Mechanical, thermal and microwave dielectric properties of Mg 2 SiO 4 filled Polyteterafluoroethylene composites

Abstract Polytetrafluroethylene (PTFE)–Mg 2 SiO 4 composites have been prepared using both micron and nano-ceramic fillers by hot pressing. The dielectric properties of the composites are investigated both at radio and microwave frequency ranges as a function of filler loading up to 50 vol%. The dielectric constant and loss tangent increases with filler volume fraction. The composite with 50 vol% micro-filler has a dielectric constant of 3.2 and loss tangent 0.009 at 5 GHz with Vickers microhardness 16 HV. The surface of ceramic particles was modified by silane treatment. The surface modification reduced porosity and moisture absorption and improved the microhardness. The CTE of the composite decreased and thermal conductivity increased with filler loading. Nanopowders of Mg 2 SiO 4 has also been prepared by sol–gel method and composite has been made with PTFE. The nanocomposite has higher moisture absorption, dielectric constant and loss tangent but lower CTE value. The PTFE–Mg 2 SiO 4 composites are possible candidate for microwave substrates applications.