Molecular insight into toughening induced by core-shell structure formation in starch-blended bioplastic composites

Binary and ternary blends with poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and thermoplastic starch (TPS) were prepared by a melt process to produce biodegradable biomass plastics with both economical and good mechanical properties. The mechanical and structural properties of each blend were evaluated. Molecular dy-namics (MD) simulations were also conducted to examine the mechanisms underlying the mechanical and structural properties. PLA/PBS/TPS blends showed improved mechanical properties compared with PLA/TPS blends. The PLA/PBS/TPS blends with a TPS ratio of 25-40 wt% showed higher impact strength than PLA/PBS blends. Morphology observations showed that in the PLA/PBS/TPS blends, a structure similar to that of core -shell particles with TPS as the embedding phase and PBS as the coating phase was formed, and that the trends in morphology and impact strength changes were consistent. The MD simulations suggested that PBS and TPS tightly adhered to each other in a stable structure at a specific intermolecular distance. From these results, it is clear that PLA/PBS/TPS blends are toughened by the formation of a core-shell structure in which the TPS core and the PBS shell adhered well together and stress concentration and energy absorption occurred in the vicinity of the core-shell structure.

Automated summary

Binary and ternary blends of PLA, PBS, and TPS were prepared to produce biodegradable biomass plastics with good mechanical properties. The mechanical and structural properties of each blend were evaluated, and molecular dynamics simulations were conducted. PLA/PBS/TPS blends showed improved mechanical properties compared to PLA/TPS blends. Morphology observations indicated the formation of a core-shell structure in the PLA/PBS/TPS blends, with TPS as the core and PBS as the shell. MD simulations confirmed the tight adhesion between PBS and TPS in a stable structure. Overall, the blends were toughened by the core-shell structure.