UV protective PET nanocomposites by a layer-by-layer deposition of TiO2 nanoparticles

The oppositely charged titanium dioxide (TiO 2 ) nanoparticles were deposited on the surface of poly(ethylene terephthalate) (PET) substrates by a layer-by-layer (LBL) assembly method. The PET films were pretreated by concentrated alkaline solution so as to introduce functional groups to attract TiO 2 nanoparticles onto the surface. The oppositely charged TiO 2 nanoparticles in the suspension can be controlled by adjusting the pH value. The multilayer buildup was monitored by UV-vis spectroscopy, which showed a linear increase of the film absorbance with the number of adsorbed TiO 2 layers. Moreover, the morphology, structural, and chemical composition of the multilayer nanocomposite films were analyzed by scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results confirmed the presence and even distribution of TiO 2 nanoparticles on the PET surfaces. The UV protective properties, thermal stability, and mechanical properties of the nanocomposite films were investigated. The values of ultraviolet protection factor (UPF) showed that the multilayer nanocomposite films exhibited high UV protective property. The TGA curves showed that TiO 2 nanoparticles enhanced the thermal stability of nanocomposite films. Additionally, the nanocomposite films showed a lower tensile strength but a higher elongation than that of PET film