Study On Flexible Thermal Conductive Composite Based On Exfoliated Graphite

The research on advanced thermal interface materials(TIMs) due to the continuous increase of power density in electronic devices. Flexible TIMs, which are commonly used to dissipate heat efficiently from heat spreader and heat sink, with high thermal conductivity in vertical direction and excellent mechanical compressive property(MCP) are required. Thermal conductive fillers have been dispersed into silicone rubber(SR) to enhance λ of SR. Graphite nano-platelets(GNP) is reported to have high λ, what’s more, GNP can be easily achieved and inexpensive.Some studies of dispersing GNP into polymers have been reported, λ has an enhancement comparing with the neat polymers, while the λ of GNP/polymer fabricating using mixing method is still far from the potential GNP λ value. One probably reason based on the existence of thermal contact resistance between the GNP free ends and the surfaces comprising the interface, the other probably factor is the orientation of GNP. As a consequence, the key to enhance λ of GNP/polymers is let GNPs forming oriented networks offering more effective thermal conductive paths.The orientation of GNP is expected as increasing density of compacted exfoliated graphite(CEG), as a result, the anisotropy of CEG is achieved. CEG acts as an offer of oriented GNP networks, which will further on forms the thermal conductive paths. λ of composite will be enhanced if the GNP networks is used. λ of CEG would influence the composite λ, then it will be necessary to investigate the perpendicular λ of CEG. Three methods have been applied to improve λ of CEG. λ are enhanced exceptionally using the impregnation method and which also has an outstanding mechanical compressive properties.Compacted exfoliated graphite(CEG) or other composite, theoretically, the flash method could not be used on measuring λ of composites. The influences of thickness and density on the thermal conductivity of CEG are studied. It was found that the flash method could be applied to determining the thermal conductivity of heterogeneous composite like CEG.