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[pt] Hidratos de gás natural são sólidos cristalinos, formados pela associação de moléculas de água a certos hidrocarbonetos leves, sob condições adequadas de pressão e temperatura. No cenário de produção de petróleo offshore, sua ocorrência é motivo de preocupação constante para a indústria de petróleo, pois podem resultar em bloqueios das linhas submarinas e interrupção completa do fluxo. Os custos de prevenção, no entanto, têm se tornado proibitivos, forçando uma mudança conceitual em projetos e privilegiando métodos de gerenciamento desse risco. Dentro dessa estratégia, uma vertente promissora é a avaliação das propriedades reológicas de suspensões de hidrato: seu conhecimento pleno pode determinar as condições em que a formação de hidratos no sistema submarino não vai resultar em bloqueio, constituindo-se em ferramenta valiosa na análise de risco de diversas atividades. O presente trabalho se insere nesse esforço, empregando uma emulsão combinada a ciclopentano (agente formador de hidratos à pressão atmosférica) e examinando diferentes metodologias. Para cumprir esse objetivo, estudou-se o comportamento reológico de emulsões água em óleo, com e sem ciclopentano, sob condições de formação de hidratos, submetidas a ensaios rotacionais e oscilatórios. A resposta do sistema a variações em parâmetros térmicos (temperatura mínima e taxa de resfriamento) e hidrodinâmicos (cisalhamento) também foi brevemente investigada. / [en] Hydrates of natural gases are crystalline solids, composed of water and light hydrocarbon molecules that assemble in special structures under certain conditions of pressure and temperature. For most offshore production facilities, it is a major concern for the oil and gas industry, given that it can lead to a full blockage of subsea and a complete stop of petroleum flow. However, avoidance costs have grown too high, so the industry began shifting towards a risk management methodology. Within this strategy, a promising field is the evaluation of rheological properties of hydrate slurries: its full understanding can help predicting if hydrates formation will lead to a blockage, becoming a valuable tool in risk assessment of many activities. The present work is a part of this effort, employing an emulsion combined with cyclopentane (known hydrate former at atmospheric pressure) to evaluate different methods. In order to fulfill this objective, the rheological behavior of water-in-oil emulsion, with and without cyclopentane, was studied in rotational and oscillatory tests, under hydrate forming conditions. The system response to changes in thermal (minimum temperature and cooling rate) and hydrodynamic (shear) parameters was also briefly investigated.

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Thesis: M.S., Massachusetts Institute of Technology, Department of Chemical Engineering, 1980 / Includes bibliographical references. / by Ravinder Kumar Oswal. / M.S. / M.S. Massachusetts Institute of Technology, Department of Chemical Engineering

Paxymer AB is a company that manufactures and sells flame retardants for plastics, based on their patented technology. The flame retardants are often sold as a master-batch that the customers mix into their own plastic products. Paxymer has two master-batches with the exact same formulation, but are produced with different temperature profiles. The high temperature extrusion process produces pellets with good properties whereas the low temperature process do not. The aim of this study was to define what rheological properties are important in the extrusion process, and how they can be correlated to the pellet quality. The aim was also to predict the processing parameters for the low temperature extrusion process to improve the pellet quality. The rheological behavior of the two master-batches was investigated through analysis of the batches, as well as their additional components, in the rheometer. According to the results the viscosity of the melt is very temperature dependent, and were found to be significantly lower for the high temperature process. My studies show that the poor pellet quality in the low temperature process is most likely due to the high melt viscosity, which leads to poor mixing of the components. To get equal melt viscosity in the low temperature process as in the high temperature process, I found that the screw speed and feed rate in the extruder needs to be increased. According to my analysis the desired screw speed should be approximately 500 rpm if the temperature was increased with 10°C. To get the right viscosity at the die exit, the feed rate would need to be 20 kg/h. / Paxymer är ett företag som tillverkar och säljer flamskyddsmedel för plaster, baserad på deras patenterade teknik. Flamskyddsmedlet säljs oftast som en master-batch vilket kunderna blandar ner i deras egna plastmaterial. Paxymer har två master-batches med samma innehåll men som är tillverkade med olika temperaturprofiler. Tillverkningsprocessen med högre temperaturprofil producerar pellets med hög kvalitet och processen med lägre temperaturprofil gör inte det. Syftet med den här studien var att ta reda på vilka reologiska egenskaper som är betydande för framställningen av pellets med god kvalitet. Ett ytterligare syfte med projektet var att förutsäga extruderingsparametrar för processen med lägre temperatur för att uppnå en bättre kvalitet. De reologiska egenskaperna för båda master-batcherna och deras innehållande komponenter analyserades i en reometer. Enligt mina resultat så är plastsmältans viskositet väldigt temperaturberoende och visade sig därför vara betydligt lägre vid extruderingsprocessen med högre temperaturprofil. Den låga produktkvaliteten från processen med låg temperaturprofil beror sannolikt på att smältans viskositet var för hög, vilket leder till sämre blandning av komponenterna. För att få samma viskositet på smältan vid den lägre temperaturen i extrudern, som vid den högre temperaturen, så måste hastigheten på skruven samt inmatningshastigheten ökas. Enligt mina analyser så måste hastigheten på skruven ökas till 500 rpm om temperaturen även höjs med 10°C. För att få rätt viskositet i matrishålen så måste inmatningshastigheten öka till 20 kg/h.

Yes / Poloxamers or Pluronics®-based nanogels are one of the most used matrices for developing delivery systems. Due to their thermoresponsive and flexible mechanical properties, they allowed the incorporation of several molecules including drugs, biomacromolecules, lipid-derivatives, polymers, and metallic, polymeric, or lipid nanocarriers. The thermogelling mechanism is driven by micelles formation and their self-assembly as phase organizations (lamellar, hexagonal, cubic) in response to microenvironmental conditions such as temperature, osmolarity, and additives incorporated. Then, different biophysical techniques have been used for investigating those structural transitions from the mechanisms to the preferential component’s orientation and organization. Since the design of PL-based pharmaceutical formulations is driven by the choice of the polymer type, considering its physico-chemical properties, it is also relevant to highlight that factors inherent to the polymeric matrix can be strongly influenced by the presence of additives and how they are able to determine the nanogels biopharmaceuticals properties such as bioadhesion, drug loading, surface interaction behavior, dissolution, and release rate control. In this review, we discuss the general applicability of three of the main biophysical techniques used to characterize those systems, scattering techniques (small-angle X-ray and neutron scattering), rheology and Fourier transform infrared absorption spectroscopy (FTIR), connecting their supramolecular structure and insights for formulating effective therapeutic delivery systems. / The Sao Paulo Research Foundation - FAPESP (Grant 2019/20303-4; 2019/14773-8), National Council for Scientifc and Technological Development - CNPq (308819/2022-0), ERASMUS Program Fellowship, and The Coordination for the Improvement of Higher Education Personnel - Brazil (CAPES) - Finance Code 001. / The full-text of this article will be released for public view at the end of the publisher embargo on 29th July 2024.