Thermal, electrical, and mechanical properties of talc‐ and glass microsphere‐Reinforced Cycloaliphatic epoxy composites

Cycloaliphatic epoxy (CE) is used in high voltage and temperature applications because of its high glass transition temperature and resistance to ultraviolet, ozone, and hydrothermal aging mechanisms. Fillers can be used to increase the tensile modulus and thermal conductivity (TC) without a corresponding increase in electrical conductivity (1/electrical resistivity [ER]), which would be detrimental in a high voltage environment. In this study, two fillers were examined in a CE system: talc and glass microspheres (MS). Up to 20 wt% talc/CE and up to 40 wt% glass MS/CE composites were fabricated and tested for ER, TC, and tensile properties. As desired, all composites remained electrically resistive. Composite TC increased with increasing filler content from 0.15 W/m‐K for the neat epoxy to 0.25 W/m‐K for 20 wt% talc and for 40 wt% glass MS. This TC increase could be helpful to dissipate heat in high voltage and temperature applications. Tensile modulus increased from 2.7 GPa for the neat epoxy to 3.6 GPa for 20 wt% talc/CE and to 5.2 GPa for 40 wt% glass MS/CE composites. Increasing the tensile modulus is useful in the newly developed Polymer Core Composite Conductors that are used to transmit power. POLY COMPOS., 39:E1581–E1588, 2018. © 2017 Society of Plastic Engineers