Temperature stable low loss PTFE/rutile composites using secondary polymer

Abstract

Rutile filled PTFE composites have been fabricated through Sigma Mixing, Extrusion, Calendering and Hot pressing (SMECH) process. Dielectric constant ($\varepsilon_{r}'$) and loss tangent (tan δ) of filled composites at microwave frequency region were measured by waveguide cavity perturbation technique using a Vector Network Analyzer. The temperature coefficient of dielectric constant ($\tau_{\varepsilon_{r}'}$) was measured in the 0–100°C temperature range. In order to tailor the temperature coefficient of dielectric constant of the composite, thermoplastic Poly (ether ether ketone) (PEEK) has been used as a secondary polymer. Flexible laminate having a dielectric constant, $\varepsilon_{r}'\sim10.4$, loss tangent tan δ∼0.0045 and $\tau_{\varepsilon_{r}'}\sim-40\mbox{ ppm}/\mbox{K}$ was realized in Polytetrafluroethylene (PTFE)/rutile composites with the addition of 8 wt% PEEK. The reduction in $\tau_{\varepsilon_{r}'}$ is mainly attributed to the positive $\tau_{\varepsilon_{r}'}$ of PEEK and increased interface region in the composites as a result of the PEEK addition.