Recent works indicate that polypropylene (PP) and ethylene-vinylacetate (EVA) filled by nanosilicates may present low content of space charge and high electric strength. It has been proved that the dispersion of an inorganic phase in the polymeric matrix may improve voltage endurance, dielectric strength, thermal stability and mechanical properties in relation to particle size and arrangement on nanometric scale. Two polymeric materials, widely employed as electrical insulation for apparatus involved in energy transport, that is, ethylene vinylacetate (EVA) and isotactic polypropylene (PP) are examined. The nanofiller consists of an organophilic layered silicate (MEE), the purified MEE will be named MEE-w.Dielectric spectroscopy in time and frequency domain constitutes a useful tool for electrical insulation evaluation and diagnosis, and it can contribute to the understanding of electrical behaviour of complex solid polymer systems. In this paper, the results of dielectric spectroscopy analysis in time and frequency domain, for purified and unpurified filler nanocomposites, in a wide temperature range, are presented.Frequency-domain dielectric measurements were performed in order to appreciate the relaxation processes taking place at lower temperatures (-20 to 20 °C) over the 10 2 -10 6 Hz frequency range.The charging-discharging current measurements, through Fourier time to frequency data transformation, gave information about the slowest polarisation processes, that are usually hidden by the conduction current contribution. Space charge measurement data are also considered in order to understand the effect of nanostructuration and purification on charge carriers. While the relaxation process of EVA, α process, associated with glass transition of the material amorphous phase, results unchanged from base to nanostructured material (i.e., the nanofiller particles do not affect the chain mobility of the polymer), nanocomposites EVA and PP have shown the rise of a new process at higher temperatures respect to the typical host material processes, as well as a different distribution of relaxation processes. In Fig. 1, that displays the imaginary permittivity of EVA+MEE-w nanocomposite, the loss peaks, due to the α and α' process, can be clearly seen. The α' process can be ascribed to the interaction between the polymer matrix and MEE nanolayers.The temperature location of the process, which approaches the melting region of EVA, and its absence in the pure polymer let us argue that the α' relaxation process can be ascribed to a charge polarization of the Maxwell-Wagner-Sillars type, which is due likely to charge trapping at the interfaces between the nanofiller particles and the polymer. All the presented relaxation processes are thermally-activated and their activation energies, reported in Table 1, were estimated reporting the loss peak frequency and temperature of the isothermal measurements in the Arrhenius plot.The EVA nanocomposite obtained by an unpurified filler has shown a huge increment of real and imaginary...