No description available.

Made available in DSpace on 2014-06-11T19:23:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-08-13Bitstream added on 2014-06-13T18:50:38Z : No. of bitstreams: 1 tavares_ll_me_sjrp.pdf: 1771695 bytes, checksum: ae4d9f94fd6915f2e3ae8fda69b172e0 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O propósito deste estudo foi verificar alterações na estrutura e em algumas propriedades funcionais de biofilmes produzidos com zeína adicionados de argilas modificadas. As argilas modificadas Cloisite® 15A e Cloisite® 30B foram adicionadas na solução filmogênica sob agitação nas proporções de 1, 2 e 4% em relação à massa de zeína e os filmes formados pelo método “casting”. Ácido oléico e glicerol foram utilizados como agentes plasticizantes. Para a caracterização da microestrutura dos biofilmes foram realizadas as análises de Microscopia Eletrônica de Varredura (MEV), Ótica (MO) e Espectroscopia no Infravermelho (FTIR) e as propriedades funcionais avaliadas foram Opacidade, Solubilidade e Permeabilidade ao Vapor d’Água. Por meio das imagens obtidas na MEV observou-se que os acréscimos de argilas nos filmes resultaram na formação de uma microestrutura heterogênea, ou seja, estrutura de fase separada chamada de microcompósito ou tactóide, uma vez que as argilas não dispersaram no filme, o que proporcionou a formação de agregados. No entanto, por meio das imagens obtidas com a MO, observou-se uma distribuição uniforme dos glóbulos de lipídeos na matriz protéica, para todos os filmes. Em concordância com a característica da microestrutura dos filmes elaborados identificados na MEV, o FTIR foi capaz de identificar número de onda referente às argilas, indicando que a mesma não estabeleceu estruturação com a proteína, confirmando a formação de uma estrutura de fase separada tipo tactoide. Todos os filmes elaborados apresentaram maior opacidade quando comparados com o polietileno em razão da presença de pigmentos carotenóides. Pequenas diferenças na espessura das amostras e a quantidade de argila adicionada não influenciaram na transparência dos materiais. Os testes... / The purpose of this study was to evaluate changes in the structure and some functional properties of zein edible films added with modified clays. The modified clays Cloisite® 15A and Cloisite® 30B were added in the solution under agitation in the proportions of 1, 2 and 4% based on the weigh of zein. The films were formed pouring the solution on a surface to dry by casting method. Oleic acid and glycerol were used as plasticizer agents. Analyses of Scanning Electron Microscopy (SEM), Optical Microscopy (MO) and Infrared Spectroscopy (FTIR) were performed to characterize the microstructure of biofilms. The functional properties evaluated were opacity, solubility and permeability of water vapor. SEM images showed that the additions of clays in the films resulted in the formation of a heterogeneous microstructure, i.e. the phase separated structure called microcomposite or tactoids, since the clays were not dispersed in the film, which forms points of aggregates. However, the images obtained with MO showed an even distribution of lipids globules in the protein matrix, for all films. In agreement with the characteristic of the microstructure of the films showed by SEM, FTIR analyses pointed out the absence of wave number related to the clays, indicating that it was not established a really binding of the clays with the protein molecule. This confirms the formation of a material with phase separated, tactoid type. All the films prepared showed higher opacity when compared with polyethylene because of the presence of carotenoid pigments. Little differences in thickness of the samples and the amount of clay added did not influence the transparency of materials. Statistical mean tests of water solubility of the samples showed no differences among those films added with clay and the control. Water... (Complete abstract click electronic access below)

Orientador: José Francisco Lopes Filho / Banca: Elisângela Corradini / Banca: José Antônio Gomes Vieira / Resumo: O propósito deste estudo foi verificar alterações na estrutura e em algumas propriedades funcionais de biofilmes produzidos com zeína adicionados de argilas modificadas. As argilas modificadas Cloisite® 15A e Cloisite® 30B foram adicionadas na solução filmogênica sob agitação nas proporções de 1, 2 e 4% em relação à massa de zeína e os filmes formados pelo método "casting". Ácido oléico e glicerol foram utilizados como agentes plasticizantes. Para a caracterização da microestrutura dos biofilmes foram realizadas as análises de Microscopia Eletrônica de Varredura (MEV), Ótica (MO) e Espectroscopia no Infravermelho (FTIR) e as propriedades funcionais avaliadas foram Opacidade, Solubilidade e Permeabilidade ao Vapor d'Água. Por meio das imagens obtidas na MEV observou-se que os acréscimos de argilas nos filmes resultaram na formação de uma microestrutura heterogênea, ou seja, estrutura de fase separada chamada de microcompósito ou tactóide, uma vez que as argilas não dispersaram no filme, o que proporcionou a formação de agregados. No entanto, por meio das imagens obtidas com a MO, observou-se uma distribuição uniforme dos glóbulos de lipídeos na matriz protéica, para todos os filmes. Em concordância com a característica da microestrutura dos filmes elaborados identificados na MEV, o FTIR foi capaz de identificar número de onda referente às argilas, indicando que a mesma não estabeleceu estruturação com a proteína, confirmando a formação de uma estrutura de fase separada tipo tactoide. Todos os filmes elaborados apresentaram maior opacidade quando comparados com o polietileno em razão da presença de pigmentos carotenóides. Pequenas diferenças na espessura das amostras e a quantidade de argila adicionada não influenciaram na transparência dos materiais. Os testes... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The purpose of this study was to evaluate changes in the structure and some functional properties of zein edible films added with modified clays. The modified clays Cloisite® 15A and Cloisite® 30B were added in the solution under agitation in the proportions of 1, 2 and 4% based on the weigh of zein. The films were formed pouring the solution on a surface to dry by casting method. Oleic acid and glycerol were used as plasticizer agents. Analyses of Scanning Electron Microscopy (SEM), Optical Microscopy (MO) and Infrared Spectroscopy (FTIR) were performed to characterize the microstructure of biofilms. The functional properties evaluated were opacity, solubility and permeability of water vapor. SEM images showed that the additions of clays in the films resulted in the formation of a heterogeneous microstructure, i.e. the phase separated structure called microcomposite or tactoids, since the clays were not dispersed in the film, which forms points of aggregates. However, the images obtained with MO showed an even distribution of lipids globules in the protein matrix, for all films. In agreement with the characteristic of the microstructure of the films showed by SEM, FTIR analyses pointed out the absence of wave number related to the clays, indicating that it was not established a really binding of the clays with the protein molecule. This confirms the formation of a material with phase separated, tactoid type. All the films prepared showed higher opacity when compared with polyethylene because of the presence of carotenoid pigments. Little differences in thickness of the samples and the amount of clay added did not influence the transparency of materials. Statistical mean tests of water solubility of the samples showed no differences among those films added with clay and the control. Water... (Complete abstract click electronic access below) / Mestre

One portion of this work was concerned with injection molding pregenerated microcomposites composed primarily of poly(ethylene terephthalate) (PET) as the matrix and HX1000 as the thermotropic liquid crystalline polymer (TLCP). Several factors were examined to maximize the mechanical properties of these composites, including injection molding temperature, matrix viscosity, and nozzle tip exit diameter. In addition, concentrated strands of HX1000/PET (50/50 wt%) were diluted using both an injection molding grade of PET and an injection molding grade of PBT. From this work, it was determined that the best mechanical properties were produced when the microcomposites were processed at the lowest injection molding temperatures, diluted with PBT, and injection molded using a large nozzle tip exit diameter. The pregenerated microcomposite properties were compared against theoretical predictions as well as glass-filled PET. It was found that the pregenerated microcomposites had tensile moduli of approximately 70% of theoretical expectations in the machine direction. Additionally, the comparisons against glass-filled PET revealed that at the same weight fraction of reinforcement, the pregenerated microcomposites had lower properties. Still, the composites were found to have smoother surfaces than glass-filled PET and at temperatures up to 150° C the storage and loss moduli of the pregenerated microcomposites were similar to those of glass filled PET. It was concluded that if the theoretically expected levels of reinforcement could be attained, the pregenerated microcomposites processing scheme would be a viable method of producing light weight, wholly thermoplastic composites with smoother surfaces than are obtained with glass reinforcement. An additional focus of this research was to evaluate the ability to modify the crystallization behavior of a high melting TLCP (HX6000, Tm = 332° C) with a lower melting TLCP (HX8000, Tm = 272°C). It was found that it was possible to tailor the crystallization behavior of these TLCP/TLCP blends by varying the weight fraction of each component, as determined by rheological cooling scans and differential scanning calorimetric cooling tests. Based on the analysis of these TLCPs at the maximum injection molding temperature of 360° C, it was speculated that they had reacted with one another. / Ph. D.

The scope of this research entailed the synthesis of novel polyorganosiloxanes with pendent phosphine, phosphine oxide, nitrile and carboxylic acid moieties. Such polysiloxanes were prepared with controlled concentrations of both the polar moieties and hydrido or vinyl pendent crosslinkable sites to afford precursor materials for well-defined networks. The intention was to generate stable microcomposite dispersions with very high concentrations of polar thermally conductive fillers. Lightly crosslinked elastomeric networks with controlled amounts of polar moieties were prepared via a hydrosilation curing mechanism. High concentrations of thermally conductive micro-fillers were dispersed throughout the resins and the microcomposites were investigated as thermally conductive adhesives. Random polysiloxane copolymers containing controlled number average molecular weights (Mns) and compositions with systematically varied concentrations of hydridomethylsiloxy- or vinylmethylsiloxy- units were prepared via ring-opening equilibrations of cyclosiloxane tetramers. These precursors were functionalized with precise concentrations of polar pendent moieties via hydrosilation (nitrile) or free radical addition reactions (phosphine and carboxylic acids). Valuable additions to the family of polysiloxanes were prepared by oxidizing the phosphine moieties to form phosphine oxide containing polysiloxanes. Defined concentrations of residual hydrido- or vinyl- reactive sites were crosslinked via hydrosilation to yield elastomeric adhesives. Specific interactions between the nitrile and phosphine oxide substituted polysiloxanes and the acidic proton of chloroform were shown using 1H NMR. The magnitude of the shift for the deshielded chloroform proton increased with the degree of hydrogen bonding, and was larger for the phosphine oxide species. The polar polysiloxane resins were filled with high concentrations of thermally conductive fillers including silica-coated AlN, Al spheres, BN and Ag flake, then hydrosilated to form microcomposite networks. Microcomposite adhesive strengths, thermal properties (glass transition temperature (Tg) and high temperature stability), and thermal conductivities were studied. An unfilled polysiloxane network containing only 15 mole percent phosphine oxide exhibited a dramatic improvement (46 N/m) in adhesive strength to Al adherends relative to a control polydimethylsiloxane network (2.5 N/m). Importantly, stable polysiloxane micro-dispersions were obtained with up to 67 volume percent (86 weight percent) silica-coated AlN. TEM data confirmed the dispersion homogeneity and XPS demonstrated that the particle surfaces were well-coated with the functionalized polysiloxanes. A microcomposite comprised of 67 volume percent silica-coated AlN and a polysiloxane containing only 9 molar percent nitrile groups had a thermal conductivity of 1.42 W/mK. The glass transition temperatures of the microcomposites were controlled by the amounts of polar functional moieties on the resins and the network crosslink densities. All of the microcomposites exhibited Tgs lower than -44°C and the materials remained stable in dynamic TGA measurements to approximately 400°C in both air and nitrogen. / Ph. D.

The presented work deals with preparation of test samples filled microparticles of mica and nanoparticles of silicon dioxide (SiO2). Monitors the impact of climatic conditions and filler on electrical properties of composite materials. Electrical properties of composite materials are measured by dielectric relaxation spectroscopy. Test samples influence of epoxide resin TSA 220S and polyester resin DOLPHON XL 2102. Varnishes are modified with different weight percentage of nanoparticles of silicon dioxide, or micronized mica. The results of this project are frequency dependencies of parts of complex permittivity and their evaluation.