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Modeling the relaxation of polymer glasses under shear and elongational loads

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

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R.L. Moorcroft

R.G. Larson

M.E. Cates


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.


Fielding, S., Moorcroft, R., Larson, R., & Cates, M. (2013). Modeling the relaxation of polymer glasses under shear and elongational loads. The Journal of Chemical Physics, 138(12), Article 12A504.

Journal Article Type Article
Publication Date Mar 28, 2013
Deposit Date Mar 19, 2013
Publicly Available Date Jun 3, 2014
Journal Journal of Chemical Physics
Print ISSN 0021-9606
Electronic ISSN 1089-7690
Publisher American Institute of Physics
Peer Reviewed Peer Reviewed
Volume 138
Issue 12
Article Number 12A504


Published Journal Article (889 Kb)

Copyright Statement
© 2013 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of chemical physics, 138, 12A504 (2013) and may be found at

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