Anomalous discharge in copolymers of vinylidene fluoride

An anomalous discharge has been found for poly(vinylidene fluoride) of form II and vinylidene fluoride copolymers in the paraelectric phase. The anomaly consists of a current peak during isothermal discharge. The peak time, i.e., the time at which the maximum current occurs in the discharge transient, depends not only on temperature and the electric field on charging, but also on the amount of ions in polymer samples and the thickness of the specimen. The amount of charge associated with the current peak is almost independent of the applied field, but depends on temperature. Study of the charge process revealed that poly(vinylidene fluoride) and vinylidene fluoride/trifluoroethylene copolymers exhibit polarization reversal or dielectric hysteresis at high temperatures and a low electric field. Thus, the anomalous discharge process is related to retarded discharge of the ionic charge bound or trapped in the crystalline regions of these copolymers. Polarization reversal at low electric field may be responsible for the anomalous behavior in homopolymer and copolymers of vinylidene fluoride. >