Extensional rheology is an important component to understanding the behavior of viscoelastic fluids in many processes including: electro spinning, nozzle flow, biaxial tension, blow molding, droplet formation, adhesives, and food. Extensional viscosity is an intrinsic property and cannot be measured through shear rheology. Many materials that show little difference in shear rheology may show drastic differences in extensional Rheology.
The Capillary Breakup Extensional Rheometer (CaBER) achieves extensional flow by placing a fluid between 2 plates, the plates are then rapidly separated creating a filament. The flow in the filament, driven by surface tension, forces the material into extensional deformation. Understanding of the evolution of the filament with respect to time and the surface tension of the material allows extraction of intrinsic extensional properties.