RESUMO
Reduced graphene oxide (rGO) was incorporated into plasticized cornstarch (TPS), poly(lactic acid) (PLA) and their blends. Small-angle X-ray scattering (SAXS) was used to investigate rGO dispersion within the materials. For the TPS/PLA blend at 70:30 composition, the incorporation of rGO led to a larger fraction of small-sized rGO sheets, which at 5.0 mass% content developed stable fractal structures and domains of correlated sheets. The formation of fractal structures resulted in substantial enhancements in macroscopic properties. For these hybrids, the electrical conductivity, melt viscosity, storage moduli and biodegradation rates presented enhancements in relation to the neat blend. For the TPS/PLA blend at 30:70 composition, SAXS results indicated the formation of smaller fractions of well-dispersed rGO sheets and of segregated larger rGO sheets. With rGO at 5 mass% content, less expressive increases in electrical conductivity, melt viscosity, storage moduli and biodegradation rates were observed.
RESUMO
Glycerol-plasticized cornstarch and poly(lactic acid) (PLA) were melt-blended alone and at a constant 70:30 (m/m) composition, in the present of an organoclay. The effect of increasing contents of the organoclay on extruded and compression-molded samples was evaluated by X-ray diffraction (XRD), capillary rheometry, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and tensile tests. XRD and shear viscosity results obtained for the hybrid components (TPS/organoclay and PLA/organoclay) were correlated with the hybrid blends properties. XRD and TGA results suggested that the organoclay was similarly dispersed within both phases. SEM images revealed improved adhesion between the phases. Shear viscosities results indicated improved compatibilization as the organoclay content was increased. Some of the extruded materials were also submitted to injection molding, and characterized by SEM and by tensile tests. For the extruded and compression-molded samples, improved mechanical properties were obtained for the samples with higher contents of the organoclay. For the injection-molded samples, the mechanical properties seemed to be dependent on the organoclay dispersion.