Ultra-highly electrically insulating carbon materials and their use for thermally conductive and electrically insulating polymer composites

Abstract

Anisotropic carbon materials such as carbon nanotubes (CNTs) and carbon fibers exhibit extremely high thermal conductivity (TC). However, due to their high electrical conductivity, they have not been used in applications that require both high TC and electrical insulation. Herein, ultra-highly electrically insulating CNTs were prepared by layer-by-layer self-assembly method using various oxide nanomaterials (ONMs) such as titania nanosheets, silica nanoparticles, and water glasses (WGs). ONM-coated CNTs (ONM-CNTs) showed high surface resistivity and ultra-high volume resistivity in acrylate polymer matrices (∼1017 Ω cm) even at high CNT loadings (∼10 vol%). WG-coated CNTs (WG-CNTs) after calcination exhibited the highest heat resistance, showing high electrical insulation even after heat treatment at 500 °C under air. WG-CNTs were stable in the poly (1,4-phenylenesulfide) (PPS) matrix during melt-mixing at high temperature (300 °C), giving the WG-CNT/PPS composites with extremely high volume resistivity (≥1015 Ω cm) even at high WG-CNT loadings (∼16.7 vol%) and enhanced through-plane TC (∼2.0 W m−1 K−1). The TC is much superior to those of previously reported CNT/polymer composites with electrical insulation (≤0.57 W m−1 K−1). This method is scalable, nondestructive, and applicable to various carbon materials. The presented approach is promising for preparing electrically insulating materials for various thermal management applications.