Morphology and Electrical Properties of Biaxially-oriented Polypropylene Films

BO-PP films have fairly different morphologies to those of non-oriented PP films. These morphological differences were found to originate from the orientation of the crystalline and amorphous phases. The orientation of the amorphous phase causes a pronounced decrease observed both in ionic conduction and in dielectric loss. Two types of BO-PP films were found to have fairly different morphologies: the tubular type seems to exhibit a network structure made of oriented crystalline zones which are linked with slightly entangled amorphous chains, while the tenter type shows a spherulite-deformed structure made of a highly oriented cyrstalline phase connected with elongated and highly oriented amorphous chains. Despite their dissimilar structures, the two BO-PP films studies were found to have generally the same dielectric behavior except for the activation energy of the conduction and the dielectric relaxation processes.