Cette thèse a pour objet l'élaboration et l'étude des propriétés de revêtements d'oxyde de zinc en vue de protéger le polycarbonate (PC) contre la photodégradation et ainsi d'augmenter la durabilité de ce polymère. Ces revêtements ont été déposés par pulvérisation cathodique radiofréquence à effet magnétron dans un plasma argon-oxygène. La phase plasma a été caractérisée par spectroscopie d'émission optique en fonction des paramètres de pulvérisation. Les couches de ZnO ont été soumises à des traitements thermiques dans différentes atmosphères (air, azote, vide). Il en résulte une modification de leur composition, de leurs propriétés structurales et optiques et de leurs contraintes internes.<br />L'adhésion du revêtement sur un film de polycarbonate a été caractérisée au moyen du test de pelage. Elle dépend des conditions de dépôt. Pour l'améliorer, différents traitements plasma (Ar, Ar-O2, CO2) de courte durée ont été appliqués au polymère. Ils ont augmenté l'énergie de surface du PC, le meilleur traitement étant celui à base de dioxyde de carbone. Ils ont permis une fonctionnalisation de la surface qui a été mise en en évidence par XPS.<br />L'étude de la photodégradation du PC montre que l'effet photoprotecteur du revêtement de ZnO dépend de son épaisseur et de ses conditions d'élaboration. L'introduction de couches supplémentaires d'alumine a apporté une meilleure protection du PC en évitant l'action photocatalytique de ZnO et en améliorant ses propriétés mécaniques.

The presence of partial discharges (PD) in high voltage components is generally a sign of defects and degradation in the electrical insulation. To diagnose the condition of high voltage insulation, PD measurements is commonly used. The Variable Frequency Phase Resolved PD Analysis (VF-PRPDA) technique measures PD at variable frequency of the applied voltage. With this technique, the frequency dependence of PD can be utilized to extract more information about the insulation defects than is possible from traditional PD measurements at a single applied frequency. In this thesis the PD process in a disc-shaped cavity is measured and modelled at variable frequency (0.01 - 100 Hz) of the applied voltage. The aim is to interpret the PD frequency dependence in terms of physical conditions at the cavity. The measurements show that the PD process in the cavity is frequency dependent. The PD phase and magnitude distributions, as well as the number of PDs per voltage cycle, change with the varying frequency. Moreover, the PD frequency dependence changes with the applied voltage amplitude, the size of the cavity and the location of the cavity (insulated or electrode bounded). A physical model is presented and used to dynamically simulate the sequence of PDs in the cavity at different applied frequencies. The simulations show that essential features in the measured PD patterns can be reproduced. The PD frequency dependence is interpreted as a variation in influence on the PD activity from the statistical time lag of PD and the charge transport in the cavity surface, at different applied frequencies. The simulation results also show that certain cavity parameters, like the cavity surface conductivity and the rate of electron emission from the cavity surface, change with the time between consecutive PDs, and accordingly with the applied frequency. This effect also contributes to the PD frequency dependence. / QC 20100722

Droplet microfluidics is a promising field since it overcomes many of the limitations of single phase microfluidic systems. The improved mixing time scale, the increase of number of samples and the isolation of droplets are some of its virtues. The core of droplet microfluidics is a two-phase flow condition that is subjected to scaling of the confining geometry. With the scaling the complexities of the flow phenomena arise. For that reason both the processes of droplet generation and transport are not fully understood for various flow and fluid conditions. The work in this thesis aims to experimentally examine droplet generation and transport in microchannels for flow and fluid conditions that are experimentally challenging to perform. Examination of droplet generation in a T-junction microchannel design was performed with a quantitative velocity field approach known as micro particle image velocimetry (μPIV). The studies on droplet generation focused on very fast generation regimes, namely transition and dripping that have not been studied for a T-junction design. This achievement was accomplished because of the development of a fast optical detection and triggering system that allowed for acquiring images of different identical droplets at the same position. μPIV results indicate that the quantitative velocity field patterns of different regimes share some similarities. The filling stage in the transition and dripping regimes had some resemblance in their velocity patterns. The velocity patterns for the start of droplet pinch-off were alike for the squeezing and transition regimes. Furthermore, the presence of a surfactant in the droplet phase above the critical micelle concentration (CMC) did not have an effect on the general velocity patterns as long as the capillary number Ca was matched with the no-surfactant condition. The studies of hydrodynamic properties of droplet transport were performed in hard materials to avoid cumulative error sources, such as material pressure compliance and swelling effects. The project had several parts: designing a microchannel network that allowed studying the hydrodynamic properties of small droplets, surface treatments of the channel material for stable droplet generation and examining the hydrodynamics of small liquid droplets with sizes that have not been reported in the literature. The studies examined effects of changing the interfacial tension, viscosity, and flow conditions on the transport of droplets. The experimental results from the hydrodynamic transport studies indicated that for the droplet sizes that were examined the pressure drop of droplets was affected by the capillary number Ca and length of the droplet Ld. Also, the presence of surfactants altered the hydrodynamic properties of droplets. At a high concentration of surfactants the droplets pressure drop was reduced significantly. Moreover, the type of surfactant affected the magnitude of the pressure drop. Experimental results indicate that if the concentration of surfactants was very low (below CMC) it did not have an effect on the droplet excess pressure. These findings are important to consider in designing droplet microfluidic systems with complex channel networks that involve droplet sorting, splitting, and merging for droplets that contain surfactants.

Universiẗat, Diss., 2003--Freiburg (Breisgau).

Made available in DSpace on 2014-06-11T19:22:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2006Bitstream added on 2014-06-13T18:49:26Z : No. of bitstreams: 1 santos_mc_me_ia.pdf: 1765927 bytes, checksum: 9b85ab73869c40bb0a116bced37220f6 (MD5) / O presente estudo buscou utlizar o policarbonato, polímero plástico, como matriz de gravura em côncavo. Assim, este trabalho teve como objetivo tomar a gravura em côncavo sob o ponto de vista de sua prática, experimentando técnicas de gravação diretas, indiretas e aditivas, pesquisando também outros procedimentos passíveis de aplicação no policarbonato, explorando desta forma suas possibilidades expressivas. Foram pesquisadas as relações decorrentes da prática da gravura, entre a mão, a ferramenta e a matriz, assim como os aspectos físicos e químicos do policarbonato relacionados a essa prática. Os processos de gravação e impressão descritos nesta pesquisa ressaltam os momentos de aproximação e afastamento dos resultados obtidos na gravura em côncavo tradicional. Ao final, são apresentadas vinte e três estampas produzidas a partir de matrizes em policarbonato. / This research investigated the use of polycarbonate, a plastic polymer, as a plate to intaglio printing. The main objective of this research was the approach of intaglio printing from the point of view of its practice, trying on direct, indirect and additive engraving techniques, also searching for other procedures to use on polycarbonate, therefore exploring its expression possibilities. The relation concerning the hand, the tool and the plate on the results of intaglio practice was also researched, as well as the chemical and material aspects of polycarbonate linked to this practice, The engraving and printing process described here shows results obtained from moments of approximation and spacing on traditional intaglio printing. At the end, twenty three stamps made of polycarbonate plates are presented.

Orientador: Milton Terumitsu Sogabe / Banca: Percival Tirapeli / Banca: Ana Kalassa El Banat / Resumo: O presente estudo buscou utlizar o policarbonato, polímero plástico, como matriz de gravura em côncavo. Assim, este trabalho teve como objetivo tomar a gravura em côncavo sob o ponto de vista de sua prática, experimentando técnicas de gravação diretas, indiretas e aditivas, pesquisando também outros procedimentos passíveis de aplicação no policarbonato, explorando desta forma suas possibilidades expressivas. Foram pesquisadas as relações decorrentes da prática da gravura, entre a mão, a ferramenta e a matriz, assim como os aspectos físicos e químicos do policarbonato relacionados a essa prática. Os processos de gravação e impressão descritos nesta pesquisa ressaltam os momentos de aproximação e afastamento dos resultados obtidos na gravura em côncavo tradicional. Ao final, são apresentadas vinte e três estampas produzidas a partir de matrizes em policarbonato. / Abstract: This research investigated the use of polycarbonate, a plastic polymer, as a plate to intaglio printing. The main objective of this research was the approach of intaglio printing from the point of view of its practice, trying on direct, indirect and additive engraving techniques, also searching for other procedures to use on polycarbonate, therefore exploring its expression possibilities. The relation concerning the hand, the tool and the plate on the results of intaglio practice was also researched, as well as the chemical and material aspects of polycarbonate linked to this practice, The engraving and printing process described here shows results obtained from moments of approximation and spacing on traditional intaglio printing. At the end, twenty three stamps made of polycarbonate plates are presented.

Made available in DSpace on 2014-12-17T14:58:03Z (GMT). No. of bitstreams: 1 DiltonS_DISSERT.pdf: 1329458 bytes, checksum: 93af6e35d0ed131c06c793e3af29ce95 (MD5) Previous issue date: 2010-10-20 / Universidade Federal do Rio Grande do Norte / It was studied a system for heating water to be used to obtain water for bathing at home, the absorbing surface of the collector is formed by one plate of polycarbonate. The polycarbonate plate has 6 mm thick, 1.050 mm wide and 1.500 mm long with an area equal to 1,575 m?. The plate was attached by its edges parallel to PVC tubes of 32 mm. The system worked under the thermo-siphon and was tested for two configurations: plate absorber with and without isolation of EPS of 30 mm thick on the bottom surface in order to minimize heat losses from the bottom. The tank's thermal heating system is alternative and low cost, since it was constructed from a polyethylene reservoir for water storage, with a volume of 200 liters. Will present data on the thermal efficiency, heat loss, water temperature of thermal reservoir at the end of the process simulation and baths. Will be demonstrated the feasibility of thermal, economic and material pickup proposed for the intended purpose. / Estudou-se um sistema para aquecimento de ?gua a ser utilizada para obten??o de ?gua destinada ao banho em resid?ncias, a superf?cie absorvedora do coletor ? formada por uma placa de policarbonato. A placa de policarbonato tem 6 mm de espessura, 1.050 mm de largura e 1.500 mm de comprimento com ?rea correspondente a 1,575 m2. A placa foi ligada pelas extremidades em paralelo a tubos de PVC de ? 32 mm. O sistema funcionou em regime de termo-sif?o e foi testado para duas configura??es: placa absorvedora com e sem isolamento de EPS de 30 mm de espessura na superf?cie inferior para minimizar as perdas t?rmicas pela parte de baixo. O reservat?rio t?rmico do sistema de aquecimento ? alternativo e de baixo custo, pois foi constru?do a partir de um reservat?rio de polietileno para armazenamento de ?gua, com volume de 200 litros. Ser?o apresentados dados de efici?ncia t?rmica, perda t?rmica, temperatura da ?gua do reservat?rio t?rmico no final do processo e de simula??o de banhos. Ser?o demonstradas as viabilidades t?rmica, econ?mica e de materiais do coletor proposto, para o fim desejado

Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro / Neste trabalho foram investigados os comportamentos térmico e mecânico e as características morfológicas de amostras de policarbonato de bisfenol-A (PC) com cristalinidade induzida por exposição ao vapor de solvente. A técnica de indução de cristalização foi empregada em três amostras de policarbonato de bisfenol-A de diferentes massas molares. Filmes vazados a partir de soluções de PC em clorofórmio e amostras moldadas por compressão foram expostos a um ambiente contendo vapor de acetona. Os filmes foram expostos por diferentes períodos de tempo e analisados em equipamentos de Calorimetria Diferencial de Varredura, Microscopia Óptica com luz polarizada e Espectroscopia na Região do Infravermelho com Transformada de Fourier, para caracterizar a indução de cristalinidade. A indução de cristalinidade foi confirmada e a fase cristalina apresentou estrutura esferulítica. As amostras de maior massa molar mostraram maior teor de cristalinidade. O desempenho mecânico das amostras cristalinas de policarbonato mostrou diferenças, com a mudança de seu comportamento mecânico de dúctil para frágil, independente da massa molar / In this work were investigated the thermal and mechanical behaviors and the morphological characteristics of bisphenol-A polycarbonate (PC) samples with crystalline induction by solvent vapor exposure. The crystallization induction technique was employed on three samples of bisphenol-A polycarbonate of different molar mass. Films cast from PC solutions in chloroform and compression molded samples were exposed to an environment containing acetone vapor. The films were exposed for different periods of time and analyzed on Differential Scanning Calorimeter, Polarized Light Optical Microscope and Fourier Transform Infra Red devices to characterize crystalline induction. The crystalline induction was confirmed and the crystalline phase has presented spherulitic structure. The highest molar mass samples have shown higher crystallinity degrees. Mechanical performance of crystalline samples has shown differences with the change of its mechanical behavior from ductile to fragile, independently of the molar mass

Four novel high performance soft thermoplastic polyurethane elastomers utilizing methylene bis(4-cyclohexylisocyanate) as a hard segment, 1,4 butanediol as a chain extender and modified low crystallinity carbonate copolymer as a soft segment were synthesized. The samples were characterized by infrared spectroscopy (FTIR), tensile, elongation, hardness, abrasion resistance and atomic force microscopy (AFM). SAXS data shows evidence of an interdomain "center-to-center" distance of 45Å. DSC traces show evidence of one glass transition temperature and a weak melting region. DMA analysis reveals a low temperature secondary relaxation and the glass to rubber transition followed by a rubbery plateau. All samples demonstrated the ability to maintain excellent physical and mechanical properties in hardness below 70 Shore A. Thermoplastic polyurethanes in this study do not possess surface tackiness usually observed in soft polyurethanes. Biocompatability testing showed no toxicity of these samples as indicated by USP Class VI, MEM Elution Cytotoxicity and Hemolysis toxicology reports. This novel type of polyurethane material targets growing markets of biocompatible polymers and can be utilized as peristaltic pump tubing, balloon catheters, enteral feeding tubes and medical equipment gaskets and seals. Polyimides are a family of engineering polymers with temperature stability, high polarity and solvent resistance. These high-performance materials are used in aerospace applications, in the production of semi-dry battery binders, and in a host of other high temperature demanding situations. However, their glass transition and melt temperatures are characteristically very high and close to one another, making them difficult to melt process and limiting them to thin film formulations from their polyamic acid precursors. Here, a new series of thermoplastic polyether-polyimides (PE-PIs) are synthesized by incorporating a polyetherdiamine monomer to reduce rigidity and break up an otherwise fully aromatic backbone as seen with most conventional polyimides. It will be shown that control of the stoichiometric ratio between the aromatic 4,4'-methylenebis(2,6-dimethylaniline) and aliphatic polyetherdiamines relative to PMDA (pyromellitic dianhydride), along with the molecular weight of the polyetheramine, can be used to tune the Tg to best balance between temperature performance and processability.

Since their discovery in the 1930s, polymeric foams have been widely used in the industry for a variety of applications such as acoustical and thermal insulation, filters, absorbents etc. The reason for this ascending trend can be attributed to factors such as cost, ease of processing and a high strength to weight ratio compared to non-foamed polymers. The purpose of this project was to develop an “indestructible” material made of polycarbonate (PC) for industrial applications. Due to the high price of polycarbonate, two foaming methods were investigated to reduce the amount of material used. Samples were foamed physically in supercritical CO2 or chemically with 5-phenyl-1H-tetrazole. After thermal characterization of the foams in differential scanning calorimetry (DSC), we saw that none of the foaming methods had an influence on the glass transition of polycarbonate. Micrographs taken in scanning electron microscopy (SEM) showed that foams obtained in physical and chemical foaming had different structures. Indeed, samples foamed in supercritical CO2 exhibited a microcellular opened-cell structure with a high cell density and a homogeneous cell distribution. On the other hand, samples foamed with 5-phenyl-1H-tetrazole had a macrocellular closed-cell structure with a much smaller cell density and a random cell distribution. Compression testing showed that polycarbonate foamed physically had a compression modulus a lot greater. Then, XLPE mesh 35 or 50 and wollastonite were added to the polymeric matrices to enhance the foaming process and the mechanical properties. DSC experiments showed that the addition of fillers changed the thermal properties of polycarbonate for both foaming methods by inducing a shift in glass transition. SEM revealed that fillers lowered the average cell diameter and increased the cell density. This phenomenon increased the compression modulus for polycarbonate foamed in supercritical CO2. However, mechanical properties decreased for samples foamed with 5-phenyl-1H-tetrazole due to their relative brittleness and the propagation of microcracks.