Charge relaxation in electrets at high surface potentials

Experiments were carried out to investigate the effect that the surface potential has on the relaxation of the negative homocharge in electrets consisting of films of a copolymer of tetrafluoroethylene with hexafluoropropylene (TFE-HEP) as well as of TFE-HEP films whose surfaces have been exposed to media containing hydrogen. Qualitative changes are shown to occur in the properties of the TFE-HEP films as the initial surface potential is decreased. The spectrum of the thermally stimulated depolarization current and the curves of the thermally stimulated relaxation of the surface potential of electrets charged to /V sub 0/ = 2000 V reveal a low-temperature charge relaxation which is not exhibited by electrets with a lower value of V sub 0. If the free surface of a TFE-HEP film is treated in H2O2, a 'crossing' of the relaxation curves of the surface potential occurs. It is shown that these effects result from the surface properties of the electrets.