The decreased average particle size indicates a lower agglomeration tendency resulted from the modification with aluminate coupling agent. The similar results for the surface modification of nano-TiO2 particles were also reported by Godnjavec et al. and Veronovski et al. [38, 39]. Figure 3 Particle size distribution YM155 research buy of the nano-TiO 2 samples. (a) Without modification and (b) modified with aluminate coupling agent; FE-SEM images of the polyester/nano-TiO2
composites: (c) the nano-TiO2 was not modified, and (d) the nano-TiO2 was modified with aluminate coupling agent. Figure 3c,d compared the dispersion homogeneity of nano-TiO2 with 1.5 wt.% in the polymeric matrix. The unmodified nano-TiO2 agglomerated obviously, and the particle size was about 350 nm. It is resulted from limited compatibility of the unmodified nano-TiO2 with hydrophilic (Figure 3c). Nevertheless, selleckchem Figure 3d exhibits
fewer agglomerates of modified nano-TiO2 in the sample. Although the dispersion of nanoparticles is also limited due to the melt-blend extrusion, the size of the modified nano-TiO2 is uniform of about 100 nm. This is in accordance with the DLS result. Here, we could see significantly improved dispersion of nano-TiO2 particle in the polyester matrix, which further illustrates the importance of the surface modification process. In addition, the effect of surface modification on the UV shielding C646 cost ability of the nano-TiO2 particles was studied. Figure 4 presents the UV-vis
reflection spectra of the nano-TiO2 before and after surface modification. The reflection of modified sample in the visible nearly region (400 to 700 nm) is a little higher than that of the unmodified sample, which may be caused by the colour deviation in the modification process . Furthermore, both of the UV reflection of the nano-TiO2 before and after surface modified are around 10% in the range of 190 to 400 nm, which is resulted primarily from the absorption and scattering of nano-TiO2. This means that the nano-TiO2 exhibits excellent UV shielding ability and could protect the polymeric composites from UV degradation. Although the surface modification did not affect the UV shielding ability of the nano-TiO2, the UV shielding property of the polyester/nano-TiO2 composite is determined largely by the dispersion homogeneity of the nano-TiO2 powder. So, an increased uniformity in dispersion of nano-TiO2 in the polyester matrix will lead to larger amount of aggregated particle with smaller size in the matrix. Figure 4 UV-Vis reflection spectra of the nano-TiO 2 samples. (a) Without modification and (b) modified with aluminate coupling agent. We noticed that the carboxyl-terminated polyester could be used as a thermosetting resin with TGIC as crosslinking agent. The crosslinking takes place through the reaction between the COOH of polyester and epoxy group of TGIC . The mechanism is described in Figure 5a.