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Made available in DSpace on 2014-10-09T12:26:10Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:21Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:26:10Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:21Z (GMT). No. of bitstreams: 0 / A enxertia de estireno induzida pela radiação gama nos filmes fluorados, poli(tetrafluoroetileno-co-hexafluoropropileno) (FEP), poli(etileno-cotetrafluoroetileno) (ETFE), poli(fluoreto de vinilideno) (PVDF), poli(tetrafluoroetileno-co-perfluoro alquil vinil eter) (PFA) e poli(tetrafluoroetileno) (PTFE) foi realizada pelo método simultâneo de irradiação utilizando uma fonte de cobalto-60. Os filmes fluorados foram imersos em soluções de estireno/tolueno, estireno/isopropanol e estireno/metanol (1:1 v/v) sob atmosfera inerte e temperatura ambiente e, então, submetidos a doses de 20, 40, 80 e 100 kGy. Após a reação de enxertia os filmes foram mantidos à temperatura ambiente, e ainda sob atmosfera inerte, por 7, 14, 21 e 28 dias para avaliar a variação no grau de enxertia em relação ao tempo de pós-irradiação. No final de cada período os filmes foram sulfonados para conferir às membranas fluoradas a propriedade de hidrofilicidade. O grau de enxertia (DOG) foi determinado gravimetricamente e as mudanças químicas e morfológicas nos filmes enxertados e sulfonados foram analisadas por espectroscopia no infravermelho, termogravimertria (TG), calorimetria exploratória diferencial (DSC), microscopia eletrônica de varredura (MEV) e capacidade de troca iônica (IEC). Os testes em célula a combustível foram, também, efetuados pelo levantamento de curvas de polarização. Pela técnica de espectroscopia no infravermelho foi possível confirmar a presença do estireno nos filmes enxertados. O grau de enxertia nos filmes fluorados foi dependente do tipo de solvente utilizado. A análise termogravimétrica dos filmes enxertados mostrou duas etapas de decomposição, enquanto que a dos filmes sulfonados mostrou quatro. Pelos dados de DSC dos filmes enxertados constatou-se pequena variação na temperatura do pico de fusão, sugerindo a formação de poliestireno enxertado pouco penetrado na matriz polimérica. As figuras de MEV mostraram que o solvente tem maior influência na morfologia dos enxertos do que a dose de irradiação. Os testes em célula das membranas de ETFE, PFA e FEP apresentaram uma resposta de polarização satisfatória quando comparadas à membrana comercial Nafion®. POLYMER / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

This project investigated the manufacturing of large diameter welded PTFE rings.This welding process is time consuming and can take over ten hours for one complete weld cycle. Additionally, the welds can have poor quality in the center of the material due to insufficient heating across the weld face. The goal of this research was to address these two issues by analyzing the current process to determine the root cause of weld failures while also determining the feasibility of reducing the weld cycle time. The scope of this thesis was to develop a model to better understand and simulate the current process which could then be used for design future improvements.<div><br></div><div>A MATLAB model of the current process was developed to simulate the transient heating cycle of the most common weld cycle for PTFE currently used by a manufacturer of PTFE seals. The data for the material properties was gathered from the manufacturer test data as well as from Lau et al. (1984). Temperature dependent material properties were used in the program because the PTFE is heated above its melting point during the weld cycle. Because of the complexity of this heat transfer problem, the heat flux in the model was tuned so that it accurately reflected the current process. This is because the goal of this study was not to determine the exact heat fluxas it was unknown, but to develop an accurate model. Thus, the heat flux was assumed and the model was then verified with process data. Results from the model were compared to validation results from a FLIR thermal camera. The model predicted the compared temperatures to within 3.1% error at both 15-minute and 90-minute intervals. Though there are many potential sources of error in the process and the thermal camera measurement, the model was deemed acceptable as a model of the current process. A semi-infinite heat analysis was calculated to simulate a hot plate welding method on the PTFE. This showed that the temperature of the weld face could be raised by 57.275°C. It is believed that a method similar to hot plate welding applied to PTFE could heat the material faster and more evenly than the current process, reducing the weld failures and cycle time.<br></div>

Lubrificantes são produtos gasosos, líquidos, semi sólidos ou sólidos (pó) que formam um filme entre duas partes evitando o atrito. Lubrificantes de alto desempenho são designados para trabalharem em condições severas de temperatura, pressão e contaminação. Os mais utilizados são os líquidos (óleos) e semi sólidos (graxas). As graxas são aplicadas aonde o óleo pode escorrer e em pontos de difícil acesso e são divididas basicamente em duas classes, sabão e não sabão. A graxa não sabão mais utilizada é a poliuréia, obtida pela reação entre aminas e isocianato, possui elevada tixotropia, alta rigidez dielétrica e excelente poder anticorrosivo, por isso é amplamente utilizada para lubrificação de motores elétricos e maquinário naval. Para obter uma graxa com altíssimo desempenho, nesse estudo foi utilizado o fluido lubrificante sintético polialfaolefina e também foi empregado o aditivo lubrificante sólido politetrafluoroetileno (PTFE) por apresentar o menor coeficiente de atrito conhecido, é comercialmente encontrado irradiado em ar para obter partículas menores e produzir grupos terminais oxigenados que são mais compatíveis com a superfície metálica. Os ensaios foram realizados de forma comparativa usando a graxa de poliuréia pura e aditivada com PTFE. As caracterizações foram feitas por espectroscopia de infravermelho, análise elementar de C, N, e H e índice de NCO livre, comprovando a formação de poliuréia de quatro carbonos (tetrauréia). As propriedades funcionais de ponto de gota e separação de óleo mostraram alta compatibilidade e estabilidade entre os polímeros, que aumentaram quando foi adicionado PTFE. A excelente resistência da graxa de tetrauréia pura ao desgaste e extrema pressão foram demonstradas pelo teste de quatro esferas e teste prático em rolamentos, caracterizando esta graxa como de alto desempenho quando comparada com as graxas mais utilizadas no mercado. / Lubricants are gaseous, liquid, semi solid or solid (powder) materials those form a film between two parties preventing friction. High performance lubricants are designed to work under severe conditions of temperature, pressure, and contamination. The most used are liquids (oils) and semi solids (greases). Greases are applied where oils can drain or in inaccessible places and are divided generally into two classes, soap and no soap. The most used non soap grease is polyurea, obtained by the reaction between amine and isocyanate, has highly thixotropic, high dielectric strength and excellent anticorrosive property, so it is widely used for lubrication of electric motors and shipbuilding machinery. For a grease with high performance, in this study was used a synthetic lubricant fluid, polyalphaolefin, and was also employed solid lubricant additive polytetrafluoroethylene (PTFE) due its lowest coefficient of friction, is found commercially irradiated in air to obtain smaller particles and to produce oxygenated terminal groups those are more compatible with the metal surface. The tests conducted were comparatively between pure polyurea grease and with PTFE additive. The characterizations were made by infrared spectroscopy and elemental analysis of C, N and H and Free NCO index, proving the formation of four carbons polyurea (tetraurea). The functional analysis of drop point and oil separation showed high stability and compatibility between the polymers increased when PTFE was added. The excellent resistance of pure tetraurea grease to wear and extreme pressure were demonstrated by four-ball and practical bearings tests, characterizing this grease as a high performance lubricant, when compared to most used greases in the market.

Lubrificantes são produtos gasosos, líquidos, semi sólidos ou sólidos (pó) que formam um filme entre duas partes evitando o atrito. Lubrificantes de alto desempenho são designados para trabalharem em condições severas de temperatura, pressão e contaminação. Os mais utilizados são os líquidos (óleos) e semi sólidos (graxas). As graxas são aplicadas aonde o óleo pode escorrer e em pontos de difícil acesso e são divididas basicamente em duas classes, sabão e não sabão. A graxa não sabão mais utilizada é a poliuréia, obtida pela reação entre aminas e isocianato, possui elevada tixotropia, alta rigidez dielétrica e excelente poder anticorrosivo, por isso é amplamente utilizada para lubrificação de motores elétricos e maquinário naval. Para obter uma graxa com altíssimo desempenho, nesse estudo foi utilizado o fluido lubrificante sintético polialfaolefina e também foi empregado o aditivo lubrificante sólido politetrafluoroetileno (PTFE) por apresentar o menor coeficiente de atrito conhecido, é comercialmente encontrado irradiado em ar para obter partículas menores e produzir grupos terminais oxigenados que são mais compatíveis com a superfície metálica. Os ensaios foram realizados de forma comparativa usando a graxa de poliuréia pura e aditivada com PTFE. As caracterizações foram feitas por espectroscopia de infravermelho, análise elementar de C, N, e H e índice de NCO livre, comprovando a formação de poliuréia de quatro carbonos (tetrauréia). As propriedades funcionais de ponto de gota e separação de óleo mostraram alta compatibilidade e estabilidade entre os polímeros, que aumentaram quando foi adicionado PTFE. A excelente resistência da graxa de tetrauréia pura ao desgaste e extrema pressão foram demonstradas pelo teste de quatro esferas e teste prático em rolamentos, caracterizando esta graxa como de alto desempenho quando comparada com as graxas mais utilizadas no mercado. / Lubricants are gaseous, liquid, semi solid or solid (powder) materials those form a film between two parties preventing friction. High performance lubricants are designed to work under severe conditions of temperature, pressure, and contamination. The most used are liquids (oils) and semi solids (greases). Greases are applied where oils can drain or in inaccessible places and are divided generally into two classes, soap and no soap. The most used non soap grease is polyurea, obtained by the reaction between amine and isocyanate, has highly thixotropic, high dielectric strength and excellent anticorrosive property, so it is widely used for lubrication of electric motors and shipbuilding machinery. For a grease with high performance, in this study was used a synthetic lubricant fluid, polyalphaolefin, and was also employed solid lubricant additive polytetrafluoroethylene (PTFE) due its lowest coefficient of friction, is found commercially irradiated in air to obtain smaller particles and to produce oxygenated terminal groups those are more compatible with the metal surface. The tests conducted were comparatively between pure polyurea grease and with PTFE additive. The characterizations were made by infrared spectroscopy and elemental analysis of C, N and H and Free NCO index, proving the formation of four carbons polyurea (tetraurea). The functional analysis of drop point and oil separation showed high stability and compatibility between the polymers increased when PTFE was added. The excellent resistance of pure tetraurea grease to wear and extreme pressure were demonstrated by four-ball and practical bearings tests, characterizing this grease as a high performance lubricant, when compared to most used greases in the market.

Barium sulfate (BaSO₄)-containing polytetrafluoroethylene (PTFE) granular powder was prepared through a two-phase emulsion dispersion granulation method. Because of its large bulk density, small average particle size, narrow particle size distribution, and superior powder flowability, the granular powder is suitable for use in automatic molding machines. The effects of granulation on the tensile strength of the BaSO₄/PTFE composite were investigated, and the composite’s microstructures were characterized and analyzed using scanning electron microscopy. All these indicated that the granulation could make BaSO₄ disperse more homogeneously in PTFE and reduce many defects in molded articles. So the properties of the BaSO4/PTFE composites made by the granular powder were superior to the composite obtained from the nongranular powder. The tensile strength and elongation of the composite obtained from the granular powder could be achieved to a level of 19.4 MPa and 420%, respectively.

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In the past decade, the design and manufacturing of intelligent multipurpose underwater vehicles has increased significantly. In the wide range of studies conducted in this field, the flexibility and autonomy of these devices with respect to their intended performance had been widely investigated. This work is related to the design and manufacturing of a small and lightweight autonomous underwater vehicle (AUV) with vision capabilities allowing detecting and contouring obstacles. It is indeed an exciting challenge to build a small and light submarine AUV, while making tradeoffs between performance and minimum available space as well as energy consumption. In fact, due to the ever-increasing in equipment complexity and performance, designers of AUVs are facing the issues of limited size and energy consumption. By using a pair of thrusters capable to rotate 360o on their axis and implementing a mass shifter with a control loop inside the vehicle, this later can efficiently adapt its depth and direction with minimal energy consumption. A prototype was fabricated and successfully tested in real operating conditions (in both pool and ocean). It includes the design and embedding of accurate custom multi-purpose sensors for multi-task operation as well as an enhanced coordinated system between a high-speed processor and accustomed electrical/mechanical parts of the vehicle, to allow automatic controlling its movements. Furthermore, an efficient tracking system was implemented to automatically detect and bypass obstacles. Then, fuzzy-based controllers were coupled to the main AUV processor system to provide the best commands to safely get around obstacles with minimum energy consumption. The fabricated prototype was able to work for a period of three hours with object tracking options and five hours in a safe environment, at a speed of 0.6 m/s at a depth of 8 m.