Poly(lactic acid)/low-density polyethylene blends and its nanocomposites based on sepiolite

Poly(lactic acid) (PLA) nanocomposite ternary blends based on unmodified sepiolite were prepared by melt blending using a corotating twin-screw extruder. Two grafted polymers were used as compatibilizer agents, in an effort to increase the PLA tensile toughness. The influence of incorporating a low-cost commodity low-density polyethylene, as dispersed phase to the composites on thermal degradation, and rheological and tensile properties was studied. The morphology of the blends and composites was determined through transmission and scanning electron microscopy techniques. Results showed that the compatibilized blends prepared without clay have higher thermal degradation susceptibility and tensile toughness than those prepared with sepiolite and significant changes in complex viscosity and melt elasticity values were observed between them. The nanocomposite blends exhibited similar thermal degradation, lower tensile strength, and Young's modulus values and increased elongation at break and tensile toughness, complex viscosity, and storage modulus compared with those of the nanocomposite of PLA. These results are related to the clay dispersion, to the type of morphology of the different blends, to the localization of the sepiolite in the different phases, the thermomechanical degradation of the PLA matrix phase during melt blending and the grafting degree of the compatibilizers used. POLYM. ENG. SCI., 2012. (C) 2011 Society of Plastics Engineers