Distribution and stability of charges in porous polypropylene films

The porous polypropylene films have an interesting morphology and peculiar charge distribution. Electric breakdown, which takes place in the voids during high voltage corona charging, is responsible for their internal distribution. The heterocharges created during this process are trapped around the voids. The homocharges injected into the outer layers during the corona charging initially outweigh the heterocharges. However, the homocharges are dissipated more rapidly during heating, and so the surface potential changes sign during charge-TSD. The complex charge distribution within porous propylene was calculated from the pyrocurrent spectra using an approximation suggested by Ploss (1994). This method is rarely used despite its simplicity.