Modeling the in-plane thermal conductivity of a graphite/polymer composite sheet with a very high content of natural flake graphite

Natural flake graphite/polymer composite sheets were prepared using tape casting method. The in-plane thermal conductivities, i.e. the thermal conductivities along the tape casting plane, of the composites were measured and the results compared to the predictions by the Maxwell and Agari models. The comparison indicated that both models cannot predict the thermal conductivity of the natural flake graphite/polymer composite at a very high graphite concentration where the flakes were shown from scanning electron microscopy (SEM) images to have a good orientation parallel to the tape casting direction. The SEM images also illustrated that the well oriented flakes formed a continuous graphite-graphite network. Based on the observed structure, a new thermal conductivity model was constructed. The new model applies well to the composites at a large content of highly oriented graphite flakes. The model was also validated by the experimental results from samples with the same graphite content but with different degrees of graphite flake orientation. (c) 2012 Elsevier Ltd. All rights reserved.