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Structural Changes in Glassy Polycarbonate Due to Cyclic Loading

Published online by Cambridge University Press:  16 February 2011

Liang Bao Liu,
Albert F. Yee,
John C. Lewis,
Xiaowei Li and
David W. Gidley
Liang Bao Liu
Affiliation:
Dept. of Materials Science and Engineering
Albert F. Yee
Affiliation:
Dept. of Materials Science and Engineering
John C. Lewis
Affiliation:
Dept. of Materials Science and Engineering
Xiaowei Li
Affiliation:
Dept. of Materials Science and Engineering
David W. Gidley
Affiliation:
Dept. of Physics The University of Michigan, Ann Arbor, MI 48109-2136
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Abstract

Glassy polycarbonate was subjected to cyclic stresses and the changes in its structure were studied by DSC, positronium annihilation lifetime spectroscopy (PALS), and small and medium angle X-ray scattering. Upon increased exposure to cyclic loading, the enthalpy overshoot near Tg increased in a manner similar to increasing physical aging. However, the “hole” size as revealed by PALS increased, unlike physical aging. SAXS reveals an increase in the short range order and the amplitude of density fluctuation. These results can be explained in a consistent manner. We conclude that mechanical loading does cause changes in the glassy structure.

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