Effect of elongation on the electrical properties and morphology of polypropylene

Variations of electrical properties of polypropylene film due to elongation have been investigated. The conductivities of PP films have been decreased with the increase of elongation ratio (/spl lambda/) and the activation energy (/spl phi/) of elongated PP films were slightly higher than that of nonelongated PP film. From TSC experimental data, we have found, in the elongated PP films (/spl lambda/=6, 8), that trap density shows a slight increase trend with the increase of elongation ratio for peak P/sub 1/, but trap density for second P/sub 2/ decrease largely in the elongated samples. We have also observed the increase of AC breakdown strength with the increase of elongation ratio. We conclude that the decrease of conductivity and increase of dielectric strength with elongation originate from the increase of trap density and trap depth for TSC peak P/sub 1/, and also may be attributed to the dominance of dipolar process at room temperature.