The Investigation of Dilute and Semi-Dilute Polymer Solutions with the aid of Home-Built Extensional Rheometers

Several polymer solutions and emulsions exhibit time-dependent or thixotropic behavior. In other words, the characteristics of the solution not only depend on the instantaneous environment but also on the deformation history in the past. When deformation is applied, structures can build up in a solution or suspension which take time to form.

Deformation can come in 2 forms, either shear or extension. This PhD focuses on the extensional flow behavior or rheology. A key factor in characterizing the extensional rheology of a fluid is determining the extensional viscosity. To acquire this viscosity, a filament stretcher is constructed at the lab. In this setup, 2 circular plates (with a sample of fluid in between) are pulled apart in such a way that a constant strain rate is applied. By measuring the force the fluid exerts on the plates and the fluid filament’s diameter in the middle, it is possible to determine the extensional viscosity.

Thixotropic behavior of dilute polymer solutions will be investigated using the home-built filament stretcher. And although this behavior is present in many industrial processes, it remains poorly understood. Therefore, the goal of this PhD is to gain a better fundamental understanding of thixotropy and to explore which parameters dominantly govern this phenomenon.