Polymers are typically insulators and in the frequency range called "microwaves" (between 300 MHz and 300 GHz), they behave as lossy dielectric materials, with a permittivity or dielectric constant (Dk) ranging between 2 and 4 and a dielectric loss or tandelta (Df) ranging from 0.00001 to 0.1 (see here a selection of experimental data).
The dielectric data in this frequency range are strongly affected by water: in particular, Df data can vary of more than one order of magnitude as a function of humidity conditions and water uptake.
The measurement of the dielectric properties at microwaves can be performed by several non-contact methods, with a variety of commercial or home-made fixtures. Specific methods allow to determine the dependence of the values on the water content. Here a summary of the equipment available in Solvay Materials
