Electrically insulating materials are integral components in many devices including coatings for electric wires and cables, circuit boards, electric machines, and high-voltage devices. Within electrical machines like motors, common electrical insulating components are extensively used to isolate components at different voltages. In this paper, we focus on slot liners that isolate the copper windings from the stator within an electric motor. Although manufacturers routinely provide the electrical and mechanical properties of these materials, their thermal properties, including thermal conductivity, are not often reported. However, their thermal properties are critical for understanding the temperatures of operating devices. To address this gap, this research characterizes the thermophysical properties of different commercially-available sheet-like insulation materials commonly employed as slot liners and other similar materials for benchmarking. We report essential thermophysical properties (in-plane thermal conductivity, through-plane thermal conductivity, density, and specific heat capacity). These parameters, while often overlooked in datasheets, are crucial to gauging the thermal performance of the (electrical) insulation materials in such thermally demanding applications. This new data provides insight required to improve the selection of electrically insulating materials for applications in electric machines.