Analysis of temperature‐dependent AC dielectric loss data

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Abstract
The analysis of dielectric loss data is frequently complicated by the presence of ohmic conductivity, especially at lower frequencies. Two simple methods are discussed for locating transition temperatures and for determining activation energies in such cases. In the first method the permittivity derivative [dε′(T)/dT] is used; in the second, permittivity difference spectra ε′(T, v1) – ε′(T, v2) (v1 ≪ v2 are used. The latter technique, however, cannot be used for activation energy determination. The theoretical basis of these methodologies and an analysis of representative experimental data are presented. The data set include measurements of pure and filled polyurethanes and of radiation‐cured unsaturated polyester resins. Finally, the advantages of data presentation in the form of ε′ and ε″ instead of tan δ are discussed.