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ABSTRACT: PAAm–MC hydrogels as a potential delivery vehicle for the controlled release of paraquat pesticide was investigated, as they
play an essential role to use hydrogels in controlled release technology. The release kinetics of paraquat was determined
using UV–Vis measurements. The release mechanism of paraquat from PAAm–MC hydrogels was investigated through a semi-empirical
model proposed by Ritger and Peppas. In general, the initial rate of paraquat release was fast, decreasing after several days,
hence indicating that paraquat on the surface (or close to) of hydrogels diffused rapidly after the initial swelling of the
gel. Later, the cumulative release occurred in a very controlled and sustained manner, with the paraquat concentration maintaining
constant from 15 to 46days. The paraquat release capacity was dependent on the swelling of the matrix and the density of
the network chains. The curves obtained from Peppas’s model presented good linearity (R
2≥0.999), indicating that such model can be applicable to analyze the systems. The n values for the pesticide release from hydrogels indicate that paraquat release has Fickian and non-Fickian diffusion, depending
of hydrogel formulation. The values of k showed that the release of paraquat becomes slower when the MC and AAm concentration increases. Finally, to the best of our
knowledge, we report a hydrogel-based vehicle (first carrier) that is able to prolong the sustained release of paraquat pesticide
up to 45days, which is essential for its application in controlled release systems.
Journal of Materials Science 04/2012; 45(18):4977-4985. · 2.02 Impact Factor
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ABSTRACT: One of the overall goals of industries is to use packages that do not cause environmental problems at disposal time, but that have the same properties as the conventional ones. The goal of this study is to synthesize edible films based on hydroxypropyl methylcellulose (HPMC) with guava puree and chitosan (CS) nanoparticles. This was divided into two stages, the first is the synthesis of chitosan nanoparticles and the second is the production of the films. For the nanoparticles, average size and zeta potential measurements were performed. The characterizations of mechanical and thermal properties, solubility and water vapor permeability tests were conducted in the films. It was observed that when the nanoparticles were added to HPMC and guava puree films, they improved their mechanical and thermal properties, as well as decreased the films solubility and permeability. The potential application of the films prepared would be in edible films with flavor and odor to extend the shelf life of products.
Journal of Nanoscience and Nanotechnology 03/2012; 12(3):2711-7. · 1.56 Impact Factor
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ABSTRACT: In this work, clay-based nanocomposites films were prepared by addition of clay-Na+ natural montmorillonite in pectin and hydroxypropyl methylcellulose (HPMC) matrices. Mechanical (tensile strength, elastic modulus, and elongation) and barrier (Water Vapor Permeability (WVP), and Oxygen permeability (O2P)) properties were investigated. From results, it was observed that the WVP and O2P decreased when nanoclay was included into the HPMC and pectin matrix films. Additionally, the incorporation of nanoclay in the films significantly improved the mechanical properties because the reinforcing effect of clay from its high aspect ratio and its enormous surface area. These results are very important in packaging area.
Polymer-Plastics Technology and Engineering 09/2011; 50(13):1323-1328. · 1.28 Impact Factor
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ABSTRACT: The main objective of this article was to report a simple, fast, and low cost strategy for the synthesis of micro- and nanocomposites by adding cellulose nanofibers, obtained by acid hydrolysis, and added to hydrogels as reinforcing agents. Specifically, when cellulose nanofibers were added to hydrogels, morphologic analyses showed significant decreases in pore size and formation of three-dimensional well-oriented porous microstructure. It was also observed that cellulose nanoparticles improved the mechanical and structural network properties without negatively impacting their thermal and hydrophilic properties. The value of maximum compressive stress was 2.1 kPa for the PAAm-MC, and it increased to 4.4 kPa when the cellulose nanofiber was incorporated into the hydrogel. By investigation of XRD patterns, it was found that the incorporation of cellulose nanofiber affected the crystallinity of PAAm-MC hydrogels, thus contributing to improvements in mechanical, structural, and hydrophilic properties of the PAAm-MC hydrogels.
Journal of Agricultural and Food Chemistry 08/2011; 59(17):9433-42. · 2.82 Impact Factor
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ABSTRACT: This research studied the characteristics of poly(acrylamide) and methylcellulose (PAAm-MC) hydrogels as a novel adsorbent material for removal of pesticide paraquat, from aqueous solution, with potential applications in curbing environmental risk from such herbicides. PAAm-MC hydrogels with different acrylamide (AAm) and MC concentrations were prepared by a free-radical polymerization method. The capability of the hydrogels in removing paraquat dichloride from aqueous solution was determined using UV–Vis analysis. The scanning electron microscopy method was used to study the morphological properties of the hydrogels, and swelling degree (Q) of the hydrogels was also measured. The entrapped MC in PAAm chains provoked significant changes in morphological, hydrophilic, and adsorption properties of the PAAm-MC hydrogels. The adsorption capacity of hydrogels was strongly influenced by AAm, MC, and paraquat concentrations with the highest adsorption capacity (qeq = 14.3 mg g−1) was observed for hydrogels synthesized with 6.0% AAm with 0.75% MC swollen in 45.7 mg L−1 of paraquat solution. Freundlich model performed better than Langmuir model in describing the adsorption isotherm of PAAm-MC/paraquat system, implying a heterogeneous surface. These results suggest that PAAm-MC hydrogels are potentially viable absorbents for removal of paraquat pesticide from aqueous solution and cleaning water contaminated with dyes, heavy metals, and others pesticides. © 2009 Wiley Periodicals, Inc. Journal of Appl Polym Sci, 2009
Journal of Applied Polymer Science 07/2009; 114(4):2139 - 2148. · 1.29 Impact Factor
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ABSTRACT: In this work the preparation of chitosan nanoparticle was investigated using methacrylic acid in different conditions and studied by particle size analyzer, zeta-potential, Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM). The particle size was dependent on the chitosan concentration used during the preparation method. Nanoparticles with sizes as small as 60 nm were achieved, that can be extremely important for several applications. The nanoparticles solution was also pH-sensitive, due to swelling and aggregation of the nanoparticles. The nanoparticles obtained presented a very homogeneous morphology showing a quite uniform particles size distribution and a rather spherical shape.
Journal of Colloid and Interface Science 06/2008; 321(2):477-83. · 3.07 Impact Factor
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ABSTRACT: Chitosan/tripolyphosphate nanoparticles were prepared and incorporated in hydroxypropyl methylcellulose (HPMC) films. FT-IR and transmission electron microscopy (TEM) analyses of the nanoparticles, mechanical properties, water vapor permeability, thermal stability, scanning electron microscopy (SEM) of the films were analyzed. Incorporation of chitosan nanoparticles in the films improved their mechanical and film barrier properties significantly. The chitosan nanoparticles tend to occupy the empty spaces in the pores of the HPMC matrix, increasing the collapse of the pores and thereby improving film tensile properties and water vapor permeability. The thermal stability of the films increased with addition of nanoparticles. This study is the first to investigate the use of CS-TPP nanoparticles for the purpose of strengthening HPMC films.
Journal of Food Engineering.
