Relaxations in amorphous and semi-crystalline polyesters - A study by thermally stimulated depolarization currents. Kattan, M.; Dargent, E.; and Grenet, J. Journal of Thermal Analysis and Calorimetry, 76(2):379–394, 2004.
abstract   bibtex   
Thermally stimulated depolarization currents and differential scanning calorimetry are performed on thermoplastic polyesters to characterize both alpha and beta 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 alpha relaxation while the standard two-phases model is sufficient to explain the variations of the beta relaxation mode. Elementary analysis of both alpha and beta relaxations show that the beta 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 alpha relaxation exhibits a prominent maximum of the activation energies at the glass transition temperature.
@article{kattan_relaxations_2004,
	title = {Relaxations in amorphous and semi-crystalline polyesters - {A} study by thermally stimulated depolarization currents},
	volume = {76},
	issn = {1388-6150},
	abstract = {Thermally stimulated depolarization currents and differential scanning calorimetry are performed on thermoplastic polyesters to characterize both alpha and beta 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 alpha relaxation while the standard two-phases model is sufficient to explain the variations of the beta relaxation mode. Elementary analysis of both alpha and beta relaxations show that the beta 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 alpha relaxation exhibits a prominent maximum of the activation energies at the glass transition temperature.},
	language = {English},
	number = {2},
	journal = {Journal of Thermal Analysis and Calorimetry},
	author = {Kattan, M. and Dargent, E. and Grenet, J.},
	year = {2004},
	keywords = {DSC, behavior, cooperative   relaxations, crystallization, differential scanning calorimetry, discharge, glass-transition, poly(ethylene-terephthalate), polymers, relaxation, saturated polyester, spectroscopy, terephthalate), thermally stimulated   depolarization current (TSDC)},
	pages = {379--394}
}
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