Thermal characterization of expanded graphite and its composites

Using the guarded hot plate method, we have measured the thermal conductivity of compressed expanded graphite (EG) samples (densities from 0.4 to 1.95 g/cm3) along the compression direction (c axis) in the range 150–675 K and that of EG/epoxy composites (5–75 wt % EG) in the range 150–425 K. We also have measured the specific heat of EG samples at temperatures from 200 to 675 K. Their c-axis thermal diffusivity has been shown to decrease with increasing EG density. The thermal conductivity of the EG/epoxy composites and its variation with EG content are well represented by a rule of mixtures that takes into account the anisotropy in the thermal conductivity of the EG particles and their preferential alignment in the composites.