Dielectric Responses of Hybrid Polymer Matrix Composites at 2–3 GHz Microwave Frequencies

Abstract

Abstract

Measurement of dielectric properties of polymeric materials in the 2–3 GHz frequency region is very important for strategic applications such as communication electronics, rapid prototyping, and radiation assisted heating. As per international standards for industrial, scientific and medical applications (ISM) 0.9, 2.45 and 5.8 GHz microwaves can be used both for heating and communication purposes, of this 2.45 GHz is most widely used frequency, hence it is important to characterize the dielectric responses of the materials at this frequency. In the present work, dielectric properties such relative permittivity, loss tangent, conductivity and penetration depth of epoxy based matrices and their glass composites with specifically selected reinforcements such as silicon carbide, carbon, copper and carbon nanotubes (CNT) has been carried out using micro-strip based ring resonator technique. The effect of composition, size of particulate reinforcement and degree of cure on the dielectric responses has been determined. The relative permittivity (e_r) of the base epoxy resin can be increased from 2.6 to 5.2 or could be reduced to 1.6 by addition of 5 wt.% of carbon powder and 5 wt.% CNT respectively. The loss tangent (tand) can be increased from 0.05 to 0.15 by addition of 5 wt.% of silicon carbide powders. Addition of equal amount of CNT would result in tand value of 0.25, which is 500% more than pure resin. The conductivity at these polymer composites at microwave frequencies can be increased from 0.02 to 0.07 S/m, by adding coarse and fine grade silicon carbide powders and the penetration depth can be reduced from 0.22 to 0.06. These are valuable inputs to effectively design polymeric formulations for microwave assisted heating, miniaturization of electronic devices, and for 3D printing processes.

Keywords: Dielectric, microwave, polymer, composites, penetration depth, conductivity

Cite this Article

Krupashankara M.S. , Suresh Patil, B.K. Sridhara., Dielectric Responses of Hybrid Polymer Matrix Composites at 2-3 GHz Microwave Frequencies. Journal of Polymer & Composites. 2015; 3(1): 1–11p.