The ac corona discharge is the most widely-used technique for the neutralization of electric charges accumulated at the surface of insulating materials. The aim of this paper is to validate the possibility of obtaining robust optimum operating conditions for the neutralization of corona-charged polymer films using the design of experiments methodology combined with Taguchi approach. The study was made on a 70 μm thick PP film and took into account four factors. The amplitude and the frequency of the ac high voltage applied to the neutralization electrodes were considered as “design” factors. The two “noise” factors were the grid voltage and grid current of the triode-type electrode system employed for the corona charging of the samples. Analysis of variance was used to evaluate the effects of these factors on the neutralization process. The results show that both “design” factors considered for this process had highly significant effects on the neutralization rate. Of the two “noise” factors, only the grid voltage was found to have a significant effect. The optimum conditions for the neutralization process can be predicted by the commercial software MODDE 8.0. The calculation of the signal/noise ratios, according to the Taguchi approach, gives the values of the voltage amplitude and frequency that ensure the robust neutralization process.

Keywords: Ac corona, Neutralization process, Polypropylene (PP), Design of experiments methodology, Taguchi approach