Polylactide toughening by poly(butylene adipate-co-terephthalate) and inorganic nanoparticles

In this study, polylactide (PLA) toughening by poly(butylene adipate-co-terephthalate) (PBAT) was investigated. Effects of incorporating nano-sized inorganic fillers into the toughened PLA system were also studied in different model composites. Nano-sized CaCO₃ (NCC) and organically modified layered silicate (OMLS) were used for this study. The blends and composites were melt compounded using a co-rotating twin screw extruder. PLA is high in strength and modulus but brittle, while PBAT is flexible and tough. The PLA/PBAT blend showed decreased tensile strength and modulus but improved tensile toughness and impact strength over neat PLA. Sample failure mode changed from brittle fracture of neat PLA to ductile fracture of the blend as demonstrated by stress-extension curves and SEM micrographs of the impact fracture surfaces. Incorporation of NCC and OMLS into the blends could significantly change the performance of the blends. With filler dispersed in the PLA matrix (separate from the PBAT phase), the failure mode of the blend changes from ductile to brittle. When the filler was enclosed as a core in the PBAT phase, a substantial increase in impact strength resulted.