Tailoring the toughness of sustainable polymer blends from biodegradable plastics via morphology transition observed by atomic force microscopy

Abstract Super-toughened polylactide/polybutylene succinate/polybutylene adipate terephthalate (PLA/PBS/PBAT) ternary blends can be prepared by reactive extrusion in the presence of peroxide. However, the high peroxide contents always lead to lowered biodegradability and decreased flowability of the prepared materials. In this study, a strategy to prepare such super-toughened PLA ternary blends with a small amount of peroxide, by simultaneous phase transition and interfacial compatibilization, was demonstrated. Firstly, based on thermodynamic predictions, a core-shell PBS/PBAT structure was successfully prepared that worked as a toughening agent for PLA. Secondly, the viscosity ratio between PLA and PBS/PBAT was adjusted via the introduction of a small amount of peroxide because of the different reactive priority between peroxide and the polymers. Via transferring the co-continuous PBS/PBAT to droplet structure with optimum size and improving the compatibility between PLA and core-shell PBAT-PBS, two different super-toughened PLA ternary blends with high impact strength and melt strength were successfully prepared. The resulting ternary blends showed super toughness with significantly improved notched impact strength (∼530 J/m). The mechanism behind the morphology transformation is discussed based on the phase inversion theory with the help of relaxation time spectrum analysis and atomic force microscopy (AFM). The studies show that both the morphology transition of the different components and improved compatibility make contributions together to the improved mechanical properties. The research provides a new approach to improving the toughness of the polymer blends in reaction extrusion by tailoring the viscosity ratios between different components. The ternary blends developed are expected to be used widely in industrial applications.