Study on the Corona Resistance of Si–B–Mg/ FPI Nanocomposites

ABSTRACT This study prepared silicon–boron–magnesium composite oxides (molar ratio Si:B:Mg = 12:3:0.5) using phenyl triethoxysilane, tributyl borate, and ethoxylated magnesium as raw materials. Subsequently, trifluoromethyl groups were introduced into the polyimide backbone using 4,4′‐(hexafluoroisopropylidene)bisphthalic anhydride (6FDA) as a comonomer at a molar ratio of n (PMDA): n (6FDA) = 2:8. Si–B–Mg/FPI ternary composite films with varying doping concentrations were prepared via in situ polymerization. The effects of doping concentration on the composite films' corona resistance and dielectric properties were investigated. Results indicate that the incorporation of Si–B–Mg composite oxides significantly enhances corona resistance. Specifically, the FPI‐32 sample (32 wt% doping) exhibited a corona endurance time of 474.72 min under conditions of 50 Hz, 155°C, and 60 kV mm −1 , representing a 1.26‐fold increase over pure PI. Moreover, both the dielectric constant and dielectric loss of the composite material remained at low levels. These data indicate that the incorporation of Si–B–Mg composite oxides can enhance the corona resistance and dielectric properties of fluorinated polyimides.