Tuning the compatibility to achieve toughened biobased poly(lactic acid)/poly(butylene terephthalate) blends†
A series of sustainable biobased polymer blends from poly(lactic acid) (PLA) and poly(butylene terephthalate) (PBT) were fabricated and characterized. These blends are engineered to achieve optimal mechanical properties and toughness with a reactive epoxidized styrene-acrylic copolymer (ESAC) compatibilizer, and an ethylene-n-butyl-acrylate-co-glycidyl methacrylate (EBA-GMA) elastomer-based compatibilizer. The results showed that the tensile strength, modulus, flexural strength and modulus of the PBT increase, while the elongation at break and notched impact strength decrease after blending with the biopolymer PLA. The full co-continuity of PLA in PBT was confirmed at a 50/50 wt% blend ratio. The droplet size of the PLA was reduced and the distinct phases of the blends were gradually diminished with the increasing content of the ESAC compatibilizer. The increase in the complex viscosity of the blends was due to the formation of PLA-g-PBT copolymers in the blend after addition of reactive compatibilizers. The incorporation of both compatibilizers in the blends led to superior notched impact strength in comparison to only a single compatibilizer used in the blends. The synergistic effect of both compatibilizers effectively reduces the PLA droplet size and improves the dispersion of PLA in PBT as evidenced by atomic force microscopy (AFM) topography observations. The high toughness of the blends corresponds to the formation of effective EBA-GMA structures and enhanced interfacial compatibilization due to the synergistic effect of the compatibilizers.