Enhanced breakdown strength of the BaTiO3/polypropylene nanocomposite film based on the biaxial stretching process

The significant progresses of polymer-based nanocomposites with improved dielectric performances are urgently calling for an effect way to realise commercial production. Up to now, the biaxial stretching technology is still a powerful method to produce the high-performance dielectric films applied in the film capacitors due to its full-blown applications. In this work, a classical composite system of BaTiO₃/polypropylene was applied to reveal the connection between the microstructure changes and dielectric properties of the corresponding nanocomposite films in the biaxial stretching process. The permittivity of BT-30 wt% nanocomposite reached 2.8 at 10³ Hz after stretching, and its breakdown strength reached 340 MV/m. In addition, the breakdown strength of BT-10 wt% nanocomposite could even be promoted to 452 MV/m, which was 1.3 times higher than that before stretching. The microstructure test demonstrated that the rearrangement of nanofillers, high crystallinity and the oriented polypropylene crystals were advantageous to the improvement of breakdown strength for the stretched nanocomposite films. Therefore, the application of biaxial stretching technology into the preparation of nanocomposite dielectric film is an enormous potential way for the energy storage film capacitors.