Papers by LUISIANA MORALES ZAMUDIO
Bioresources, 2019
Microcellulose has shown advantageous character as a reinforcement in polymeric materials and pro... more Microcellulose has shown advantageous character as a reinforcement in polymeric materials and produces relatively light compounds with high specific properties. This research aimed to obtain microcellulose (crystals and fibers) from the macrophyte Typha domingensis for use as a polypropylene reinforcement material for impact strength improvement and to use stearic acid as an interfacial modifier (surfactant) between the polypropylene and cellulosic materials. A commercial cellulose was used to compare the effectiveness of the microcellulose isolated from the macrophyte. The results demonstrated the procedures were efficient at obtaining microcellulose. The analysis of the chemical composition indicated an increase in the α-cellulose content from 63.2% in the raw material to 97.9% in the bleached cellulose. The X-ray diffraction patterns showed that the chemical treatments changed the crystallinity. The thermogravimetric analysis revealed an increase in the thermal stability of the b...
Materials Chemistry and Physics
Abstract Polycarbonate (PC) was reinforced with pristine and chemically modified graphene oxide (... more Abstract Polycarbonate (PC) was reinforced with pristine and chemically modified graphene oxide (GO) to assess its effect on the PC mechanical properties. Commercial graphene with oxygen contents of 4.7 at %, was used as reference to corroborate the affinity of a GO with oxygen content of 25.6 at. % with PC. GO was modified with 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDAC). Commercial graphene, unmodified and modified GO were characterized by FTIR, Raman, XRD and XPS to determine the effects of their structure on the mechanical properties of the reinforced PC. The concentration of graphene oxides in the PC nanocomposites was 0.25, 0.50 and 0.75 weight %. The nanocomposites were characterized by tensile and impact resistance tests as well as by TGA. The distribution of graphene oxides within the PC matrix was evaluated by optical microscopy and scanning electron microscopy. Samples with unmodified GO and commercial graphene showed better dispersion into the polymer matrix than EDAC-modified GO. The unmodified GO increased show increased impact resistance with respect to PC as well as a 291% increment in the elongation at break, with an optimal content of 0.25 wt % of the filler. The EDAC-modified graphene oxide as well as commercial graphene did not increase the impact resistance at any used concentration. The structural and chemical analysis of the EDAC-GO indicate GO reduction during its modification, suggesting that the oxygen functional groups in pristine GO, particularly carboxyl moieties are the responsible for the dispersion and interactions with the polymer and the improvement in mechanical properties.
Quimica Hoy
El azul de metileno se adsorbió sobre la superficie del óxido de grafeno (GO). El óxido de grafen... more El azul de metileno se adsorbió sobre la superficie del óxido de grafeno (GO). El óxido de grafeno fue purificado conácido clorhídrico. El potasio (K+) y el manganeso (Mn+2) se eliminaron principalmente durante la purificación. ElGO purificado fue llamado GO aniónico de la misma forma el GO no tratado fue llamado GO catiónico, poseedor ensu mayor parte de carga positiva. La purificación condujo a una mejor adsorción del azul de metileno. El áreaespecífica superficial BET tuvo también una explicación para la adsorción del colorante. El GO aniónico dio un áreaespecífica superficial más alta. La adsorción fue determinada por un espectrofotómetro UV-VIS. El contenido de K+ yMn+2 fue determinado por Espectroscopía de Dispersión de Energía (EDS). La descomposición del colorante siguióel modelo de Langmuir-Hinshelwood.Las interacciones entre el colorante catiónico y el GO aniónico fuero clave para la adsorción. Los grupos carbonilo ycarboxílico detectados por FTIR en el GO generaron sitios...
Journal of Applied Polymer Science, 2019
A study of the improvement of the mechanical and thermal properties of nanocomposites prepared wi... more A study of the improvement of the mechanical and thermal properties of nanocomposites prepared with polypropylene (PP) and different graphene samples [graphene oxide (GO), reduced GO (RGO), and commercial graphene (G)] is presented. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy characterization were applied to the graphene samples. The nanocomposites were characterized by thermogravimetric analysis, XRD, differential scanning calorimetry, transmission electron microscopy (TEM), tensile, and impact resistance tests. PP/RGO nanocomposites showed significant improvement in mechanical and thermal properties. Sample PP/RGO-0.75 resulted in an increment in Young's modulus (51%), tensile strength (24%), and elongation at break (15%). This is attributed to a good dispersion state, a higher crystallinity percentage, and a good interfacial adhesion between PP and RGO. Sample PP/RGO-0.50 exhibited an increase of 197 C in the temperature at which a loss in weight of 5% occurred, compared to that for pure PP. The height of stacked layers calculated by XRD measurements was similar to the value observed by TEM.
Polymer Engineering & Science, 2019
Journal of Composite Materials, 2016
The mechanical properties of polypropylene-bentonite nanocomposites were studied in this work. In... more The mechanical properties of polypropylene-bentonite nanocomposites were studied in this work. In this study, stearic acid was used as both a new surface modifier of the nano bentonite and a new interface modifier during the compounding of the nanocomposites with a twin-screw extruder. Three different weight concentrations (1.5 wt.%, 2.5 wt.%, and 5.0 wt.%.) were chosen for each type of nanobentonite compounds. Fourier transform infrared spectroscopy allowed us the possibility to discard any chemical interaction between the nanobentonite and stearic acid. Nevertheless, the physical interactions between both components favored the mechanical properties, resulting in around 150% improvement in the elongation of the nanocomposites containing stearic acid as surface and interface modifier. This can be due to the good intercalation of the nanobentonite platelets as found by wide angle X-ray diffraction and this was further confirmed by scanning electron microscopy, where the fracture sur...
Journal of Cardiovascular Pharmacology, 2000
We sought to examine whether the antiarrhythmic effect of E4031 (E), or I(Kr) channel blocker, is... more We sought to examine whether the antiarrhythmic effect of E4031 (E), or I(Kr) channel blocker, is affected by beta-adrenergic stimulation using isoproterenol (Iso) or by beta-adrenergic blockade (betaB) using, ONO1101, in a canine myocardial infarction model. Electrophysiologic studies were performed in 10 dogs with 7-day-old myocardial infarctions. Local QT intervals were measured at 47 sites on the infarcted myocardium using a mapping electrode. QT dispersion (QTd), as defined by the coefficient of variation of QT intervals, was obtained. Inducibility of ventricular arrhythmias was examined by programmed stimulation. These procedures were repeated during administration of E, E + Iso, and E + betaB. The effect of prolonging local QT intervals by E was counteracted by Iso, and was accentuated by betaB. The amount of prolongation was dependent on the baseline QT intervals, and QTd showed a tendency to decrease with E, to increase with E + Iso, and significantly decreased with E + betaB. Ventricular tachyarrhythmias were induced in a half of dogs with E + Iso, but were not induced with E + betaB. In the presence of adrenergic activation, I(Kr) blockers may exhibit a decreased antiarrhythmic effect. Beneficial synergism can be expected when an I(Kr) blocker is combined with a beta-blocker in the subacute phase of myocardial infarction.
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Papers by LUISIANA MORALES ZAMUDIO