Temperature stable low loss PTFE/rutile composites using secondary polymer

Rutile filled PTFE composites have been fabricated through Sigma Mixing, Extrusion, Calendering and Hot pressing (SMECH) process. Dielectric constant (e_r￠\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 (t_er￠\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, e_r￠ ~ 10.4\varepsilon_{r}'\sim10.4, loss tangent tan δ∼0.0045 and t_er￠ ~ -40 ppm/K\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 t_er￠\tau_{\varepsilon_{r}'} is mainly attributed to the positive t_er￠\tau_{\varepsilon_{r}'} of PEEK and increased interface region in the composites as a result of the PEEK addition.