Dielectric Relaxation-Times of Solid Solutions of Aliphatic Long-Chain Esters and Ketones in Paraffin Wax and n-Hexacosane

Abstract

IN the search for relationships between electrical properties and the chemical and physical structures of solid dielectrics, the experimental investigations by Jackson¹, Sillars² and Pelmore³ are of considerable interest. These workers incorporated small quantities of aliphatic long-chain esters in paraffin wax and measured the dielectric loss (tan δ) of the resulting mixtures over a range of frequencies, the inverse of the angular frequency (ω) for the maximum tan δ giving the relaxation time (τ) of the ester molecules. This Work was extended by Fröhlich⁴ in a theoretical study of a model comprising a crystalline paraffin hydrocarbon in which a small proportion of the molecules was assumed to be replaced by molecules of a polar compound, such as a ketone or ester, of a shorter chain-length. The transition of the polar molecules from one position of the equilibrium to another having opposite dipole direction required the crossing of an energy barrier which increased in proportion to the chain-length. This led to an equation for the relationship between the relaxation time and chain-length, in which some of the constants were determined from the experimental results referred to above.