Dielectric and Microwave Properties of Siloxane Rubber/Carbon Black Nanocomposites and Their Correlation

In this paper, the dielectric and microwave properties of carbon black/siloxane rubber-based nanocomposites have been investigated in the frequency range from 1？GHz till 12？GHz according to the content of carbon black and the frequency. It has been established that the increasing frequency and filler content lead to an increase in the relative permittivity and tangent of dielectric loss angle. At higher filler content, the effects become more pronounced, especially those upon dielectric loss. It has been also established that there are two well-distinguished areas in all dependences of microwave properties on frequency and filler content increasing. The first is between 1 and 8？GHz wherein the reflection and attenuation of microwaves do not change considerably with frequency and filler content alternation while shielding effectiveness worsens. The second area is between 8 and 12？GHz wherein the reflection and attenuation of microwaves increase drastically with the increasing frequency and filler content. Shielding effectiveness improves, too. It has been established that in all cases the degree of correlation between dielectric and microwave properties evaluated on the basis of the coefficients of correlation calculation is perfect. 1. Introduction As the central processing units (CPU) of personal computers become faster, in the near future, they are projected to reach a few tens of gigahertz (GHz). In wireless telecommunication systems, microwaves in the range of GHz have extensively been used. The electromagnetic interference (EMI) of unwanted waves, which cause malfunctions in electronic equipment, has been of concern up to the frequency range of GHz. To solve the EMI problem, two methods have been suggested, the shielding and the absorbing of the electromagnetic field. In respect to shielding, most shielding materials have high conductivity. There is a possibility of electric leakage in the shielding method because the electronics have become more integrated in a limited area, and the gap between circuit units has become narrower. In addition, the conductive material setting on a circuit for the shielding of the electromagnetic field can act as an antenna that causes malfunctions in the electronic equipment. Therefore, electromagnetic absorbing materials, which are usually nonconductive materials, are known as a safer method for solving the EMI problem [1]. Siloxane elastomers are unusual synthetic polymers whose backbone is composed of an “inorganic” repeating unit, that is, silicon to oxygen bonds. In addition, the silicone atoms are attached to