Efficient surface modification of highly thermal conductive graphite particles by polydopamine coating for thermal management materials*

Spherical artificial graphite (SAG) has the potential to enhance the thermal conductivity of polymer-based composites. However, the poor compatibility and weak interaction between silicone rubber (SR) matrix and SAG particles brings about undesirable interfacial thermal resistance (Rb) and phonon scattering, impeding heat transfer in SR composites. The adoption of polydopamine (PDA) coating reduces the specific surface area and oil absorption value of SAG, thereby increasing the loading of SAG. More importantly, the provided hydrogen bonding between PDA and SR improves their compatibility, further enhancing the dispersion of the filler and reducing Rb. PDA has simultaneously thermal insulation effect, which has a negative effect on the reduction of Rb. In this work, the above competitive effects are balanced by adjusting the grafting amount of PDA. Among prepared samples, the SR-based composites filled with 76 vol% SAG@PDA-2 exhibit a relatively high thermal conductivity (1.76 W m-1 K-1), which is about 1.80 times and 8.80 times that of SAG/SR-73 vol% composites (0.98 W m-1 K-1) and pure SR (0.20 W m-1 K-1), respectively. This work opens a feasible avenue to address the surface engineering of highly thermal conductive carbon-based materials for potential applications in the thermal management of advanced electronic devices.