Low Permittivity Porous Polymer Composites for High PDIV Electrical Insulation Systems

In response to the increasing power demands in modern aircraft, insulation materials must ensure exceptional performance and reliability, while withstanding higher voltage levels. To maintain reasonable material thicknesses, one approach is to increase the Partial Discharge Inception Voltage (PDIV) by reducing the permittivity of the insulation materials. This strategy involves introducing inorganic porous fillers into the polymer matrix. Flat PEKK samples were prepared by incorporating 10, 20, 30, 40, and 50 vol.% of porous silica-based fillers in a dried powder form. After thorough mixing, the samples were pressed at high temperatures. Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) revealed no significant variations in the thermal properties of the composites. Dielectric characterizations demonstrated a marked improvement in permittivity, particularly at low temperatures and under medium to high frequencies at elevated temperatures. These findings were corroborated by PDIV measurements and simulations, which indicated a substantial increase in the threshold voltage. However, as expected, the breakdown strength decreased with the addition of the micro-inorganic fillers. The improvements in permittivity and PDIV are promising, suggesting that these composites could be further explored for industrial applications, particularly in assessing their processing and insulation performance within complete systems.