Nanosecond pulse corona charging of polymers

A needle-plane electrode system was used to study charging properties of non woven polypropylene (PP) films exposed to nanosecond pulse discharge. A discovery of polarity reversal charging (PRC) was found that the accumulated charges on the non woven PP films sometimes show an opposite polarity against the applied pulses. Different polarity and different width of pulses produce different turning point of pulse peak (TPPP) where polarity of the net charges turns. The TPPP of negative pulse increases with the increase of pulse width, while that of positive one decreases. In order to make the charging process clear, PP films were also used and the pulsed electro-acoustic (PEA) space charge measuring method was used. The measurements showed that charges of different polarities, whose amount increases with the growth of pulse peak and charging time, have been simultaneously injected into the bulk of the PP films. Based on the mechanism of gaseous discharge, a combination effect of high filed injection (HFI) and return stroke injection (RSI) caused by a triple-junction effect is put forward here and the PRC phenomena is also discussed