Dipole polarization of polypropylene electret

The improvement of adhesion in polypropylene(PP) films have been required from industrial applications. Generally, the presence of polar groups and the morphology of the PP film surface play a crucial role for gaining good adhesion. Corona discharge to the films is one of the techniques to change a surface, widely used for the production of electrets. In recent researches, a good piezoelelctric activity in polypropylene electret has been found in foams with thin walls. However, the polarization origin of PP electret with hetero- and homo-charges by corona discharge treatment is unclear.