Dielectric properties of polyols, at frequency range 0.2-3 GHz and temperature range 293-473 K: an analysis in the frequency and temperature domain

摘要

The use of polyols as green solvents in conjunction with microwave heating (MH) has become a very attractive synthetic protocol nowadays. However, among the needs of this area, as well as any other that uses MH, figure the electromagnetic properties of the materials. In this context, the contribution of this work is provide dielectric data of three polyols: glycerol, 1,2-propanediol and 1,3-propanediol. The data are presented in two ways: in frequency domain and in temperature domain (whose parameters were denominated f-dispersion and T-dispersion, respectively). In the frequency domain analysis, f-dispersion parameters were obtained for the Cole-Davidson model - one of Debye's models. From the analysis in this domain, the uncertainty and accuracy of the data was established. In the temperature domain analysis, an empirical model is proposed to represent the complex permittivity as a function of temperature - ε*(T) of the polyols. From the analysis in this domain, concluded that the presented model can be applied to other materials. In addition, that can to conclude that the phenomena of thermal runaway and self-limitation of heating are, in fact, subsequent opposite phenomena associated to the variation of the loss factor with the temperature.