Thesis (Ph. D.)--Ohio State University, 1982. / Includes bibliographical references (leaves 153-156). Available online via OhioLINK's ETD Center

Thesis--University of Michigan. / Includes bibliographical references.

Thesis--University of Michigan. / Includes bibliographical references.

No description available.

Thesis (Ph. D.)--Victoria University (Melbourne, Vic.), 2007. / Includes bibliographical references.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Vita. / Includes bibliographical references. / by Ronald James Salig. / M.S.

In 2007 the production of expanded polystyrene (EPS) in the world was over 4 million tonnes and is expected to grow at 6 percent per year. With the increased concern about environmental protection, alternative biodegradable materials from renewable resources are of interest. The present doctoral thesis work successfully demonstrates that starch-based foams with mechanical properties similar to EPS can be obtained by reinforcing the cell-walls in the foams with cellulose nanofibers (MFC). High cellulose nanofiber content nanocomposites with a highly plasticized (50/50) glycerol-amylopectin starch matrix are successfully prepared by solvent-casting due to the high compatibility between starch and MFC. At 70 wt% MFC, the nanocomposites show a remarkable combination of high tensile strength, modulus and strain to failure, and consequently very high work to fracture. The interesting combination of properties are due to good dispersion of nanofibers, the MFC network, nanofiber and matrix properties and favorable nanofiber-matrix interaction. The moisture sorption kinetics (30% RH) in glycerol plasticized and pure amylopectin film reinforced with cellulose nanofibers must be modeled using a moisture concentration-dependent diffusivity in most cases. The presence of cellulose nanofibers has a strong reducing effect on the moisture diffusivity. The decrease in zero-concentration diffusivity with increasing nanofiber content could be due to geometrical impedance, strong starch-MFC molecular interaction and constrained swelling due to the cellulose nanofiber network present. Novel biomimetic starch-based nanocomposite foams with MFC contents up to 40 wt% are successfully prepared by freeze-drying. The hierarchically structured nanocomposite foams show significant increase in mechanical properties in compression compared to neat starch foam. Still, better control of the cell structure could further improve the mechanical properties. The effect of cell wall composition, freeze-drying temperature and freezing temperature on the resulting cell structure are therefore investigated. The freeze-drying temperature is critical in order to avoid cell structure collapse. By changing the starch content, the cell size, anisotropy ratio and ratio between open and closed cells can be altered. A decrease in freezing temperature decreases the cell size and increases the anisotropy ratio. Finally, mechanical properties obtained in compression for a 30 wt% MFC foam prepared by freeze-drying demonstrates comparable properties (Young's modulus and yield strength) to expanded polystyrene at 50% RH and similar relative density. This is due to the reinforcing cellulose nanofiber network within the cell walls. / QC 20100913

Orientador: José de Assis Fonseca Faria / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-17T11:59:55Z (GMT). No. of bitstreams: 1 Castro_CliviaDanubiaPinhodaCosta_D.pdf: 9653916 bytes, checksum: 19a90b0b7e1f0c7ee22bb23a84e04c6c (MD5) Previous issue date: 2011 / Resumo: Dentre as fibras vegetais, a fibra de coco (Cocos nucifera L.) é uma das mais utilizadas no desenvolvimento de produtos ecológicos. Apesar da grande disponibilidade, devido ao consumo de água de coco, a fibra do coco verde apresenta menor aplicação do que a proveniente do coco maduro. Em embalagens secundárias e de transporte, as fontes celulósicas provenientes de árvores coníferas, apresentam intensa utilização, contudo, ainda não se constatou a utilização de fibras lignocelulósicas no setor de produtos hortícolas. Neste trabalho, buscou-se investigar o desempenho da fibra de coco verde como material de acolchoamento em sistemas de embalagens para duas frutas tropicais: mamão (Carica papaya L.) e manga (Mangifera Indica L.). A parte experimental consistiu na obtenção da fibra de coco, desenvolvimento de mantas de fibra, avaliação do desempenho mecânico como material de acolchoamento e avaliação quanto à vibração em teste de simulação de transporte. Em todos os experimentos, utilizou-se como comparativo, a palha de madeira proveniente de coníferas (Pinus eliottii). Para o mamão, a fibra de coco foi tão eficiente quanto à palha na prevenção de injúrias na polpa, mas não evitou abrasões na superfície. Observou-se também redução na taxa de respiração, sem interferência na perda de massa e na variação da cor da epiderme. Por outro lado, o sistema de embalagem com a fibra de coco foi mais eficiente para a manga do que para o mamão, pois a fibra protegeu o fruto contra injúrias internas. Tal comportamento contribuiu para os bons resultados de cor e de produção de gás carbônico. Assim, como material de acolchoamento, a fibra de coco verde apresentou desempenho mecânico comparável à classe de materiais celulósicos. Quanto à aplicabilidade, é possível proteger frutos tropicais, utilizando a fibra de coco verde no seu estado natural, sendo que a viabilidade poderá tornar-se mais expressiva com o desenvolvimento de bandejas ou mantas de fibra com aglutinantes naturais, tais como o gel de fécula e o látex de seringueira utilizados neste trabalho / Abstract: Among the vegetable fibers, the coir (Cocos nucifera L.) is one of the most used in the development of environmentally friendly products. Despite the large amounts, due to the consumption of coconut water, green coconut fiber has less application than that of the mature coconut. The cellulosic sources from coniferous trees have extensive use in secondary packaging and transportation; however, one has still not found its use of lignocellulosic fibers in the vegetable sector. In this study, it was sought to investigate the performance of green coconut fiber as a cushioning material in packaging systems from two tropical fruits: papaya (Carica papaya L.) and mango (Mangifera Indica L.). The experimental part consisted of obtaining the coconut fiber, development of webs of fiber and evaluating mechanical of the cushioning material on the vibration test to simulate transport. In all experiments, was used for comparison, the straw of wood from conifers (Pinus eliottii). For papaya, coconut fiber was as efficient as the straw in the prevention of damage in the pulp, but did not prevent abrasions on the surface. It was observed reductions in respiration rate, without interference in the weight loss and the variation in skin color. Moreover, the packaging system with coconut fiber was more efficient than the sleeve for papaya, as the fruit fiber protected against internal injuries. Such behavior has contributed to get good results of color and carbon dioxide production. Thus, as a cushioning material, the green coconut fiber had mechanical performance comparable to the class of cellulosic materials. In relation to applicability, it is possible to protect tropical fruits, using green coconut fiber in their natural state, and its viability may become more significant with the development of fiber mats or trays with natural binders such as starch gel and latex rubber used in this work / Doutorado / Engenharia de Alimentos / Doutor em Tecnologia de Alimentos