Fundamental Characterization of Elongation Behavior of Viscoelastic and Viscoplastic Materials

Polymer and Suspension behavior under various stress fields is used in the design of many applications. There is increasing need to fine tune the characterization of dilute versions of these materials for medical and electronic applications.

The ability to characterize the extensional stresses and behavior of dilute polymer solutions is an important and difficult area of research. For viscoplastic materials, little fundamental research exists. While the field has focused primarily on measuring the elastocapillary relaxation time, this work focuses on understanding the state of the polymer chain required to induce elastic effects. A Newtonian fluid is well understood to undergo thinning that balances viscous forces and capillary forces. However, dilute polymer solutions exhibit nearly no change in shear rheology, but a significant departure of Newtonian capillary break up dynamics. Under the right kinematic conditions, the uniaxial extension of a dilute polymer solution elicits an additional elastic force component. These kinematic conditions and their resulting impact on polymer state are modeled and validated using experimental data using a VADER extensional rheometer. In viscoplastic solutions, the kinematic conditions leading to transition states of yield stress materials are evaluated.