ABSTRACTExpanded graphite (EG)/polydimethylsiloxane (PDMS) composites with high thermal conductivity and high flexibility are prepared in this work. EG derived from natural graphite flake is infiltrated in PDMS prepolymer solution and then hot pressed in a steel mould at 80 °C for 2 h. Optical microscope and scanning electron microscope investigation reveals the interpenetrating network structures in the EG/PDMS composites. When mass fraction of EG increases to 10.0 wt %, the thermal conductivity of EG/PDMS reaches to 4.70 W/m K which should be attributed to the conductive path of graphite platelets. Meanwhile, the composites have excellent flexibility (the compressive modulus is 0.68 Mpa) because of its continuous PDMS network. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44843.