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Search Results: 1 - 10 of 662 matches for " Soldi Valdir "
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Poly(ethylene-co-methyl acrylate)/poly(caprolactone) triol blends for drug delivery systems: characterization and drug release
Kanis, Luiz A.;Soldi, Valdir;
Química Nova , 2012, DOI: 10.1590/S0100-40422012000200012
Abstract: poly(ethylene-co-methyl acrylate) (ema) and poly (caprolactone) triol (pcl-t) blends, a biodegradable aliphatic polyester with low molecular weight and moderate water solubility containing diltiazem hydrochloride (dz) were studied in terms of the thermal and morphological properties, and drug release mechanism. an increase in the pcl-t content in the ema/pcl-t/dz films decreased the degree of dz crystallinity. drug release from these films is temperature-dependent, and it is possible to modify the drug release rate by adjusting the ema/pcl-t composition of the blends. the mechanism of drug release is governed by pcl-t melting and pcl-t leaching from ema matrix.
Dynamic light scattering and viscosimetry of aqueous solutions of pectin, sodium alginate and their mixtures: effects of added salt, concentration, counterions, temperature and chelating agent
Lima, Aline M. F.;Soldi, Valdir;Borsali, Redouane;
Journal of the Brazilian Chemical Society , 2009, DOI: 10.1590/S0103-50532009000900020
Abstract: the effects of added salt, concentration, counterions, temperature and chelating agent on aqueous solutions of pectin, sodium alginate and their mixtures were analyzed by viscosimetry and dynamic light scattering (dls) techniques. the intrinsic viscosity of the binary systems decreased with the addition of salt and with temperature, while it was found to be insensitive to the addition of naedta. as expected the intrinsic viscosity of the ternary alginate/pectin/water system was equal to the average of the intrinsic viscosity for the binary systems. the dls studies indicated a bimodal distribution (fast and slow relaxation modes) for both binary and ternary systems at 25 °c, reflecting aggregation. a significant increase in the hydrodynamic radius, in the case of the slow mode, was observed for the binary and ternary systems in the presence of nacl and kcl at 25 °c. however, at 80 °c the hydrodynamic radius for the slow mode in kcl solutions was practically constant for all the studied systems, except for the alginate binary solutions in which were not observed.
Influência da sequência de mistura do PP-MA nas propriedades dos compósitos de PP e fibra de bananeira
Becker, Daniela;Kleinschmidt, Ana C.;Balzer, Palova S.;Soldi, Valdir;
Polímeros , 2011, DOI: 10.1590/S0104-14282011005000012
Abstract: this work analyzed the influence from the sequence of mixture for the composite of polypropylene (pp) with 10% by volume of banana fiber (fb) using maleic anhydride grafted polypropylene (pp-ma) as the coupling agent. the thermal, mechanical, water absorption and morphology of the composites were characterized. three different sequences were used to mix: the processing of all components together (pp + pp-ma + fb), extrusion of pp / pp-ma and after grinding, the mixture was processed with fb ((pp / pp - ma) + fb), and the mixture of pp-ma with fb followed by extrusion of the composite with pp (pp + (pp-ma + fb)). the composites showed higher thermal stability and lower percent crystallinity than the pure pp, regardless of the sequence of mixing. it was found that the mixture of pp + pp-ma + fb processed once had a higher impact resistance. the composites modified with pp-ma, regardless of the sequence of mixture used, showed higher modulus and lower water absorption than the composite without coupling agent. for the tensile strength and modulus of elasticity no significant changes were observed. the images from scanning electron microscopy indicated that fb had higher adhesion for the composites with pp-ma, especially for composition pp + (pp-ma + fb).
Influência da adi??o de plastificante do processo de reticula??o na morfologia, absor??o de aguá e propriedades mecanicas de filmes de alginato de sódio
Lima, Aline Margarete Furuyama;Andreani, Larissa;Soldi, Valdir;Borsali, Redouane;
Química Nova , 2007, DOI: 10.1590/S0100-40422007000400014
Abstract: the effects of sorbitol and formaldehyde on the morphology, water absorption and mechanical properties of sodium alginate films were analyzed. the morphology of the films indicated the presence of small aggregates in the surface of uncrosslinked films, which disappeared with the crosslinking process. the water uptake and percentage of elongation increased with the addition of sorbitol in uncrosslinked films. at the same time, a decrease in tensile strength and young's modulus occurred. the swelling ratio and water uptake of crosslinked alginate/sorbitol films decreased with an increase in sorbitol content suggesting an enhanced crosslinking density due to the presence of plasticizer.
Efeito da adi??o de polietilenoglicóis nas formula??es de microesferas de acetobutirato de celulose sobre a eficiência de encapsula??o da carbamazepina e morfologia das partículas
Zanetti, Betina Giehl;Soldi, Valdir;Lemos-Senna, Elenara;
Revista Brasileira de Ciências Farmacêuticas , 2002, DOI: 10.1590/S1516-93322002000200012
Abstract: with the aim of obtaining carbamazepine (cbz) prolonged release dosage forms, cellulose acetate butyrate (cab70) microspheres have been prepared by the emulsion/solvent evaporation method. in order to modulate the cbz release, the addition of polyethylene glycols (peg) in the internal phase of the emulsion was carried out. when compared with microspheres prepared only from cab70, the encapsulation efficiency and the cbz content were drastically reduced by the peg 4000 addition. on the other hand, the incorporation of 10% (w/w) of peg1500 did not affect the drug content in the microspheres. most porous particles werw observed by sem when peg 1500 or 4000 was added to the formulations, however the lost of the spherical shape of the particles was verified when an abc70:peg 4000 1:1 mixture was used to prepare the microspheres. the addition of pegs did not appear to affect the mean diameter of the particles. the decrease of the cbz content was related to the peg extraction during the solvent evaporation step and to its ability to dissolve the cbz in the external phase of the emulsion. the porosity development control, by adjusting the amount or the molecular weight of peg, can be useful in the drug release from microparticles.
Potassium ions release from polysaccharide films
Oliveira, Aline F;Silveira, Cristian B;Ernani, Paulo R;Balbinot, Elisandro S;Soldi, Valdir;
Journal of the Brazilian Chemical Society , 2011, DOI: 10.1590/S0103-50532011000200004
Abstract: in plant growth media of low negative charge, potassium (k) is leached out easily with adverse consequences on its availability to plants and on the environment, since all k fertilizers are completely soluble. the objective of this study was to prepare films based on sodium carboxymethylcellulose (cmc), sodium alginate (sa) and a 1:1 (v/v) cmc:sa mixture to incorporate k and investigate its subsequent release. the film properties were evaluated considering miscibility, glass transition temperature, morphology and permeation of potassium. the absence of strong interactions, the small variation in the glass transition temperature and the roughness detected in the cross-section micrographs of the 1:1 cmc:sa mixtures, indicated a partial miscibility among the components. as a consequence of the above-mentioned characteristics, film release of potassium was highest for the 1:1 cmc:sa mixture and lowest for sa. the release mechanism of k from the 1:1 cmc:sa mixture was controlled by a diffusion process, however, associated effects due to swelling and erosion of the matrix films, were observed for the pure cmc and sa systems. films of cmc, sa and their 1:1 mixture were able to delay the k release, which can bring considerable benefits in terms of plant growth when media with low negative charges are used.
Protein-based films cross-linked with 1-ethyl-3-(3-dimethylamino-propyl) carbodiimide hydrochloride (EDC): effects of the cross-linker and film composition on the permeation rate of p-hydroxyacetanilide as a model drug
Cristiano, Cláudia M. Z.;Fayad, Samira J.;Porto, Ledilege C.;Soldi, Valdir;
Journal of the Brazilian Chemical Society , 2010, DOI: 10.1590/S0103-50532010000200021
Abstract: cross-linked films of gelatin (gel), casein (cas) and their (1:1, m/m) mixture (gel/cas) were studied in terms of their thermal, morphological and water absorption properties and the permeation profile of p-hydroxyacetanilide (p-haa) as a model drug. the degrees of cross-linking by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (edc) were 90.6% for gel films and approximately 70% for cas and gel/cas films. the totally soluble non cross-linked films achieved only 21 - 22% of solubility after cross-linking with edc. despite the high cross-linking degree, the swelling of gel films (87.2%) was practically twice that determined for gel/cas and cas films. the permeation rate of p-haa followed the order gel>gel/cas ? cas for cross-linked films, which is consistent with the gel film showing a greater swelling than the other two systems studied. lower permeation rates were observed for cas and gel/cas films, suggesting that these could be used as rate-controlling systems for drug permeation. for the different mathematical models applied, the systems studied did not show a good fit with the first-order equation and only a partial fit with the zero-order equation and higuchi's model. however, good correlations (r2 > 0.99) were obtained using the power law equation (n = 0.70 - 0.87), indicating that the p-haa permeation through the films was mainly controlled by a diffusion mechanism.
Adhesion of L929 mouse ribroblast cells on poly(styrene)/poly(methyl methacrylate) films
Melo, Adriana de;Bet, ?ngela Cristina;Assreuy, Jamil;Debacher, Nito Angelo;Soldi, Valdir;
Journal of the Brazilian Chemical Society , 2009, DOI: 10.1590/S0103-50532009000900026
Abstract: films of pure poly(styrene) (ps), pure poly(methyl methacrylate) (pmma), a 1:1 ps/pmma blend and a ps-b-pmma copolymer, were prepared and tested for cell adhesion using l929 mouse fibroblasts. all polymer films were found to be good substrates for cell adhesion and proliferation, and both processes were slightly favored on films of the 1:1 ps/pmma blend. the same results were obtained in terms of cell number and morphology for cells cultured on films, glass coverslips or plastic plates. the chemical characteristics of polymer films make them suitable supports for cell attachment and proliferation, indicating that these films are good candidates for biomedical uses.
Biodegradable films made from raw and acetylated cassava starch
Larotonda, Fábio D. S.;Matsui, Kátia N.;Soldi, Valdir;Laurindo, Jo?o B.;
Brazilian Archives of Biology and Technology , 2004, DOI: 10.1590/S1516-89132004000300019
Abstract: studies were carried out to produce biodegradable films from cassava starch. two alternatives were investigated. in the first, films were obtained by starch gelatinization followed by thermopressing and glycerol was used at different concentrations as a plasticizer. in the second, starch acetate films were obtained by solubilization of cassava starch acetate in organic solvents, followed by casting on a glass plate and drying at room temperature. the films obtained by gelatinization were transparent and resistant to traction. the starch acetate films were also transparent but breakable. the use of these starch acetate films in paper impregnation improved the mechanical properties of the paper.
Blendas de poliamida 6/elast?mero: propriedades e influência da adi??o de agente compatibilizante
Barra, Guilherme M. O.;Roeder, Jerusa;Soldi, Valdir;Pires, Alfredo T. N.;Agnelli, José A. M.;
Polímeros , 2003, DOI: 10.1590/S0104-14282003000200006
Abstract: this study describes the micro- and macroscopic properties of polyamide 6 (pa6) and ethylene /propylene/diene copolymer (epdm) blends, and the effects from small quantities of epdm or epm grafted with maleic anhydride in this polymer mixture. the components and polymer blends at different compositions were analyzed by differential scanning calorimeter (dsc) and infrared spectroscopy (ftir). the results suggest immiscible mixture in all ranges of the blend's compositions. scanning electron microscopy (sem) micrographs of the blends indicated that the size of rubber aggregates decreases as the functionalized elastomer (epdm-g-ma or epm-g-ma) is added to the pa6/epdm mixture, and the impact strength of the pa6 matrix increases significantly.
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