Syndiotactic polypropylene based nanocomposites: Short and long term electrical characterisation

In these last years, different research studies constantly investigated the possibility to find a new class of materials in the field of medium/high voltage insulation. Nowadays, the conventional materials that are commonly used in this field of interest are non-recyclable. In this research activity, the electrical behavior of new recyclable nanostructured materials is investigated in order to study the feasibility of their future employment as substitutes for the currently employed materials. The materials have been prepared by adding different kinds of nanofiller to the syndiotactic polypropylene matrix; in order to obtain a good dispersion of the considered nanofillers, the materials have been processed by extrusion and their final homogeneity have been investigated by means of a scanning electron microscope. In order to investigate the electrical performances of these materials, suitable film specimens have been prepared by hot compression molding technique and subsequently electrical aging tests have been performed to evidence the short and the medium term behavior of the tested materials. The short term behavior has been investigated by dielectric strength measurements, while the medium term behavior has been evaluated by electrical aging tests. During the aging tests, the specimens have been subjected to 50 Hz frequency sinusoidal voltage waveform: different voltage amplitudes have been considered and the breakdown condition has been chosen as end-point criterion. The relevant times to breakdown have been collected and used to plot the life curves. Analyzing and comparing the obtained results it has been possible to highlight a different behaviour among the nanocomposites and the pure polymer.