Charging conditions for cellular-polymer ferroelectrets with enhanced thermal stability

The application of most polymer ferroelectrets is limited because of their relatively low charge stability at high temperature. By means of electrical charging at elevated temperatures, the thermal stability of the ferroelectret charge can be enhanced. Polyethylene naphthalate (PEN) ferroelectrets charged at room temperature show stability up to 80degC, which is already 20degC higher than the polypropylene (PP) ferroelectrets, but PEN can still not be employed when higher working temperatures are required. Here, we investigate the thermal stability of PEN ferroelectrets after charging at various elevated temperatures.