Role of Interfacial Postreaction during Thermal Treatment: Toward a Better Understanding of the Toughness of PLLA/Reactive Elastomer Blends

The toughening of poly(L-lactide) (PLLA) with reactive elastic polymers is regarded as an efficient long-standing modification strategy. Extensive investigation indicated the mathematical correlation between the crystallinity of PLLA matrix (X-c,X-PLLA) and impact toughness by cold crystallization (thermal annealing), but the detailed mechanism has not been clarified. Herein, we present a systematic study on PLLA/reactive elastomer (RECM) blends and demonstrate the significant role of interfacial postreaction during thermal treatment in enhancing toughness. It was confirmed that impact toughness was directly dependent on the time of thermal treatment rather than crystallinity: for the nucleated blend, notched impact strength with identical X-c,X- PLLA increased from 15.0 to 45.3 kJ/m(2) on prolonging the melt crystallization time from 1 to 60 min. The results lead to the conclusion that in situ interfacial postreaction is a critical factor in initiating shear yielding within the entire deformation region and thereby leading to the drastic toughening of PLLA/RECM systems. Furthermore, this work provides deeper insight into the underlying toughening mechanism. The newfound role of interfacial postreaction may offer an industrially scalable relevant model to fabricate high-performance PLLA materials.