical in the application performance and consumer perceptions of products
such as paints, lotions, etc.

In this talk, we will use practical examples of these
ubiquitous products to describe some of these complex flows. We will describe
how rheological characterization of these systems is fraught with complications
of high normal stresses, high inertia and slip behavior while surface flow
behavior characterization is confounded by multi-component dynamic wetting,
time-dependent behavior and fluid instabilities. We will describe 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 also endeavor to outline a few of the open-ended flow problems
that remain important but not well understood.