Largely enhanced dielectric and thermal conductive properties of polypropylene composites by adding mixture of exfoliated boron nitride and liquid metal

• A simple strategy was proposed to exfoliate boron nitride (BN) by grinding it in liquid metal (LM). • The one-pot exfoliation product containing exfoliated BN and LM, is directly used as hybrid filler for preparing polypropylene (PP) composites to improve the polarization and heat transfer of composites. • A high dielectric constant of 3.5, high thermal conductivity of 1.9 W/m·K, and low dielectric loss of 0.005, low conductivity of 10 −11 S/cm 3 are achieved in PP/LM@BN composites. For microelectronic fields, high dielectric, high insulating and high thermal conductive performances need to be simultaneously integrated in materials to improve devices’ performance, safety, and thermal management ability. Despite the huge potential of exfoliated boron nitride (BN)/polymer composites in them, the exfoliation of BN is difficult, leading to limited increases of dielectric and thermal conductive performance. Herein, BN is first exfoliated in liquid metal (LM) matrix by mechanical grinding, which activates the interaction between LM and BN to promote exfoliation. Then the one-pot mixture containing exfoliated BN and LM, is used as hybrid fillers (LM@BN) without separation for preparing polypropylene (PP)/LM@BN composites. The composites behave a remarked dielectric constant of 3.5 and thermal conductivity of 1.9 W/m·K at LM@BN content of only 5.5 vol%. Extra low dielectric loss (0.005) and low conductivity (10 −11 S/cm 3 ) of PP could be also maintained, due to suppressed space charges by the uniformly-dispersed exfoliated BN.