Abstract
Using self-designed particle visualization instrumentation, startup
shear and step-strain tests were conducted under a series of
systematically varied rheological and geometrical conditions, and the
velocity profiles in three different well-entangled
polybutadiene/oligomer solutions were obtained. For startup shear tests,
in the regime of entanglement densities up to 89 and nominal reptation
Weissenberg numbers up to 18.6, we generally observe either wall slip
and a linear velocity/strain profile or simply the linear profile with
no wall slip unless a massive edge fracture or instability has occurred
in the sample. Meanwhile, step-strain tests conducted at similar and
higher step Weissenberg numbers revealed little particle motion upon
cessation. These results lead us to a conclusion that there is no
compelling evidence of shear banding or nonquiescent relaxation in the
range of entanglement density and Wi investigated; we interpret the
results to imply that any observed banding proba
Original language | English |
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Pages (from-to) | 1411-1428 |
Number of pages | 18 |
Journal | Journal of Rheology |
Volume | 57 |
Issue number | 5 |
DOIs | |
State | Published - Sep 2013 |
Keywords
- Edge fracture
- Flow instability
- Flow visualization
- Non-linear flow
- Particle imaging velocimetry
- Particle tracking velocimetry