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The morphological, thermal and electrical properties of nanocomposites based on polypropylene (PP) filled with 2 wt% and 6 wt% of organo-clay montmorillonite (MMT) were studied in this research. X-ray diffraction show an increase of the inter-lamellar distance indicating that PP chains have been well intercalated in the galleries of the montmorillonite. Transmission electron microscopy

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For studying the electrical properties (charge trapping, transport and secondary electron emission) of the polypropylene-based nanocomposites with different contents of natural clay, the specimens were submitted to electron irradiation of a scanning electron microscope. A device, suitably mounted on the sample holder of the scanning electron microscope, was used to measure two currents (i.e. leakage and displacement currents) induced in the polypropylene-based nanocomposites (polymer nanocomposites) under electron irradiation. The evolution of trapped charge during irradiation for each type of studied polymer nanocomposites is deduced. The amount of trapped charge at the steady state is also determined by measuring the change of secondary electron image size associated to the electron trajectory simulation. It is found, surprisingly, that not only the leakage current increases as a function of clay loading level but also trapped charge. However, this could be related to the increase of conductivity in one hand and to proliferation of interfaces between nanoparticles and neighbouring materials on the other hand. These two processes play crucial role in controlling the carrier transport (through polymer nanocomposites or/and along its surface) closely related to the charge storage and leakage current. Additional experiment using dielectric spectroscopy were performed to show the effect of clay concentration in changing the dielectric relaxation behaviour and to evidence the existence of interfaces between nanoparticles and polymer. The secondary electron emission during electron irradiation is also studied through the total electron yield that is deduced by correlating the measured leakage and displacement currents.

With the growing demand for electrical energy, the need for optimized designs of electrical insulating materials with dielectric, mechanical and thermal properties for many applications has become important. Polypropylene (PP) resin is widely used in high voltage apparatus for insulation. The addition of nanoparticles to a polymer seems to enhance the overall properties of the nanocomposite. In this work, the effect of nanoclay particles supplementation on optical and dielectric properties of PP nanocomposites was evaluated by means of several analytical techniques. UV–visible spectroscopy and dielectric spectroscopy in the frequency range 0.1 Hz to 1 MHz, and the temperature range between 40 °C and 120 °C. Optical properties were recorded at room temperature using UV–visible spectroscopy in the spectral range between 200 nm and 800 nm. The optical band gap was found to decrease with the supplementation of nanoclay while the refractive index increased. Dielectric spectroscopy showed the effect of nanoclay concentration in changing the dielectric relaxation behavior and the existence of interfaces between nanoparticles and polymer. The permittivity increase compared with unfilled PP was attributed to the appearance of two thermally activated relaxation processes in this frequency range.