Charge stability of teflon-FEP electrets charged at melting temperatures

To reach as high charge stability as possible we tried to charge FEP at temperatures in the melting region. Therefore the foil was heat sealed on a metal plate. After charging the samples were also thermally aged at melting temperature in some experiments. Charge stability was investigated by thermally stimulated charge decay (TSCD) and thermally stimulated current in open circuit (TSC-O).