RELATIONSHIPS BETWEEN MICROWAVE PERMITTIVITIES OF SOLID AND PULVERIZED PLASTICS

The complex permittivities (dielectric properties) of solid and pulverised samples of two plastics, Rexolite 1422 and Kynar, were measured at frequencies of 2.45, 11.5 and 22.0 GHz at 25 degrees C by the short-circuited waveguide technique. Several dielectric mixture equations and extrapolation of functions of the dielectric constants and loss factors that are linear with bulk density were then used to estimate the permittivities at solid-material densities from measurements on the pulverised samples. For these materials, the best estimates of the permittivities were provided by extrapolations that are consistent with the complex refractive index and Landau and Lifshitz, Looyenga mixture equations. The Bottcher mixture equation often gave values very close to the Landau and Lifshitz, Looyenga equation, and the Bruggeman-Hanai, Rayleigh and Lichtenecker mixture equations gave increasingly larger permittivity estimates in that order. © 1990 IOP Publishing Ltd.