3. Result and discussion
3.1. Optical properties of the nanocomposites
The optical properties of the epoxy nanocomposites were studied by UV–Vis analysis. Variation of transmittance versus
wavelength of the coatings loaded with various loadings of nano alumina particles is shown in Fig. 1.
It is clear from Fig. 1 that transmittance values at both UV (300–400 nm) and visible (400–700 nm) wavelength regions are greater for the blank sample than nanocomposites. Results showed that addition of the nanoparticles caused a decrease in transmittance at both UV and visible regions. The decrease in transmittance was most pronounced at 3.5 wt%. The decrease in transmittance can be attributed to the presence of agglomerated nanoparticles in the coating matrix. In fact, nanoparticles, having high refractive index (RI = 1.72), larger than 100 nm could scatter visible light resulting in a decrease in coating clarity [15]. However, it can be seen that the transmission values for all the coatings are around 90% in the visible wavelength region. This indicates that the transparency of the coating system is not affected significantly by addition of nanoparticles even at highest loading. These observations clearly show proper dispersion of the nanoparticles in the coating.