Measure and analysis of potential decay in polypropylene films after negative corona charge deposition

Surface potential decay after negative corona charge deposition has been studied for polypropylene films 50 μm thick, over a wide range of decay times and charging voltage (500–2800 V). At low initial potential (500–800 V), the surface potentials were stable and did not decay. At high initial potential (1200–2800 V), the surface potential decay has been clearly observed with differences in the decay rate. The observed decay behavior has been computer simulated to elucidate the transport mechanism in polypropylene films. A good agreement between measured and calculated decay curves was obtained with a model in which charges are transported by hopping of injected carriers between localized trapping centers. The model is characterized by parameters such as the free carrier mobility, the mean free time of carrier between traps and the mean capture time in trap. The transport parameters have been determined by a fitting procedure.