A positron lifetime study of structural relaxation in UV irradiated poly (ethylene terephthalate)

Sathyanarayana, P. M. and Shariff, Gani and Thimmegowda, M. C. and Ashalatha, M. B. and Ramani, R. and Ranganathaiah, C. (2002) A positron lifetime study of structural relaxation in UV irradiated poly (ethylene terephthalate). Polymer Degradation and Stability, 78 (3). 449 - 458. ISSN 1873-2321

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Official URL: https://doi.org/10.1016/S0141-3910(02)00183-0

Abstract

Structural relaxation in UV irradiated poly (ethylene terephthalate) (PET-UV) has been investigated using positron lifetime techniques. Positron lifetime results show that the structural relaxation processes in PET-UV encompass three different time regimes, unlike the unirradiated poly (ethylene terephthalate) (PET) where only two relaxation times were observed. The relaxation functions constructed from the measured ortho positronium intensity, I3, exhibit non-exponential character that can be best fitted with two additive exponentials. To determine the extent of deviation from exponential relaxation, we have used the Narayanaswamy model (KWW function) and evaluated the stretching parameter β. From the relaxation times derived from the exponential decay curves, the activation energies have been calculated and from these activation energies it seems possible to label the different kinetic units of the UV irradiated poly (ethylene terephthalate) structure participating in the relaxation processes.

Item Type: Article
Uncontrolled Keywords: Poly (ethylene terephthalate), UV irradiation, Structural relaxation, Free volume, Relaxation time, Activation energy
Subjects: D Physical Science > Physics
Depositing User: manjula User
Date Deposited: 25 Sep 2019 06:09
Last Modified: 25 Sep 2019 06:09
URI: http://eprints.uni-mysore.ac.in/id/eprint/8505

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