Paper Number
GG17
Session
Rheology of Gels, Glasses and Jammed Systems
Title
Yield-stress fluids with tunable extensibility
Presentation Date and Time
October 10, 2022 (Monday) 5:25
Track / Room
Track 3 / Sheraton 5
Authors
- Sen, Samya (University of Illinois Urbana-Champaign, Department of Mechanical Science and Engineering)
- Fernandes, Rubens R. (University of Illinois Urbana-Champaign, Department of Mechanical Science and Engineering)
- Ewoldt, Randy H. (University of Illinois at Urbana-Champaign, Mechanical Science and Engineering)
Author and Affiliation Lines
Samya Sen, Rubens R. Fernandes and Randy H. Ewoldt
Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL 61801
Speaker / Presenter
Sen, Samya
Keywords
experimental methods; gels; glasses; jammed systems; polymer blends; polymer solutions; rheometry techniques; suspensions
Text of Abstract
This work introduces a family of yield-stress fluids with variable extensibility. We term these “Boger yield-stress fluids” when the formulations independently vary the extensional properties without significantly changing the shear viscosity or linear viscoelastic behavior, stretching the definition of the well-known Boger fluids [1]. Extensibility is outside the standard paradigm of yield-stress fluids, be it model materials or constitutive equations. Model yield-stress fluids have been designed with significant extensional properties, but they are based on emulsions [2] which are poor candidates for fluid mechanics studies of yield-stress fluids, since they are opaque and their microstructure may significantly evolve due to droplet breakup or coalescence. In this work, we specifically seek to develop extensible yield-stress fluids based on the well-studied system of Carbopol microgel particle suspensions (a model yield-stress fluid) with poly(ethyleneoxide), a high molecular weight polymer. We characterize its rheology both in shear and extension, and find that key properties in shear, such as the yield stress and linear viscoelastic moduli, do not change significantly with the addition of the polymer. Filament stretching tests, however, show that addition of polymers changes the extensional properties many fold. These results exemplify that it is possible to dramatically change the behavior in extension with minimal change in linear and nonlinear shear properties, with a well-studied yield-stress fluid relevant to fluid dynamics experiments such as droplet impact [3].
[1] Boger, D. “A highly elastic constant-viscosity fluid”. J. Non-Newt. Fluid Mech., 3, 87-91 (1977/1978).
[2] Nelson, A. Z., R. E. Bras, J. Liu, and R. H. Ewoldt. “Extending yield-stress fluid paradigms.” J. Rheol., 62, 357–369 (2018).
[3] Sen, S., A. G. Morales, and R. H. Ewoldt. “Viscoplastic drop impact on thin films” J. Fluid Mech., 891, A27 (2020).