Experimental study of controlled active neutralization of polypropylene films

Abstract

AC corona discharge is widely employed for neutralizing the electric charges at the surface of insulating bodies: films, plates, granules, etc. If uncontrolled, this active neutralization process is accompanied by the persistence of a residual charge at the surface of the treated bodies. The aim of this present work is to demonstrate experimentally the efficiency of the controlled active neutralization using AC corona generated in a triode-type electrode configuration, with the grid connected to the ground. The experimental study was carried out on DC corona charged polypropylene films that were neutralized by a sinusoidal corona discharge at industrial frequency (50 Hz). The distribution of the electric potential at the surface of the charged and neutralized samples were measured by a non-contact electrostatic voltmeter. The factors under study were: the amplitude of the AC voltage applied to the corona electrode of the triode system, the duration of exposure to the corona discharge, the scanning speed, and the spacing between the grid and sample. The experimental results obtained show that the neutralization rate is close to 100%, i.e. the electric potential profiles obtained at the surface exposed to AC corona discharge show the absence of the residual charge. The results show that the efficiency of the controlled active neutralization depends on the energy that the AC corona discharge imparts to the charged samples, and that affects the trapped bulk charge.