Largely Enhanced Thermal Conductivity and High Dielectric Constant of Poly(vinylidene fluoride)/Boron Nitride Composites Achieved by Adding a Few Carbon Nanotubes

A small amount of carbon nanotubes (CNTs) was added into poly(vinylidene fluoride) (PVDF)/boron nitride (BN) composites through melt blending processing. The thermal conductivity, microstructure changes including the crystallization behavior of PVDF matrix and the dispersion states of fillers in the composites, and the electrical conductivity of the composites were comparatively investigated. The results demonstrated that compared with the PVDF/BN composites at the same BN content, the ternary PVDF/BN/CNT composites exhibited largely enhanced thermal conductivity. In the PVDF/BN/CNT composites, the crystallinity of the PVDF matrix was slightly increased while the crystal form remained invariant. BN particles exhibited homogeneous dispersion in the PVDF/BN composites, and they did not affect the rheological properties of the PVDF/BN composites when the BN content was lower than 10 wt %. The presence of CNTs did not affect the interfacial adhesion between BN and PVDF, but they facilitated the formation of denser BN/CNT network structure in the composites. The mechanisms were then proposed to explain the largely enhanced thermal conductivity of the PVDF/BN/CNT composites. Furthermore, the dielectric property measurements demonstrated that the PVDF/BN/CNT composites containing relatively low BN content exhibited a high dielectric constant with a low dielectric loss. This endowed the PVDF/BN/CNT composites with a greater potential application in the field of electronic devices.