High field dielectric properties of Polyethylene Terephthalate

Polyethylene Terephthalate (PET) is a polar polymer and is best known as the material that constitutes a soft drink bottle. PET has excellent physical properties, such as, high heat resistance, low cold resistance, high transparency, good electrical insulation, good chemical resistance, solvent resistance, and so on. It is also used as electrical insulation or a dielectric material, such as, insulation tape, condenser, flat cable, and so on. So far, the high field dielectric properties of a nonpolar polymer, such as LDPE and PP, were reported from the results of dissipation current waveform and electroluminescence (EL) simultaneous observation. It was reported that in high field, charge injection from the electrode will dominant. In this paper, in order to grasp the specific dielectric properties of polar polymers like dipole polarization phenomenon, by using PET film, the simultaneous observations of dissipation current and EL were carried out at the frequencies 50 and 400 Hz. As the result of experiments, it was found that the electric field dependence of power loss density at 50 Hz is saturating above 24 kV/mm and is not saturating at 400 Hz.