Rheology is the study of the flow of materials that behave in an interesting or unusual manner. Oil and water flow in familiar, normal ways, whereas mayonnaise, peanut butter, chocolate, bread dough, and Silly Putty flow in complex and unusual ways. In rheology, they study the flows of unusual materials.
Anyone who has cooked, baked, or played in a sandbox or bubble bath has experimented with rheology. Discussing the deformation of food is a way to introduce the subject of rheology, but the rheology of food is only one subfield of the broad science of rheology. Flows of elastic solutions and of those containing long-chain polymers, including coatings, as well as flows in extruders, molds, and other processing equipment, dominate rheology today. Many industrial problems involve rheological concerns. These include the need to understand the transport of foams and yield-stress fluids in oil drilling and enhanced oil recovery, and the importance of understanding the behavior of biological macromolecules in microfluidic devices for lab-on-a-chip applications. Geoscientists invoke rheology in studies of volcanism and the convection through Earth’s mantle and outer core.
The word rheology comes from rheo, from the Greek word for flow, and –ology, meaning study of. Scientists who study the mathematical relationships that describe the behavior of non-Newtonian fluids are called rheologists, and 1,800 of them from around the world are members of the Society of Rheology (SOR), a founding member society of the American Institute of Physics. The Society was officially formed on Dec. 9, 1929, the outgrowth of a burgeoning interest in the behavior of colloidal materials, including the flow behavior of newly discovered synthetic rubbers and polymers.
The Society’s core mission is the advancement of rheology and its applications, and to that end, it sponsors yearly meetings and publishes the Journal of Rheology and the Rheology Bulletin. The journal, a peerreviewed scholarly publication, appears 6 times a year. The Rheology Bulletin is a twice-a- year newsletter that keeps SOR members informed of Society activities and of other topics of interest to rheologists.