Outstanding mechanical properties, high thermal stability and enhanced breakdown strength of PDA@BNNS/PMIA-coated meta-aramid paper with sandwich structure

Because of excellent insulation properties and thermal stability, meta-aramid paper can be commonly applied to a vast number of fields, like power systems. But poriferous and relatively lax structure of meta-aramid paper would limit its applications in high-voltage environment. This paper proposes a sandwich structure design to combine PDA@BNNS/PMIA film and meta-aramid paper with high breakdown strength. After coating with 6 wt% PDA@BNNS/PMIA solution, this kind of paper became more compact, so there were few pores in the paper and it further enhanced the mechanical and dielectric performances of specimens. The tensile strength in the cross direction increased from 31.3 to 40.5 MPa, and the performance in the machine direction was from 75.5 to 78.9 MPa. Furthermore, the breakdown strength of compound-coated paper achieved 55 kV/mm, which is much higher than meta-aramid paper. Additionally, compound-coated paper still remained outstanding thermal stability. Overall, our fabricated PDA@BNNS/PMIA compound-coated paper has excellent comprehensive properties, which provides a broad prospect for the applications in high-temperature and high-voltage transformers.