Deformation of Glassy Polymers¹

A. L. Volynskii*², T. E. Grokhovskaya*, A. S. Kechek’yan**, and N. F. Bakeev**

* Faculty of Chemistry, Moscow State University,
Leninskie gory, Moscow, 119899 Russia

** Enikolopov Institute of Synthetic Polymeric Materials, Russian Academy of Sciences,
ul. Profsouyznaya 70, Moscow, 117393 Russia

Received June 5, 2002;
Revised Manuscript Received October 7, 2002

Abstract—Thermally stimulated shrinkage of amorphous PET and polystyrene (PS) after their deformation via
uniaxial compression at room temperature was studied by direct microscopic observations. Experimental evi-
dence allows one to conclude that the deformation of a glassy polymer may be conditionally divided into two
stages. At the first stage (below the yield point), the polymer is transformed into very thin layers localized in
shear bands which are separated by blocks of the initial undeformed polymer. In such layers, the glass transition
temperature is reduced. This fact is responsible for the appearance of a low-temperature component of the ther-
mal shrinkage of an oriented glassy polymer. At the second stage (after the yield point), an overwhelming vol-
ume transition of the polymer to its oriented state takes place. This process is not accompanied by any marked
volume changes and is similar to the deformation of an amorphous polymer at temperatures above the glass
transition temperature. Thermal shrinkage related to this deformation mode occurs in the glass transition region
of a bulk polymer.

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