Complex permittivity of organic solvents at microwave frequencies

Abstract

The complex electrical permittivity of industrially produced organic solvents of several classes with different abilities to form hydrogen bonds, such as ketones (acetone, 2-butanone), alcohols (ethyl alcohol, isopropyl alcohol), acetic esters (ethyl acetate, propyl acetate, butyl acetate), hydrocarbon solvents (toluene, ortho-xylene, heptane, solvent Nefras), chlorine-containing solvents (carbon tetrachloride, tetrachlorethylene), as well as a mixed solvent based on acetone, butyl acetate and ortho-xylene of brand R-5A, were studied. The frequency dependences of permittivity were measured by the coaxial probe method in a wide frequency range from 200 MHz to 20 GHz. It is shown that the chemical nature of solvents has a significant effect on their permittivity. It was found that solvents with weak hydrogen bonds (hydrocarbons and chlorine-containing solvents) have low values of the permittivity (not higher than 2.6) and negligible dielectric losses. Solvents with moderately strong bonds (acetic acid esters and ketones) have high values of permittivity with pronounced frequency dispersion, noticeable dielectric losses and Debye relaxation frequency above 20 GHz. Strong hydrogen bonded solvents (alcohols) are characterized by high values of the permittivity with significant frequency dispersion and Debye relaxation frequency below 1.5 GHz.