Relaxations IN amorphous and semi-crystalline polyesters |
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Authors: | M Kattan E Dargent J Grenet |
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Institution: | (1) AECS Damas, P.O. Box 6091, Syrie;(2) 76821 Laboratoire d'Etude et de Caractérisation des Amorphes et des Polymeres, Université de Rouen, Site du Madrillet UFR Sciences Laboratoire d'Etude et de Caractérisation des Amorphes et des Polymeres Avenue de l'Université, BP 12, 76801 Saint Etienne du Rouvray, France |
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Abstract: | Thermally stimulated depolarization currents and differential scanning calorimetry are performed on thermoplastic polyesters
to characterize both a and b relaxations. The influence on the different relaxations phenomena of the chemical structure (size
of the naphthalene groups, presence of cyclohexane, length of the aliphatic group, ...) as well as the influence of the crystallinity
are discussed. The three phases model with a crystalline part, a rigid amorphous part unable to relax and an amorphous phase
able to relax at various temperatures depending on the distribution of the relaxation times is used to explain the evolution
of the main α relaxation while the standard two-phases model is sufficient to explain the variations of the β relaxation mode.
Elementary analysis of both α and β relaxations show that the β relaxation characterized by a continuous variation of activation
energies as a function of temperature follows the activated state equation with a zero activation entropy while the cooperative
a relaxation exhibits a prominent maximum of the activation energies at the glass transition temperature.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | DSC relaxation saturated polyester thermally stimulated depolarization current (TSDC) |
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