Morphology and electrical properties of biaxially oriented polypropylene

The BO-PP films have fairly different morphologies when compared 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 the remarkable decrease observed 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 crystalline phase connected with elongated and highly oriented amorphous chains. Despite their dissimilar structures, the two Bo-PP films studied were found to have generally the same dielectric behavior.