Highly thermally conductive and negative permittivity epoxy composites by constructing the carbon fiber/carbon networks

The geometry of electronic devices is shrinking, while electronic components are moving towards miniaturiza-tion, integration and high frequencies. Polymer composites with high thermal conductivity, low cost and light weight are urgently needed for thermal management areas such as clean energy, 5G mobile phones, artificial intelligence and so on. In this paper, pre-oxygenated fibers (POF) are firstly prepared into POF felt using air-flow netting and needling. The POF felts are graphitized to form carbon felts (CF). Finally, the CF/C felt are prepared by vacuum impregnation-lamination cured-carbonization-graphitization-purification. Epoxy resin/carbon fiber/ carbon (EP/CF/C) composite prepared by a simple vacuum encapsulation method. Test results show that the prepared epoxy composites have a thermal conductivity of up to 2.83 W/mK and 0.57 W/mK in-plane and through-plane with 8.94 vol% CF/C. The maximum thermal conductivity enhancement of the epoxy composites is 1389% and 202% compared to the pure epoxy resin. The composite's maximum in-plane and through-plane conductivity can reach 0.17 S/cm and 0.04 S/cm respectively. Composites show a certain negative dielectric behavior. With increasing of graphitization, the negative permittivity appears in the low frequency region. Infrared imaging shows that the prepared epoxy composites have excellent thermal management properties. The carbon fiber thermally conductive composites prepared in the above manner may have promising applications in advanced thermal management.