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Comparison of Dielectric Properties between Semi-Crystalline and Amorphous Polymers

1961; Society of Materials Science; Volume: 10; Issue: 92 Linguagem: Inglês

10.2472/jsms1952.10.383

0372-7971

Motowo Takayanagi, Yōichi Ishida, Kaoru Yamafuji,

High voltage insulation and dielectric phenomena

The dielectric properties of several kinds of amorphous and semi-crystalline polymers have been measured by using mutual inductance bridge. The dielectric absorptions (called α and β in their turns of appearance from high temperature side or low frequency side) have been observed for each polymer and these absorptions attributed to the dipoles in the amorphous regions are discussed. The absorptions due to the crystalline region or those related to hydrogen bonding are not discussed in this paper.As for the α-absorption, remarkable differences are observed between semi-crystalline and amorphous polymers. That is, (1) the magnitudes of semi-crystalline polymers are considerably smaller than those of the amorphous polymers, even if the correction of the degree of crystallinity is made. The temperature-dependence of the magnitude for semi-crystalline polymers is smaller than that of the amorphous polymers. (2) the shape of the α-absorption of semi-crystalline polymer is much broader than that of amorphous polymers. Such differences could be explained from the view-point that the α-absorption is attributed, irrespectively of amorphous or semi-crystalline, to the re-orientation of the dipoles due to the segmental micro-Brownian motions of the main chains. The activation energy for the α-absorption calculated theoretically from such a view-point agrees with the observed value.As for the β-absorption, there can not be found so remarkable differences as the α-absorption between amorphous and semi-crystalline polymers. Such results suggest that the β-absorption is due to local relaxation much more than the α-absorption. The magnitude, its temperature dependence and activation energy are derived theoretically from the view-point that the β-absorption is attributed, irrespectively of amorphous and semi-crystalline, to the rotating diffusional motions of the dipoles due to local micro-Brownian motions of the main chains and the derived result agrees with the observed data.