Surface Discharge Property of Polypropylene/BN Nanocomposite for HTS Apparatus Application

Surface discharge can lead to the failures of insulation materials in LN2, especially when the bubbles are generated during the quenching process. In this paper, the surface discharge properties of polypropylene (PP)/boron nitride (BN) nanocomposites were investigated in the normal and quench conditions. The results showed that the surface discharge voltage was improved in the normal condition as the BN filler content was increased from 5 wt% to 10 wt%. But it was reduced as the BN filler content was 15 wt%. As the filler content was less than 10 wt%, the free charges were captured by traps, which were with deeper trap energy level. In quench condition, the bubbles were decreased as the BN filler content increased, which were associated with the higher thermal conductivity of BN to rapidly release the joule heat. Therefore, the surface discharge voltage was increased with the BN filler content. The research has the potential to restrain the surface discharges and extent the lifetime of insulation materials in high-temperature superconducting devices.