Interfacial and rheological properties of PLA/PBAT and PLA/PBSA blends and their morphological stability under shear flow

Blends of 75 wt. % amorphous polylactide (PLA) with 25 wt. % poly[(butylene succinate)-co-adipate] (PBSA) and poly[(butylene adipate)-co-terephthalate] were separately prepared using an internal batch mixer. The morphology and viscoelastic properties of these two blends were analyzed and compared. Annealing did not cause any pronounced morphology changes nor a subsequent modification of the viscoelastic behavior for both blends. However, applying a shear for 20 min at a rate of 0.05 s^-1 induced significant droplet coalescence in both blends, although the changes in the viscoelastic response were more prominent in the PLA/PBSA blend. It was also shown that applying a shear for 10 and 20 min at a rate of 0.2 s^-1 caused a slight droplet coalescence and minor changes in the viscoelastic behavior of both blends. Moreover, the Palierne model was used to calculate the interfacial tensions between the blend components. It was also utilized to estimate the droplet size after applying annealing and shearing.