Thermal treatment of polyethylene-2, 6-naphthalate (PEN) film and its influence on the morphology and dielectric strength

Polyethylene-2, 6-naphthalate (PEN) film can be modified through exposure to the temperatures exceeding its glass transition temperature (122°C) and crystallization temperature (185°C), where the biaxially oriented and semicrystalline structure of the film can undergo reorganization. Experiments were designed to characterize the effects of this type of treatment on the morphology and dielectric properties of the film. Several heat treatments, with some approaching the film´s melting temperature (265°C), were applied. Following the exposure, the dielectric properties of film samples were characterized and correlated to changes in the morphology. Increase in the breakdown strength was observed in samples where the percentage of crystallinity increased through thermal treatments. Increases from 8.5% for free standing samples to 15% for restrained samples were achieved