Breakdown Strength and Energy Density Improvement of Polypropylene by Parylene Deposition for Film Capacitor

In this article, a surface modification method is proposed for improving the breakdown strength and the energy density of polypropylene (PP) films for power capacitors based on chemical vapor deposition (CVD). The results indicate that after 5% thickness deposition, the leakage conductivity of the composite films decreases by 77% at 30 °C and declines by 96.2% at 85 °C compared with the pristine PP samples. The dielectric constant is increased from 2.19 to 2.34 at 1 kHz. The dielectric loss decreases from 0.0425 to 0.0047. The dc breakdown strength is enhanced from 553.7 to 658.5 kV/mm, and the energy density is improved by 40%–50%. The parylene deposition successfully increases the withstand voltage and the energy density by inhibiting charge injection. The results provide a reference for optimizing the performance of capacitor by interface modification.