Résumé:
In this work, an experimental study and analysis of the effects of environmental relative
humidity (RH %) on the transport mechanisms of electrical charges in PI films have been
presented. The evolution of the surface potential decay after negative corona charge
deposition have been investigated and analyzed by examining the characteristics to
straightly obtain information about trap energy distribution in PI films for different relative
humidity levels. The calculating method of trap energy distribution is based on the double
exponential fitting analysis of surface potential decay measurements. The results indicate that
for different charging voltage levels, the surface potential decays faster in humid air than in
relatively dry ones. The recorded corona charging current confirms the interpretation of
surface potential decay measurements. Both shallow and deep trap distribution moves towards
lower energy levels, indicating an increase in the film’s electrical conductivity.
A model has been developed for the simulation of a positive corona discharge in a
needle-plane configuration at atmospheric pressure. The spatial-temporal variations of the
electric field, the electrons, positive and negative ions have been investigated.
