17 resultados para Algodão - Fisiologia


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The present research deals with the modernization process of the Cidade da Parahyba2, between 1850 and 1924, and its relation with the cotton economy, which represented the main source of wealth accumulation for both the private and the public sectors throughout the First Republic. This study on urban history was developed by focusing on the understanding of the city s spatial formation, and despite its emphasis on the economic aspects involved, other factors that also contribute to the development of the social life were not put aside. The modernization process of the Cidade da Parahyba was also analyzed during the period established for the study according to a chronological and thematic approach that established comparisons with the financial situation of the State, whenever this was necessary, with special attention to the contribution of the cotton economy to the State´s revenues. It was possible to detect a lack of financial help and loans from the federal and municipal administrations for finishing several public works already underway in the capital, since the federal funds allocated to the State of Parahyba do Norte were rather employed in emergency works against droughts and in agricultural development. One can then conclude that the financial resources required for the urban interventions were withdrawn from the State s treasury itself, resources that were collected mainly from activities such as cotton exportation and cotton trading. Another factor shows the interdependence between the urban remodeling and the cotton economy: during the years marked by great droughts or by hard plagues on the cotton plantations, cotton production decreased, as well as the State s finances. The first measures taken by the State s administrators were to halt all projects of urban remodeling in progress in the Cidade da Parahyba, which was, clearly, the most privileged city by the State s presidents during the period analyzed. 2 The city of João Pessoa was named Cidade da Parahyba, a designation that remained until September 1930, when it received its present-day name in order to pay homage to the president of the State, João Pessoa Cavalcanti de Albuquerque, murdered in the city of Recife in August of that same year. At that time, the State of Paraíba was known as Parahyba do Norte. Since this work is limited to a period of time comprised within the First Republic, the names employed respect the terms used in those days

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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