Preparation, characterization and properties of FEP modified PTFE/glass fiber composites for microwave circuit application

Abstract

Polytetrafluoroethylene (PTFE)/glass fiber (GF) composites modified by Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) was investigated. This study included the manufacturing process of PTFE/GF/FEP composites and the effects of the content of FEP on the properties of composites, such as porosity, dielectric properties (${{D}_{k}}$, ${{D}_{f}}$), water absorption, temperature coefficient of dielectric constant (${{\tau }_{\varepsilon }}$) and coefficient of thermal expansion (CTE). Furthermore, the miscibility of PTFE and FEP was also investigated. The compositions of the resin mixture are x wt% FEP + (100 − x) wt% PTFE (x = 0, 10, 20, 30, 40). The results show that as the content of FEP is 30 wt%, the composite has a minimum porosity, at the same time achieves optimum properties, including dielectric constant (${{D}_{k}}$) of 2.2343, dielectric loss (${{D}_{f}}$) of 1.4  ×  10⁻³, water absorption of 0.019%, CTE of 29, 36 and 231 ppm/°C (X, Y, Z direction, respectively) and temperature coefficient of dielectric constant (${{\tau }_{\varepsilon }}$) of −71 ppm/°C. It has been found that FEP addition results in improved performance of the composites than that of previous reported work.