Thermal transport phenomena and limitations in heterogeneous polymer composites containing carbon nanotubes and inorganic nanoparticles

An Off-Lattice Monte Carlo model was developed to investigate effective thermal conductivities (Keff) and thermal transport limitations of polymer composites containing carbon nanotubes (CNTs) and inorganic nanoparticles. The simulation results agree with experimental data for poly(ether ether ketone) (PEEK) with inclusions of CNTs and tungsten disulfide (WS2) nanoparticles. The developed model can predict the thermal conductivities of multiphase composite systems more accurately than previous models by taking into account interfacial thermal resistance (Rbd) between the nanofillers and the polymer matrix, and the nanofiller orientation and morphology. The effects of (i) Rbd of CNT–PEEK and WS2–PEEK (0.0232–115.8 × 10−8 m2K/W), (ii) CNT concentration (0.1–0.5 wt%), (iii) CNT morphology (aspect ratio of 50–450, and diameter of 2–8 nm), and (iv) CNT orientation (parallel, random and perpendicular to the heat flux) on Keff of a multi-phase composite are quantified. The simulation results show that Keff of multiphase composites increases when the CNT concentration increases, and when the Rbd of CNT–PEEK and WS2–PEEK interfaces decrease. The thermal conductivity of composites with CNTs parallel to the heat flux can be enhanced ∼2.7 times relative to that of composites with randomly-dispersed CNTs. CNTs with larger aspect ratio and smaller diameter can significantly improve the thermal conductivity of a multiphase polymer composite.