Not available / text

Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1938. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed May 6, 2010) Includes bibliographical references (p. 42-44) and index (p. 45-47).

no abstract provided by author / Master of Science

This thesis aims to examine the issues involved in utilising digital images and assess whether image processing techniques can be used as a cost-effective method of reconstructing the image found in a deteriorated cellulose acetate negative. Negatives affected by the vinegar syndrome are found in large numbers within Australian institutions. This was confirmed by a survey (using a questionnaire) undertaken at the National Library of Australia in 2000. The survey also found that although these collections are large, and hence the level of deterioration variable, little could be done to restore any of the negatives once deterioration had begun. Storing negatives at low temperature and low relative humidity slows down the breakdown of cellulose acetate; however, it cannot reverse the process once it has commenced. Although removing the gelatine pellicular from the deteriorated cellulose acetate support (making the image easier to view) a possible method of restoration, this becomes unfeasible when dealing with a large collection. As a result, how to manage cellulose acetate negatives once they have deteriorated becomes problematic. Image-processing techniques used to digitally restore these negatives were examined via a series of case studies. These examinations were undertaken using two software packages-the Image Processing Tool kit (IPTK) and OPTIMAS. Deteriorated cellulose acetate negatives were scanned, then a number of program filters were applied to the digital image to determine whether disfiguring elements (referred to as channelling elements) resulting from the deteriorated support could be digitally removed. IPTK and OPTIMAS were not completely successful in removing the deteriorated elements from the digital version. The results highlighted that a number of issues relating to the use of digital technology needed to be addressed. These issues included knowledge of basic technical terms, an understanding of digital language, and how to include the use of digital technology into a long-term strategy for archiving a digitised collection. This thesis showed that issues relating to utilising digital systems could be addressed by implementing a preservation management plan. A preservation management plan can be used to incorporate the goals of digitising, the long-term issues of retaining digital files, ongoing access relating to the digital file, hardware and software, and the importance of having the relevant expertise when undertaking such a project. Due to the limitations of the printed hardcopy displaying features in a number of the images (figures) outlined in this thesis, a compact disk (CD) has been included with this submission and can be found at the end of this document.

Thesis (Ph. D.)--Institute of Paper Chemistry, 1940. / Includes bibliographical references (p. 96-97).

Orientador: Maria do Carmo Gonçalves / Tese (doutorado) - Universadade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-13T18:47:11Z (GMT). No. of bitstreams: 1 Romero_RafaelleBonzanini_D.pdf: 28876791 bytes, checksum: 2296e157df643bcd91224ad26360f6ce (MD5) Previous issue date: 2009 / Resumo: Nanocompósitos de biopolímeros com silicatos lamelares podem ser desenvolvidos para criar uma nova classe de materiais eco-friendly, podendo contribuir para aplicações inovadoras de polímeros. Esses materiais têm despertado grande interesse, devido principalmente à facilidade de obtenção, bem como às suas propriedades químicas, físicas e mecânicas. Neste trabalho foram preparados nanocompósitos de acetato de celulose pelos métodos de intercalação em solução e no estado fundido, onde os efeitos de diferentes solventes, de agentes modificadores da argila e de condições de processamento foram investigados nas suas propriedades estruturais, morfológicas, térmicas e mecânicas. No método de intercalação em solução, os resultados obtidos indicaram que a dispersão e delaminação da argila são alcançadas somente quando ocorreram interações favoráveis entre o solvente, a argila e o polímero. Neste caso, os nanocompósitos apresentaram melhores propriedades térmicas e dinâmico-mecânicas em relação ao acetato de celulose puro. No método de intercalação no estado fundido, os resultados obtidos evidenciaram a intercalação do acetato de celulose entre as lamelas da argila, promovida pela afinidade química favorável entre o polímero, o plastificante e a argila. Além disso, as estruturas intercaladas foram parcialmente delaminadas sob ação do cisalhamento imposto durante o processo de extrusão, resultando em nanocompósitos com partículas intercaladas e também esfoliadas. Devido a estas características, os nanocompósitos obtidos apresentaram propriedades mecânicas e de barreira superiores às apresentadas pelo acetato de celulose puro. Baseado nos dois métodos investigados neste trabalho, pode-se concluir que a escolha apropriada dos aditivos e das condições de preparação é extremamente importante para promover interações favoráveis entre as partículas de argila e o polímero, que por sua vez são necessárias para a desejada melhora nas propriedades finais desses materiais / Abstract: Nanocomposites of bio-based polymers with layered silicates can be used to create new eco-friendly materials, and can open ways towards the innovative applications of polymers. These materials are interesting, mainly due to their easy preparation, as well as their chemical, physical and mechanical properties. Cellulose acetate nanocomposites was prepared in this work by using solution and melt intercalation methods, where the effect of the different solvents, clay modified agents and processing conditions were investigated in terms of their structural, morphological, thermal and mechanical properties. The obtained results, in the solution intercalation method, showed that the dispersion and delamination of the clay were reached only when favorable interactions were promoted between the solvent, clay and polymer. In this case, the nanocomposites presented enhanced thermal and dynamic-mechanical properties in relation to the pure cellulose acetate. The results obtained in the melt intercalation method showed the intercalation of the cellulose acetate chains into the silicate platelets, which was promoted by the favorable chemical affinity between the polymer, plasticizer and clay. Apart from this, the intercalated structures were partially delaminated by the shearing imposed during the extrusion process, resulting in nanocomposites formed by intercalated as well as exfoliated clay particles. Due to these characteristics, the nanocomposites presented enhanced mechanical and barrier properties compared to pure cellulose acetate. Based on the two methods investigated in this work, it can be concluded that the appropriate choice of additives and preparation conditions of preparation is extremely important to promote favorable interactions between the clay particles and the polymer, that in turn are necessary for the desired enhancement in the final properties for these materials / Doutorado / Físico-Química / Doutor em Ciencias Quimicas

Orientadores: Lucia Helena Innocentini Mei, Marcos Akira dÁvila / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-19T17:34:43Z (GMT). No. of bitstreams: 1 Nista_SilviaVazGuerra_M.pdf: 12755531 bytes, checksum: ed049fb5fccf4416e7f0b8a0290222af (MD5) Previous issue date: 2012 / Resumo: Este projeto foi desenvolvido em duas fases, usando a tecnologia de eletrofiação. A primeira fase foi dedicada a obtenção de membranas eletrofiadas com acetato de celulose, as quais formaram nanofibras que foram carregadas com Sulfato de gentamicina, na segunda fase, para estudos da liberação controlada deste fármaco. Na primeira fase as membranas de nanofibras de Acetato de Celulose, chamadas de nanomembranas, foram produzidas utilizando-se quatro misturas de solventes (Acido Acético/Água (75:25 m/m), Acetona/Água (85:15 m/m), Dimetilacetamida (DMAc)/Acetona (1:2 m/m), Dimetilacetamida/Acetona/Água (32/63/5 m/m)). Usando a ferramenta de planejamento de experimentos (DOE), foram definidos os melhores parâmetros para preparação das membranas nanoestruturadas, em cada sistema de solvente. Três variáveis, sendo a distância entre a agulha e o coletor, a concentração de acetato de celulose na solução e a tensão aplicada, em dois níveis (alto e baixo), foram estudadas em cada sistema. As respostas avaliadas para obtenção da melhor condição, em cada caso, foram o diâmetro médio da fibra obtida e aspecto da membrana formada. Foi realizado também, no sistema de solvente Acido Acético/Água (70:30 m/m), um comparativo entre fiação horizontal, utilizando-se uma taxa de alimentação controlada por uma bomba de infusão, e um sistema vertical onde o fluxo era governado pela gravidade e viscosidade da solução. Um estudo da influencia da taxa de alimentação no diâmetro e aspecto da membrana também foi realizado. Todas as soluções foram avaliadas quanto a sua viscosidade, tensão superficial e condutividade elétrica. Nas soluções de cada sistema de solvente, que apresentaram a melhor condição de processabilidade e melhor membrana, foi realizada uma avaliação do comportamento reológico com a construção de uma curva de Viscosidade versus Taxa de cisalhamento. As melhores membranas obtidas para cada sistema de solvente foram submetidas a um teste de Citotoxicidade para confirmar a biocompatibilidade e sua independência com os resíduos dos solventes utilizados. Na segunda fase utilizaram-se as melhores condições obtidas para cada sistema de solvente e incorporou-se o fármaco Sulfato de Gentamicina em duas concentrações 6 e 60% em massa com base no acetato de celulose. Observou-se a influencia da concentração do fármaco no processo de eletrofiação, no aspecto da membrana formada bem como no diâmetro da nanofibra obtida. A melhor membrana obtida nesta etapa foi produzida a partir do sistema de solventes DMAc/Acetona/Água. As condições de processo utilizadas foram 1 ml/h de vazão, 10 cm de distância entre agulha-coletor e 15 kV de tensão e concentração de acetato de celulose de 15%. Este sistema apresentou-se como um processo bastante viável, não havendo alteração na qualidade da membrana e no processo com a variação da concentração do fármaco. À membrana obtida nestas condições, foi adicionado 50% do fármaco e realizado um teste de liberação com o objetivo de verificar o perfil de liberação do mesmo. Foi realizado um comparativo entre o perfil de liberação desta membrana com o de outras membranas preparadas por casting e com recobrimento de HPMC, Eudragit® L100 e nanofibra eletrofiada de acetato de celulose. O melhor perfil obtido, onde ocorreu uma redução no efeito burst, foi com a membrana revestida com nanofibra, onde foi obtido um ganho de liberação de 9 horas em relação às demais. A melhor membrana obtida também foi submetida a uma análise microbiológica, onde se verificou que o fármaco não perdeu suas propriedades com o processo de eletrofiação / Abstract: This project was developed in two phases, using the technology of electrospinning. The first phase was devoted to obtaining electrospun membranes with cellulose acetate, which formed nanofibers that were loaded with Gentamicin sulphate, in the second phase, for the studies of this drug release. In the first step, these membranes were composed of electrospun nanofibers made of cellulose acetate, here called nanomembranes, using four solvents mixtures (acetic acid/water (75:25 w/w) acetone/water (85:15 w/w), dimethylacetamide(DMAC)/acetone (1:2 w/w), DMAc/acetone/water (32/63/5 w/w). Using the tool for design of experiment (DOE), the best parameters for preparation of nanostructured membranes in each solvent system were fixed. Three variables, such as the distance between the needle and the collector, the concentration of cellulose acetate in solution and the applied voltage, in two levels (high and low), were used in each system. The responses evaluated to obtain the best condition, in each case, were the average diameter of the fiber obtained and the aspect of the membrane formed. In the solvent system formed by acetic acid/water (70:30 w/w), a comparison was carried out between horizontal electrospinning, using an infusion pump to control the feed rate, and a vertical system, whose flow was governed by both gravity and viscosity of the solution. A study of the influence of feed rate on the diameter and aspect of the membranes was done. The viscosity, surface tension and electrical conductivity of all solutions were evaluated. For each system of solvent used, the best parameters of processing ant the best membrane aspect obtained were the chosen for the studies of the rheological behavior of the system by plotting a curve of Viscosity versus Shear rate. The best membranes obtained, for each mixture of solvent used, were submitted to a cytotoxicity test to confirm their biocompatibility and if the residues of any solvent could influence on this test. In the second step of the project, the best conditions obtained for each solvent system were used to electrospun the membranes loaded with gentamicin sulfate in two concentrations, i.e. 6 and 60 wt%, based on cellulose acetate. We observed the influence of the drug concentration in the electrospinning process, as well as the aspect of the membrane formed and the diameters of the nanofibers formed. The best membranes obtained in this step were produced using the solvent system DMAC/acetone/water. The process conditions used were 1 ml/h flow rate, 10 cm distance between needle-collector, 15 kV voltage and 15% cellulose acetate concentration in the solution. This system proved to be a quite feasible process, with no change in the membrane aspect or in the process, for several drug's concentration. To the membrane obtained in these conditions, 50% of the drug was added and the profile of its delivery was observed. A comparison of the releasing profile was also done among this membrane and other membranes prepared by casting and by coating with HPMC, Eudragit ® L100 and electrospun nanofibers of cellulose acetate. The best delivery profile obtained was the membrane coated with nanofiber of acetate solution in DMAC/acetone/water since there was a reduction in the burst effect and a gain in the releasing of 9 hours over the others. The best membrane obtained was also submitted to a microbiological analysis, in which it was verified that the drug did not lose its function during the electrospinning process / Mestrado / Ciencia e Tecnologia de Materiais / Mestre em Engenharia Química

Orientadores: Maria Isabel Felisberti, Marco-Aurelio De Paoli / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-18T14:10:14Z (GMT). No. of bitstreams: 1 Gutierrez_MiguelChavez_D.pdf: 7288460 bytes, checksum: bbbd520c11973e6ce92e1852b824c208 (MD5) Previous issue date: 2011 / Resumo: Neste trabalho foram desenvolvidos biocompósitos baseados em acetato de celulose e fibras curtas de Curauá. Os compósitos foram preparados por extrusão em escala laboratorial e piloto, sendo estudada a influência do processamento, teor de fibras, teor e tipo de plastificante e tratamento das fibras, sobre as propriedades mecânicas e térmicas. As fibras foram tratadas com solução alcalina ou submetidas à extração com acetona. O tratamento das fibras com solução alcalina resultou em mudanças na rugosidade e do diâmetro das fibras, além da remoção parcial de hemicelulose e lignina. Já as fibras extraídas com acetona apresentaram principalmente uma diminuição do diâmetro. Biocompósitos reforçados com fibras tratadas apresentaram maior modulo elástico e maior condutividade térmica com relação aos compósitos reforçados com fibras não tratadas, sendo este efeito atribuído a uma melhor adesão interfacial. Dentre os plastificantes utilizados, o ftalato de dioctila (DOP) ou citrato de trietila (TEC), o DOP mostrou-se mais eficiente, causando uma diminuição mais acentuada da temperatura de transição vítrea (Tg) e do módulo elástico, resultando em materiais com maior resistência ao impacto em relação as formulações plastificadas com TEC. Os biocompósitos preparados em escala piloto apresentaram maior ganho do módulo elástico com relação à matriz plastificada e maior resistência ao impacto, que aqueles que foram preparados em escala laboratorial, associado principalmente a fibrilação e a diminuição da razão de aspecto das fibrilas. Devido a este fato, o modelo modificado da regra das misturas (ROM) mostrou-se mais adequado para prever o comportamento do módulo elástico dos biocompósitos preparados em escala piloto. A análise termogravimétrica mostrou que a presença das fibras não modifica o comportamento termo-oxidativo do acetato de celulose plastificado. Por último, biocompósitos de acetato de celulose plastificados com DOP apresentaram maior coeficiente de expansão térmica com relação às formulações com TEC, a temperaturas abaixo e acima da Tg. Acima da Tg, biocompósitos reforçados com fibras tratadas apresentaram maiores coeficientes de expansão térmica, devido a capacidade das fibras tratadas em sorver água / Abstract: In this work, biocomposites based on cellulose acetate and short Curaua fibers were prepared by extrusion in pilot and laboratory scale. The influence of processing method, content of fiber, content and type of plasticizer and treatment of the fibers were studied. The fibers were treated with alkali or extracted with acetone. Mercerization may result in partial hemicellulose and lignin extraction and decrease of the roughness and diameter of the fibers. Fiber s extracted with acetone had lower diameter. Biocomposites with treated fibers show higher Young modulus and lower thermal conductivity than composites with pristine fibers, due to better interfacial adhesion. Cellulose acetate was plasticized with dioctyl phthalate (DOP) or triethyl citrate (TEC). DOP is a better plasticizer for cellulose acetate, exhibiting lower glass transition (Tg), lower Young modulus and higher impact strength than formulations with TEC. Biocomposites prepared in pilot scale showed higher Young modulus with respect to the matrix and lower impact strength than composites prepared in laboratory scale, due to fibrilation and decrease in the aspect ratio. From this, the model of the modified rule of mixtures (ROM) was more efficient to predict the results of the Young modulus for composites prepared in pilot scale. In the thermogravimetric analysis, the Curaua fibers do not change the thermo-oxidative behavior of plasticized cellulose acetate. Cellulose acetate biocomposites with DOP showed higher thermal expansion coefficient than formulations with TEC, below and above Tg. Above Tg, biocomposites with treated fibers showed higher thermal expansion coefficients than biocomposites with pristine fibers, due to the ability of treated fibers to absorb water / Doutorado / Físico-Química / Doutor em Ciências

The fabrication of electrospun nanofibers has sparked great interest in both academia and industry owing to their unique properties, such as a high surface area to volume ratio, porosity, interconnected porous structure, or controllable fiber morphology. They are highly desired in numerous application areas such as filtration, biotechnology, and energy storage. Cellulose acetate is an ester of cellulose, one of the most abundant natural polymers, that is biodegradable, non-toxic, and has good stability. Electrospinning of cellulose acetate has received significant interest in a broad spectrum of applications, including membranes and air filters, drug-delivery systems, scaffolds for tissue engineering, sensors, and batteries. The electrospinning of cellulose acetate predominantly suffers from the use of toxic and hazardous solvents, which makes the final products less suitable for application in biosystems. In this work, the sustainable electrospinning of cellulose acetate has been shown using renewable-based green solvents, dimethyl carbonate, and cyclopentanone. A binary system consisting of these solvents has been applied. The addition of green salts and biosurfactants substantially improved the spinnability of the cellulose-based solutions. Altering the composition of the solvents allowed tuning of the fiber texture from highly porous to smooth fiber morphology. The thermal analysis revealed that the polymer’s thermal behavior had not been influenced by the salt in nanofibers. Incorporating additives into the polymer matrix resulted in enhanced mechanical properties of nanofibers. Uniform cellulose acetate-based porous nanofibers from green solvents and additives could be successfully fabricated, which has not been reported yet. Based on the reported advantageous properties of electrospun CA nanofibers, it may serve as a possible green and biodegradable porous support layer in thin-film composite membranes replacing the conventional fossil-derived polymeric membrane supports.

Organic solvent nanofiltration (OSN) is a membrane-based sustainable alternative to conventional separation techniques because it is non-thermal and energy-efficient. The fabrication of membranes usually includes fossil-based polymers and toxic solvents that present significant challenges. For example, its declining availability, concerns about its degradability and cross-contamination that involve toxicity risks. Nowadays, there is an increasing interest in the development of more sustainable membranes that maintain an optimum performance even in harsh solvents. The aim of my thesis research is to develop stable OSN membranes from cellulose acetate and explore the use of deacetylation reactions. The effect of the degree of acetylation on the membrane performance and stability in different organic solvents was investigated. The chemical composition and morphology were investigated using Fourier Transform Infrared (FTIR), Scanning Electron Microscope (SEM), and Atomic Force Microscopy (AFM). It was found that cellulose acetate membranes with less than 22% acetylation present a satisfactory solvent resistance and rejection in harsh solvents, such as DMF and acetone. In the performance tests were identified two main trends: one for polar protic solvents and one for polar aprotic solvents. This was attributed to their capacity to interact with the membrane via H-bond formation. The molecular weight cutoff (MWCO) was in the range of 735–325 g mol–1 in aprotic solvents and higher than 885 g mol–1 for polar protic solvents. The results found in this research can be translated into a reduce in costs, waste generated, energy required, and time employed in the fabrication of membranes. Also, it opens potential areas in the industry as it can be implemented in harsh solvent environments.