The transitions/relaxations of polycarbonate around its glass transition temperature, T~, have been investigated by differential scanning calorimetry and thermally stimulated current spectroscopy. A sub-glass transition/relaxation has been observed with higher intensity in the quenched sample. This precursor of Tg is characterized by relaxation times following a Fulcher-Vogel equation. It might be explained by the diffusion of conformational defects all along the chain. The glass transition/relaxation is constituted of two components: (i) The lower-temperature component is associated with a distribution of relaxation times obeying a compensation law. It corresponds to cooperative movements of sequences of various length in the 'true' amorphous regions. (ii) The upper-temperature component is enhanced by annealing above T~. It has been attributed to the 'constrained' amorphous regions. Note that such domains with high local order have been previously observed by electron microscopy and X-ray diffraction
Посилання на статтю:
Thermally stimulated current study of relaxation in glassy polycarbonate / A. Bernes, D. Chatain and C. Lacabanne* // Polymer. – 1992. – Vol 33. – P. 4682-4686.
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