Surface Charge Stability of High Temperature Phosphatized Biaxially Oriented Polypropylene Film

Biaxially-oriented polypropylene (BOPP) films are extensively used as dielectrics in capacitor designs due to their good electrical and mechanical properties. However, the relative poor surface-charge stability of BOPP has hold it back to be qualified as an advanced dielectric for applications especially at harsh conditions. This work is to explore the potential of high temperature phosphatization on improving the surface charge stability of BOPP films, which encourages the 24 h chemical treatment at 120 °C and 140 °C by phosphoric acid. The finding of phosphorus on the surface of treated samples is confirmed by the attenuated total reflection infrared spectroscopy (FTIR) and more phosphorus elements are possible to be introduced by the phosphatization at higher temperature of 140 °C which is evidenced by the X-ray photoelectron spectroscopy (XPS). Correspondingly, the samples phosphatizated at 140 °C show slower surface potential decay comparing to the group prepared at 120 °C. It is further found that the phosphatization leads to increased surface roughness and the formation of phosphorus-rich nano-islands is considered as the sites of deep traps.