Factors that influence the surface potential decay on a thin film of polyethylene terephthalate (PET)

The initial potential at the surface of the sample, as well as the temperature and the relative humidity of the ambient air are known to influence the surface-potential decay characteristics of corona-charged thin insulating films. The aim of the present work is to demonstrate the effectiveness of the Experimental Design methodology for evaluating the effects of these factors. Thus, a full factorial experimental design was carried out on a thin film of polyethylene terephthalate (thickness: 0.5 mm; surface: 50 mm × 50 mm). A negative corona discharge produced in a needle–grid–plate electrode system was employed to charge the surface of the film samples. The variation domains for the three factors were respectively: −1000 V to −1800 V; 25 to 55 °C; 50% to 80%. The surface-potential decay process was characterized by two output variables: the time needed for the potential to reduce to respectively 50% and 10% of the initial value. It was found that the former is more affected by the temperature, while the latter is more sensitive to the variation of the relative humidity.