Examinando por Materia "NANOCOMPUESTOS"
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- Artículo de Publicación PeriódicaArapey sweet potato peel waste as renewable source of antioxidant: extraction, nanoencapsulation and nanoadditive potential in films(2021-01) Guerrero-León, Beatriz; Corbino, Graciela; Dufresne, Alain; Errea, María Inés; D'Accorso, Norma Beatriz; García, Nancy L."In this work, the peel of Arapey Sweet Potato (Ipomoea batatas), a vegetable waste, was used as a source of phenolic compounds which are widely recognized as beneficial antioxidants for human health. The extract obtained from Ipomoea batatas exhibited an antioxidant activity significantly higher than many antioxidant agents reported in literature (476.96 mg of TROLOX mL-1), as well as good thermal stability. Nanocapsules of the extract coated with low molecular weight polylactic acid were prepared by the emulsification-solvent evaporation method and the nanoparticles obtained were characterized physical; thermal; and morphologically. An analysis of the variables that were investigated to increase the encapsulation efficiency is presented here. Besides, PLA films prepared via the solution-casting method exhibited good compatibility with the nanoparticles loaded with the antioxidant extract, as was evidenced by the uniform and stable dispersion of these particles in the films. Furthermore, an improvement of the mechanical properties of the PLA films due to the presence of the nanoparticles were clearly observed. Results reported here are encourage enough to propose the nanocapsules described in this work as additives or to be used immersed in films for controlled release of antioxidants, putting in value a vegetable waste."
- Artículo de Publicación PeriódicaBarrier properties and structural study of nanocomposite of HDPE/Montmorillonite modified with polyvinylalcohol(2013-02) Carrera, María C.; Erdmann, Eleonora; Destéfanis, Hugo A."In this work was studied the permeation of CO2 in films of high-density polyethylene (HDPE) and organoclay modified with polyvinylalcohol () obtained from melt blending. Permeation study showed that the incorporation of the modified organoclay generates a significant effect on the barrier properties of HDPE. When a load of 2 wt% of was incorporated in the polymer matrix, the flow of CO2 decreased 43.7% compared to pure polyethylene. The results of TEM showed that clay layers were dispersed in the polymeric matrix, obtaining an exfoliated-structure nanocomposite. The thermal stability of nanocomposite was significantly enhanced with respect to the pristine HDPE. DSC results showed that the crystallinity was maintained as the pure polymeric matrix. Consequently, the decrease of permeability was attributable only to the effect of tortuosity generated by the dispersion of . Notably the mechanical properties remain equal to those of pure polyethylene, but with an increase in barrier properties to CO2. This procedure allows obtaining nanocomposites of HDPE with a good barrier property to CO2 which would make it competitive in the use of packaging."
- Artículo de Publicación PeriódicaDevelopment of poly(lactic acid) nanocomposites reinforced with hydrophobized bacterial cellulose(2020-01) Ávila Ramírez, Jhon Alejandro; Bovi, Jimena; Bernal, Celina; Foresti, María Laura; Errea, María Inés"Poly(lactic acid)/bacterial cellulose nanocomposites were prepared by solvent casting. Aiming to reduce the incompatibility between polar bacterial cellulose (BC) and the nonpolar poly(lactic acid) (PLA) matrix which induces filler aggregation and poor reinforcement dispersion, BC was acetylated by the use of a non-conventional route catalyzed by citric acid. The derivatized BC (AcBC) was incorporated into de PLA matrix at varying filler loadings, and optical, morphological, structural, thermal, tensile and barrier (water vapor) properties of PLA/AcBC in comparison with PLA/BC were evaluated. Noticeable changes in the nanocomposite properties were ascribed to the success of the route proposed to surface hydrophobize BC, which significantly improved its dispersibility within the PLA matrix and the matrix-filler interaction. By the way, the variation of filler loading allowed attaining remarkable increases in the nanocomposite films stiffness without significant reductions in tensile strength and water vapor permeability."
- Artículo de Publicación PeriódicaMejora en el comportamiento a la fatiga de compuestos nanoestructurados bidireccionales de fibra de vidrio y poliuretano bajo cargas uniaxiales y altas deformaciones(2020-04) Belardi, Alberto; Oyarzábal, Nicolás Andrés; Chiacchiarelli, Leonel Matías"Se fabricaron placas de material compuesto con refuerzo en fibra de vidrio bidireccional [+/-45]4S y matriz poliuretano nanoestructurado usando la técnica de infusión asistida por vacío. Se utilizó nanosílice (NS) hidrofóbica con porcentajes del 1 y 2 % en peso. A pesar de la NS, la permeabilidad de la preforma no aumentó significativamente, obteniéndose valores elevados de Vf (52%) y una buena impregnación del refuerzo, comprobada mediante microscopía SEM. Los ensayos de tracción uniaxial cuasiestáticos presentaron una elevada deformación a rotura (emax>10%) y valores de resistencia última (RUTS) y módulo elástico (E) que disminuyeron en función del agregado de NS. Por el contrario, los ensayos de fatiga controlados por tensión indicaron que el agregado de NS hasta el 2% permitió mejorar la performance en fatiga. En concreto, los parámetros a y b del modelo empírico lineal aumentaron su valor absoluto en un 77 % y 92,7 %, respectivamente. Esta mejora se corroboró a través de la evaluación del módulo elástico residual. Finalmente, los laminados presentaron una acumulación inelástica de deformación (“ratchetting”), aspecto que fue evaluado para dos frecuencias, 0.2Hz y 2 Hz."
- Artículo de Publicación PeriódicaNanocomposites based on poly(lactic acid) and bacterial cellulose acetylated by an α-hydroxyacid catalyzed route(2019-01) Ávila Ramírez, Jhon Alejandro; Cerrutti, Patricia; Bernal, Celina; Errea, María Inés; Foresti, María Laura"Poly(lactic acid) (PLA) nanocomposite films reinforced with acetylated bacterial cellulose nanoribbons were prepared by solvent casting. Acetylation of bacterial cellulose (BC) was performed by an innovative and sustainable direct solventfree route catalyzed by citric acid. The effect of derivatization and its extent on the morphological, optical, thermal and mechani-cal properties of the nanocomposites was analyzed. Data collected from the above studies showed that acetylation of BC nanoribbons clearly improved the nanofibers dispersion in the PLA matrix with respect to unmodified BC, which in turn resulted in increased transparency and mechanical properties of the nanocomposites produced."