Thesis--University of California, Berkeley, 1959. / Includes bibliographical references (p. 81-84).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 105-111). Also available in electronic version.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Keith P. Johnston. Vita. Includes bibliographical references.

Thesis (Ph. D.)--Florida State University, 2006. / Advisor: Alan G. Marshall, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Sept. 21, 2006). Document formatted into pages; contains xxii, 198 pages. Includes bibliographical references.

The films formed by tetradecylamine (TDA) at the water-dodecane interface in the presence of hydrogen phosphate ions have been studied. Between pH 5 and 8, tetradecylammonium cations bind to hydrogen phosphate anions to form needle-shaped crystallites of tetradecylammonium hydrogen phosphate (TAHP). Fourier Transform Infrared Spectroscopy (FTIR) shows that these films consist of two tetradecylammonium cations and one hydrogen phosphate anion. Light microscopy and Small Angle Neutron Scattering (SANS) results show that these crystallites self-assemble into films with a hierarchical structure. On the molecular level, the TAHP has lamellar order. On a mesoscopic level, these lamellae assemble into needle-shaped crystallites with a size on the order 0.1-100 μm. These crystallites assemble into interfacial films with a range of morphologies; below pH 7 they form continuous sheets, at pH 8 they form lace-like networks. The films have both unusually high elastic shear moduli (G's ≈ 10 N/m) and a structure that can be directly imaged using light microscopy. Varying the structure of the films affects their rheology. The lace-like networks deform plastically when sheared, whilst the continuous sheets are highly brittle. The films are temperature-responsive: when the system is heated the film thins and its rheological moduli drop. The temperature response is caused by dissolution of the film into the bulk fluid phases. The TAHP film also stabilises water-in-oil emulsions. The rheological properties of the film are directly related to the stability of the TAHP-stabilised droplets: the droplets coalesce upon being heated, suggesting potential applications in controlled release of active molecules. TAHP and colloidal PMMA particles stabilise emulsions by compatible mechanisms, and can be used to synthesise ('patchy') droplets with an inhomogeneous particle coverage, and ('hairy') droplets, from which long, tendril-like aggregates extend. Finally, the temperature-responsive nature of TAHP is applied to the composite interfaces. As the droplets are heated the lipid film dissolves, and the PMMA particles become mobile at the interface. The electrostatic interactions between the particles lead to competition between the ordering that the electrostatics would favour, and the defect structure favoured by the topology of the spherical surface. I investigate the freezing transition on a spherical surface, and show the emergence of hexagonal order as particle density is increased.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2009. / This study investigated water-in-oil (WIG) super-concentrated emulsions used as pumpable explosives. The aqueous phase of the emulsions is a supersaturated nitrate salt solution (at room temperature), with a volume fraction usually greater than 0.8. Aqueous phase droplets are deformed by packing and contact with neighbouring droplets. Compounds of this kind are thermodynamically unstable and their instability is related to the coarsening of emulsions (droplet coalescence) and phase transition (crystallisation) in the dispersed phase. However, it was demonstrated that the dominating mechanism is slow crystallisation inside the supercooled droplets. The main goal of this thesis therefore concerned a phenomenological study of the dependence of type and concentration of surfactant, as well as the ageing processes, on the rheological properties of these emulsions. The bulk rheological measurements were carried out using a rotational dynamic rheometer MCR 300 (Paar Physica). Samples of different types of surfactant (Pibsa-MEA, Pibsa-UREA, Pibsa-IMIDE, SMO and SMO/Pibsa-MEA) and different concentrations of surfactants were studied. The results of the measurements include the flow and viscoelastic properties of the materials. The rheological parameters have been correlated with the kinetics of structural changes during ageing as a function of emulsion formulation content. The emulsions under study were non-Newtonian liquids. It was demonstrated that different surfactant types yield different interfacial properties. In fact, both the interfacial tension and the interfacial elastic modulus were found to decrease according to the sequence MEA-UREAMEAlSMG- IMIDE-SMG. It was established that the surfactant type and surfactant concentration affected the bulk rheological properties of explosive emulsions. Indeed, both the elastic modulus and the yield stress as function of surfactant type decreased in the following order: MEA-IMIDE-UREA-MEAlSMG, whereas they also decreased as the surfactant concentration increased. However the sensitivity of the rheological parameters to the type or concentration of surfactant was found to decrease as the droplet size increased. Moreover, the changes in rheological parameters were more strongly expressed than any changes in interfacial tension. This last finding is considered as rather important. It seems reasonable to assume that it provides proof of an active role of a surfactant not only as a compound responsible for the interfacial tension, but also creating additional sources of elasticity.

Orientadores: Rosiane Lopes da Cunha, Carolina Siqueira Franco Picone / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-24T19:15:34Z (GMT). No. of bitstreams: 1 Furtado_GuilhermedeFigueiredo_M.pdf: 18093423 bytes, checksum: b729daeeb37b89f139cadf453b74178b (MD5) Previous issue date: 2014 / Resumo: Este trabalho teve como objetivo estudar a desestabilização de emulsões visando desenvolver processos tecnológicos para a produção fermentativa de biocombustíveis. Os sistemas foram compostos por água deionizada, hexadecano e levedura comercial Saccharomyces cerevisiae. Para avaliar o efeito da levedura na estabilização das emulsões sua concentração foi variada de 0,75 a 22,11% (m/m). As leveduras foram caracterizadas quanto à composição química, hidrofobicidade superficial e densidade de carga. As emulsões obtidas foram submetidas a análises de estabilidade e composição química das fases, distribuição do tamanho das gotas, microscopia óptica, microscopia de fluorescência, densidade de carga, medidas reológicas e tensiometria. A separação do óleo foi realizada com diferentes processos físicos e químicos: centrifugação, alterações de temperatura e adição de diferentes agentes desemulsificantes. Como agentes desemulsificantes foram usados sais, polímeros catiônicos, alcoóis, ácidos, bases e nanopartículas magnéticas. Estes agentes foram adicionados em diferentes concentrações para averiguar sua influência na eficiência de separação do óleo, na distribuição de tamanho de gotas e potencial zeta das emulsões. As emulsões obtidas inicialmente, após um período de 24 horas de estabilização, apresentaram-se em três fases distintas: a fase superior ou creme, a fase intermediária e a fase de sedimentado. A fase creme das emulsões apresentou-se estável por um período de sete dias, indicando que os mecanismos responsáveis por sua estabilidade estavam associados à formação de compostos pela levedura, ao aumento da viscosidade, causado pelo empacotamento das gotas, e uma possível repulsão eletrostática entre as gotas. O mecanismo de estabilização por Pickering também foi considerado como relevante no início do processo. A maior parte dos processos de desestabilização foi baseada na interação eletrostática entre os componentes presentes na interface, e os compostos desemulsificantes adicionados. O uso de forças centrífugas, por um período de 2 horas, não foi suficiente para causar a separação total dos componentes da emulsão e as temperaturas utilizadas não reduziram a viscosidade a ponto de ocorrer a separação total dos componentes. A utilização de um álcool (butanol) levou a um índice de separação de óleo de 96%. A separação do óleo foi mais eficiente quando as estratégias adotadas de se reduzir a viscosidade mediante o aumento da temperatura, solubilizar o óleo em alcoóis com maior afinidade química e a formação de complexos eletrostáticos foram combinadas com aplicação de elevada força mecânica. Neste caso, a desestabilização da fase creme das emulsões utilizando extração alcoólica foi de 100%. No entanto após o processo de desemulsificação seria necessária uma etapa adicional para a separação e recuperação do solvente de forma a se obter o óleo puro. A utilização de nanopartículas magnéticas levou a um índice de separação de óleo de 96%, sendo considerada uma alternativa viável para a desestabilização deste tipo de emulsão / Abstract: This work aimed to study the destabilization of emulsions to develop technological processes for the fermentative production of biofuels. The systems were composed of deionized water, hexadecane and commercial yeast Saccharomyces cerevisiae. To evaluate the stability of the emulsions the yeast concentration was varied from 0.75 to 22.11 % (w/w). The yeasts were characterized for chemical composition, surface hydrophobicity and charge density. The emulsions obtained were analyzed for stability and chemical composition of the phases, droplet size distribution, optical microscopy, fluorescence microscopy, charge density, rheological measurements and tensiometry. The oil separation was performed with different physical and chemical processes: centrifugation, changes in temperature and addition of demulsifiers agents. Salts, cationic polymers, alcohols, acids, bases, and magnetic nanoparticles were used as demulsifiers. These agents were added at different concentrations to determine their influence on the efficiency of oil separation, droplet size distribution and zeta potential of the emulsions. The emulsions obtained after 24 hour of stabilization presented three distinct phases: the upper or cream phase, the intermediate phase and the sedimented phase. The cream phase of the emulsion was stable for seven days, indicating that the mechanisms responsible for its stability were associated with the formation of compounds by the yeast, the increase in viscosity caused by the packing of the droplets, and a possible electrostatic repulsion between the drops. Initially the mechanism of Pickering stabilization was also regarded as important in the process. Most destabilization processes was based on electrostatic interaction between the components present in the interface and the demulsifiers added. The use of centrifugal forces for 2 hours was insufficient to cause total separation of the components of the emulsion and the temperature used did not reduce the viscosity to the point of occurring total separation of the components. The use of an alcohol (butanol) led to an oil separation index of 96%. The oil separation was more effective when strategies adopted to reduce the viscosity by increasing the temperature, to solubilize the oil in alcohols with greater chemistry affinity and the formation of electrostatic complexes were combined with the application of high mechanical force. In this case, the destabilization of the cream phase of emulsions using alcohol extraction was 100%. However after the demulsification process would require an additional separation and recovery of the solvent to give the pure oil phase. The use of magnetic nanoparticles led to an oil separation index of 96 % and is considered a viable alternative to the destabilization of this type of emulsion / Mestrado / Engenharia de Alimentos / Mestre em Engenharia de Alimentos

Orientador: Daniel Barrera Arellano / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-25T11:28:26Z (GMT). No. of bitstreams: 1 Chaves_KamilaFerreira_M.pdf: 1834021 bytes, checksum: 17ab04d365f81e6b3faf3237da71b9f0 (MD5) Previous issue date: 2014 / Resumo: A redução do consumo de ácidos graxos saturados (AGS) na dieta, a fim de reduzir o risco de doenças cardiovasculares, tornou indispensável a busca por substitutos desse tipo de gordura, mediante novas alternativas tecnológicas, como a dos organogéis. O uso de estruturantes em sistemas lipídicos é visto como uma alternativa promissora, pois altera as propriedades físicas de óleos vegetais, sem que ocorram modificações químicas e aumento do teor de AGS, abrindo novas possibilidades para a produção de margarinas e spreads low sat e livres de ácidos graxos trans. O objetivo desse trabalho foi produzir margarinas utilizando a tecnologia de estruturação de óleos para reduzir a quantidade de AGS em comparação às margarinas comerciais convencionais. As matérias-primas, óleo de girassol alto oleico (OGAO), óleo de soja (OS), gordura interesterificada (GI), cera de candelilla (CC) e monoacilgliceróis (M), foram caracterizadas quanto a composição, qualidade e propriedades térmicas. O processo de elaboração das margarinas teste foi realizado em escala de bancada (1 kg), a fase lipídica foi fundida a 80ºC e misturada com a fase aquosa a uma temperatura de 60ºC, sob agitação de 300 rpm. O resfriamento até 30ºC ocorreu sob agitação a 37 rpm em uma sorveteira elétrica com parede de isolamento duplo, previamente resfriada em estufa B.O.D. a 5ºC. As margarinas comerciais avaliadas apresentaram composição de AGS entre 20,52 e 23,93% e teores de lipídios de 70 a 82%. A redução do teor de AGS foi calculada considerando a diferença da quantidade de AGS das margarinas teste em comparação com a média das margarinas comerciais. Foi possível notar através do planejamento experimental que quanto menores os teores de GI, CC e M nas formulações, maior a redução de AGS. As margarinas teste apresentaram melhor estabilidade da emulsão para as temperaturas avaliadas em comparação com as margarinas comerciais. Ocorreu maior exsudação de óleo nas margarinas comerciais em comparação às margarinas desenvolvidas conforme o planejamento experimental na temperatura de 35ºC por 48 horas. As margarinas testadas com OGAO e OS apresentaram menor valor na luminosidade (*L) em comparação às margarinas comerciais. A consistência e a espalhabilidade das margarinas testadas foram significativamente iguais a pelo menos 2/3 das margarinas comerciais avaliadas e a dureza foi estatisticamente igual para todas as margarinas testadas quando comparadas com as margarinas comerciais. Conclui-se que é possível produzir margarinas, mediante a tecnologia de estruturação de óleos, utilizando CC, M e GI como estruturantes, com redução do teor de AGS de 17,3 a 36,6% para as margarinas produzidas com OS e OGAO, respectivamente, em comparação com margarinas comerciais / Abstract: Reduce the consumption of saturated fatty acids (SFA) in the diet in order to reduce the risk of cardiovascular diseases, has made indispensable the search for substitutes for this kind of fat, through new technological alternatives, such as organogels. The use of structuring agents in lipid systems has been presented as a promising alternative, once that they change physical properties without any chemical modification or increase on the amount of SFA, which open new possibilities to the production of low sat and trans free margarines and spreads. The aim of this study was to produce margarines using oil structuring technology in order to reduce the amount of SFA compared to commercial margarines. Raw materials such as high oleic sunflower oil (HOSO), soybean oil (SO), interesterified fat (IF), candelilla wax (CW) and monoacylglycerols (M), were characterized due to their quality parameters, chemical composition and thermal properties. The processing of margarines were conducted in workbench scale (1kg per batch), the oil phase was melted, heating up to 80°C, and then mixed with an aqueous phase at 60°C, under controlled speed at 300 RPM. Cooling up to 30°C occurred under shear at 37 rpm using an electrical ice cream machine with a double wall isolated cube, previously cooled to 5°C. Commercial margarines with a SFA content between 20.52 and 23.93% and 70 to 82% amount of lipids were used as comparative standars. The reduction of SFA was calculated considering the amount of SFA on trial margarines and commercial comparative standards. It was possible to notice, through an experimental design, that smaller amounts of IF, CW and M on the formulations, resulted on reduction of SFA. Trial margarines presented better emulsion stability that commercial products. A higher oil exudation occurred for commercial margarines compared to the trial samples at 35°C for 48 hours. Tested margarines using HOSO and SO presents lower luminosity values (*L) when compared to commercial ones. Consistency and spreadability of trial margarines were statistically equal to, at least, 2/3 of the commercial margarines evaluated and hardness presented no statistical difference among all trial margarines when compared to commercial margarines. In conclusion, margarines produced by oil structuring technology using CW, M and IF as structuring agents, reduced the amount of SFA from 17.3 up to 36.6% in trial margarines with SO and HOSO, respectively when compared to commercial margarines / Mestrado / Tecnologia de Alimentos / Mestra em Tecnologia de Alimentos

Orientador: Elias Basile Tambourgi / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-22T23:37:11Z (GMT). No. of bitstreams: 1 Rodrigues_JacquelineRegodaSilva_D.pdf: 5156627 bytes, checksum: 01745397f1f98c7c763ca0b7f0bdbeb5 (MD5) Previous issue date: 2013 / Resumo: Nos processos de perfuração do petróleo, a emulsão gerada entre a água e o óleo deve ser quebrada com o uso de desemulsificantes, a fim de reduzir os problemas de corrosão em tubulações e equipamentos resultantes de impurezas presentes na água produzida; além disso, o excesso de água emulsionada no óleo cru aumenta os custos de transporte do óleo até as refinarias. Como consequência da desemulsificação tem-se a água produzida a qual muitas vezes é descartada junto com desemulsificante químico no meio ambiente sem nenhum tratamento; o que vem impulsionando a indústria de petróleo a substituir o uso destes por biodesemulsificantes. Apesar da alta eficiência na quebra de emulsão, os biodesemulsificantes apresentam um baixo rendimento e um elevado custo de produção quando comparados com os desemulsificantes químicos. Mesmo assim, as bactérias com capacidade desemulsificante representam uma solução inovadora na desemulsificação de emulsões de óleo em água ou água em óleo, devido à baixa toxicidade, biodegradabilidade e alta eficiência em condições não apropriadas. Diante deste fato despertou-se o interesse em minimizar o custo e, portanto no emprego de resíduos da agroindustrial como uma fonte alternativa de substrato para uma produção economicamente viável de biodesemulsificante. Os biodesemulsificantes produzidos por cepas de Alcaligenes sp. e Bacillus Subtillis empregando como fonte de carbono alternativa a manipueira que é um rejeito líquido rico em amido resultante do processo de prensagem da mandioca, representa uma solução promissora para a produção de biodemulsificantes; além de reduzir o descarte da manipueira no meio ambiente e o custo do bioproduto. Os resultados demonstraram que os biodesemulsificantes de ramnolipídeos e de sulfactinas são eficientes na quebra de emulsões do tipo W/O (água em óleo), além de serem menos tóxicos e mais biodegradáveis quando comparados com os desemulsificantes químicos, tornando-se um produto alternativo no mercado / Abstract: On the petroleum extraction process, the emulsion created between the water and the oil must be broken with the use of demulsifiers, in order to reduce the corrosion problems on pipes and equipment resultant of impurities present in the produced water; furthermore, the excess of emulsified water on the raw oil increases the oil transport costs to the refineries. As a result of the demulsification has been produced water which is often discarded along with the de-emulsifying chemical environment without any treatment; which has been pushing the petroleum industry to replace these by the use biodemulsifiers. Despite its high efficiency in emulsion breaking, the biodemulsifiers have a low yield and high production cost when compared with demulsifiers chemicals. Moreover, bacterias with demulsification capability represent an innovative solution on the demulsification of a W/O emulsion or an O/W emulsion, due to the low toxicity, biodegradability and high efficiency in extreme conditions. On this fact, arose the interest of minimizing costs and therefore the use of agro-industrial waste as alternative substrate for an economically viable production of biodemulsifier. The biodemulsifiers produced by strains of Alcaligenes sp. and Bacillus subtilis using as an alternative carbon font to cassava toxic, which is a liquid reject rich on starch resultant of the cassava pressing process, represents a promising solution to the production of demulsifiers; also reducing the discard of the cassava toxic on the environment and the cost of the . The results showed that the rhamnolipids and surfactins biodemulsifiers are efficient on the breaking of W/O type emulsions, in addition to being less toxic and more biodegradable when compared with the chemical biodemulsifiers, making it an alternate product on the market / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutora em Engenharia Quimica