Electret properties of cycloolefin-copolymer-polypropylene blends

The electret properties of cycloolefin copolymer (COG)-polypropylene blends with three different percentages of PP-were investigated. Films metalized on one side were charged with electron beam or corona methods. Measurements of the isothermal decay of the surface potential at elevated temperatures and high humidities as well as measurements of thermally-stimulated currents indicate that the charge storage properties of the corona charged blends are significantly better than those of PP. In particular, positively corona charged blends with up to 25 percent PP are very good electrets. They might be of interest in membrane applications for microphones and other sensors, where their excellent mechanical properties make them superior to Teflon FEP, and in air filter applications where the better charge-storage capabilities make them preferable to PP