Optical and dielectric properties of polypropylene/montmorillonite nanocomposites

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.