974 resultados para resina
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Pós-graduação em Reabilitação Oral - FOAR
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Pós-graduação em Ciência dos Materiais - FEIS
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Pós-graduação em Odontologia - ICT
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Pós-graduação em Odontologia Restauradora - ICT
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Pós-graduação em Odontologia Restauradora - ICT
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Pós-graduação em Odontologia Restauradora - ICT
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Pós-graduação em Odontologia Restauradora - ICT
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In the present work it was studied the behavior of four water bath curing cycles of heat activated acrylic resin considered as long duration (I – 65ºC for 30 min;50ºC for 23h and 30min; and 100º C for 1h; II- 50ºC for 24h and the rapid cycle), compared to the known long time curing cycle (9 hours for 72ºC) and short curing cycle (1 h for 65ºC; 30 min to elevate at 100º C and 1:00 to 100º C). Analysis consisted of observations and verification of the residual monomer, weight alterations, dimensional, dimensional lineal, porosity and hardness to determine material performance. The results pointed out that residual monomer presented statistical significant differences in the factor storage and interaction among the factors cycle X storage for weight alteration; statistical significant differences for the factor storage for lineal dimensional alterations, without significant differences for hardness. Porosity was verified in minimum degree in the cycle III and in appreciable amount in the cycle IV
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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The glassy carbon is a material with a huge technological evolution. Due to its lightness, biocompatibility and their thermal and electrical properties this material finds applications in several industrial fields such as electronics, medical, aerospace and chemical. In order to explore the conductive properties of glassy carbon for use as modified electrodes, the present work aims the processing of monolithic and reticulated glassy carbon with colloidal copper for use in electrochemical applications. First, the best parameters for the cure of furfuryl alcohol resin doped were established through viscosimetry measurements and pressurized differential scanning calorimetry. The analysis of the micrographs of the cured resins show that copper concentrations above 3% weight, generate higher porosity in the material. The characterizations of the monolithic and reticulated glassy carbon resulting from carbonization were performed by scanning electron microscopy (SEM), Raman and Electrochemical impedance spectroscopy, and although it was not possible to detect the presence of copper by SEM, the influence of these particles have been observed by Raman and FT-IR spectra and electrochemical behavior of the material. The decrease in conductivity of monolithic and reticulated glassy carbon in the presence of copper may be related to the defects caused by the presence of copper in the structure of the material.
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According to ABIPA (2009), Brazil is currently among the major producers of reconstituted wood panels, with one of the main factors for this condition, its climate and its large land area, which allows the cultivation of forests, which provide raw materials for these industries. To establish that market as power, Brazil has invested about R$ 1.3 billion in the last 10 years, yet designed an investment of 0.8 billion dollars over the next three years (BNDES, 2008). With the new investments in this segment, we expect a growth of about 66% in the resin consumption of urea-formaldehyde (GPC, 2009) which should also result in major investments by the companies producing this polymer. Currently employees are mainly three types of resins in the production industry panels, as follows: Urea-Formaldehyde Resin (R-UF), melamine-formaldehyde resin (R-MF) and Phenol-Formaldehyde Resin (R-FF). Especially the cost factor, the urea-formaldehyde resin is the most used by companies producing reconstituted wood panels. The UF-R is a polymer obtained by condensation of urea and formaldehyde reactors (usually batch type), characterized by being a thermosetting polymer which makes it very efficient for bonding wood composites. The urea-formaldehyde polymer, to present a quite complex, it becomes very difficult to predict the exact chain resulting in the process of condensation of urea with formaldehyde, so that a greater knowledge of its characteristics and methods for their characterization can result in greater control in industrial processes and subsequent decrease cost and improve the quality of reconstituted wood panels produced in Brazil
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In civil engineering, a structure is the whole sustainment of a construction and, thus, it is important that it remains intact throughout its lifetime. An engineering construction must last for decades without losing its functionality. However its purpose may be altered and several times the original structure does not meet the new needs of use. Still, in new buildings, the functionality is altered due to possible flaws in execution and the structure, invariably does not reach the desired solicitation needs. In cases like this, the commonly adopted solutions are, basically, the demolishment followed by the reconstruction of the desired mold or the structural reinforcement. This second option, for long years, has not been put to practice due to certain factors such as the high costs for its implantation, use of inadequate reinforcement execution techniques, and the culture of people involved in the area regarding its use and, in this case, the option would always be the reconstruction. Thoughtout the years, some techniques were developed to allow the execution of structural reinforcements with low costs and in efficient ways. An interesting, fast, efficient and economical technique is the structural reinforcement through metal sheets put together with epoxy resin that can be applied in beams, slabs and pillars. In the present work the different behavior of beams reinforced with this technique. Steel is a very recommended material for these reinforcements due to its characteristics related to traction, compression and the effectiveness of the technique related to its cost. For the attachment the epoxy resin is recommended, since it allows the joining of two materials, in this case, steel and concrete. The efficiency of this union is so considerably high that it rarely produces any flaws in adherence and, normally, when it happens it is due to problems in the execution process, not in the union of materials