Paper Number
PO16
Session
Poster Session
Title
Strain shifts in stress-controlled oscillatory shear: Probing zero-shear viscosity and TTS shifting factors of polymer melts
Presentation Date and Time
October 17, 2018 (Wednesday) 6:30
Track / Room
Poster Session / Woodway II/III
Authors
- Lee, Ching-Wei (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)
- Rogers, Simon A. (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)
Author and Affiliation Lines
Ching-Wei Lee and Simon A. Rogers
Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801
Speaker / Presenter
Lee, Ching-Wei
Text of Abstract
Strain responses under stress-controlled oscillatory shearing often oscillate about a non-zero value. Conventionally, the strains are shifted so that they oscillate about zero, and the corresponding shifting factors are ignored. Investigating three distinct types of polymer systems, including polymer-like micelles, concentrated polyethylene oxide solutions, and molten entangled polystyrene, we show that the shifted strain is a manifestation of a moving equilibrium strain, and a theory describing the shifting is provided. We further demonstrate that the shifting factors collected at different imposed frequencies and stress phases can be superimposed into one master curve. These strain shifting factors contain information about fundamental material properties, and are shown to be an alternative measure of zero-shear viscosity. The zero-shear viscosity can be independently and efficiently measured in the linear regime across distinct regimes of dynamics, including the terminal and Rouse regimes, and the rubbery plateau, where avoiding edge fracture is crucial. This approach can be further applied to directly determine the time-temperature superposition (TTS) shifting factors. In-situ time-resolved small-angle neutron scattering under varying stress imposes confirms that microstructural evolution is independent of the shifted lab-frame strain, yet correlates well with the recoverable strain.