Revisiting the Dielectric Relaxation of Ethylene-Vinylacetate Copolymers: Influence of Microstructure
作者:
I. ŠICS,
T.A. EZQUERRA,
F.J. BALTÁ CALLEJA,
V. TUPUREINA,
M. KALNINŠ,
期刊:
Journal of Macromolecular Science, Part B
(Taylor Available online 2000)
卷期:
Volume 39,
issue 5-6
页码: 761-774
ISSN:0022-2348
年代: 2000
DOI:10.1081/MB-100102486
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
The dielectric relaxation behavior of a series of ethylene-vinylacetate (EVA) copolymers was investigated by measuring the complex dielectric permittivity in a broad frequency and temperature range. Crystallinity of EVA copolymers was estimated by differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS). The shape of the higher temperature relaxation, appearing above the glass transition temperatureTgdepends on the VA content. It was found that this relaxation was asymmetric for VA concentrations higher than 40 wt% and changed to a symmetric shape at lower VA values. Concurrently, as the VA content decreased, a major broadening of the relaxation over a wide frequency range was observed. It is found that the dielectric relaxation was preserved on going through the melting range of the semicrystalline samples, although it exhibited changes of its characteristic parameters that are typical for segmental relaxation appearing atTg. This finding allows one to associate this relaxation to the segmental motions atTgin the amorphous phase and not to the existence of interfacial regions.
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