Organic materials like simple, long chain n-alkanes have high latent heat and find application as a phase change material (PCM). In this work, we measure the thermal conductivity, k, and viscosity, mu, of n-eicosane (C20F48) as a function of temperature, and examine the effect of homogenously dispersed graphite particles (GP) in the PCM. Our results show a large enhancement in k (450%) and mu (1200%) for a 3.5% vol. concentration of GP fillers. The surprising reduction of the interfacial thermal resistance (R-eff) with increasing filler concentration, together with the high thermal conductivity of GP contributes to the large enhancement in k. R-eff increases with temperature when n-eicosane is in solid phase and decreases after phase transition. The enhancement in mu is attributed to the layering of liquid n-eicosane at the graphene surfaces, and agglomeration of GP at higher concentrations. (C) 2017 Elsevier Ltd. All rights reserved.