Highly Thermally Conductive and Superior Electrical Insulation Polymer Composites via In Situ Thermal Expansion of Expanded Graphite and In Situ Oxidation of Aluminum Nanoflakes

Polymer composites with highly thermally conductive and electrical insulation are urgently demanded for thermal management in modern electrical and energy applications. However, the incorporation of metal fillers in traditional polymeric composites usually fails to meet the requirements for simultaneously high thermal conductivity and high electrical insulation. Here, we successfully fabricated composites with high thermal conductivity and high electrical insulation by in situ thermal expansion of expandable graphite (EG) and in situ oxidation of aluminum (Al) nanoflakes in aluminum-plastic package waste (APPW). Due to the synergistic effect of the hybrid filler framework, the maximum thermal conductivity reached as high as 8.7 W m–1 K–1 for APPW/EG10/Al60-F composites. In addition, the formation of the nano Al2O3 layer around the Al filler surface brings extremely low electrical conductivity (<10–14 S cm–1) and low dielectric loss (<0.06). Based on the results of finite element simulation, the heat flowed mainly along the effective filler framework and the high thermal conductivity is attributed to the interconnection of the high aspect ratio filler. Furthermore, the strong thermal management capability of the prepared composites was demonstrated in the heat dissipation experiment. The present work suggests that surface-oxidized Al nanoflakes demonstrate fascinating performance and show promising application as thermal management materials in emerging electrical systems and electronic devices.