Novel polybenzoxazine and polybenzoxazine/epoxy thermosetting copolymers containing polysilsesquioxane nanostructures for high-performance thermal protection systems

This work focuses on the development of novel thermosetting systems derived from a siloxane-based benzoxazine hybrid precursor [Pr(BA-3aptms)], a conventional benzoxazine (BA-a) and a commercial epoxy resin (DGEBA) based on bisphenol A, as a strategy to prepare benzoxazine/benzoxazine and epoxy/benzoxazine copolymers with different amounts of polysilsesquioxanes in their chemical structure. The effect of the siloxane composition on the morphology was investigated, and their influence on the thermal, dynamo-mechanical and flammability properties was elucidated. The obtained results allowed to conclude that an increase of the BA-a or DGEBA content in the copolymers, considerably affects the morphology of the materials. In this sense, the laminar arrangement changed to a nanocluster arrangement when the contents of Si were below 17% w/w for the epoxy/benzoxazine and below 10% w/w for benzoxazine/benzoxazine systems, respectively. Also, the thickness of the organic sheets in the matrices was increased when increasing the content of BA-a or DGEBA in the materials. In addition, the incorporation of the polysilsesquioxane-based precursor in the crosslinked materials improved the investigated properties, such as: thermal, mechanical and flame resistance, and hydrophobic behavior.Fil: Forchetti Casarino, Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Bortolato, Santiago Andres. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Departamento de Química Analítica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Casis, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Spontón, Marisa Elisabet. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Use of rice husk for the removal of methylene blue in fixed-bed columns

Este trabajo muestra la utilización de la cascarilla de arroz para la remoción del colorante catiónico azul de metileno bajo sistema continuo. Un diseño factorial 23, con puntos centrales y distribución aleatoria, fue implementado para evaluar la correlación de los factores experimentales en el proceso de adsorción. Las variables consideradas fueron pH, tamaño de partícula, presencia salina, velocidad de entrada, concentración inicial del colorante y altura de columna. Las muestras fueron analizadas a intervalos definidos de tiempo. La cantidad del colorante removido fue cuantificado por medio de espectroscopia Ultravioleta - Visible. Los modelos de Adams-Bohart, Thomas y BDST (Bed-depht/service time analysis) fueron utilizados para predecir las curvas de ruptura usando regresión no lineal y establecer los parámetros característicos del proceso. Se encontró que la transferencia de colorante al material adsorbente se favorece a pH básico, menor tamaño de partícula, flujo y concentración baja y mayor altura. El diseño de experimentos estableció que la concentración inicial de colorante y la altura del lecho fueron los factores más significativos. Con respecto a los modelos, el de Thomas presentó el mejor ajuste para la descripción de las curvas de ruptura a las condiciones experimentales y el de Adams-Bohart resultó adecuado para el comportamiento dinámico limitado a la parte inicial. Finalmente, el modelo BDST mostró una buena correlación y permitió establecer que la altura es determinante para el escalado del proceso.This work shows the use of rice husk in the removal of cationic dye methylene blue on continuous system. A factorial design 23 with center points and random distribution was implemented to evaluate the correlation of the experimental factors in the adsorption process. The considered variables were pH, particle size, salt presence, flow rate, dye initial concentration, and bed depth. The samples were analyzed in defined time intervals. The amount of removed dye was quantified by UV spectroscopy - Visible. Adams-Bohart, Thomas and BDST (Bed-depht/service time analysis) models were used to predict the breakthrough curves using non-linear regression and establish the characteristic parameters of the process. It was found that the transference of dye toward the adsorbent is favored by a basic pH, a small particle size, low flow rate and dye concentration, and high bed depth. The design of experiments established that the initial dye concentration and the bed depth were the most significant factors. Regarding the models, the Thomas provided the best fit to describe the breakthrough curves in experimental conditions and Adams-Bohart was found suitable for dynamic behavior limited to the initial part. Finally, BDST model exhibited a good correlation and allowed to establish that bed depth is a determinant factor for scaling process

Morphology modulation of silica mesoporous nano- and microparticles for atrazine - controlled release

Atrazine is a moderately toxic triazine, used as a selective pre- and post-emergence herbicide. After application, it remains in the environment due to its low biodegradability causing severe environmental effects. Several controlled release systems have been proposed in order to minimize the negative impact of the herbicide on the environment. In particular, mesoporous silica nanoparticles have shown great potential in the agricultural area due to their controlled size and porosity, high surface area and non-toxicity. In this work, silica nano- and microparticles were synthesized and evaluated as atrazine delivery systems. The morphology and size distribution of the particles were characterized using dynamic light scattering (DLS) and scanning electron microscopy (SEM). The release profiles were studied by in vitro assays in water. In addition, phytotoxicity tests were performed using Lactuca sativa seeds. The mesoporous nano- and microparticles exhibited sustained release for at least 24 h and reduced phytotoxicity compared to free atrazine.Fil: Fookes, Federico Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Busatto, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Taverna, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Casis, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Lescano, Maia Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

High thyrotropin is critical for cardiac electrical remodeling and arrhythmia vulnerability in hypothyroidism

Background: Hypothyroidism, the most common endocrine disease, induces cardiac electrical remodeling that creates a substrate for ventricular arrhythmias. Recent studies report that high thyrotropin (TSH) levels are related to cardiac electrical abnormalities and increased mortality rates. The aim of the present work was to investigate the direct effects of TSH on the heart and its possible causative role in the increased incidence of arrhythmia in hypothyroidism. Methods: A new rat model of central hypothyroidism (low TSH levels) was created and characterized together with the classical propylthiouracil-induced primary hypothyroidism model (high TSH levels). Electrocardiograms were recorded in vivo, and ionic currents were recorded from isolated ventricular myocytes in vitro by the patch-clamp technique. Protein and mRNA were measured by Western blot and quantitative reverse transcription polymerase chain reaction in rat and human cardiac myocytes. Adult human action potentials were simulated in silico to incorporate the experimentally observed changes. Results: Both primary and central hypothyroidism models increased the L-type Ca2+ current (ICa-L) and decreased the ultra-rapid delayed rectifier K+ current (IKur) densities. However, only primary but not central hypothyroidism showed electrocardiographic repolarization abnormalities and increased ventricular arrhythmia incidence during caffeine/dobutamine challenge. These changes were paralleled by a decrease in the density of the transient outward K+ current (Ito) in cardiomyocytes from animals with primary but not central hypothyroidism. In vitro treatment with TSH for 24 hours enhanced isoproterenol-induced spontaneous activity in control ventricular cells and diminished Ito density in cardiomyocytes from control and central but not primary hypothyroidism animals. In human myocytes, TSH decreased the expression of KCND3 and KCNQ1, Ito, and the delayed rectifier K+ current (IKs) encoding proteins in a protein kinase A–dependent way. Transposing the changes produced by hypothyroidism and TSH to a computer model of human ventricular action potential resulted in enhanced occurrence of early afterdepolarizations and arrhythmia mostly in primary hypothyroidism, especially under b-adrenergic stimulation. Conclusions: The results suggest that suppression of repolarizing K+ currents by TSH underlies most of the electrical remodeling observed in hypothyroidism. This work demonstrates that the activation of the TSHreceptor/protein kinase A pathway in the heart is responsible for the cardiac electrical remodeling and arrhythmia generation seen in hypothyroidism.Fil: Fernandez Ruocco, Maria Julieta. Universidade Federal do Rio de Janeiro; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; ArgentinaFil: Gallego, Monica. Universidad del País Vasco; EspañaFil: Rodriguez de Yurre, Ainhoa. Universidade Federal do Rio de Janeiro; Brasil. Universidad del País Vasco; EspañaFil: Zayas Arrabal, Julian. Universidad del País Vasco; EspañaFil: Echeazarra, Leyre. Universidade Federal do Rio de Janeiro; BrasilFil: Alquiza, Amaia. Universidad del País Vasco; EspañaFil: Fernández López, Victor. Universidad del País Vasco; EspañaFil: Rodriguez Robledo, Juan M.. Universidad del País Vasco; EspañaFil: Brito, Oscar. Instituto Nacional de Cardiologia; BrasilFil: Schleier, Ygor. Universidade Federal do Rio de Janeiro; BrasilFil: Sepúlveda, Marisa Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; ArgentinaFil: Oshiyama, Natalia F.. University of Campinas. Center for Biomedical Engineering; BrasilFil: Vila Petroff, Martin Gerarde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; ArgentinaFil: Bassani, Rosana A.. University of Campinas. Center for Biomedical Engineering; BrasilFil: Medei, Emiliano H.. Universidade Federal do Rio de Janeiro; BrasilFil: Casis, Oscar. Universidad del País Vasco; Españ

Synthesis, Characterization and Mathematical Model of High-Impact Polystyrene

Se presenta un modelo matemático que simula la polimerización de estireno en presencia de polibutadieno (PB) para la prodcción de Poliestireno de Alto Impacto (HIPS) via el proceso heterogeneo. El modelo sigue la polimerización en dos fases, y calcula en cada una de ellas las principales variables de la reacción y la estructura molecular de los 3 componentes poliméricos: poliestireno libre, PB residual, y copolímerode injerto. Varias polimerizaciones se llevaron a cabo y fueron además simuladas. El modelo se validó con las mediciones.A mathematical model is presented that simulates the polymerization of styrene in the presence of Polybutadiene (PB) for producing high-impact polystyrene (HIPS) via the heterogeneous bulk process. The model follows the polymerization in two phases, and calculates in each phase the main reaction variables and the molecular structure of the 3 polymeric components: free polystyrene, unreacted PB, and graft copolymer. Several polymerizations were carried out and simulated, the model was validated with measurements

Novel monomers with N-methyl-D-glucamine segments and their application in structured porous materials for arsenic capture

The N-methyl-D-glucamine moieties exhibit high ability and selectivity toward arsenate ions in water by a complexation mechanism that involves their hydroxyl groups. In this work, the syntheses of two monomers containing N-methyl-D-glucamine, namely 4-vinylbenzyl-N-methyl-D-glucamine (VbNMDG), and N-methyl-D-glucamine methacrylamide (MNMDG) were studied. Different synthetic routes were considered in order to obtain liquid monomers able to polymerize and selectively capture arsenic. Furthermore, the incorporation of protective groups like trimethylsilyl moieties in the molecular structure was assessed to prevent transfer reactions during further polymerization. After polymerization, hydroxyl groups were deprotected using hydrofluoric acid. Following this methodology, structured microporous polymeric films based on colloidal crystal templates were prepared. NMR and FTIR techniques were used to follow the reactions and to determine the chemical structure of the obtained products. The morphology of materials was characterized by SEM. The performances of the developed polymeric films to selectively capture arsenic were determined. Films showed an improved and reproducible sensitivity to arsenic detection exhibiting high values of arsenic capturing capability (around 90%).Fil: Caretti, Daniele. Universidad de Bologna; ItaliaFil: Binda, Lorenzo. Universidad de Bologna; ItaliaFil: Casis, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Elaboración de Membranas Poliméricas Porosas a partir de Cristales Coloidales

Se elaboraron membranas poliméricas porosas con elevado control de la morfología y de los tamaños de poros a partir de cristales coloidales constituidos por partículas de sílice. El método empleado permite obtener diferentes morfologías dependiendo del tamaño de las partículas y del número de capas involucradas en los depósitos. Para la síntesis de las partículas se emplearon dos métodos, originándose distintos tamaños. Los cristales coloidales se obtuvieron por deposición vertical de las partículas sobre un sustrato de vidrio y por la técnica de Langmuir-Blodgett. Se fabricaron membranas de poliestireno (PS) y de copolímero de estireno (St)-vinil bencil timina (VBT). El procedimiento involucró la infiltración de los monómeros seguida por la polimerización por irradiación con luz UV. El método propuesto provee una alternativa relativamente simple, muy versátil y a la vez económica para la elaboración de polímeros macroporosos

Synthesis and characterization of polybenzoxazine/silica-based hybrid nanostructures for flame retardancy applications

The objective of this study is to develop polybenzoxazine-silica nanocomposite systems endowed with greater thermal and fire performance. For this purpose, the 3-aminopropyltrimethoxysilane and bisphenol A-based benzoxazine (BA-3aptms) was synthesized. Also, smooth and spherical silica nanoparticles of 50 nm size were prepared following the Stöber's method. The influence of the nanoparticle size and geometry on the properties (laminar morphology, thermal, dynamic-mechanical, hydrophobicity, and flame retardancy) of the polybenzoxazine/polysilsesquioxane material was investigated. Also, nanocomposites from the conventional benzoxazine (BA-a) and SiO2 nanoparticles were synthesized for comparative purposes. The addition of nanoparticles in both polybenzoxazines improved the mechanical, thermal and flammability properties. Likewise, the presence of these nanoparticles conferred to the material a more hydrophobic surface (contact angle around 95°). Particularly, the Pr(BA-3aptms)/NP nanocomposites presented better properties than the BA-a-based systems, due to the presence of laminar-oriented polysilsesquioxane networks chemically bonded to the silica nanoparticles at nanoscale.Fil: Forchetti Casarino, Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química; ArgentinaFil: Casis, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química; ArgentinaFil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química; ArgentinaFil: Spontón, Marisa Elisabet. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química; Argentin