Enhancing high-frequency dielectric and mechanical properties of SiO2/PTFE composites from the interface fluorination

Abstract

To achieve polytetrafluoroethylene (PTFE)-based composites for high-frequency applications with low dielectric constant, low dielectric loss tangent and low coefficient of thermal expansion (CTE), a novel pentafluorostyrene (PFS) interface modifier was used to achieve excellent performance for SiO2/PTFE composite materials. The effects of PFS modification on the microstructure, dielectric properties and thermal properties of SiO2/PTFE composites were investigated. It is found that the use of PFS greatly improves the interfacial compatibility of the composites, on the one hand the dielectric properties are effectively improved, on the other hand the steric resistance of PTFE matrix is enhanced and the CTE is reduced. When the PFS content of 5 wt%, the CTE of SiO2/PTFE is reduced to 86 ppm/°C. The dielectric loss of the composites varies from 0.71 × 10−3 to 1.53 × 10−3 at frequencies from 5 to 40 GHz. The composites also show stable dielectric properties across the applied temperature (0–150 °C). Benefiting from the high density and uniform microstructure of the PFS-modified composite, enabling it to withstand higher frequency and temperature applications.