Constant-Current Corona Charging Of Biaxially Stretched Pvdf Films In Humidity-Controlled Atmospheres

A special version of a constant current corona triode has been developed for charging samples in controlled atmospheres. Measurements performed on biaxially stretched polyvinylidenefluoride (PVDF) samples show that the buildup of the surface potential is dependent on air humidity. In a dry air atmosphere, the polarization clearly shows the ferroelectric behavior of the PVDF sample. For samples charged under humid conditions, the surface potential vs. time curves pass through a maximum value which decreases with increasing relative humidity. A tentative explanation for the surface potential dependence on the humidity is given, based on the increase in conductivity originating from the dissociated water molecules absorbed into the sample.