Roles of Chain Architecture and Polymorphic Form in Tailoring the Properties of Surface‐Roughened Biaxially Oriented Polypropylene Films for Capacitors

Abstract Surface‐roughened films of biaxially oriented polypropylene (BOPP) are the most common polymeric dielectrics for oil‐immersed capacitors in electrical engineering. How to balance the roughness of film surfaces as well as the mechanical and high‐temperature electrical properties of film ontology remains a challenge. In this study, three grades of electrical specialized isotactic polypropylene resins with different distributions of molecular mass and stereo‐defects are surveyed for crystalline polymorphic behavior. The relationship of the chain microstructure, film surface topography, and mechanical and electrical properties determined through a comprehensive study of the resins’ chain architecture to the morphology of cast sheets and the characteristics of resultant films is elaborated. The chain features of wide molecular mass distribution and uniform stereo‐defects result in excellent β‐crystallization ability, leading to a fine, roughed topography on the film surface. The narrow distribution of molecular mass and the relatively high tacticity play a positive role in the physico‐mechanical properties of the films, especially in the improvement of breakdown strength at high temperatures. An appropriate chain architecture is vital to achieving the balance between surface topography and bulk performance in surface‐roughened BOPP films.