Electrical properties of 12 μm biaxially oriented poly(ethylene naphthalate 2,6 dicarboxylate), films related to ageing

摘要

PEN films, 12μm thick, yield original characteristics both with regard to their structure and to their properties. Obviously, the structural originality may explain the properties. This originality lies in the twinning of chains of PEN intheβ-lattice morphology at shorter distances than 4 A, presumably even shorter than 3.5 A.This twinning of chains contributes to the upgrading of mechanical properties of films. Moreover, the proximity of twinned chains allows transesterification processes between the chains under irradiation. This twinning characterized by a slowering and aweakening of electrical relaxations of local modes may also explain conductivity behaviour through aβ-＞αphase transition process, allowing a moderation of the internal field increase under electrons injection. The prematurate breakdown of filmssubmitted to UV irradiation is attributed to an increase of the local field in the bulk due to extraction of electrons from molecular orbitals and their trapping inα crystalline states where untrapping through a phase transition process is unlikelyenergetically.