Structure and optic properties of the nanocomposites based on polypropylene and amorphous silica nanoparticles

Abstract

The structure and optic properties of the transparent PP+SiO2 nanocomposites with a relatively high refractive index and enhanced luminescence properties were investigated. X-ray analysis, Fourier-transform infrared (FTIR), Visible-ultraviolet, and photoluminescence spectroscopic methods were used for investigation. The XRD analysis indicated that the fraction of the amorphous phase of the polycrystalline polymer decreases with the introduction of SiO2 nanoparticles. Even though SiO2 nanoparticle is amorphous itself, they play the role of the crystallinity centers in the polymer matrix, and the degree of crystallinity increases in polymer nanocomposites. According to UV-vis spectroscopic analysis that, with the increasing of the concentration of SiO2 nanoparticles distributed in the polymer matrix, the absorption intensity of the samples also increases. It was explained by the hyperchromic effect which is related to raising the optical density of the polymer by introducing the filler particles (SiO2). It was calculated bandgap energy and refractive index on the base of the UV spectra of samples. It has been found that at low concentrations of amorphous silica nanoparticles, the polymer nanocomposite retains its transparency despite having a relatively high refractive index (1.96). Furthermore, the photoluminescence (PL) spectrum of nanocomposites was investigated depending on filler concentration. It was clear that the intensity of the PL spectrums increases with the increase of the filler concentration that is explained by the raising of the luminescence centers in the nanocomposite material. These luminescence centers are oxygen-deficit centers in the spatial structure of the amorphous silica nanoparticles.