Modeling the relaxation of polymer glasses under shear and elongational loads

S. M. Fielding*, R. L. Moorcroft, R. G. Larson, M. E. Cates

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Glassy polymers show "strain hardening": at constant extensional load, their flow first accelerates, then arrests. Recent experiments under such loading have found this to be accompanied by a striking dip in the segmental relaxation time. This can be explained by a minimal nonfactorable model combining flow-induced melting of a glass with the buildup of stress carried by strained polymers. Within this model, liquefaction of segmental motion permits strong flow that creates polymer-borne stress, slowing the deformation enough for the segmental (or solvent) modes then to re-vitrify. Here, we present new results for the corresponding behavior under step-stress shear loading, to which very similar physics applies. To explain the unloading behavior in the extensional case requires introduction of a "crinkle factor" describing a rapid loss of segmental ordering. We discuss in more detail here the physics of this, which we argue involves non-entropic contributions to the polymer stress, and which might lead to some important differences between shear and elongation. We also discuss some fundamental and possibly testable issues concerning the physical meaning of entropic elasticity in vitrified polymers. Finally, we present new results for the startup of steady shear flow, addressing the possible role of transient shear banding. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769253]

Original languageEnglish
Article numberARTN 12A504
Number of pages11
JournalThe Journal of Chemical Physics
Volume138
Issue number12
DOIs
Publication statusPublished - 28 Mar 2013

Keywords

  • STRONG EXTENSIONAL FLOW
  • COUPLING THEORY
  • MOLECULAR MOBILITY
  • CONSTITUTIVE MODEL
  • DEFORMATION
  • RHEOLOGY
  • STRESS
  • THERMOPLASTICS
  • DYNAMICS
  • DILUTE

Fingerprint

Dive into the research topics of 'Modeling the relaxation of polymer glasses under shear and elongational loads'. Together they form a unique fingerprint.

Cite this