998 resultados para Etileno acetato de vinilo (EVA)


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El artículo quiere a partir de un recuento crítico de los análisis tradicionales del ROI y del IR dar una mirada analítica a estos indicadores comparándolos entre sí, mirando su alcance e importancia reales, igualmente sus problemas conceptuales y limitaciones. Al final se introduce el EVA, como medida y filosofía, mirando lo novedoso de la misma y los aspectos comunescon el ROI y el IR.

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Fondo Margaritainés Restrepo

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Las organizaciones buscan trabajar con el mínimo riesgo de proporción equilibrada entre el endeudamiento y la inversión de los socios, mediante la evaluación de cobertura de los diferentes riesgos en las tasas de intereses y los valores bursátiles, buscando finalmente disponer de niveles óptimos de liquidez -- Al evaluar el EVA en las empresas se mide el valor generado en un determinado periodo -- Aumentar el valor de las empresas, y por lo tanto la riqueza de los propietarios se logra maximizando la utilidad con la mínima inversión, buscando alcanzar el mínimo costo de capital -- Proporcionada la relevancia del uso de la herramienta EVA en la generación de valor de las organizaciones, nos inclinamos por el desarrollo de un caso práctico en el sector agrícola (Ingenio Azucarero) -- En el marco actual este ingenio es una compañía innovadora, confiable, transparente, representa el mejor lugar para trabajar y hacer negocios, adquirir compañías e invertir; por tanto se ve obligado a aprovechar las oportunidades que ofrece el mercado global, diversificando productos, incursionando en el mundo de la bioenergía, producción de alcohol carburante y la cogeneración de energía, abasteciendo el mercado nacional y mundial -- Al destacar la relevancia de las actividades que desarrolla el ingenio, es importante el manejo de herramientas que le permitan optimizar y agilizar los procesos en la de toma de decisiones, evaluándolo así por línea de producto

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Among the options for plastics modification more convenient, both from a technical-scientific and economic, is the development of polymer blends by processing in the molten state. This work was divide into two stages, with the aim to study the phase morphology of binary blend PMMA / PET blend and this compatibilized by the addition of the poly(methyl methacrylate-co-glycidyl methacrylate-co-ethyl acrylate) copolymer (MMA-GMA-EA). In the first stage is analyzed the morphology of the blend at a preliminary stage where we used the bottle-grade PET in a Haake torque rheometer and the effect of compatibilizer in this blend was evaluated. In the second stage the blend was processed using the recycled PET in a single screw extruder and subsequently injection molding in the shape of specimens for mechanical tests. In both stages we used a transmission electron microscopy (TEM) to observe the morphologies of the samples and an image analyzer to characterize them. In the second stage, as well as analysis by TEM, tensile test, scanning electron microscopy (SEM) and atomic force microscopy (AFM) was performed to correlate the morphology with the mechanical properties. The samples used in morphological analyzes were sliced by cryo-ultramicrotomy technique for the analysis by TEM and the analysis by SEM and AFM, we used the flat face of the block after cut cryogenic. It was found that the size of the dispersed phase decreased with the addition of MMA-GMA-EA in blends prepared in a Haake. In the tensile test, the values of maximum tensile strength and modulus of elasticity is maintained in a range between the value of pure PMMA the pure PET, while the elongation at break was influenced by the composition by weight of the PMMA mixture. The coupling agent corroborated the results presented in the blend PMMA / PETrec / MMA-GMA-EA (80/15/5 %w/w), obtained by TEM, AFM and SEM. It was concluded that the techniques used had a good morphologic correlation, and can be confirmed for final analysis of the morphological characteristics of the blends PMMA / PET

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The growing concern with the solid residues management, observed in the last decade, due to its huge amount and impact, has motivated the search for recycling processes, where these residues can be reprocessed to generate new products, enlarging the cycle of materials and energy which are present. Among the polymeric residues, there is poly (ethylene terephthalate) (PET). PET is used in food packaging, preferably in the bottling of carbonated beverages. The reintegration of post-consumer PET in half can be considered a productive action mitigation of environmental impacts caused by these wastes and it is done through the preparation of several different products at the origin, i.e. food packaging, with recycling rates increasing to each year. This work focused on the development and characterization mechanical, thermal, thermo-mechanical, dynamic mechanical thermal and morphology of the pure recycled PET and recycled PET composites with glass flakes in the weight fraction of 5%, 10% and 20% processed in a single screw extruder, using the following analytical techniques: thermogravimetry (TG), differential scanning calorimetry (DSC), tensile, Izod impact, Rockwell hardness, Vicat softening temperature, melt flow rate, burn rate, dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM). The results of thermal analysis and mechanical properties leading to a positive evaluation, because in the thermograms the addition of glass flakes showed increasing behavior in the initial temperatures of thermal decomposition and melting crystalline, Furthermore was observed growing behavior in the mechanical performance of polymer composites, whose morphological structure was observed by SEM, verifying a good distribution of glass flakes, showing difference orientation in the center and in the surface layer of test body of composites with 10 and 20% of glass flakes. The results of DMTA Tg values of the composites obtained from the peak of tan ä showed little reductions due to poor interfacial adhesion between PET and recycled glass flakes.

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Studies indicate that a variation in the degree of crystallinity of the components of a polymer blend influences the mechanical properties. This variation can be obtained by subjecting the blend to heat treatments that lead to changes in the spherulitic structure. The aim of this work is to analyze the influence of different heat treatments on the variation of the degree of crystallinity and to establish a relationship between this variation and the mechanical behavior of poly(methyl methacrylate)/poly(ethylene terephthalate) recycled (PMMA / PETrec) with and without the use of compatibilizer agent poly(methyl methacrylate-al-glycidyl methacrylate-al-ethyl acrylate) (MMAGMA- EA). All compositions were subjected to two heat treatments. T1 heat treatment the samples were treated at 130 ° C for 30 minutes and cooled in air. In T2, the samples were treated at 230 ° C for 5 minutes and cooled to approximately -10 ° C. The variation of the degree of crystallinity was determined by the proportional relationship between crystallinity and density, with the density measured by pycnometry. The mechanical behavior was verified by tensile tests with and without the presence of notches and pre-cracks, and by method of fracture toughness in plane strain (KIC). We used the scanning electron microscopy (SEM) to analyze the fracture surface of the samples. The compositions subjected to heat treatment T1, in general, showed an increase in the degree of crystallinity in tensile strength and a tendency to decrease in toughness, while compositions undergoing treatment T2 showed that the opposite behavior. Therefore, this work showed that heat treatment can give a polymer blend further diversity of its properties, this being caused by changes in the crystal structure

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This work studied the immiscible blend of elastomeric poly(methyl methacrylate) (PMMA) with poly(ethylene terephthalate) (PET) bottle grade with and without the use of compatibilizer agent, poly(methyl methacrylate-co-glycidyl methacrylate - co-ethyl acrylate) (MGE). The characterizations of torque rheometry, melt flow index measurement (MFI), measuring the density and the degree of cristallinity by pycnometry, tensile testing, method of work essential fracture (EWF), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were performed in pure polymer and blends PMMA/PET. The rheological results showed evidence of signs of chemical reaction between the epoxy group MGE with the end groups of the PET chains and also to the elastomeric phase of PMMA. The increase in the concentration of PET reduced torque and adding MGE increased the torque of the blend of PMMA/PET. The results of the MFI also show that elastomeric PMMA showed lower flow and thus higher viscosity than PET. In the results of picnometry observed that increasing the percentage of PET resulted in an increase in density and degree crystallinity of the blends PMMA/PET. The tensile test showed that increasing the percentage of PET resulted in an increase in ultimate strength and elastic modulus and decrease in elongation at break. However, in the phase inversion, where the blend showed evidence of a co-continuous morphology and also, with 30% PET dispersed phase and compatibilized with 5% MGE, there were significant results elongation at break compared to elastomeric PMMA. The applicability of the method of essential work of fracture was shown to be possible for most formulations. And it was observed that with increasing elastomeric PMMA in the formulations of the blends there was an improvement in specific amounts of essential work of fracture (We) and a decrease in the values of specific non-essential work of fracture (βWp)

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The development of new materials to fill the demand of technological advances is a challenge for many researchers around the world. Strategies such as making blends and composites are promising alternatives to produce materials with different properties from those found in conventional polymers. The objective of this study is to evaluate the effect of adding the copolymer poly(ethylene methyl acrylate) (EMA) and cotton linter fibers (LB) on the properties of recycled poly(ethylene terephthalate) (PETrec) by the development of PETrec/EMA blend and PETrec/EMA/LB blend composite. In order to improve the properties of these materials were added as compatibilizers: Ethylene - methyl acrylate - glycidyl methacrylate terpolymer (EMA-GMA) and maleic anhydride grafted polyethylene (PE-g-MA). The samples were produced using a single screw extruder and then injection molded. The obtained materials were characterized by thermogravimetry (TG), melt flow index (MFI) mensurements, torque rheometry, pycnometry to determinate the density, tensile testing and scanning electron microscopy (SEM). The rheological results showed that the addition of the EMA copolymer increased the viscosity of the blend and LB reduces the viscosity of the blend composite. SEM analysis of the binary blend showed poor interfacial adhesion between the PETrec matrix and the EMA dispersed phase, as well as the blend composite of PETrec/EMA/LB also observed low adhesion with the LB fiber. The tensile tests showed that the increase of EMA percentage decreased the tensile strength and the Young s modulus, also lower EMA percentage samples had increased the elongation at break. The blend composite showed an increase in the tensile strength and in the Young`s modulus, and a decrease in the elongation at break. The blend formulations with lower EMA percentages showed better mechanical properties that agree with the particle size analysis which showed that these formulations presented a smaller diameter of the dispersed phase. The blend composite mechanical tests showed that this material is stronger and stiffer than the blend PETrec/EMA, whose properties have been reduced due to the presence of EMA rubbery phase. The use of EMA-GMA was effective in reducing the particle size of the EMA dispersed phase in the PETrec/EMA blend and PE-g-MA showed evidences of reaction with LB and physical mixture with the EMA

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O espaço rural na Amazônia vem passando por mudanças em termos de ordenamento territorial e produtividade, buscando-se alternativas para o interior do Estado do Amazonas. A cultura de citros torna-se promissora com a crescente demanda do mercado local. Neste contexto, a presente pesquisa tem por objetivo mapear e espacializar a produção de citros no Município de Rio Preto da Eva, AM, que mais tem se destacado na produção, com a espacialização dos atributos geográficos de acordo com a localização das propriedades, quantidade da produção em toneladas e concentração da área plantada, sistematizadas em banco de dados, além de informações adicionais referentes à produção, como as principais dificuldades para o desenvolvimento da atividade no município.

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Se ha podido determinar que en el medio empresarial, en relación al contador dependiente, por ejemplo, en una empresa industrial dedicada a la fabricación de calzado, se encuentra solamente para efectuar los registros contables y la elaboración de los estados financieros de la entidad; de igual forma se critican a los que ejercen los cargos de gerentes financieros, de quienes manifiestan que no es mucho su aporte, excepto por su supervisión sobre las actividades del área financiera contable. Sin embargo, si se consideran los conocimientos adquiridos en su proceso de formación académica, o por obtener en el ejercicio profesional, se puede comprender que sus funciones van, o deberían de ir más allá de lo anteriormente expresado, por tanto pueden dar mucho valor agregado a la empresa. Mediante un sondeo preliminar se comprobó que un gran porcentaje de los contadores y de los gerentes financieros, de las empresas industriales dedicadas a la fabricación de calzado, desconocen los procedimientos para la formulación y análisis del valor económico agregado (EVA). Los análisis financieros que efectúan actualmente, son los que tradicionalmente se han venido aplicando desde hace muchas décadas: utilidad neta por acción, flujo de caja, rentabilidad del activo (ROI) etc., pero no lo hacen respecto al EVA. Considerando la importancia del EVA, se realizó una investigación que se llevó a cabo utilizando el paradigma hipotético-deductivo, el cual permitió obtener respuestas a determinados fenómenos relacionados con el campo de estudio, asimismo, el tipo de estudio que se utilizó fue el descriptivo, el cual consistió en identificar propiedades, características y rasgos importantes del problema. Las técnicas utilizadas fueron la encuesta y la entrevista, para obtener la información necesaria, con el propósito de conocer aspectos específicos del tema y comprender la problemática existente. En dicha investigación se comprobó que la mayoría de contadores y gerentes financieros específicamente los de las empresas dedicadas a la fabricación de calzado no tienen conocimiento sobre la formulación y análisis del Valor Económico Agregado (EVA); ni cuentan con un documento que contenga los lineamientos para desarrollar paso a paso el proceso de elaboración del mismo. De tal manera, el presente documento expone de forma práctica y sencilla, la formulación y análisis del indicador, con el propósito que los contadores y gerentes financieros de las empresas dedicadas a la fabricación del calzado puedan calcular y evaluar la riqueza que la compañía genera, asimismo teniendo en cuenta el nivel de riesgo con el que opera, lo cual es útil al momento de la toma de decisiones.

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The DGT technique allows one to measure quantitatively free and labile metal species in aquatic systems. Nevertheless, for this approach, knowledge is required of the diffusion coefficients of the analytes in a diffusive layer. In this study, the diffusion coefficients of Hg(II), As(III), Mn(II), Mg(II), Cu(II), Cd(II) were determined in agarose gel and those of Ba(II), Cd(II), Cu(II), Mg(II), Mn(II) e Zn(II) in cellulose acetate membranes. These materials presented good performance and the reported results can be used as a data base for further DGT studies.

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Este trabalho objetivou relatar que, possivelmente, o uso da comunicação rural e de práticas de comunicação comunitária adequadas à realidade local, pelos técnicos de assistência técnica/Instituto de Desenvolvimento Agropecuário e Sustentável do Estado do Amazonas (Idam), foi determinante para a adoção da bananicultura (cultivar Thap Maeo, resistente à sigatoka-negra e mais produtiva) como alternativa econômica ao produtor rural assentado no Ramal ZF-9, Distrito Agropecuário da Suframa, Rio Preto da Eva, no Estado do Amazonas, em substituição à prática insustentável de produção de carvão. Os relatos citados são frutos de observações ex post facto, registradas durante as avaliações de impacto econômico, social e ambiental da Empresa Brasileira de Pesquisa Agropecuária (Embrapa), realizadas nos anos de 2012, 2013 e 2014. A metodologia foi exploratória, realizada por meio de entrevistas e aplicação de questionário. Com os dados obtidos foi possível concluir que estabelecer parâmetros dialógicos e utilizar instrumentos de comunicação adequados à estrutura psicossocial, tecnológica e à vivência da comunidade facilita e oportuniza a adoção de tecnologias recomendadas pela pesquisa.