Thermal Aging of Bi-axially Orifnted Pet Films: Relation between Structural Changes and Dielectric Behavior

The structural changes in bi-stretched poly(ethylene-terephthalate) films induced by thermal aging have been studied by recording the variations of crystallinity, orientation of aromatic rings, and elongation at break. An attempt has been made to correlate the variations of the activation energy of the a relaxation process to the changes in physical properties. A simultaneous decrease of activation energy and of elongation at break has been observed on aged samples.