The Study of the Low K of PTFE Composites with Hollow Glass Spheres

Abstract

This study uses air-filled hollow glass spheres (HGS) to study the dielectric constant of different high-frequency electric circuits following the evidence cited in our previous experiment, which found that air has a low dielectric constant (K), and is an excellent thermal insulating medium. A polytetrafluoroethylene (PTFE)/HGS composite board was fabricated using various proportions of PTFE as the matrix, and nitrogen gas-filled glass spheres as the fillers. In order to measure the dielectric properties of particular composites, composite boards were made from 60% solid content PTFE emulsion with HGS. A composite board was compounded with the help of a barbender with evenly spread HGS. To obtain a composites board, the gel was mixed in a blender and then molded and calendared to release bubbles and increase the surface uniformity. After cooling and sintering, this material formed a composites board. Furthermore, composite boards were made by the sandwich method, with one layer of PTFE emulsion mixed with HGS between two PTFE films. Several series of boards were made by varying a wide range of parameters, including the addition of different amounts of HGS powders, the powder size of HGS, and different fabrication procedures. All these parameters appeared to have varying effects on the dielectric properties. Both the dielectric constant and the dielectric loss factor were increased by additions of HGS loading. The amount of HGS was found to be 30%, which would achieve a dielectric constant of 1.65 and a dielectric loss factor of 0.0008. Both the dielectric constant and the dielectric loss factor were decreased by increasing the hollow pores; these factors reached minimal levels with 5000 rpm of blender rotation speed, then increased to add an HGS ball of 20 μm powder size with 1% loading to obtain the best conditions for the dielectric properties of PTFE/ HGS composite materials.