Further observations on the decay of surface potential of corona charged polyethylene films

Abstract

For the authors' previous work see ibid., vol.10, p.487 (1977). Further measurements are reported on the decay of surface potential of negative corona charged polyethylene films and on the crossover effect reported earlier by Ieda and co-workers (1967). It is shown that when the duration of charging is short ( approximately 25 ms) the subsequent decay curves of surface potential are well-behaved and do not exhibit the crossover effect even though the initial surface fields are high. Experiments are also reported in which an air stream is directed along the surface of the films while corona charging. This also removes the crossover effect and is in agreement with results reported in which an air stream is directed along the surface of the films while corona charging. This also removes the crossover effect and is in agreement with results reported by Okumura (1976) for polystyrene-hexamethacrylate. It is concluded that excited molecules as well as photons produced in the corona discharge play an important role in inducing charge from surface states to enter the bulk of the polymer where they are much more mobile. This leads to rapid decay of surface potential at higher initial surface fields and the crossover effect is then observed.