Enhanced energy density of BOPP film by MAH grafting for metallized capacitors

Abstract In this paper, maleic anhydride (MAH) was grafted on the surfaces of biaxially oriented polypropylene (BOPP) film by ultraviolet irradiation treatment to improve the breakdown strength. The addition of MAH, with abundant deep traps, effectively hinders charge injection from the electrode, leading to improved dielectric performance, particularly at elevated temperatures. The experimental results show that the received modified film exhibits an improved permittivity of 2.37 alongside a low dielectric loss of 0.0022 at 1000 Hz. Remarkably, the DC breakdown strength reaches 633.9 kV mm −1 , marking a notable 21.4% increase compared to the unmodified BOPP film at 120 °C. Moreover, the film exhibits an energy density of 2.58 J m −3 , which is 1.59 times that of the pure film. The charging and discharging efficiency is also greatly improved due to the reduction of conductance losses. Through simulation results, it becomes evident that the enhanced performance is attributed to the alleviation of electric field distortion due to the suppression of injected charge. This work paves a facile route to design scalable polymeric dielectrics with outstanding performance, which facilitates the development of film capacitors.