Electret characteristics of hybrid films consisting of porous Polytetrafluoroethylene and teflon fluoroethylenepropylene with corona charging

We have prepared hybrid films consisting of porous polytetrafluoroethylene (PTFE) and Teflon fluoroethylene-propylene (FEP) and we have investigated their charge dynamics of injection, transport and trapping using corona charging, isothermal and thermally stimulated surface-potential decay measurements. The results indicate that the hybrid film samples show different electret characteristics when charged through side PTFE or side FEP. The samples charged negatively through side porous PTFE show the best charge stability. Their charge dynamics differs very much from a single film. The effect of corona polarity on the electret behaviour in the hybrid film is very large. The experimental results are explained with the three structure level model of charge storage in electrets.