Influence of surface modifications with orthophosphoric acid on the charge stability of polypropylene electrets

It is known that both, physico-chemical surface modification and thermal treatment, can lead to enhanced electret properties of dielectric polymers. To further investigate the influence of surface modifications on charge storage in polypropylene (PP) electrets, a combined thermal and chemical treatment with orthophosphoric acid (H
₃
PO
₄
) is applied to PP films. Charged samples are then studied by means of thermally-stimulated-discharge (TSD) experiments, contact-angle measurements and Fourier-transform infrared (FTIR) spectroscopy. From the results, it can be concluded that additional deeper traps have been formed along with the treatment-induced conformation variations on the surface of the PP films. The new traps significantly improve the surface charge-stability of PP electrets.