Studies on electrostatic surface discharges on corona-chargedpolymer surfaces

Electrostatic surface discharge phenomena on corona-charged thin polymer films such as FEP or PTFE Teflon, with surface potentials from 1 to 5 kV in both polarities, were studied. A grounded sphere electrode, 5 mm in diameter, approached the charged surface by a computer-controlled step motor until the surface discharge occurred. Discharge-current waveforms, with a very short risetime (a few nanoseconds), were observed to be related to the length (5-30 cm) or type (single wire or plain mesh) of the earth line. The discharge gap length between the film surface and the grounded electrode was also calculated. The results were strongly dependent on the polarity of the surface charge and were widely divergent, indicating the complicated surface discharge mechanism