Thesis (M.S.)--University of Florida, 2004. / Title from title page of source document. Document formatted into pages; contains 50 pages. Includes vita. Includes bibliographical references.

Würzburg, Univ., Diss., 2009

Resumo: O presente trabalho aborda as condições de reticulação do polímero termoplástico polietileno e, para isso, foram avaliadas diferentes temperaturas de processo (60 e 90°C), bem como diferentes tempos de permanência em imersão em banho termostatizado (1, 3, 6 e 9 horas). Esta avaliação foi realizada a partir dos ensaios de teores de gel e fator de uptake, de massa específica, de calorimetria exploratória diferencial (DSC), de análise termogravimétrica (TGA), de espectrofotometria no infravermelho com transformada de Fourier (FT-IR) e de ensaios de tração. Desta forma, o grau de reticulação do polietileno de baixa densidade reticulado em água, foi correlacionado com sua morfologia, com seu desempenho térmico e mecânico. Os resultados mostraram que o teor de gel do polietileno reticulado aumentou com o aumento da temperatura e do tempo de exposição desta matriz polimérica em água, sendo que, este aumento ocorreu de forma significativa até 3 horas de exposição, não sendo observados ganhos significativos na formação de ligações cruzadas após este período / Abstract: The present work deals with the crosslink conditions of polyethylene polymer using different process temperatures (60 and 90°C). For this different water immersion times in thermostated bath (1, 3, 6 and 9 hours) have been analyzed by using gel content and uptake factor, density tests, dynamic scanning calorimetric analyses (DSC), thermogravimetric analysis (TGA), infrared spectroscopy (FT-IR) and tensile tests. This way, it was evaluated the degree of crosslinking of low density polyethylene crosslinked into water, and these parameters were correlated with the morphology and its thermal and mechanical performance. According to found results, it was observed that the gel content of polyethylene crosslinked increased with increasing of exposition temperature and time of this polymeric matrix in water, therefore, this increase was significantly up to 3 hours of exposition, not being observed significant gains in crosslinking density after this time / Orientador: Edson Cocchieri Botelho / Coorientador: Antonio Fernando Branco Costa / Banca: Luiz Claudio Pardini / Banca: Michelle Leali Costa / Mestre

The purpose of this research is to test the effects of methyltrimethoxysilane coupling agent on composite material containing calcium sulfite obtained from the Southern Illinois Power Co-operative. This scrubber material and the miscanthus plant are of interest due to their use in coal burning power plants to reduce toxic emission. When calcium sulfate is passed through coal fire gas emissions it absorbs mercury and sulfur. In these composites it is used as filler to reduce cost. Miscanthus is a source of both cellulose reinforcement and some natural resin. This plant has low care requirements, little mineral content, useful energy return, and positive environmental effects. Under investigation is whether a post-cure procedure or a silane coupling agent will positively impact the composite. Hot pressing alone may not be enough to fully cure the phenolic. It is hoped that the silane will increase the strength characteristics of the composite by enhancing adhesion between the calcium sulfite and phenolic resin. Possible effects on the miscanthus by the silane will also be tested. Phenolic is being utilized because of its recycling and biodegradable properties along with cost effectiveness in mass production. Composite mechanical performance was measured through 3-point bending to measure flexural strength and strain at breakage. A dynamic mechanical analyzer (DMA) was used to find thermomechanical properties. The post-cure was found to be effective, particularly on the final composite containing silane. When methyltrimethoxysilane was added to the miscanthus prior to fabrication, it was found to reduce flexural strength and density. However the addition of methyltrimethoxysilane to the calcium sulfite altered thermo-mechanical properties to a state more like pure phenolic, with added flexibility and thermal stability.

The preparation of the modified silane [special characters omitted]; a phosphinoalkylsilane or PSi) via an alkylzirconium intermediate is reported. The synthesis of [special characters omitted] was carried out by the reaction of organolithium reagents with chloro-silanes at low temperature. The PSi compounds are isolated as air-sensitive, thermally stable and very viscous liquids. The reactivity of two of the silanes was investigated with the platinum group metal complex [special characters omitted] (cod = cycloocta-1,5-diene). In both cases, square planar platinum (II) complexes were isolated. The reactivity of [special characters omitted] produces five coordinate M (III) complexes which undergo stereomutation. The isomerisation of the syn to anti forms of [special characters omitted] has been examined at several temperatures via NMR spectroscopy and the activation parameters determined for the conversion of the syn to the intermediate isomer form [special characters omitted]. The implications of the stereomutation phenomona are discussed in relation to catalysis. None of the isomers of this complex forms a stable six coordinate adduct when reacted with a number of common nucleophiles. The analogous compound where M = Ir and related complexes of the formula [special characters omitted] are reactive towards CO to form stable six coordinate adducts containing two M-P and one M-Si, M-H, M-CO and a M-Cl bond. Some of these adducts can be made directly by the reaction of the PSi ligand precursor with [special characters omitted] (M = Rh, Ir) at room temperature. The reaction of the silane [special characters omitted] produces six coordinate complexes directly. For M = Ir, the compound reacts with CO to produce a six coordinate cation by displacement of a chloride ligand, the latter of which then acts as a non-coordinating counterion. A series of organosilicon dendrimers of the type : [special characters omitted] ([G-1] : x = 3, y = 2 = q = 0; [6-2] : y = 3, x = 9 , z = q = 0; [G-3] : z = 3, y = 9, X = 27, q = 0; [G-4] : q = 3, z = 9, y = 27, x = 81) are sythesised and examined spectroscopically. All of the dendrimers are air stable liquids. Species G3 has a marked tendency to undergo what appears to be self-condensation polymerisation. End and core group substitution is presented for a carbosilane dendrimer containing one shell of identical exterior Si atoms. The dendrimeric end groups can be modified by the replacement of a terminal chloride by fluoride, hydrogen, alkyl groups or metal complexes. The selective removal of a core phenyl group can be accomplished with the strong acid [special characters omitted]. The resulting silyl triflate can in turn be used as a precusor to a silyl ether, hence facilitating selective core group modification. / Graduate

Magister Scientiae - MSc / Computational Fluid Dynamics is the analysis of a system involving fluid flow, heat transfer and associated phenomena such as chemical reactions by means of a computer-based simulation. The simulations in this study are performed using (CFD) software package FLUENT. The mixture of two gases (Silane gas (SiH4) and Hydrogen gas (H2)) are delivered into the hot-wire chemical vapor deposition system (HWCVD) with the two deposited substrates (glass and Silicon). This process is performed by the solar cells group of the Physics department at the University of the Western Cape. In this thesis, the simulation is done using a CFD software package FLUENT, to model the gas-flow patterns inside the HWCVD system. This will show how the gas-flow patterns are affected by the varying temperature of the heater in each simulation performed in this study under a constant pressure of 60μBar of the system. / South Africa

No description available.

<p> UV radiation disinfection technology is an advantageous method of wastewater disinfection as it avoids the formation of chemical by-products typically found from chlorination. One challenge with this technology is avoiding fouling on the quartz sleeves in which the UV lamps are housed. In this study, using a model fouling system, the roles in fouling of light, and the constitution of the fouling media, are examined. The systematic determination of fouling by various mixtures of human serum albumin, humic acid, Ca^2+, and Fe^3+ was carried out on quartz slides in the presence and absence of UV (254nm) light. Fouling was assessed by the reduction in transmission of UV light through the quartz slides over time. It was determined that the most important factors were the concentration of..iron and protein, which apparently act synergistically to foul the surface. Other contributing factors to the magnitude of fouling include the flow rate and the age of the fouling solution. Most important was the presence of UV light. In all solutions examined, fouling was observed to a lower degree when the system was exposed to light. On the other hand, XPS analysis has demonstrated differences in the nature of the fouling layer on the surface exposed to UV light compared to that in the dark. </p> <p> It is generally accepted that low energy surfaces are less easily fouled than polar surfaces. Therefore, hydrophobic modification of the quartz by a series of different silane coupling agents was undertaken. Irrespective of the nature of the coating (alkylamine, alkyl, aryl, fluorocarbon, silicone), the rate and magnitude of fouling on the surface were comparable to the unmodified quartz. However, the more hydrophobic surfaces were easier to clean. </p> / Thesis / Master of Science (MSc)

<p> The lattice parameters and crystal symmetry of silane (SiH4) are examined by X-ray powder diffraction. Comparisons are made with vibrational spectrum and birefringence measurements and with respect to an order-disorder transition between the two solid phases of silane.</p> / Thesis / Master of Science (MSc)

No description available.