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Oliveira J.E.,Federal University of São Carlos | Oliveira J.E.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Moraes E.A.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Marconcini J.M.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | And 4 more authors.
Journal of Applied Polymer Science | Year: 2013

The properties of mixtures of poly(lactic acid) (PLA) and poly(ethylene oxide) (PEO) were studied in polymer solutions by dilute solution viscometry, and in-solution blow-spun nanofibers were studied by microscopy (scanning electron and transmission electron microscopy) and thermal and spectral analysis. Three mixtures of PLA and PEO (3:1, 1:1, and 1:3) were solution-blended in chloroform. Dilute solvent viscometry indicated that the 3:1 mixture of PLA and PEO had a higher miscibility coefficient value than the other mixtures. The neat polymers and mixtures were solution-blow-spun into nanofibers. The fiber diameters were smallest in the neat polymers. Transmission electron micrographs revealed a core/sheath structure for the sample mixtures. X-ray analysis indicated that the crystallinity was positively correlated with the PEO content. Fibers from the mixtures had contact angle measurements similar to those of the neat PEO. Fourier transform infrared and Raman spectroscopy of the mixtures indicated interactions between ester and ether groups, which were attributed to dipole-dipole interactions between the ester groups of PLA and the ether groups of PEO. Copyright © 2013 Wiley Periodicals, Inc.

De M. Teixeira E.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | De Oliveira C.R.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Mattoso L.H.C.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Correa A.C.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | And 3 more authors.
Polimeros | Year: 2010

The thermal stability of cellulose nanofibers is related to their application and especially to polymer processing normally occurring at ca. 200 °C. In this work, nanofibers of commercial cotton were obtained by acid hydrolysis employing different acids: sulfuric, hydrochloric and a mixture (1:1; sulfuric acid: hydrochloric acid). The morphology of the nanofibers were characterized by transmission microscopy (TEM), zeta potential, elemental analysis, crystallinity by X ray diffraction (XRD) and thermal stability (TGA) in air atmosphere by thermogravimetric analysis. The results indicated a very similar morphology and crystallinity among them. The main differences were lie in the aggregation state and thermal stability. The aggregation state of the suspensions decreases in the order HCl < H2SO4:HCl < H2SO4 due to the increase in surface charge as determined by zeta potential measurements. The hydrolysis with a mixture of HCl and H 2SO4 resulted in cellulose nanofibers with higher thermal stability than those hydrolyzed with H2SO4. The hydrolysis employed with a mixture of sulphuric and hydrochloric acids also showed a better dispersion than those suspensions of nanofibers obtained by hydrolysis with only HCl.

Costa R.G.F.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Brichi G.S.,Federal University of São Carlos | Ribeiro C.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Mattoso L.H.C.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio
Polymer Bulletin | Year: 2016

Solution blow spinning (SBS) is a recent technology to produce polymer micro- and nanofibers, including nanocomposites loaded with a wide range of nanoparticles. Because of its novelty, various studies about the properties of the produced materials are necessary, especially those related to material stability. In the present study, poly(lactic acid) (PLA)/titanium dioxide anatase (TiO2) nanocomposite fibers, with different TiO2 percentages, were produced by the SBS method. The spun nanocomposite fibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry (DSC). Moreover, the photocatalytic degradation of Rhodamine B (RhB) dye and PLA degradation by UV-C lamps were investigated. SEM and TEM micrographs show that the SBS method produced PLA/TiO2 nanofibers with uniform morphology and without beads. The DSC analyses and X-ray diffraction patterns show that incorporation of TiO2 nanoparticles could influence the PLA nanocomposite crystallinity. PLA photocatalytic degradation experiments demonstrate that the weight loss of the polymer increases with an increase in TiO2 content. The present results indicate that the SBS method can be used to produce biodegradable nanocomposite fibers with good properties and potential applications. © 2016 Springer-Verlag Berlin Heidelberg

Moreira F.K.V.,Federal University of São Carlos | Moreira F.K.V.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Marconcini J.M.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Mattoso L.H.C.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio
Polymer Bulletin | Year: 2012

The selection of the composition and processing conditions for carbohydrate-based blends is of fundamental importance for many applications and plays a role in determining the mechanical behavior of these biodegradable materials. In this study, starch/pectin (PEC) blends were obtained via melt technique and an investigation of the effects of composition and processing parameters on their mechanical properties was performed. The blends were prepared by adopting an experimental design and were characterized by uniaxial tensile tests, scanning electron microscopy, and phase imaging atomic force microscopy. The starch:PEC mass ratio showed the maximum influence on the tensile properties, which were independent on the processing parameters. It was suggested that as the degree of methyl esterification of PEC decreased, the modulus and tensile strength of the blends increased, and this effect was observed up to 50 wt% starch. AFM revealed the immiscibility between the polymers and this phenomenon was associated to the mechanical behavior of the blends. © 2012 Springer-Verlag.

Oliveira J.E.,Federal University of São Carlos | Grassi V.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Scagion V.P.,Federal University of São Carlos | Mattoso L.H.C.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | And 2 more authors.
IEEE Sensors Journal | Year: 2013

A disposable low cost and simple flow-cell electronic tongue for water analysis is described. A sensor array is used that is comprised of six interdigitated microelectrodes coated with nanofiber films of poly(lactic acid)/mutliwalled carbon nanotube (MWCNT) composites. Fiber films are deposited directly on the interdigitated electrodes surface by solution blow spinning. Fiber film thickness is varied by using different deposition times (1, 3, and 15 min). Analysis of scanning electron microscopy and transmission electron microscopy micrographs indicates that average fiber diameters are 400 nm for neat poly lactic acid (PLA) and 200 nm for the PLA/MWCNT composite. The MWCNT is poorly dispersed in the PLA fiber matrix and formed aggregates interspersed throughout the fiber length. There are also MWCNTs exposed or partially exposed at the fiber surface. Fiber films containing MWCNT (1%) give the highest dc conductivity values and the most linear I-V profiles at room temperature. Sensor arrays with thin fiber film coatings (1 min deposition time) provide the best result for discriminating potable water samples using principal component analysis (PCA). The flow-cell electronic tongue coupled with PCA is used to discriminate potable water samples from non-potable water contaminated with metals or traces of pesticides. © 2001-2012 IEEE.

Takeda H.H.,Federal University of São Carlos | Takeda H.H.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Takeda H.H.,Federal University of Rondônia | Janegitz B.C.,Federal University of São Carlos | And 4 more authors.
Sensors and Actuators, B: Chemical | Year: 2012

A glassy carbon electrode (GCE) modified with functionalized multiwalled carbon nanotubes within a poly(allylamine hydrochloride) film (CNTs-PAH) to determine ciprofibrate using differential pulse voltammetry (DPV) is proposed. The CNTs/PAH film was previously valued and characterized with the zeta potential technique and scanning electronic microscopy (SEM). The DP voltammograms presented a ciprofibrate oxidation peak potential at 0.98 V in a 0.1 mol L -1 phosphate buffer solution (pH 7.0). The analytical curve was linear in the ciprofibrate concentration range from 1.33 × 10 -5 to 1.32 × 10 -4 mol L -1, with a detection limit of 8.34 × 10 -6 mol L -1. Precise and accurate results are in agreement with those obtained by the chromatographic method at a 95% confidence level. © 2011 Elsevier B.V. All rights reserved.

This work reported the characterization of hydrogels constituted by methylcellulose (MC) entrapped in polyacrylamide (PAAm) network prepared by cross-linking polymerization (gelling process). Spectroscopic and morphologic properties were investigated using Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. Effects of AAm, MC contents, ionic charge of salt counter-ions (NaCl, KCl, NH4Cl, CaCl2, MnCl2, MgCl2, and AlCl3), and fertilizers [(NH4)2SO4 and KH2PO4] on kinetic and hydrophilic (swelling degree) properties were investigated in detail. By decreasing the MC content or by increasing acrylamide content, there was a pronounced decrease in water uptake by the hydrogels. The increase in counter-ion X-Cl salt and the presence of fertilizer on the external swelling medium also provoked a decrease in water uptake. The water uptake mechanism of PAAm-MC hydrogels swollen in water followed the Fickian diffusion, while the mechanisms of hydrogels swollen in salt or fertilizer aqueous media followed the anomalous transport process. With their fast and high water absorption, the porous, three-dimensional matrices containing PAAm and MC are promising for agriculture as carrier vehicles.

Campos A.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Marconcini J.M.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Imam S.H.,U.S. Department of Agriculture | Klamczynski A.,U.S. Department of Agriculture | And 5 more authors.
Journal of Reinforced Plastics and Composites | Year: 2012

The incorporation of fibers as reinforcements in polymer composites has increased due to their renewability, low cost and biodegradability. In this study, sisal fibers were added to a polymer matrix of thermoplastic starch and polycaprolactone, both biodegradable polymers. Sisal fibers (5% and 10%) were extruded in a twin-screw extruder with thermoplastic starch/polycaprolactone (80:20 wt). Films were produced with a single extruder and analyzed by field emission gun scanning electron microscopy, mechanical tests, thermogravimetric analysis and differential scanning calorimetry. The morphology of the composites with 10% sisal fiber content presented an interface of fibers at the surface of the matrix, indicating poor adhesion, lower initial temperatures of thermal degradation, and decreased polycaprolactone crystallinity due to the decrease in lamellar thickness and the increase in crystalline disorder. The results were affected mainly by the lack of adhesion at the interface between the matrix and fibers. The interfacial shear strength between sisal and the matrix may be improved by chemical modification of the fiber surface. © The Author(s) 2012.

De Campos A.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Teodoro K.B.R.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Marconcini J.M.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Mattoso L.H.C.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Martins-Franchetti S.M.,São Paulo State University
Polimeros | Year: 2011

Sisal fibers treated with four methods, namely washing with water, washing with cyclohexane/ethanol, alkali treatment (NaOH) and bleaching (alkaline peroxide treatment), were incorporated in thermoplastic starch/polycaprolactone 80/20 (TPS/PCL) samples. Morphological, mechanical and thermal properties of TPS/PCL/Sisal biocomposites were analysed. The best results were obtained with the composite using the bleached fiber, which had improved tensile strength and thermal stability. An increased adhesion between the fiber and matrix was also observed with the bleached fiber, with 145% increase in the tensile strength.

Paulino A.T.,University of Campinas | Guilherme M.R.,University of Campinas | Mattoso L.H.C.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Tambourgi E.B.,University of Campinas
Macromolecular Chemistry and Physics | Year: 2010

By means of a conventional cross-linking/co-polymerization reaction of modified gum arabic (M-GA), acrylamide (AAm), and potassium acrylate (KAAc) in the presence of magnetite (Fe3O4) nanoparticles, a magnetic field-sensitive M-GA-based hydrogel (smart hydrogel) was synthesized to investigate its potential as a magnetic biomaterial and as a intelligent hydrogel. Characterizations through FT-IR, NMR, XRD, Mössbauer, SEM, and EDX inferred that the smart hydrogel was efficiently formed. Theoretically, the smart hydrogel obtained in this work may effectively be applied as biomaterial either on remote controlled release or tissue engineering or even in other areas of science and technology. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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