Comparison of the dielectric and viscoelastic properties of two poly (propylene glycol) liquids

Abstract

The complex relative permittivities of two poly(propylene glycol) liquids, of molecular weights 380 and 3030, have been determined. Measurements were made in the frequency range 60 Hz to 200 MHz and at temperatures from −64° to +25°C. The lower molecular weight liquid showed only one relaxation region, which could be described by the Williams-Watts function with \\ ̄ gb = 0.51 . The higher molecular weight liquid exhibited a similar main relaxation region and a secondary relaxation, of smaller amplitude, at lower frequencies. The relaxation times and their temperature dependencies are compared with previously determined viscoelastic relaxation and retardation times for the same liquids, and with the results from earlier dielectric studies by Baur and Stockmayer, and by Williams. The differences between the dielectric and mechanical times are discussed.