Enhanced thermal conductivity of polyamide nanocomposites involving expanded graphite–carbon nanotube network structure using supercritical CO2

In this study, supercritical carbon dioxide (scCO2) was used to form a network structure of expanded graphite (EG) and multi-walled carbon nanotube (MWCNT) to achieve high thermal conductivity. Continuous processes, such as supercritical drying and rapid expansion of supercritical solutions were applied to pristine graphite and MWCNT. Polyamide 6 (PA6) nanocomposites with scCO2-treated EG and MWCNT were prepared by twin-screw extruder-based melt compounding. In the PA6 nanocomposites, the EG sheets were homogenously dispersed, while the MWCNTs were located between the EG sheets, thereby acting as a bridge for the EG. Subsequently, the 35 wt.% imbedding in PA6 nanocomposite had an effective heat transfer pathway and high thermal conductivity (2.12 W m−1 K−1). It was observed that supercritical fluid processing is a facile and effective strategy to improve the thermal conductivity of polymer nanocomposites. Graphical Abstract