Multifunctional polymer composites with both high dielectric constants and high thermal conductivity are urgently needed by high-temperature electronic devices and modern microelectromechanical systems. However, high heat-conduction capability or dielectric properties of polymer composites all depend on high-content loading of different functional thermal-conductive or high-dielectric ceramic fillers (every filler volume fraction ≥ 50%, i.e., ffiller ≥ 50%), and an overload of various fillers (fthermal-conductivefiller + fhigh-dielectricfiller > 50%) will decrease the processability and mechanical properties of the composite. Herein, series of alumina/barium titanate/polypropylene (Al₂O₃/BT/PP) composites with high dielectric- and high thermal-conductivity properties are prepared with no more than 50% volume fraction of total ceramic fillers loading, i.e., ffillers ≤ 50%. Results showed the thermal conductivity of the Al₂O₃/BT/PP composite is up to 0.90 W/m·K with only 10% thermal-conductive Al₂O₃ filler, which is 4.5 times higher than the corresponding Al₂O₃/PP composites. Moreover, higher dielectric strength (Eb) is also found at the same loading, which is 1.6 times higher than PP, and the Al₂O₃/BT/PP composite also exhibited high dielectric constant ( ε r = 18 at 1000 Hz) and low dielectric loss (tan δ ≤ 0.030). These excellent performances originate from the synergistic mechanism between BaTiO₃ macroparticles and Al₂O₃ nanoparticles.
Keywords: ceramic; dielectric properties; polymer composites; synergistic effect; thermal conductivity.