Orientador: Maria do Carmo Gonçalves / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-05T15:56:25Z (GMT). No. of bitstreams: 1 Segatelli_MarianaGava_M.pdf: 3623345 bytes, checksum: 223789f87f6234b864c485f4c771efa2 (MD5) Previous issue date: 2005 / Resumo: O objetivo principal deste trabalho foi avaliar a incorporação de fibras curtas de sílica (FS) e da borracha etileno-propileno-dieno funcionalizada com anidrido maleico (EPDM-g-AM) em polimérica de poliamida 6 (PA 6). A fibra utilizada como carga é um produto natural constituído de sílica amorfa proveniente da fossilização de animais multicelulares. Com a finalidade de promover a melhor adesão interfacial entre a fibra e a matriz polimérica, as fibras foram modificadas com aminopropiltrietoxissilano (APTS), um agente de acoplamento. Os materiais foram preparados em extrusoras monorosca e duplarosca e, submetidos a ensaios mecânicos de tração, flexão e de impacto Izod. Foram também avaliadas as características térmicas e morfológicas desses materiais. As fibras de sílica não alteraram a estabilidade térmica da PA 6 e apresentaram eficiência de reforço, dentro do intervalo de composição estudado; entretanto, o alongamento na ruptura foi comprometido. A resistência ao impacto do polímero não variou significativamente com a incorporação de FS. Por outro lado, o tipo de extrusora utilizada para processamento alterou a cristalinidade da PA 6 e, conseqüentemente, as propriedades mecânicas nos compósitos binários de PA 6/FS. A modificação da superfície da fibra com APTS não foi adequada para melhorar as propriedades mecânicas, no entanto, a análise da microestrutura dos compósitos obtidos indicou adesão entre as fases. Em relação às blendas de PA 6/EPDM-g-AM, o tamanho médio de partícula da fase dispersa promoveu um efeito de tenacificação da PA 6. Os compósitos ternários de PA 6 contendo 20% de EPDM-g-AM e proporções diferentes de FS (5 a 20%) apresentaram redução na resistência ao impacto quando pequenas quantidades de FS foram adicionadas. Apesar da redução no valor desta propriedade, os compósitos obtidos exibiram boa tenacidade. Desta forma, a combinação de fibras curtas de sílica e borracha de EPDM-g-AM em poliamida 6 permitiu recuperar parcialmente a rigidez e a resistência ao impacto, que são comprometidas quando esses aditivos são utilizados separadamente. / Abstract: The main goal of this work was to evaluate the incorporation of short silica fibers (SF) and ethylene-propylene-diene rubber, functionalized with maleic anhydride (EPDM-g-MA), in a polyamide 6 (PA 6) matrix. The fiber used as filler is a natural product made up of amorphous silica from the fossilization of multicelular animals. In order to promote a better interfacial adhesion between the fiber and the polymeric matrix, fibers were modified with the aminopropyltriethoxysilane (APTS) coupling agent. The materials were prepared in single and twin-screw extruders for tensile, flexural and Izod impact mechanical tests. The mechanical, morphological and thermal properties of these materials were evaluated. Silica fibers did not change the thermal stability of the polymer and presented efficiency for reinforcement. However, the elongation at break was impaired. The impact strength of the polymer did not change significantly with the SF content. On the other hand, the type of extruder used for processing changed the mechanical properties and the crystallinity of PA 6 in the PA 6/SF binary composites. The fiber surface modification with APTS was not effective, as verified by the decrease of the mechanical properties. The morphology of composites showed adhesion between the phases. Taking into account the PA 6/EPDM-g-MA blends, the average size of dispersed phase, associated to impact strength in the 20% EPDM-g-MA composition promoted a toughening effect of the blends. Ternary PA 6 composites containing 20% EPDM-g-MA and different SF amounts (5-20%) presented tendency towards the reduction of the impact strength when small SF amounts were added. In spite of the reduction in the value of this mechanical property, the composites obtained exhibited good toughness. Thus, combining short silica fibers and EPDM-g-MA rubber with polyamide 6, the stiffness and the impact strength, that are impaired when these additives are separately used, were partially recovered. / Mestrado / Físico-Química / Mestre em Química

Orientadores: Carlos Kenichi Suzuki, Jacinta Enzweiler / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-24T12:58:32Z (GMT). No. of bitstreams: 1 Santos_MuriloFerreiraMarquesdos_M.pdf: 35876462 bytes, checksum: 9ccb2d6d6d03821c52795bf16da4325e (MD5) Previous issue date: 2014 / Resumo: Este trabalho foi conduzido com base em avaliar o potencial de jazidas de quartzo localizadas no Brasil para a utilização na fabricação de sílica vítrea para as indústrias de alta tecnologia (principalmente focando a manufatura de utensílios para a purificação e processamento de silício e de vidro óptico transparente no UV). As jazidas foram escolhidas conforme sua importância econômica no passado, seus níveis de produção, sua pureza química e a disponibilidade de minério. Elas foram avaliadas quanto à sua geologia, composição química (pela técnica de ICP-MS) e comportamento quando submetidas à fusão em sílica vítrea. Para esta fusão duas técnicas foram utilizadas, a técnica de Verneuil e a fusão em plasma pulsado (Spark Plasma Sintering). Os vidros fundidos com o material de cada jazida foram caracterizados quanto à transmitância óptica no visível e no UV. O trabalho também buscou identificar qual seria a melhor maneira de processar industrialmente o mineral proveniente de cada jazida. Os resultados obtidos mostram que várias jazidas são capazes de produzir vidros de alta qualidade, em especial aqueles provenientes de amostras da formação Serra de Santa Helena, localizada no norte do Estado de Minas Gerais e de Brotas de Macaúbas, no Estado da Bahia. Outras jazidas localizadas no Estado da Bahia também se mostraram alternativas economicamente viáveis / Abstract: This work aimed to evaluate the use of Brazilian quartz in the manufacture of silica glass for high tech industries (specially focused in the production of quartz crucibles for the high purity silicon industry and in the production of optical glass transparent to UV radiation). The mines which were studied here were selected according to its economic importance in the past, its production levels, its chemical purity and the amount of mineral contained in it. All mines were evaluated according to its geology, its chemistry (using the ICP-MS technique), and its behavior during fusion. In order to conduct this fusion, two different fusion techniques were used: Verneuil method, for flame fusion, and Spark Plasma Sintering (SPS) for electrical fusion. After fusion, each glass was evaluated according to its optical transmittance. It was also proposed some ways of industrially processing the minerals in order to obtain a better powder for fusion. Obtained results show that Brazilian mines are highly capable of producing good quality glasses using simple processing methods. The work emphasize the quality of the minerals original from the Santa Helena Formation, in northern Minas Gerais State, and from Brotas de Macaúbas, in the State of Bahia. Other minerals from the state of Bahia might also be a viable alternative / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

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Three alkyldihydrochlorosilanes were synthesized; ethyldihydrochlorosilane, octyldihydrochlorosilane and octadecyldihydrosilane. Ethyldihydrochlorosilane was produced by the reaction of ethylsilane with mercuric chloride and the other two chlorosilanes were produced by the reaction of the alkyl Grignard reagent with dichlorosilane. Each alkyldihydrochlorosilane was reacted with porous silica in an attempt to discover the extent of reaction or the highest surface concentration of bonded groups attainable. The reaction between these alkydihydrochlorosilanes and porous silica was compared to the reaction between silica and the analogous alkyldimethylchlorosilane. The rate of reaction of both type of chlorosilane was found to be essentially the same. The maximum surface concentration of bonded surface groups attainable by alkyldihydrochlorosilanes was found to be approximately 1.3 #moles/m² greater than that attainable by alkyldimethylchlorosilanes. This increased surface coverage seemed to depend very little on the chain length of the alkyl group and was attributed to the decrease in steric hindrance of the bonding silicon atom of the silane. Surface bound silyl hydrides could be oxidized selectively and sequentially to form silane silanols. Surface silanes also appeared to reduce chloroplatinic acid, but were not observed to add efficiently to olefins. The chromatographic properties of silica modified with alkyldihydrochlorosilanes were compared to those of equivalent silicas modified with alkyldimethylchlorosilanes and alkyltrichlorosilanes before and after the surface silanes were oxidized. Both normal and reversed-phase liquid chromatographic studies were conducted. In general, it was found that alkyldihydrochlorosilanes yielded the most polar modified silicas. This greater surface polarity was attributed to an increase in the activity of water in the near surface region of the bonded phase.

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No description available.

The field of mesoporous materials has been expanding rapidly in recent years, and has come to include a wide variety of different types of materials from organic to inorganic, as well as hybrid materials that encompass both worlds. The following account explores one type of mesoporous materials, specifically those consisting of silica with an attached organic group that have come to be known as periodic mesoporous organosilicas (PMOs). Much of the work here involves incorporating new types of organic groups into a mesoporous framework for the purpose of adding a useful functionality, either chemical or physical, to the material. Firstly it is shown that a borazine moiety can be successfully incorporated into a mesoporous material with a very high loading. It was further shown that once incorporated into the material many of the borazine moieties are available for further chemical reactions with acids and transition metals. Next, a new class of materials termed hybrid periodic mesoporous organosilicas (HPMOs) was developed that was able to circumvent many of the problems associated with PMO self-assembly. Now, using very simple techniques, virtually any type of silsesquioxane can be incorporated into a PMO, and the organic group can be specifically at the surface of the pores, thereby maximizing its accessibility. And finally, a PMO is made that incorporates buckyballs, and it is shown that, given the right synthetic conditions, the buckyballs are homogeneously distributed throughout the material.

Faculty of Science School of Geography,Achaeology and Enviromental Studies 9905929t thodgskiss@yahoo.com / This study was stimulated by questions that arose on the Middle Stone Age (MSA) tools from Sibudu cave, KwaZulu-Natal, South Africa. Many stone tools were found to have ochre traces or ochre plant resin traces on their proximal ends, as well as bending fractures on their laterals caused by hafting. This placement of ochre is unusual because it would be expected that ochre would be found on the working edges of the tools if they had been used to prepare ochre. A possible explanation is that the ochre is part of the hafting process and that ochre was used as an aggregate in the adhesive that held the stone tool to the haft. The question this research aims to answer is why ochre was used as an aggregate in plant resin instead of other easily acquirable substances, such as sand or ash. I have experimented with a variety of aggregates and then performed various activities with the hafted tools to test the strength and effectiveness of the different adhesive recipes. The chemical and physical properties of the ingredients used in the adhesives are also explored, together with principles of geological cementation and the methods involved in the creation of industrial concrete. Results of my replications are varied and they show that uncontrollable variables influence the resultant adhesive quality. Results contribute to understanding the uses and implications of the ochre on the MSA sites, and illuminate that people living in the MSA had an understanding of the best physical and chemical properties needed in adhesives, even though they could not have had an understanding of attributes like mineralogy and pH.

A sílica obtida da queima de casca de arroz foi convertida nas fases α e β. A estabilização da fase β foi obtida pela introdução de alumínio e cálcio na rede de sílica, 10001100 °C, na proporção CaO:2Al2O3:38SiO2. Foi observado que a transição de fase α→β da cristobalita α tem sua temperatura de transição reduzida de 175°C bem como sua entalpia de transição, de 16,0 J/g para 7,0 J/g. Esse efeito é causado pela introdução de íon K+, presente na casca de arroz, na estrutura da sílica. O processamento empregado nessa conversão usa equipamentos normalmente encontrados em empresas de cerâmica tradicional moinho, atomizador, prensa e forno / Silica generated from burned rice shells has been converted to the β and &#945 phases of cristobalite. The β phase stabilization was acomplished by instilling aluminum and calcium into the silica structure, at 1000-1100 °C, in the following proportion CaO:2Al2O3:38SiO2. The phase transition α→β of the α-cristobalite has a lower transition temperature, as compared with cristobalite made from pure silica, from 270°C to 170°C. Also the transition entalphy was reduced from 16,0 J/g to 7,0 J/g. These changes were attributed to the K+ ion present in the silica structure of the burned silica. The process used in this convertion makes use of standard equipments, regularly used in ceramic producing companies mill, spray dryer, furnaces, and press.

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