Enhanced thermal conductivity by constructing 3D-networks in poly(vinylidene fluoride) composites via positively charged hexagonal boron nitride and silica coated carbon nanotubes

Abstract

Thermal-conductive yet electrical-insulating polymer composites with outstanding mechanical properties have attracted increasing attention in the electronic field. Herein, three-dimensional (3D) thermal-conductive networks were built in PVDF matrix via electrostatic repulsion of positively charged hexagonal boron nitride (m-hBN) and bridging of silica-coated carbon nanotubes (MWCNTs-SiO2). The results indicated that 25 wt% m-hBN/MWCNTs-SiO2/PVDF presented fascinating characteristics: a high thermal conductivity of 1.51 W/(m·K) and an excellent tensile strength of 55.02 MPa, with the enhancements of 586% and 25% respectively compared to pure PVDF; besides, superior dielectric properties and electrical insulation were obtained, with dielectric constant of 4.95, dielectric loss tangent of 0.14 at 1 MHz, and volume resistivity of 3.45 × 1012 Ω·cm. The Effective Medium Approximation (EMA) model revealed that the formation of 3D-networks could significantly decrease thermal resistance and promote phonon transmission. The outstanding heat dissipation capability of m-hBN/MWCNTs-SiO2/PVDF was verified by infrared imaging test, indicating its potential applications for thermal management.