Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph.D.) -- McMaster University, 2001. / Includes bibliographical references (leaves 204-228). Also available via World Wide web.

Thesis (PhD.(Mechanical Engineering))--University of Pretoria, 2005. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (M.E.)--University of Canterbury, 2005. / Typescript (photocopy). "August 2005." Includes bibliographical references (p. 107-115). Also available via the World Wide Web.

Thesis (Ph. D.)--Ohio State University, 2007. / Full text release at OhioLINK's ETD Center delayed at author's request

Made available in DSpace on 2014-06-11T19:28:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-06-27Bitstream added on 2014-06-13T20:37:54Z : No. of bitstreams: 1 claro_fa_me_sjc.pdf: 1230472 bytes, checksum: aa7d0bf88466ef0f58ce0587136a08c1 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O propósito deste trabalho foi estudar a reação do tecido ósseo após a implantação de polietileno poroso em defeitos cirúrgicos confeccionados no osso parietal de ratas diabéticas tratadas com calcitonina, mediante análise microscópica. Avaliou-se também a eficiência da aplicação da estreptozotocina na indução do diabete melito em ratos, em dose única de 45mg/Kg, através da utilização de um glicosímetro digital e do exame clínico. Foram utilizadas 27 ratas adultas, divididas em grupo não diabético-controle (C), grupo diabético (D) e grupo diabético tratado com calcitonina (DCa). Os animais do grupo DCa receberam aplicações subcutâneas do hormônio em doses de 16UI/Kg, em dias alternados, desde o pós-operatório imediato até o sacrifício e foram sacrificados após 15, trinta e sessenta dias. Diante dos resultados observados, pode-se concluir que o polietileno poroso foi tolerado pelos tecidos hospedeiros nos animais do grupo C e grupo DCa, provocando reações inflamatórias mais intensas nesse segundo grupo, em todos os períodos de observação. O polietileno poroso não foi tolerado pelos tecidos hospedeiros dos animais do grupo D. Os poros do implante foram preenchidos por um tecido conjuntivo bem vascularizado, conferindo estabilidade ao material no leito receptor, não ocorrendo osteointegração. A calcitonina utilizada nos animais do grupo DCa foi eficaz no tratamento pós-operatório dos animais diabéticos que receberam o polietileno poroso, inibindo o processo de reabsorção e/ou estimulando a neoformação óssea. A estreptozotocina, administrada em dose única de 45 mg/Kg, foi um método eficaz na indução do diabete melito nas ratas, permitindo boas condições de sobrevida. / The purpose of this work was to study the reaction of the bone tissue after the porous polyethylene implantation in confectioned surgical defects in the parietal bone of diabetic rats treated with calcitonin, by means of microscopical analysis. The efficiency of a single dose of streptozotocin, 45mg/Kg, in the induction of diabetes mellitus in rats was also evaluated through the use of a digital glicosimeter and the clinical examination. Twenty-seven adult female rats had been used, divided in not diabetic-control (C), diabetic (D) and diabetic treated with calcitonin (DCa) groups. The animals of group DCa had received subcutaneous applications from the hormone in doses of 16U/Kg, in alternated days, since immediate postoperative until the sacrifice, and all the animals had been sacrificed after 15, 30 and 60 days. Ahead of the results, it can be concluded that the porous polyethylene was tolerated by the host tissue in groups C and DCa, disclosing more intense inflammatory response in group Dca. The pores of the implants had been filled with well vascularizated connective tissue, conferring stability to the material in the receiving site, not occurring osteointegration. Calcitonin used in the animals of group DCa was efficient in the postoperative treatment of the diabetic animals that had received the porous polyethylene implants, inhibiting the bone resorption and/or stimulating the bone formation. Streptozotocin, managed in a single dose of 45 mg/Kg, was an efficient method in the induction of the diabetes mellitus in the rats, allowing good conditions of survival.

Materiais naturais nanoestruturados, tipo smectita, têm sido amplamente usados em nanocompósitos poliméricos, com ganhos expressivos em muitas propriedades. Porém, devido a sua natureza polar, seu uso em nanocompósitos de poliolefinas apresenta uma série de problemas. Entre esses problemas está a dificuldade de esfoliação na matriz, o que geralmente resulta um sistema não nano-estruturado e, por conseqüência, com pouco ou nenhum ganho em propriedades. Para tentar resolver esse problema, materiais tipo esmectita têm sido modificados com sais de amônio quartenário. Esses, por sua vez, possuem características tóxicas, impedindo seu uso em embalagens de alimentos. Com o objetivo de estudar uma nova alternativa que contorne esses problemas, dois materiais lamelares nano-estruturados, tipo esmectita, contendo grupos alquila ligados por ligação sigma com a rede inorgânica, foram sintetizados. Ambos apresentaram excelente ordem mesoestrutural. Um dos materiais sintetizados, formado por um Alsilsesquioxano lamelar, contendo alto teor de cadeia alquila entre as lamelas inorgânicas, foi usado na formação de compósito de polietileno. Comparativamente, uma argila natural, modificada com sais de amônio quaternário (Cloisite 15A), foi usada para fins comparativos. Os compósitos, então obtidos, foram caracterizados para avaliar diferenças microestruturais, morfológicas e mudanças em suas propriedades mecânicas e reológicas. Comparativamente à argila comercial Cloisite 15A, os compósitos contendo os materiais sintéticos apresentaram reologia diferenciada, melhor resistência ao impacto e ao Tensofissuramento Acelerado pelo Ambiente (ESCR). / Nanostructured natural materials, as smectites, have been widely used in polymeric nanocomposites, with significant gains in many properties. However, due to its polar nature, the use in nanocomposites of polyolefins presents a series of drawbacks. Among these problems, its difficulty exfoliation in the matrix, which generally results in a system not nanostructured and, consequently, with little or no gain on properties. To try to resolve this problem, materials type smectite have been modified with quaternary ammonium salts. These salts, in turn, have toxic characteristics, preventing its use in food packaging. In order to study a new alternative that bypasses these problems, two lamellar nanostructured materials, like smectite, with alkyl groups containing sigma links connected to lamellar inorganic network, were synthesized. Both materials had excellent mesostructural order. One of the synthesized materials, formed by a lamellar Al-silsesquioxane, containing high levels of alkyl chain between the inorganic lamella, was used in the formation of a polyethylene composite. Commercial natural clay, modified with quaternary ammonium salts (Cloisite 15A), was used for comparative purposes. The composites then obtained, were characterized to assess microstructural differences, morphological change, and its mechanical and rheological properties. Comparatively to commercial clay (Cloisite 15A), the composites containing synthetic materials, showed differented rheologics properties, better impact resistance and better Environmental Stress Cracking Resistance (ESCR).

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Nesse estudo foi realizado o processo de co-pirólise de resíduo de plástico de polietileno com gás-óleo com variação de temperatura. Primeiramente, as amostras de polietileno e gás-óleo foram submetidas a co-pirólise térmica em atmosfera inerte a 550C e depois foram avaliada a eficiência do processo a 500C e 450C. Os líquidos pirolíticos obtidos por este tratamento térmico foram caracterizados por cromatografia gasosa acoplada a espectrometria de massas (CG/EM) objetivando a avaliação do potencial energético destes líquidos. Os picos identificados no espectro de massas indicam a elevada geração de parafinas e olefinas, comprovando que o processo é promissor na utilização de resíduos plásticos na obtenção de óleos combustíveis que podem servir como insumos para a indústria petroquímica. / In this study the process of co-pyrolysis of plastic polyethylene residue was carried through with gas-oil under temperature variation. Initially the two samples had been submitted the thermal co-pyrolysis in inert atmosphere 550C, furtherly evaluated the efficiency of the process 500C and 450C. The pyrolysed liquids produced by this thermal treatment had been characterized by gaseous chromatography connected to the spectrometry of masses (CG/EM) objectifying the evaluation of the energy potential of these liquids. The peaks identified in the spectra of masses indicated the high paraffin generation and olefinas, proving that the process is promising in the use of plastic residues in the combustible oil attainment that can serve as feedstock for the petrochemical industry.

Materiais naturais nanoestruturados, tipo smectita, têm sido amplamente usados em nanocompósitos poliméricos, com ganhos expressivos em muitas propriedades. Porém, devido a sua natureza polar, seu uso em nanocompósitos de poliolefinas apresenta uma série de problemas. Entre esses problemas está a dificuldade de esfoliação na matriz, o que geralmente resulta um sistema não nano-estruturado e, por conseqüência, com pouco ou nenhum ganho em propriedades. Para tentar resolver esse problema, materiais tipo esmectita têm sido modificados com sais de amônio quartenário. Esses, por sua vez, possuem características tóxicas, impedindo seu uso em embalagens de alimentos. Com o objetivo de estudar uma nova alternativa que contorne esses problemas, dois materiais lamelares nano-estruturados, tipo esmectita, contendo grupos alquila ligados por ligação sigma com a rede inorgânica, foram sintetizados. Ambos apresentaram excelente ordem mesoestrutural. Um dos materiais sintetizados, formado por um Alsilsesquioxano lamelar, contendo alto teor de cadeia alquila entre as lamelas inorgânicas, foi usado na formação de compósito de polietileno. Comparativamente, uma argila natural, modificada com sais de amônio quaternário (Cloisite 15A), foi usada para fins comparativos. Os compósitos, então obtidos, foram caracterizados para avaliar diferenças microestruturais, morfológicas e mudanças em suas propriedades mecânicas e reológicas. Comparativamente à argila comercial Cloisite 15A, os compósitos contendo os materiais sintéticos apresentaram reologia diferenciada, melhor resistência ao impacto e ao Tensofissuramento Acelerado pelo Ambiente (ESCR). / Nanostructured natural materials, as smectites, have been widely used in polymeric nanocomposites, with significant gains in many properties. However, due to its polar nature, the use in nanocomposites of polyolefins presents a series of drawbacks. Among these problems, its difficulty exfoliation in the matrix, which generally results in a system not nanostructured and, consequently, with little or no gain on properties. To try to resolve this problem, materials type smectite have been modified with quaternary ammonium salts. These salts, in turn, have toxic characteristics, preventing its use in food packaging. In order to study a new alternative that bypasses these problems, two lamellar nanostructured materials, like smectite, with alkyl groups containing sigma links connected to lamellar inorganic network, were synthesized. Both materials had excellent mesostructural order. One of the synthesized materials, formed by a lamellar Al-silsesquioxane, containing high levels of alkyl chain between the inorganic lamella, was used in the formation of a polyethylene composite. Commercial natural clay, modified with quaternary ammonium salts (Cloisite 15A), was used for comparative purposes. The composites then obtained, were characterized to assess microstructural differences, morphological change, and its mechanical and rheological properties. Comparatively to commercial clay (Cloisite 15A), the composites containing synthetic materials, showed differented rheologics properties, better impact resistance and better Environmental Stress Cracking Resistance (ESCR).

abstract: Improved knowledge connecting the chemistry, structure, and properties of polymers is necessary to develop advanced materials in a materials-by-design approach. Molecular dynamics (MD) simulations can provide tremendous insight into how the fine details of chemistry, molecular architecture, and microstructure affect many physical properties; however, they face well-known restrictions in their applicable temporal and spatial scales. These limitations have motivated the development of computationally-efficient, coarse-grained methods to investigate how microstructural details affect thermophysical properties. In this dissertation, I summarize my research work in structure-based coarse-graining methods to establish the link between molecular-scale structure and macroscopic properties of two different polymers. Systematically coarse-grained models were developed to study the viscoelastic stress response of polyurea, a copolymer that segregates into rigid and viscous phases, at time scales characteristic of blast and impact loading. With the application of appropriate scaling parameters, the coarse-grained models can predict viscoelastic properties with a speed up of 5-6 orders of magnitude relative to the atomistic MD models. Coarse-grained models of polyethylene were also created to investigate the thermomechanical material response under shock loading. As structure-based coarse-grained methods are generally not transferable to states different from which they were calibrated at, their applicability for modeling non-equilibrium processes such as shock and impact is highly limited. To address this problem, a new model is developed that incorporates many-body interactions and is calibrated across a range of different thermodynamic states using a least square minimization scheme. The new model is validated by comparing shock Hugoniot properties with atomistic and experimental data for polyethylene. Lastly, a high fidelity coarse-grained model of polyethylene was constructed that reproduces the joint-probability distributions of structural variables such as the distributions of bond lengths and bond angles between sequential coarse-grained sites along polymer chains. This new model accurately represents the structure of both the amorphous and crystal phases of polyethylene and enabling investigation of how polymer processing such as cold-drawing and bulk crystallization affect material structure at significantly larger time and length scales than traditional molecular simulations. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2016