Rheological methods have been used to examine the morphology under shear of various polymer blends. The first series were polypropylene thermoplastic olefins (TPOs) containing an ethylene-octene copolymer (EOC) as the rubbery phase. Marked differences were observed between the morphology of TPOs of different viscosity ratios. A significant phase coarsening or coalescence occurred for the TPO of the low level of viscosity ratio, indicating that the low viscosity of the dispersed phase facilitated the interfacial mobility and resulted in a coarse morphology. The presence of silica nanoparticles improved morphological stability of all blends and the effect was found to be significantly more pronounced when the solid inclusions were localized in the dispersed EOC phase. These blend composites featured finer microstructures with interfacial area up to several times larger and dramatically enhanced viscoelastic properties. The nanoparticles in these samples migrated towards the interface, a phenomenon that could significantly diminish the interfacial mobility and hinder the droplet coalescence. Similar methods have been used to examine the properties of blends of an amorphous polylactide (PLA) with a poly[(butylene succinate)-co-adipate] (PBSA) or a poly[(butylene adipate)-co-terphthalate] (PBAT). The presence of nanoparticles was found to affect considerably the morphology and the properties of these blends.
