Volume control of expanded graphite based on inductively coupled plasma and enhanced thermal conductivity of epoxy composite by formation of the filler network

Expanded graphite (EG) is noticed as a thermally conductive carbon filler because of its advantages of a unique structure in which graphite sheets are intercalated and relatively a low price among carbon fillers. Nevertheless, the relationship between the volume expansion (≈interlayer spacing) of EG and the thermal conductivity of EG filled composites has been rarely reported on. We designed and developed an inductively coupled plasma (ICP) for the rapid expansion of a expandable graphite precursor. Greater extent of volume expansion of EG was observed at higher ICP treatment temperature and the thermal conductivity of the composites was increased with the expanded volume of the filler, at the same filler content. Based on a quantitative analysis on filler size within the composites using non-destructive micro-computed tomography, larger size of three dimensional (3D) thermally conductive filler networks with respect to the volume expansion were obviously confirmed. Excellent thermal conductivity (the highest value of 10.77 W/m·K) and heat dissipation characteristic of the composites were derived when the 3D thermally conductive EG filler network was generated at a larger size. These findings can contribute to realizing effective and low-priced thermally conductive carbon filler based polymer composites.