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Structural relaxation in poly(ethylene terephthalate) studied by positron annihilation lifetime spectroscopy
Author(s) -
Sathyanarayana P M,
Shariff Gani,
Thimmegowda M C,
Ashalatha M B,
Ramani R,
Ranganathaiah C
Publication year - 2002
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.924
Subject(s) - relaxation (psychology) , positron , stretched exponential function , exponential function , materials science , ethylene , poly ethylene , spectroscopy , annihilation , glass transition , exponential decay , thermodynamics , nuclear physics , chemistry , polymer , physics , composite material , organic chemistry , mathematics , quantum mechanics , mathematical analysis , psychology , social psychology , catalysis , electron
Positron lifetime technique was used to study the physical ageing process in poly(ethylene terephthalate) (PET). Positron lifetime results show that the structural relaxation processes in PET encompass two different time regimes, one short and the other long. The relaxation function constructed from the measured o ‐Ps intensity I 3 exhibits non‐exponential character, which can be best fitted with two additive exponentials. The Narayanaswamy model (Kohlraush‐William Watt (KWW) function) is invoked to extract the stretching parameter β indicating the extent of deviation from exponential relaxation. Based on the relaxation times, the activation energies calculated seem to label the different kinetic units of PET structure participating in the relaxation process. © 2002 Society of Chemical Industry