Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 797-811). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S.)--University of North Texas, Aug., 2009. / Title from title page display. Includes bibliographical references.

The viscoelastic response of polymer-based composite laminates, which may take years to develop in service, must be anticipated and accommodated at the design stage. Accelerated testing is therefore required to allow long-term compliance predictions for composite laminates of arbitrary layup, based solely upon short-term tests. In this study, an accelerated viscoelastic characterization scheme is applied to T300/5208 graphiteepoxy laminates. The viscoelastic response of unidirectional specimens is modeled using the theory developed by Schapery. The transient component of the viscoelastic creep compliance is assumed to follow a power law approximation. A recursive relationship is developed, based upon the Schapery single-integral equation, which allows approximation of a continuous time-varying uniaxial load using discrete steps in stress. The viscoelastic response of T300/5208 graphite-epoxy at 149C to transverse normal and shear stresses is determined using 90-deg and 10-deg off-axis tensile specimens, respectively. parameters In each case the seven viscoelastic material required in the analysis are determined experimentally, using a short-term creep/creep recovery testing cycle. A sensitivity analysis is used to select the appropriate short-term test cycle. It is shown that an accurate measure of the power law exponent is crucial for accurate long-term predictions, and that the calculated value of the power law exponent is very sensitive to slight experimental error in recovery data. Based upon this analysis, a 480/120 minute creep/creep recovery test cycle is selected, and the power law exponent is calculated using creep data. A short-term test cycle selection procedure is proposed, which should provide useful guidelines when other viscoelastic materials are being evaluated. Results from the short-term tests on unidirectional specimens are combined using classical lamination theory to provide long-term predictions for symmetric composite laminates. Experimental measurement of the long-term creep compliance at 149C of two distinct T300/5208 laminates is obtained. A reasonable comparison between theory and experiment is observed at time up to 10 5 minutes. Discrepancies which do exist are believed to be due to an insufficient modeling of biaxial stress interactions, to the accumulation of damage in the form of matrix cracks or voids, and/or to interlaminar shear deformations which may occur due to viscoelastic effects or damage accumulation. / Doctor of Philosophy

A study has been undertaken with the aim of preparing appropriately functionalised polyhedral oligomeric silsesquioxane (POSS) compounds to be used in ambient-cure chemistry. Numerous epoxy-functionalised compounds have been designed and synthesised and these materials have been characterised in order to determine their chemical structure. These compounds have also been incorporated into existing polymerisation reactions to test whether these materials could be used in the protective coatings industry. A glycidyl-functionalised POSS compound was prepared and reacted with a series of amines to produce ambient-cured polymers which could be used in the coatings industry. There were also a series of experiments undertaken on these polymers to identify the processes at work and to test how they compare to industry standards. As a direct comparator to this work, another set of results was obtained with a cyclic-siloxane material incorporated into the systems in place of the POSS. A linear analogue was also tested. The reactions proved to be a success and an appropriate data-set was yielded. During the synthesis of POSS precursors there are a series of residual materials produced. These materials have also been studied in this project. It was anticipated that these would behave in a similar way to the POSS compounds however the same functionality was never achieved as had been with the POSS. Ambient-cured polymers have also been targeted from a basic hydride-functionalised POSS compound and a polybutadiene system. The appropriate reactions unfortunately never took place as anticipated but there were a series of tests undertaken to identify the processes at work. A study has also been undertaken using near-I.R. to track the curing reactions. From this data, the extent of cure could be studied and the make-up of the reaction could be investigated in more detail.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Os molibdatos tÃm sido introduzido como possÃvel substituinte dos cromatos, como pigmento anticorrosivo, devido a suas propriedades de inibiÃÃo, sua baixa toxicidade e a possibilidade de formaÃÃo de um filme de conversÃo em superfÃcies metÃlicas semelhante à camada de conversÃo formada pelos cromatos. Neste trabalho, foram formuladas tintas com os seguintes pigmentos: Cromato de zinco, fosfato de zinco, fosfato Molibdato de zinco e fosfato Molibdato de zinco-cÃlcio. Foi formulado ainda, uma tinta sem pigmentos (verniz) e outra somente com a carga. O trabalho consiste em um estudo comparativo do desempenho anticorrosivo das pinturas formuladas, por testes cÃclicos em laboratÃrio (cÃmara de nÃvoa salina) e imersÃo total. As principais tÃcnicas empregadas foram: monitoramento do potencial de circuito aberto, curvas de polarizaÃÃo e impedÃncia eletroquÃmica. De um modo geral, o cromato de zinco apresentou melhores resultados. PorÃm, em certas condiÃÃes de trabalho, os pigmentos nÃo tÃxicos apresentaram resultados satisfatÃrios. / Os molibdatos tÃm sido introduzido como possÃvel substituinte dos cromatos, como pigmento anticorrosivo, devido a suas propriedades de inibiÃÃo, sua baixa toxicidade e a possibilidade de formaÃÃo de um filme de conversÃo em superfÃcies metÃlicas semelhante à camada de conversÃo formada pelos cromatos. Neste trabalho, foram formuladas tintas com os seguintes pigmentos: Cromato de zinco, fosfato de zinco, fosfato Molibdato de zinco e fosfato Molibdato de zinco-cÃlcio. Foi formulado ainda, uma tinta sem pigmentos (verniz) e outra somente com a carga. O trabalho consiste em um estudo comparativo do desempenho anticorrosivo das pinturas formuladas, por testes cÃclicos em laboratÃrio (cÃmara de nÃvoa salina) e imersÃo total. As principais tÃcnicas empregadas foram: monitoramento do potencial de circuito aberto, curvas de polarizaÃÃo e impedÃncia eletroquÃmica. De um modo geral, o cromato de zinco apresentou melhores resultados. PorÃm, em certas condiÃÃes de trabalho, os pigmentos nÃo tÃxicos apresentaram resultados satisfatÃrios.

Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2005. / Includes bibliographical references (p. 57-61).

The effects of direct plasma chemistries on carbon removal from silicon nitride (SiNx) and oxynitride (SiOxNy ) surfaces and Cu have been studied by x-photoelectron spectroscopy (XPS) and ex-situ contact angle measurements. The data indicate that O2,NH3 and He capacitively coupled plasmas are effective at removing adventitious carbon from silicon nitride (SiNx) and Silicon oxynitride (SiOxNy ) surfaces. O2plasma and He plasma treatment results in the formation of silica overlayer. In contrast, the exposure to NH3 plasma results in negligible additional oxidation of the SiNx and SiOxNy surface. Ex-situ contact angle measurements show that SiNx and SiOxNy surfaces when exposed to oxygen plasma are initially more hydrophilic than surfaces exposed to NH3 plasma and He plasma, indicating that the O2 plasma-induced SiO2 overlayer is highly reactive towards ambient corresponding to increased roughness measured by AFM. At longer ambient exposures (>~10 hours), however surfaces treated by either O2, He or NH3 plasma exhibit similar steady state contact angles, correlated with rapid uptake of adventitious carbon, as determined by XPS. Surface passivation by exposure to molecular hydrogen prior to ambient exposure significantly retards the increase in the contact angle upon the exposure to ambient. The results suggest a practical route to enhancing the time available for effective bonding to surfaces in microelectronics packaging applications.

A commercial epoxy was modified by adding fluorinated poly (aryl ether ketone) and in turn metal micro powders (Ni, Al, Zn, and Ag) and coated on mild steel. Two curing agents were used; triethylenetetramine (curing temperatures: 30 oC and 70 oC) and hexamethylenediamine (curing temperature: 80 oC). Variation in tribological properties (dynamic friction and wear) and surface energies with varying metal powders and curing agents was evaluated. When cured at 30 oC, friction and wear decreased significantly due to phase separation reaction being favored but increased when cured at 70 oC and 80 oC due to cross linking reaction being favored. There was a significant decrease in surface energies with the addition of modifiers.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / This work is focused on developing viable self-healing coatings, especially considering the viability of the coating in a commercial context. With this in mind, finding low cost healing agents, with satisfactory healing and mechanical properties as well as adapting the healing system for use in coatings was required. Seven potential healing agents were evaluated and an air-drying triglyceride (linseed oil) was identified as the candidate healing agent. Different encapsulation techniques were evaluated and ureaformaldehyde microcapsules were chosen as the candidate encapsulation technique. Self-healing coatings were fabricated using urea-formaldehyde encapsulated linseed oil. EIS, SEM and TGA technologies were used to evaluate mechanical performance, corrosion resistance, and self-healing performance.