Edge-Induced Shear Banding in Entangled Polymeric Fluids

Hemingway, Ewan J.; Fielding, Suzanne M.

Abstract

Despite decades of research, the question of whether solutions and melts of highly entangled polymers exhibit shear banding as their steady state response to a steadily imposed shear flow remains controversial. From a theoretical viewpoint, an important unanswered question is whether the underlying constitutive curve of shear stress σ as a function of shear rate ˙γ (for states of homogeneous shear) is monotonic, or has a region of negative slope, dσ/d˙γ<0, which would trigger banding. Attempts to settle the question experimentally via velocimetry of the flow field inside the fluid are often confounded by an instability of the free surface where the sample meets the outside air, known as “edge fracture.” Here we show by numerical simulation that in fact even only very modest edge disturbances—which are the precursor of full edge fracture but might well, in themselves, go unnoticed experimentally—can cause strong secondary flows in the form of shear bands that invade deep into the fluid bulk. Crucially, this is true even when the underlying constitutive curve is monotonically increasing, precluding true bulk shear banding in the absence of edge effects.

Citation

Hemingway, E. J., & Fielding, S. M. (2018). Edge-Induced Shear Banding in Entangled Polymeric Fluids. Physical Review Letters, 120(13), Article 138002. https://doi.org/10.1103/physrevlett.120.138002

• Journal Article Type: Article
• Acceptance Date: Jan 26, 2018
• Online Publication Date: Mar 30, 2018
• Publication Date: Mar 30, 2018
• Deposit Date: Apr 12, 2018
• Publicly Available Date: Apr 12, 2018
• Journal: Physical Review Letters
• Print ISSN: 0031-9007
• Electronic ISSN: 1079-7114
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 120
• Issue: 13
• Article Number: 138002
• DOI: https://doi.org/10.1103/physrevlett.120.138002
• Public URL: https://durham-repository.worktribe.com/output/1334253