Enhanced breakdown strength of multilayer polypropylene film with structured interface

Extensive research has been carried out to improve the breakdown strength (BDS) of polymer materials used in high-voltage power equipment. However, almost all the modifications, including nanocomposites, polymer blends, and multilayer films have enhanced the BDS by introducing alien material, which inevitably resulted in an increase in the dielectric losses. Therefore, we propose a multilayer structured film simplex composed of polypropylene (PP) to simultaneously achieve high BDS and low losses. By including virgin and fluorinated bi-axially oriented PP (BOPP) films, three different interface structures were constructed. All the multilayer PP films showed DC BDSs that were improved by varying degrees, compared to the single-layer film. In particular, owing to the enhanced electron trap depth and density caused by fluorination, the DC BDSs of multilayer films with fluorinated BOPP reached 458.7 kV mm-1, which was 20% higher than that of a single-layer PP film of the same thickness, while their dielectric loss was even lower than that of the single-layer film.