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Improved Electrical Properties of Epoxy Resin with Nanometer-Sized Inorganic Fillers

Nanometer-sized inorganic fillers are increasingly used as reinforcing materials for mechanical or thermal property improvement of polymers. Improvements in mechanical modulus or heat deflection temperature are often realized. These fillers may also improve some electrical properties such as corona endurance or dielectric breakdown voltage in polymers. In compact high voltage power supplies, epoxy resins are often the potting material of choice in manufacturing processes. This is often true for applications requiring a robust or position-insensitive insulation system design, such as mobile communications equipment or aerospace flight vehicles. Nanometer-sized inorganic fillers in epoxy resins can result in improved mechanical and electrical performance, without affecting the processes for component manufacturing. In our previous work, polyhedral oligomeric silsesquioxane (POSS) was selected as the nanometer-sized inorganic filler of interest. POSS-filled epoxies showed a five times improvement in ac corona lifetime for selected POSS-epoxy blends compared to unloaded epoxy. In the current study, the average dielectric breakdown voltage of POSS-filled epoxy was increased thirty-four percent compared to unloaded epoxy. Additionally, scanning electron microscopy showed uniform dispersion of the POSS filler down to a level of 10-100 nm. Dispersion uniformity appears to be a critical parameter in obtaining the desired property enhancements.