Improved Through-Plane Thermal Conductivity and Mechanical Properties of Low-Dielectric FEP/HBN Composites by Adding PTFE Nanoparticles

The development of polymer dielectric materials with low dielectric constant and dielectric loss, high-temperature resistance, and mechanical strength is of great significance to meet the requirements of high-performance, thermally conductive, and dielectric materials in the 5G field. In this study, we designed a mixing device, a push–pull mixer (PPM) based on the elongational deformation theory, to overcome problems encountered during the formation of polymer-based composites with a high content of thermally conductive fillers. Hexagonal boron nitride nanoparticles (nmHBN), HBN microparticles (μmHBN), and poly­(tetrafluoroethylene) (PTFE) fillers were introduced into the fluorinated ethylene propylene (FEP) matrix to enhance the thermal conductivity of FEP. Fillers were dispersed uniformly in the matrix, and PTFE powders effectively disrupted the transverse orientation of HBN formed during compression, as confirmed by the results of scanning electron microscopy (SEM) and rheological behavior measurements. When the ratio of FEP/nmHBN/μmHBN/PTFE was 68:12:15:5, the in-plane and through-plane thermal conductivities of the composite were 1.61 and 0.43 W/(m·K), which were ∼16 times and 4 times that of the FEP matrix, respectively, and the tensile stress of the composite was 14.73 MPa, the same level as pure FEP. In addition, the dielectric constant and dielectric loss at 1 MHz of the FEP/nmHBN/μmHBN/PTFE composites maintained low levels of 2.6 and 0.014, respectively.