Effects of the matrix crystallinity, dispersed phase, and processing type on the morphological, thermal, and mechanical properties of polylactide-based binary blends with poly[(butylene adipate)-co-terephthalate] and poly[(butylene succinate)-co-adipate]

In this study, we prepared immiscible blends of 75 wt % polylactide (PLA) with 25 wt % poly[(butylene adipate)-co-terephthalate] (PBAT) through an injection-molding (IM) process and a twin-screw extruder (TSE) followed by IM. An amorphous polylactide (A-PLA) and a semicrystalline polylactide (SC-PLA) were used as the matrixes to investigate the matrix crystallization effect on the morphology and property development of the blends with only IM. A blend of A-PLA with 25 wt % poly[(butylene succinate)-co-adipate] (PBSA) was also prepared through IM to compare its properties with those of the A-PLA–PBAT blends. The morphological, thermal, solid viscoelastic, tensile, and flexural properties of the blends were compared, and their dependency on the evolution of the blend morphology was analyzed. The tensile results show that when IM was used as the sole processing technique, the ductility and toughness were significantly improved only when SC-PLA was used as the matrix. Preprocessing through TSE also resulted in the enhancement of the blend ductility. In A-PLA–PBSA, the vitrification of PLA hindered the crystallization of PBSA to very low temperatures (<0°C) and resulted in a very nonuniform structure with weak intermolecular bonding between phases.