Two types of polymers were tested in this study; poly(ethylene terephthalate) (PET) as a synthetic example and poly(lactic acid) (PLA) as a natural polymer. DSC analyses showed that the use of nanofiller increased the degree of crystallinity (Xc) of both PET and PLA polymers, but the effect was more noticeable on PET nanocomposites. The crystallization of PLA and PET nanocomposites occurred at higher temperatures in comparison to neat polymers. According to dynamic mechanical-thermal analysis (DMTA), the damping factor of PET/TiO2 nanoparticles decreased compared to the neat matrix, but for PLA nanocomposites the opposite trend was observed. Results of the mechanical test showed that for both PET and PLA nanocomposites, the most successful toughening effect was observed at 3 wt% loading of TiO2 nanoparticles. SEM micrographs revealed uniform distribution of TiO2 nanoparticles at 1 and 3 wt% loading levels. The results of WAXD spectra explained that the polymorphs of PLA and PET was not affected by TiO2 nanoparticles. UV-visible spectra showed that TiO2 nanocomposite films had high ultraviolet shielding compared to neat polymer, but there was significant reduction in transparency.

Keywords: nanocomposites; poly(lactic acid); poly(ethylene terephthalate); crystallization; mechanical properties.