Effect of nanoparticle type and content on morphology, rheology, and crystallinity of poly(lactic acid) using titanium dioxide and polyhedral oligomeric silsesquioxane nanoparticles

In this study, under the same conditions, two different nanoparticles, namely, titanium dioxide (TiO2) and polyhedral oligomeric silsesquioxane (POSS) were added to the poly(lactic acid) (PLA) matrix via the solution casting technique. Morphological analysis showed that POSS had a better distribution within the PLA matrix. However, rheological analysis revealed the stronger influence of TiO2 on shear viscosity values, and a more notable viscosity upturn at moderate to high inclusions of TiO2 within the low shear rate zone. On the other hand, POSS was found to act as a lubricant even at a content of 3 wt% which was attributed to the very small dimensions of POSS. Such lubricating role, found from rheology, caused a boost in the crystallinity of PLA based on differential scanning calorimetry results. Moreover, it was found that TiO2 had an adverse effect on the crystallinity of PLA which was ascribed to the hindered motions of PLA chains upon addition of moderate to high inclusions of TiO2. The results of this study emphasize the crucial role of nanoparticle type and content on the properties of PLA.