Orientador: Maria Alvina Krähenbühl / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-20T01:57:06Z (GMT). No. of bitstreams: 1 Matos_FlavioCardosode_M.pdf: 4389561 bytes, checksum: a46da733dd13422f2fad87695175b3db (MD5) Previous issue date: 2012 / Resumo: Neste trabalho foi estudado o efeito do aquecimento, à pressão constante, de ácidos graxos, desde a fusão até a sua decomposição térmica, para delimitação das temperaturas de fusão, ebulição e decomposição. A Calorimetria Exploratória Diferencial, técnica na qual a medida da taxa de fluxo de calor para uma amostra é descrita em função da temperatura ou tempo, foi utilizada para realização de um estudo térmico dos ácidos graxos, ácido cáprico (C 10:0), láurico (C 12:0), mirístico (C 14:0), pentadecanóico (C 15:0), palmítico (C 16:0), esteárico (C 18:0), oleico (C 18:1), linoléico (C 18:2) e araquídico (C 20:0), nas taxas de aquecimento de 5, 10, 15 e 20 ºC.min-1. A temperatura de onset, temperatura de pico e a entalpia foram calculadas de acordo com as curvas térmicas para os eventos endotérmico e exotérmico. Os resultados experimentais foram comparados com dados reportados na literatura, quando disponíveis. Os resultados obtidos mostraram-se satisfatórios, quando comparados com dados de outros autores / Abstract: In this work it was studied the effect of heating, at constant pressure, of fatty acids, from the melting until their thermal decomposition, for delimitation of the temperatures of melting, boiling and decomposition. Differential Scanning Calorimetry, the measurement technique in which the rate of heat flow for a sample is described as a function of temperature or time, was used to conduct a thermal study of fatty acids: capric acid (C 10:0), lauric (C 12:0), myristic (C 14:0), pentadecanoic (C 15:0) palmitic (C 16:0), stearic (C 18:0), oleic (C 18:1), linoleic (C 18:2) and arachidic (C 20:0), at the heating rates of 5, 10, 15 and 20 ° C / min. The onset temperature, peak temperature and enthalpy were calculated according to the thermal curves for the exothermic and endothermic events. The experimental results were compared with data reported in the literature when available. The results were satisfactory when compared with data from other authors / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Strong underwater bonds between polycarbonate sheet and various other substrates were achieved using ethyl 2-cyanoacrylate gel cured with an anionic photoinitiator (dibenzoylferrocene). The gel reacts quickly with water on contact and forms a protective polyethyl cyanoacrylate (PECA) skin. This provides a diffusion barrier that protects the inner monomer from further reaction with or polymerisation by water (hydroxide ions). The PECA skin is, however, permeable to water and the inner monomer slowly reacts as water diffuses through the PECA skin. The application procedure for this adhesive is critical because of the fast reaction with water. The adhesive should be applied at the centre of the bond area in such a way as to cover the smallest exposed surface area and that it should not be spread out over the entire surface area. The PECA skin will rupture when the substrates are pressed together, exposing unreacted monomer to the fresh new surface between the two substrates. The adhesive displaces water as it propagates towards the joint edges. In this way it is able to form a strong underwater bond. Without a photoinitiator, ethyl cyanoacrylate adhesives will form strong bonds to smooth underwater surfaces. The addition of a photoinitiator (dibenzoylferrocene), however, increases the rate at which the bond strength develops. Photo differential scanning calorimetric (photo-DSC) analysis was used to determine the optimum photoinitiator concentration. A concentration of between 0.3% (m/m) and 0.1% (m/m) was found to be optimum for adhesive films between 0.5 and 1.2 mm thick. Epoxy-based underwater adhesives have the disadvantage that the cure rate is very slow at low water temperatures. In contrast, the current system features a negative temperature dependence. Therefore, the curing rate is faster at lower water temperatures, making it highly suitable for very cold environmental conditions. The underwater bonding properties of cyanoacrylate adhesive were measured on a wide range of metallic and non-metallic materials. Bond strengths ranged from 1 to 5 MPa respectively. Bond strength (0.2 mm film thickness) develops in a very short time (less than a minute) using a 5 mW/cm2 blue LED light source as trigger for the photo initiator. Water temperatures between 1.5 and 40 °C did not influence the ultimate bond strength achieved following 50 seconds of illumination. The reduction in bond strength due to the ethyl cyanoacrylates reacting with water was measured in artificial sea water and potable water. A 20% reduction in bond strength was found after 10 minutes of water exposure. The underwater bond should therefore be made as soon as possible following exposure to water. Bond ageing studies on both steel and polycarbonate showed an initial decrease in bond strength (during the first 50 hours); thereafter the bond strength stabilises. / Dissertation (MEng)--University of Pretoria, 2011. / Chemical Engineering / unrestricted

Orientador: Rubens Maciel Filho / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-22T07:40:50Z (GMT). No. of bitstreams: 1 BallesterosHernandez_JulieAndrea_D.pdf: 6114805 bytes, checksum: 562219ac3aa0279da3414af1b0bb263e (MD5) Previous issue date: 2013 / Resumo: Este trabalho tem como objetivo principal, estudar e propor uma nova metodologia para a remoção de ácidos e enxofres dos petróleos pesados o que poderia evitar problemas de corrosão, geração de outros componentes de alta toxicidade e/ou para a prevenção de problemas futuros relacionados com o processo de destilação. Outro objetivo deste trabalho é também propor metodologias de caracterização de petróleos brasileiros a partir da determinação de propriedades termo-físicas e físico-químicas. A proposta consiste no desenvolvimento de procedimentos para a remoção de ácidos e enxofres por meio da radiação de laser de CO2 no petróleo e na determinação de propriedades termo-físicas por meio da calorimetria diferencial de varredura (DSC), como capacidade calorífica, entalpia, temperatura de aparecimento e desaparecimento de parafinas, teor de parafinas, e propriedades físico-químicas, como densidade, massa molar, viscosidade, entre outras, importantes na modelagem matemática de processos de exploração e refino de petróleos. Este conjunto de técnicas de caracterização possibilita obter informações necessárias para tomadas de decisões no desenvolvimento de processos. Neste contexto, foi feito um planejamento experimental para o uso do laser de CO2 sobre um petróleo cru para avaliar, com análises dos componentes polares por ESI FT-ICR MS, a remoção de ácidos e enxofre do petróleo, e foram obtidos resultados apreciáveis. Além disso, dois petróleos crus foram caracterizados por meio das suas propriedades termo-físicas como calor específico, entalpia, condutividade térmica e suas propriedades físico-químicas, como a densidade, viscosidade e massa molar. Também foram analisados cortes e resíduos da destilação molecular por meio de calorimetria diferencial de varredura, termogravimetria (TG), osmometria de pressão de vapor (VPO), ressonância magnética nuclear (RMN), cromatografia a líquido de alto desempenho (HPLC) e microscopia ótica de luz polarizada (MOLP), obtendo propriedades como a temperatura de aparecimento e desaparecimento de parafinas, a curva de precipitação de parafinas, a porcentagem de parafinas, a temperatura de transição vítrea, a estabilidade térmica, a massa molar, a estrutura das moléculas e a porcentagem de aromáticos presentes nas amostras. Os resultados mostraram que existe uma diminuição da intensidade relativa dos compostos de O2 (ácidos carboxílicos) para todos os ensaios com o laser de CO2, obtendo-se um máximo de remoção de 41,3% e uma diminuição em alguns casos para os compostos de enxofre com um máximo de remoção de 9,1% / Abstract: This project has as its main focus, to study and to propose a new method for removing acids and sulfurs of heavy oil to prevent corrosion problems and the generation of other components of high toxicity and / or for the prevention of future problems related to the process of distillation and furthermore to propose methods for characterization of Brazilian oils from the determination of thermophysical properties and physicochemical. The proposal is the development of procedures for the removal of acids and sulfurs by CO2 laser radiation in oil and the determination of thermophysical properties by differential scanning calorimetry as heat capacity, enthalpy, temperature of appearance and disappearance of paraffins, paraffin content, and physicochemical properties such as density, molar mass, viscosity, among others, which are important in the mathematical modeling of exploration and refining processes of petroleum. This can be done by a set of characterization techniques which lead us to get information necessary for the development of processes. In this context, an experimental design was done considering the use of CO2 laser for a crude oil to evaluate with analyzes of polar components by ESI FT-ICR MS the removal of acids and sulfur from the oil, and significant results were obtained. Furthermore, the crude oils were characterized by their thermophysical properties such as specific heat, enthalpy, heat conductivity and its physicochemical properties such as density, viscosity and molar mass. Moreover molecular distillation residues and cuts were analyzed by means of differential scanning calorimetry (DSC), thermogravimetry (TG), vapor pressure osmometry (VPO), nuclear magnetic resonance (NMR), high performance liquid chromatography (HPLC), polarized light microscopy (PLM), obtaining properties such as the temperature of appearance and disappearance of paraffins, the curve of precipitation of paraffins, the percentage of paraffins, the glass transition temperature, thermal stability, molar mass, structure molecules and percentage of aromatics present in the samples. The results show that there is a decrease in the relative intensity of O2 compounds (carboxylic acids) for all tests with CO2 laser, giving a maximum removal of 41.3% and a decrease in some cases for the compounds sulfur with a maximum removal of 9.1%. The characterizations presented in this work are of great importance not only to the general knowledge of currents and crude oil, but also to the process modeling and to prevent future problems / Doutorado / Engenharia Química / Doutora em Engenharia Quimica

The diploma thesis deals with the preparation, crosslinking and characterization of collagen films from various animal sources. Collagen from pig, Tilapia, horse, cow and crocodile was used to prepare collagen films. Chemical crosslinking agents EDC/NHS and Lyofix were used to crosslink the prepared films. In the experimental part, differential scanning calorimetry (DSC) method was optimized to determine the denaturation temperature of individual collagen films before and after crosslinking. In addition, the ability of films to swell and degrade has been analyzed. The presence of characteristic groups present in the collagen structure was verified using infrared spectroscopy. The sample morphology was analyzed using Scanning Electron Cryomicroscopy (Cryo-SEM). The results show that EDC/NHS is a better collagen crosslinking agent compared to Lyofix. The best source for the preparation of thermally stable films is piggy collagen, whose denaturation temperature after crosslinking with EDC/NHS was about 69 °C and could represent more than adequate substitution for cow collagen, which is currently most used in the field of tissue engineering and food industry.

Diploma thesis studies the effect of temperature (75 and 105 °C) and the effect of 3 kinds of liquids (silicone and hydraulic oil and coolant) at room temperature and at 105 °C on change of the structure of 3 species butadiene-acrylonitrile (NBR) seals (o-ring and two types of bolts). The seals are inspected by the thermogravimetric analysis, differential scanning calorimetry and infrared spectroscopy, the influence of 105 °C on the o-rings is also evaluated in terms of changes in tensile properties. The greatest changes in the composition and structure are observed on o-rings particularly due to temperature of 105 °C, there was a significant reduction in dilatability and an increase in stiffness and glass transition temperature. The root cause is the surface and centre additive decomposition and oxidation. The bolts have suffered from decomposition of the protective surface layer and the additives in the centre, structural change was minor. Exposure to 75 °C has resulted in a gradual loss of low molecular weight substances. Liquids at room temperature didn‘t affect the structure of the seals, at 105 °C it caused a loss of weight due to decomposition of the protective surface layer and release of additives and the products of their decomposition. Results showed that the common use of the NBR seals at 105 °C is unsuitable, at 75 °C it leads to gradual changes, loss in mechanical and sealing properties.

Neurons depend upon neurotransmitter release through regulated exocytosis to accomplish the immense processing performed within the central nervous system. The SNARE hypothesis points to a family of proteins that are thought to enable the membrane fusion that leads to exocytosis. The secondary structure of SNAP-25 is unique among SNARE proteins in that it has two alpha helical SNARE motifs and a cysteine rich (C85, C88, C90, C92) membrane interacting region but notransmembrane domain. The cysteines may be modified by palmitoylation or oxidation but the role of these modifications in vivo is not well understood. Our goal is to elucidate possible regulatory roles of SNAP-25 that relate to its unique structure and these reversible modifications. However, the study of SNAP-25 in reconstituted systems is hampered by a lack of readily available palmitoylated SNAP-25. A method for in vitro palmitoylation of SNAP-25 by HIP14, a neuronal acyltransferase, is described along with the application of a biotinylation streptavidin assay to verify palmitoylation. Palmitoylation increases the extent to which SNAP-25 interacts with lipids as observed with an environment sensitive trpytophan fluorescence assay. Palmitoylation also alters the phase transition of DPPC lipids differently than unpalmitoylated SNAP-25.This effect on the membrane may influence fusion events. Oxidation of the cysteine residues may be responsible for the sensitivity of SNAP-25 to reactive oxygen species. Our data suggests that, when oxidized, SNAP-25 does not interact with membranes to the same extent as palmitoylated SNAP-25. This may provide a mechanism for reducing exocytosis during oxidative stress. Also, oxidized SNAP-25 is not susceptible to Botulinum Neurotoxin E. The effects of oxidation and palmitoylation on the protein interactions of SNAP-25 may shed light on its role in the SNARE complex and membrane fusion.

Shape memory alloys when deformed can produce strains as high as 8%. Heating results in a phase transformation and associated recovery of all the accumulated strain, a phenomenon known as shape memory. This strain recovery can occur against large forces, resulting in their use as actuators. The goal of this project is to lower the operating temperature range of shape memory alloys in order for them to be used in cryogenic switches, seals, valves, fluid-line repair and self-healing gaskets for space related technologies. The Ni-Ti-Fe alloy system, previously used in Grumman F-14 aircrafts and activated at 120 K, is further developed through arc-melting a range of compositions and subsequent thermo-mechanical processing. A controlled atmosphere arc-melting facility and vertical vacuum quench furnace facility was commissioned to fabricate these alloys. The facility can create a vacuum of 10-7 Torr and heat treat samples up to 977 °C. High purity powders of Ni, Ti and Fe in varying ratios were mixed and arc-melted into small buttons weighing 0.010 kg to 0.025 kg. The alloys were subjected to solutionizing and aging treatments. A combination of rolling, electro-discharge machining and low-speed cutting techniques were used to produce strips. Successful rolling experiments highlighted the workability of these alloys. The shape memory effect was successfully demonstrated at liquid nitrogen temperatures through a constrained recovery experiment that generated stresses of over 40 MPa. Differential scanning calorimetry (DSC) and a dilatometry setup was used to characterize the fabricated materials and determine relationships between composition, thermo-mechanical processing parameters and transformation temperatures.

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The performance of polymeric diphenylmethane diisocyanate (PMDI) resin is known to be highly dependent on the wood species. This species dependence may be due to differences in: cure chemistry, interphase morphology, or both of these factors. This study addresses aspects of the cure chemistry and interphase morphology of wood/PMDI bondlines; specifically these effects are compared using two woods: yellow-poplar and southern pine. In this study, the cure chemistry of wood-PMDI system was analyzed with solid state NMR (SSNMR) using wood samples cured with doubly labeled (15N,13C) PMDI resin. The kinetics of PMDI cure in the presence of wood was analyzed with differential scanning calorimetry. Thermogravimetric analysis was used to analyze the effect of resin impregnation on the degradation patterns of wood. The wood-PMDI bond morphology was probed with dynamic and static (creep) mechanical analyses in both dry and plasticized conditions. The effect of resin on wood polymer relaxations was quantitatively analyzed by both the time-temperature superposition principle and the Kohlrausch-Williams-Watts equation. The presence of a small but statistically significant species effect was observed on both the cure chemistry and bond morphology of wood-PMDI system at low cure temperatures. The cure of PMDI resin was found to be significantly faster in pine relative to corresponding poplar samples. Resin impregnation showed a significant species dependent effect on the wood mechanical properties; the resinated pine samples showed increase in compliance while the corresponding poplar samples became stiffer. The in situ lignin relaxation was studied with both dynamic and static modes, using plasticized wood samples. Results showed that the lignin relaxation was slightly affected by resin impregnation in both woods, but the effect was relatively larger in pine. Static experiments of dry wood samples showed a significant reduction in the interchain interactions of wood polymers in pine samples, exclusively. Investigation of plasticized pine samples, which focuses on the in situ lignin relaxations, showed only minor changes with resin impregnation. This led us to hypothesize that the large changes observed in dry samples, were due to the in situ amorphous polysaccharides. The wood-PMDI interactions were significantly reduced upon acetylation of wood. This study also discusses three new and highly sensitive methods for the analysis of wood-resin interactions. / Ph. D.