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AvaliaÃÃo de blendas de hidrocolÃides na estabilizaÃÃo do nÃctar de caju: aspectos reolÃgicos e sensoriais / Evaluation of blends of hydrocolloids in stabilizing the cashew nectar: rheological and sensory aspectsTatiana de Oliveira Lemos 30 November 2012 (has links)
Sucos do Brasil SA / Um dos maiores problemas na produÃÃo do nÃctar de caju à assegurar a estabilidade da dispersÃo, uma vez que a separaÃÃo de fases deprecia a aparÃncia visual e altera a sua viscosidade podendo comprometer a qualidade sensorial e conseqÃentemente a sua competitividade no mercado Diante disso esta pesquisa teve como objetivo a obtenÃÃo de uma blenda de hidrocolÃides que fosse eficiente na estabilizaÃÃo fÃsica e manuntenÃÃo das caracterÃsticas intrÃnsecas do nÃctar de caju O estudo foi realizado em trÃs etapas: caracterizaÃÃo dos nÃctares de caju comerciais (A B C e D) produÃÃo e caracterizaÃÃo dos nÃctares de caju em escala laboratorial e industrial Na primeira etapa as anÃlises mostraram que os nÃctares de caju comerciais se encontraram dentro da faixa de instabilidade eletrostÃtica (onde o menos instÃvel foi o da marca A) e de acordo com o PadrÃo de Identidade e Qualidade (PIQ) previsto na LegislaÃÃo Brasileira com exceÃÃo do teor de polpa das marcas A C e D O nÃctar da marca D mostrou maior estabilidade fÃsica quando comparado aos demais Todos os nÃctares apresentaram comportamento nÃo-newtoniano com caracterÃsticas pseudoplÃsticas Os nÃctares das marcas A e B apresentaram boa aceitaÃÃo sensorial Na etapa seguinte utilizou-se blendas de guar/xantana guar/gelana e guar/kappa-carragena e foi aplicado o planejamento experimental do tipo fatorial ortogonal de 1a ordem e testes sensoriais para selecionar o nÃctar de caju contendo a blenda de hidrocolÃides a ser utilizada na produÃÃo em escala industrial Nessa etapa o nÃctar contendo a blenda de goma guar/kappa-carragena numa concentraÃÃo total de 0,5% apresentou bons resultados quanto à estabilidade fÃsica viscosidade aparente e aceitaÃÃo sensorial sendo escolhido para a etapa industrial A blenda selecionada foi utilizada para produzir 1.000 L de nÃctar de caju os quais foram envasados assepticamente em embalagens Tetra brik de 1 L e submetidos Ãs anÃlises fÃsico-quÃmicas fÃsicas reolÃgicas e sensoriais O nÃctar produzido em escala industrial apresentou-se de acordo com o PIQ na faixa de instabilidade incipiente e com maior teor de fibras que os nÃctares comerciais TambÃm apresentou boa estabilidade fÃsica atribuÃda ao mecanismo de estabilizaÃÃo estÃrica conferida pela mistura de hidrocolÃides e comportamento pseudoplÃstico Os testes sensoriais revelaram que o nÃctar industrial apresentou boa aceitaÃÃo para os atributos cor homogeneidade aroma corpo e impressÃo global e que com alguns ajustes na formulaÃÃo pode vir a ser comercializado e possivelmente disputar o mercado com algumas marcas jà existentes no mercado de nÃctares / One of the biggest issues in the production of cashew nectar is to ensure the stability of the dispersion since the phase separation depreciates the visual appearance and alters its viscosity which can compromise the sensory quality and therefore its competitiveness in the market Thus this study was aimed at obtaining a blend of hydrocolloids that was effective in physical stabilization and maintenance of intrinsic characteristics of cashew nectar The study was conducted in three steps: characterization of the commercial cashew nectars (trademarks A B C and D) production and characterization of cashew nectars in laboratory and industrial scale In the first step the analysis showed that the commercial cashew nectars were within the range of electrostatic instability (where the nectar A was the most stable) and according to the Standard of Identity and Quality (PIQ) provided for Brazilian law except for the pulp content of the A C and D nectars The D nectar showed greater physical stability when compared to others ones All nectars exhibited non-Newtonian behavior with pseudoplastic characteristics The A and B nectars showed good sensory acceptance In the next step it was used guar/xantan guar/gellan and guar/kappa-carrageenan blends and was applied the experimental planning factorial orthogonal of first order and sensory tests to select the blend of hydrocolloids to be used for production of cashew nectar in industrial scale At this step the nectar containing the blend of guar/kappa-carrageenan (0.5% w/w) was chosen for showing good results on the physical stability viscosity and sensory acceptance tests The selected blend was used to produce 1000 L of cashew nectar aseptically packaged in Tetra Brik packages of 1 L and subjected to physicochemical physical rheological and sensory analysis The industrial nectar was found according to the PIQ in the range of incipient instability and higher fiber content than the commercial ones It also showed good physical stability which can be attributable to the steric stabilization mechanism provided by the blend of hydrocolloids and non-Newtonian and pseudoplastic behavior The sensory tests showed good acceptance for the color homogeneity aroma body and overall impression attributes and with a few adjustments in the formulation it could be marketed and possibly to compete with some brands already on the market of nectars
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Caracterização de filmes nanocompósitos biodegradáveis a base de gelatina produzidos com um aplicador automático de filmes / Characterization of gelatin-based biodegradable nanocomposite films produced using an automatic film spreaderManuel Fernando Coronado Jorge 18 May 2012 (has links)
O desenvolvimento de filmes à base de biopolímeros tem sido bastante estudado devido aos problemas ambientais causados pelas embalagens de plásticos sintéticos. Dentre os biopolímeros, merece destaque a gelatina, que tem excelente propriedade filmogênica. Entretanto, até o presente momento, os filmes de gelatina apresentam limitações de propriedades mecânicas e, tem elevada sensibilidade à umidade. Uma alternativa para melhorar as propriedades desses filmes pode ser a utilização de nanopartículas como carga de reforço. Assim, os objetivos desta tese foram o desenvolvimento e a caracterização de filmes à base de gelatina, reforçados com nanopartículas. Especificamente, foram objetivos os seguintes estudos: avaliação do efeito da concentração de gelatina sobre as propriedades reológicas das soluções formadoras de filmes e de algumas propriedades físicas de filmes de gelatina, preparados com essas soluções formadoras de filmes com um aplicador automático de filmes; e estudo dos efeitos das concentrações de gelatina e de montmorilonita sobre as propriedades físicas de filmes nanocompósitos e de suas soluções formadoras. Em ambos os estudos, os filmes foram caracterizados imediatamente após a secagem e depois de 7 dias de acondicionamento. As soluções formadoras de filmes (SFF) foram preparadas com gelatina e glicerol, e as soluções formadoras de nanocompósitos (SFN), pela mistura de uma solução de gelatina com uma dispersão de montmorilonita em água, em ambos os estudos, em proporções e temperaturas convenientes. Após a homogeneização, as SFF ou SFN foram resfriadas até a temperatura adequada para aplicação em suportes de plexiglass com a ajuda de um espalhador automático de filmes, acoplado a um banho ultratermostatizado. A altura do espalhador foi mantida constante em 1,5 mm, e a velocidade de espalhamento foi fixada em 35 mm/segundo. Em seguida, as SFF ou SFN foram desidratadas a 30ºC por 24h, em estufa com circulação de ar. No primeiro estudo, as SFF foram preparadas com 5, 8, 11 e 14g de gelatina/100g de SFF e 30 g de glicerol/100g de gelatina, e na segunda parte da tese, as SFN foram preparadas com 5 e 8g de gelatina/100g de SFN, 30 g de glicerol/100g de gelatina e 0, 5, 10 e 15g de montmorilonita/100g de gelatina. As propriedades reológicas das SFF e SFN foram estudadas com testes estacionários e dinâmicos. As propriedades reológicas dasdispersões de montmorilonita em água também foram estudadas, bem como a determinação do tamanho médio das partículas e do potencial zeta. Os filmes foram caracterizados para conhecimento da espessura, umidade, propriedades mecânicas (testes de tração e perfuração), transições de fase, microestrutura das superfícies e da criofratura, cristalinidade, espectroscopia de infravermelho com transformada de Fourier (FTIR), hidrofobicidade, isoterma de sorção de vapor de água, solubilidade em água, permeabilidade ao vapor de água, ao O2 e CO2, cor, opacidade, brilho e propriedade de barreira a luz/UV, segundo os objetivos específicos de cada estudo. Em relação ao primeiro estudo, observou-se que a concentração de gelatina na SFF influenciou fortemente todas as propriedades reológicas e inclusive, as transições sol-gel e gel-sol, determinadas nos testes dinâmicos com varredura de temperatura. A concentração de gelatina na SFF aumentou linearmente a espessura dos filmes, sem, contudo afetar nitidamente a umidade, as transições de fases e nem as propriedades mecânicas obtidas nos testes de tração. A força na perfuração aumentou, mas esse efeito foi devido ao aumento da espessura dos filmes. Em relação ao estudo sobre nanocompósitos de gelatina, observou-se inicialmente que a montmorilonita dispersa em água apresentou diâmetro médio entre 204 e 344 nm, e potencial zeta variando em torno de -43mV. A carga de nanopartícula não afetou a viscosidade da dispersão em água, mas influenciou fortemente as propriedades reológicas e de transições de fases das SFN. A carga de nanopartículas também influenciou a espessura, as propriedades mecânicas e a hidrofobicidade dos filmes nanocompósitos, sem uma função nítida. Comportamento similar foi observado nos resultados da calorimetria diferencial de varredura, embora o padrão de cristalinidade, os espectros de FTIR e as microestruturas dos filmes tenham variado com a carga de montmorilonita. O filme nanocompósito produzido com 5g de gelatina/100g de SFN e 5g de montmorilonita/100g de gelatina apresentou melhores propriedades mecânicas e menor solubilidade em água. Esse filme foi submetido a caracterizações complementares com resultados típicos de filmes de gelatina. No geral, pode-se concluir que a montmorilonita pode melhorar as propriedades dos filmes de gelatina, porém, mais estudos serão necessários para se garantir perfeita dispersão da nanopartícula na matriz do filme. / The development of films based on biopolymers has been widely studied due to the environmental problems caused by synthetic plastic packaging. Among biopolymers, gelatin has to be outlined as it has excellent filmogenic properties. However, until now, the gelatin films have mechanical properties limitations and, high humidity sensitive. An alternative to improve the properties of these films may be the use of nanoparticles as load. Thus, the objectives of this thesis were the development and characterization of gelatin-based films, charged with nanoparticles. Specifically, the objectives were the following studies: evaluation of the effect of gelatin concentration on the rheological properties of the film-forming solutions and on some physical properties of the gelatin films prepared with those film forming solutions using a automatic spreader; and the study of the effect of the gelatin and montmorillonite concentrations on the physical properties of nanocomposite films and their film forming solutions. In both studies, the films were characterized immediately after drying and then after 7 days of conditioning. The film forming solutions (FFS) were prepared with gelatin and glycerol, and the nanocomposite film forming solutions (NFS), by blending the gelatin solution with the montmorillonite dispersion in water, for both studies, in convenient proportions and temperatures. After homogenization, the FFS or NFS were cooled to a proper temperature and applied on plexiglass plates with the help of an automatic spreader, attached to an ultra thermostatized bath. The height of the spreader was kept constant at 1.5 mm, and the spreading speed fixed at 35 mm/second. After that, the FFS or NFS were dehydrated at 30ºC for 24h, in an oven with air circulation. In the first study, the FFS were prepared with 5, 8, 11 and 14g of gelatin/100g of FFS and 30g of glycerol/100g of gelatin, and in the second part of the thesis, the NFS were prepared with 5 and 8g of gelatin/100g of NFS, 30 g of glycerol/100g of gelatin and 0, 5, 10 and 15g of montmorillonite/100g of gelatin. The rheological properties of the FFS and NFS were studied by steady and dynamic tests. The rheological properties of the montmorillonite dispersions in water were also studied, along with the average particle size and zeta potential determinations. The films were characterized to determine thickness, water content, mechanical properties (tensile and puncture tests), phase transitions, surface and cryo-fracture microstructure, crystallinity, Fourier transform infrared spectroscopy (FTIR), hydrophobicity, water vapor sorption isotherm, solubility in water, water vapor, O2 and CO2 permeabilities, color, opacity, gloss, and light/UV barrier properties, according to the objectives of each study. Regarding the first study, it was observed that the gelatin concentration in the FFS strongly influenced the rheological properties and even the sol-gel and gel-sol transitions, determined by the dynamic temperature scanning tests. The gelatin concentration provoked linear increasing of films thickness without, however, affecting discernibly the water content, the phase transitions neither the mechanical properties determined by the tensile tests. The puncture force increased, but this effect was due to the thickness increasing of the films. Regarding the gelatin nanocomposites study, it was initially observed that the montmorillonite dispersed in water had average diameter between 204 and 344 nm, and zeta potential varying around -43mV. The nanoparticle filling did not affect the viscosity of the water dispersion, but strongly influenced the rheological properties and the phase transitions of the NFS. The nanoparticle filling also affected the thickness, the mechanical properties and the hydrophobicity of the films, without a clear function. Similar behavior was observed for the differential scanning calorimetry results, although the crystalline pattern, the FTIR spectra and the microstructure of the films varied with the montmorillonite filling. The nanocomposite film produced with 5g of gelatin/100g of NFS and 5g of montmorillonite/100g of gelatin showed better mechanical properties and lower solubility in water. That film was submitted to further characterizations rendering results typical of gelatin films. In general, it can be concluded that the montmorillonite can improve the properties of gelatin films, however more studies will be necessary to guarantee the perfect dispersion of the nanoparticles within the film matrix.
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Análise comparativa de argamassas colantes de mercado através de parâmetros reológicos. / Comparative analysis of commercial dry-set mortars using rheological parameters.Marienne do Rocio de Mello Maron da Costa 31 January 2006 (has links)
O presente trabalho propõe o entendimento do comportamento no estado fresco de argamassas colantes, com base na caracterização reológica e físico-química de diferentes composições comerciais, servindo de base para analisar o fenômeno de deslizamento, a partir do ensaio estabelecido na norma brasileira. Para isso, foi utilizado o ensaio Squeeze flow (escoamento por compressão axial), empregado na caracterização de argamassas de revestimento no laboratório de microestrutura do CPqDCC da EPUSP, como ferramenta de análise do comportamento de argamassas colantes. Neste ensaio, o escoamento do material decorre da aplicação de uma carga de compressão sobre a amostra no estado fresco, a qual ocasiona deslocamentos no seu interior devido a esforços de cisalhamento radiais originados durante o fluxo. O critério de seleção das argamassas colantes comerciais (tipo AC-I) se baseou nos resultados do ensaio de deslizamento, escolhendo-se duas com resultado muito abaixo do limite especificado, duas com resultado próximo do limite e outras duas com resultado acima do mesmo. A composição química e física foi caracterizada com o objetivo de embasar a análise dos resultados obtidos no Squeeze flow. A separação da fração fina das argamassas na peneira no.200 contribuiu para o conhecimento da viscosidade da pasta e da sua influência no comportamento reológico das argamassas. Foi observado que as argamassas estudadas apresentam diferenças de composição físico-química e de comportamento reológico. As diferenças de comportamento reológico das argamassas decorrem, provavelmente, de ação sinérgica de alguns parâmetros da composição, com destaque para a distribuição granulométrica. O Squeeze flow mostrou-se uma ferramenta adequada na caracterização das argamassas colantes e contribuiu para explicar o deslizamento estabelecido na norma brasileira, pela proposição de modelos hipotéticos de comportamento. / Present thesis proposes the study of plastic-state behaviour of dry-set mortars based on the rheological and physicochemical characterization of different commercially available dry-set mortar compositions. Such characterization served as basis for the analysis of dry-set mortar slip phenomena using the tests recommended by brazilian standards (NBR). The Squeeze Flow test (slip by axial compression) originally used for coating mortars characterization by the EPUSP CPqDDC Microstructure Laboratory was adopted as a test tool for analysing the dry-set mortar behaviour. In the mentioned test the material slip is obtained by compressing the sample in its plastic state which caused internal displacements due to radial shearing tensions originated during the mentioned slip. The dry-se mortars (all of them AC-I type) used in the study were selected based in the slip tests results against brazilian standards specified limits resulting in the selection of two dry-set mortars below the specified limit, two dry-set mortars close to the specified limit and dry-set mortars above the specified limit. Chemical and physical compositions were characterized in order to serve as basis for Squeeze Flow results analysis. Fine fraction segregation, using number 200 sieve contributed to understanding of plastic-state mortar viscosity and its influence in mortar rheological behaviour. It was observed diverse physicochemical and rheological behaviour among the studied dry-set mortars. The rheological behaviour diversity of dry-set mortars were due to the synergy among some composition parameters, specially the granular distribution. The Squeeze Flow was considered a suitable tool for the characterization of dry-set mortars and contributed to develop hypotetical behaviour models that allowed to explain the slip as stated by brazilian standards.
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Avaliação do impacto do uso de fíler calcário como substituição ao cimento no comportamento reológico e retração de microconcretos. / Evaluation of the impact of the use of limestone fillers as replacement for cement in the rheological behavior and shrinkage of microconcretes.Christian Mario Varhen Garcia 31 March 2017 (has links)
Atualmente o maior impacto ambiental do concreto como material de construção origina-se das emissões de CO2 durante a produção do cimento. Uma das alternativas atualmente utilizadas para minimizar este impacto, é a utilização de adições minerais como substituição ao cimento. Entre as diferentes adições utilizadas, o uso de fíler calcário parece ser uma alternativa interessante para melhorar a sustentabilidade do uso do concreto na construção. Consequentemente, o presente estudo foca a análise do impacto da substituição do cimento por fílers de origem calcária (dolomita) no comportamento do concreto em estado fresco e endurecido, especialmente focando-se numa avaliação reológica e na retração por secagem do material. Para tal fim, foram formulados três microconcretos com teores de fíler calcário de 80%, 60% e 20% em relação ao peso dos finos totais (cimento mais fíler calcário). O teor de finos totais e de água foram mantidos constantes para todas as formulações resultando em misturas com similar volume de pasta. O comportamento reológico das misturas foi avaliado num reômetro de movimento planetário. Foram moldados corpos de prova para caracterização mecânica e acompanhamento da retração por secagem. A porosidade das pastas também foi avaliada usando a porosimetria por intrusão de mercúrio. As propriedades reológicas como a tensão de escoamento e a viscosidade foram influenciadas pelo teor de substituição de cimento por fílers. Maiores volumes de fílers na pasta produziram menores tensões de escoamento e, por consequência, maiores valores de abatimento foram obtidos. No entanto, a viscosidade plástica aumentou com teor de fílers. No estado endurecido, a maior substituição de cimento por fílers diminui a intensidade da retração por secagem devido ao menor teor de cimento na pasta e a modificações na estrutura porosa do material. Os resultados experimentais da retração foram comparados com os valores obtidos pelos modelos de previsão da retração: ACI 209, CEB-FIP, B3 e GL2000. Observou-se que os modelos superestimam os valores da retração conforme aumenta a substituição de cimento por fílers na pasta. Portanto, esses modelos devem ser calibrados considerando outros fatores, tais como: a quantidade de fíler utilizado em substituição de cimento. Esta consideração poderia otimizar o uso dos modelos em fase de projeto para verificar se os valores da retração esperados estão dentro dos limites normalmente aceitos. / Currently the biggest environmental impact of concrete as a building material originates in CO2 emissions during the production of cement. For this reason, one of the alternatives currently used to reduce these emissions is the use of mineral additions as cement replacement. Among the different additions used, the use of limestone fillers to replace cement appears to be an interesting alternative for improve the sustainability of the concrete used in construction. Consequently, this study focuses on the analysis of the impact of the replacement of cement by limestone fillers in fresh and hardened concrete, especially focusing on rheological behavior and shrinkage of the material. To this end, three microconcretos were formulated with fillers limestone content of 80%, 60% and 20% by weight relative to the total fine (limestone fillers and cement). The total content of fine and water were held constant for all formulations resulted in mixtures with similar volume of paste. The rheological behavior of the mixes was evaluated in a planetary motion rheometer. For mechanical characterization and measurement of shrinkage, specimens were molded. The porosity of the pastes was also evaluated using mercury intrusion porosimetry. The rheological properties such as yield stress and viscosity were influenced by the amount of cement that was replaced by fillers. Further filers volumes in the pulp produced smaller flow stress and, consequently, higher allowance values were obtained. Larger volumes of filler in the paste produced lower yield stresses and, consequently, higher slump values were obtained. However, the plastic viscosity increased with filers content. In the hardened condition, the largest cement replacement by limestone fillers reduced the intensity of shrinkage due to the lower content of cement paste and changes in the porous structure of the material. The experimental results of shrinkage were compared with the values obtained by shrinkage prediction models: ACI 209, CEB-FIP, B3 and GL2000. It was observed that the models overestimate the shrinkage values with increasing cement replacement by limestone fillers. Therefore, these models must be calibrated considering other factors such as the amount of fillers used as cement replacement This consideration would optimize the use of these models in the design phase to verify that the values of the expected shrinkage are within the limits normally accepted.
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Estudo do Escoamento de Fluidos de Perfura??o em Dutos e em Regi?es Anulares. / Study of flow of drilling fluids in pipes and in annular regions.Braga, Eduardo Rangel 29 September 2009 (has links)
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Previous issue date: 2009-09-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior, CAPES, Brasil. / The need for technological advances in the operation of drilling wells for oil has encouraged
the research and development of drilling fluids, like the study of the its flowing in different
geometries. On this work is studied the flow of two drilling fluids in pipe and annular tube
with the objective to evaluate rheological models that describe the fluid behavior, to
characterize the flow regimes using the experimental method and compare with correlations
found in literature, to evaluate equations of hydraulic diameter found in the literature, to
evaluate correlations of friction factor in the turbulent regime and to propose new correlations
for the friction factor in turbulent regime. The data are obtained in a pilot plant consisting of a
system operating in closed circuit of 6 meters composed of horizontal tubes made of
galvanized iron, arranged in three parallel lines of independent flows that allow the
measurement of friction loss caused by a circular tube of 1" of diameter and by two ratios of
concentric annular tubes (annulus formed by 2" and 3/4 "and 1 1/4" and 1/2"). The system
consists of a tank with a capacity of 500 liters, with a mechanical stirrer, connected to a
positive displacement pump of helical type with 25HP, operating with volumetric flow up to
20m3/h. The pilot plant is instrumented with a set of three transducers of pressure. The
rheology of the fluid is evaluated with the aid of a FANN viscometer, model 35A. The
rheological models used are the power law and Casson. The results show that the choice of
equations of hydraulic diameter and friction factor are dependent on the geometry of flow and
the rheological model used, showing that should be analyzed separately. The new correlations
of friction factor for turbulent regime generate good results. / A necessidade de avan?os tecnol?gicos na opera??o de perfura??o de po?os de
petr?leo tem incentivado a pesquisa e o desenvolvimento de fluidos de perfura??o, assim
como o estudo do escoamento dos mesmos em geometrias distintas. Neste trabalho ? estudado
o escoamento de dois fluidos de perfura??o em tubos e dutos anulares, com o objetivo de
avaliar modelos reol?gicos que descrevam o comportamento do fluido, caracterizar os
regimes de escoamento utilizando m?todo experimental e comparar com correla??es
encontradas na literatura, avaliar equa??es de di?metro hidr?ulico encontradas na literatura,
avaliar correla??es de fator de atrito no regime turbulento e propor novas correla??es para o
fator de atrito no regime turbulento. Os dados s?o obtidos em uma unidade piloto constitu?da
de um sistema operando em circuito fechado de 6 metros de extens?o horizontal composto de
tubos de ferro galvanizado, dispostos em tr?s linhas paralelas de escoamento independentes
que permitem a avalia??o da perda de carga ocasionada em um tubo circular de 1" de
di?metro e em duas raz?es de anulares conc?ntricos (?nulo formado pelos tubos de 2" e 3/4",
e 1 1/4" e ?"). O sistema ? composto de um tanque com capacidade de 500 litros, dotado de
um agitador mec?nico, conectado a uma bomba de deslocamento positivo do tipo helicoidal
de 25HP, operando com vaz?es de at? 20m3/h. A unidade piloto ? instrumentada com um
conjunto de tr?s transdutores de press?o. A reologia do fluido ? avaliada com o aux?lio de um
viscos?metro FANN, modelo 35A. Os modelos reol?gicos adotados s?o o da pot?ncia e
Casson. Os resultados revelam que a escolha das equa??es de di?metro hidr?ulico e fator de
atrito s?o dependentes da geometria do escoamento e do modelo reol?gico utilizado, devendo
ser analisados separadamente. As novas correla??es de fator de atrito para o regime turbulento
geram bons resultados.
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Modélisation et identification de lois rhéologiques de polymères chargés. Application au procédé de moulage par injection de poudres de superalliages. / Modelling and identification of rheological laws adapted for loaded polymers. Applications for the process of superalloy powder injection mouldingClaudel, Dimitri 04 February 2016 (has links)
Le sujet de thèse de doctorat s’inscrit dans le cadre d’un projet de recherche collaboratif entre l’Institut FEMTO-ST et le groupe SAFRAN/SNECMA. Une partie des travaux de cette thèse concerne les caractérisations thermo-physiques de polymères chargés pour différentes nuances et granulométries de poudres de superalliage destinés à être mis en forme par le procédé de Moulage par Injection de Poudre. Pour ces travaux de thèse de doctorat, trois nuances de polymères chargés composé de poudres de superalliages ont été investiguées. Deux nuances sont composées de poudres utilisées par Snecma en réparation (René 80®/Amdry D15® et RBD61) et un autre est composée de poudre d’Inconel 718. Différentes caractérisations ont été réalisées et ont permis d’optimiser le développement de mélanges chargés conduisant à l’élaboration de matériaux homogènes et injectables tout en possédant des taux de charge en poudres les plus élevés possible.Les résultats de ces travaux sont ensuite utilisés afin d’identifier différents termes présents dans les modèles analytiques de rhéologie usuels. Le développement de modèles de rhéologies spécifiques a été réalisé en incorporant aux lois rhéologiques usuelles différents termes dépendant de la surface spécifique, de la viscosité des liants employés au sein de la formulation. Le développement de ces modèles de viscosité de plus en plus complets permet d’améliorer les lois de comportements et de mieux décrire le comportement rhéologique de polymères chargés. Enfin, une simulation de l’étape de moulage par injection d’un composant aéronautique a été réalisée à l’aide du logiciel Moldflow© pour la nuance de René 80®/Amdry D15®. / The works presented in this paper were realized in collaboration between the mechanical department of FEMTO-ST Institute and the company SAFRAN/SNECMA. A part of the works of this thesis focused the thermo-physical characterizations of loaded polymers that is mixtures based of thermoplastic binders and metallic powders suitable be shaped by powder injection molding process.For this work, three different loaded mixtures composed of superalloy powder were investigated.Two were supplied by SAFRAN/SNECMA used to repair (Rene80®/AmdryD15® and RBD61) and another is composed of Inconel 718 powder. Characterizations were to carry out to optimize the development of loaded polymers and to obtain homogenous materials with high solid fraction. Then, the data were used to identified parameters of usual rheological laws. The development of specific rheological models were realized by including different parameters related to the specific surface area, binder viscosities used in the formulation. The development of these models increasingly exhaustive allows the improvement of behavior laws and to better describe the rheological behavior of superalloy-loaded polymers. Finally, a simulation of the injection molding stage of a aeronautical component was realized in the Moldflow© software for the Rene80®/AmdryD15® loaded polymer.
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Vliv teplotní historie na vztah mezi strukturou a vlastnostmi orientovaného polypropylenu / The Effect of Temperature Annealing on Structure-Property Relationship of Oriented PolypropyleneSadílek, Jiří January 2010 (has links)
The aim of this work is to study the effect of thermal history to structure and properties not only of oriented polypropylene monofilaments with different orientation but of course of isotropic non-oriented polypropylene. Term thermal history includes thermal regimes from alpha relaxation temperature (T?) to melting temperature (Tm). This work consists of three parts. The changes of dynamic mechanical properties, strength, deformation and tensile modulus of polypropylene samples according to annealing temperature (Ta) are described in the first part of this work. In the second part, the changes of crystal phase are observed. Preferentially, calorimetric behaviour (DSC), changes of crystal dimensions and orientation function of crystal phase (X-ray) are observed. Measured values from the first and the second part of this work were used for calculation of total orientation function of PP samples. Rheological measurements are shown in the third part of this thesis. Rheological measurements consist of short isothermal creep, shrinkage of free tapes and static deformation at higher temperatures. Measured rheological values were performed using rheological models. Using these models characteristics of entropic spring, instantaneous elasticity and viscosity and tendency to get to state of ease were calculated.
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Adhezivní a reologické vlastnosti směsí na bázi chitosanu v médiích různého pH / Adhesive and rheological properties of chitosan-based mixtures in media of different pHOmar, Alaa Abdel Gawad Ahmed Osman January 2020 (has links)
Title of thesis: Adhesive and rheological properties of chitosan-based mixtures in media of different pH Author: Alaa Omar Supervisor: PharmDr. Eva Šnejdrová, Ph.D. Consultant: Mgr. Juraj Martiška The aim of the diploma thesis is the study of rheological and adhesive properties of tableting materials for matrix tablets based on chitosan. The theoretical part describes in detail the materials used to prepare the matrix tablets, which were chitosan, sodium alginate and hypromellose. The experimental section was focused on the flow and adhesive properties of the chitosan-based mixtures after exposing them to a media of different pH. The flow tests were done on an absolute rotational rheometer. Obtained viscosity curves were analysed by Power law model. Viscosity at 10 s-1 and Power Law model coefficients were used to evaluate and compare the flow behaviour of dispersions with different concentrations of retarding component in different media. The test of adhesion was carried out using a pull away test on a rotational rheometer and evaluated as maximal detachment force. The remarkably high viscosity of 5% dispersions at pH 1.2 is due to the dissolution of chitosan, as sodium alginate is not soluble in acidic media. The increase in viscosity with the concentration of the retarding component is insured...
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Évaluation de l’effet des vibrations sur le comportement du fluide magnéto-rhéologique / The effect of vibrations on magneto-rheological fluidsNovikoff, Paul-Alexis 01 April 2019 (has links)
Les fluides Magnéto-Rhéologiques (MR) de par leurs caractéristiques variant avec le champ magnétique qui leur est appliqué, sont utilisés dans la dissipation d’énergie mécanique. Ainsi, il existe de nombreux dispositifs utilisant ces fluides, par exemple des amortisseurs ou des freins, permettant de contrôler aisément leurs performances. Cependant ces dissipateurs d’énergie mécanique sont amenés à opérer dans des milieux soumis à des perturbations externes notamment des vibrations. Dans le cadre de cette thèse, nous étudions la stabilité des propriétés des fluides magnéto-rhéologiques lorsqu’ils sont perturbés par une stimulation de type vibratoire.Une comparaison analytique de l’ordre de grandeur des efforts vibratoires relativement aux efforts de cohésion magnétique ayant lieu dans le fluide laisse apparaître une possible perturbation du fluide par des vibrations.Nous avons mis en place un banc de test permettant à la fois d’injecter des perturbations vibratoires et de mesurer leur impact sur le fluide utilisé dans un mode classique de cisaillement.Dans certaines conditions, nous avons pu mesurer une diminution de la contrainte de cisaillement du fluide. La variation observée est liée à l’amplitude du mode de déformation de l’élément cisaillant. Trois directions de propagation de vibration selon un repère cylindrique sont étudiées et leurs impacts discutés. La direction normale à la surface est celle qui présente le plus d’effet. La variation maximale de la contrainte de cisaillement observée peut atteindre 40 %. Ce phénomène intervient pour des champs magnétiques faibles, inférieurs à 250 mT, et pour une vitesse de cisaillement faible, inférieure à 100 s-1.Enfin l’effet des vibrations est étudié sur des fluides de différentes viscosités et concentrations de particules, afin d’évaluer l’impact de ces derniers sur la stabilité du fluide / When subjected to a magnetic field, the Magneto-Rheological (MR) fluid increases its apparent viscosity and becomes a viscoelastic solid. They are used in applications requiring dissipation of mechanical energy such as shock absorbers or brakes. These devices operate in environments subject to external disturbances. In this thesis, we study the stability of magneto-rheological fluid properties when they are subjected to vibrations.When comparing the magnitude of the applied forces generated by the vibrations to the magnetic force between the particules it appears that these forces are of the same order. This implies a modification of the fluid behaviour.We developed a dedicated test bench allowing to induce vibration disturbances and to measure their impact on the fluid used in a shear mode configuration.We observed experimentally a decrease in the shear stress of the fluid. This variation depends on the modal deformation of the shearing element. Three propagation directions of vibration according to a cylindrical coordinate are studied and compared. The normal direction to the surface is the one with the most significant effect. The maximum shear stress variation reached was 40%. This phenomenon occurs for low magnetic fields, less than 250 mT, and low shear rate, less than 100 s-1.Finally, the vibration effect is studied on fluids with different viscosities and particle concentrations in order to assess their impact on the fluid’s stability.
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[pt] COMPORTAMENTO REOLÓGICO DE SUSPENSÕES DE ÓXIDO DE GRAFENO EM POLIETILENO GLICOL / [en] RHEOLOGICAL BEHAVIOR OF GRAPHENE OXIDE SUSPENSIONS IN POLY(ETHYLENE GLYCOL)YAGO CHAMOUN FERREIRA SOARES 29 June 2020 (has links)
[pt] O grafeno é formado por uma monocamada de átomos de cabono ligados entre si formando uma rede hexagonal. Ele tem sido bastante estudado por pesquisadores e atraído investimentos de vários setores da economia por apresentar excelentes propriedades mecânicas, térmicas, elétricas e ópticas. O presente trabalho tem como objetivo principal a caracterização reológica das suspensões de óxido de grafeno (GO) dispersas em polietileno glicol (PEG 400), com diferentes tempos de oxidação (2 e 96 horas), através do uso da reometria rotacional. O óxido de grafeno foi obtido pelo método de Hummers e caracterizado por várias técnicas. Este método é baseado na esfoliação química do grafite através de ácidos fortes, como o ácido sulfúrico. Uma vez que o óxido de grafite (GrO) é obtido, ele é esfoliado em um banho ultrassônico em PEG para a formação da suspensão com óxido de grafeno. A caracterização reológica foi realizada através de medições em escoamento de cisalhamento em regime permanente, transiente e oscilatório. A caracterização do GO foi realizada utilizando técnicas como: Difração de Raios-X (DRX), Espectroscopia Raman, Infravermelho por Transformada de Fourier (FTIR), Microscopia de Força Atômica (AFM) e Análise Termogravimétrica (TGA). Os resultados servirão de base para a compreensão da interação entre o GO e o polímero, e o comportamento reológico dos nanofluidos de polímeros à base de GO. / [en] Graphene is formed by a monolayer of cabon atoms linked together forming a hexagonal network. It has been extensively studied by researchers and attracted investment from various sectors of the economy, because it presents excellent mechanical, thermal, electrical and optical properties. The present work has as main objective the rheological characterization of the suspensions of graphene oxide (GO) dispersed in poly(ethylene) glycol (PEG 400), with different oxidation times (2 and 96 hours), through the use of rotational rheometry. Graphene oxide was obtained by Hummers method and characterized by various techniques. This method is based on the chemical exfoliation of graphite using strong acids such as sulfuric acid. Once the graphite oxide (GrO) is obtained, it is exfoliated in an ultrasonic bath in PEG to form the suspension with graphene oxide. The rheological characterization is fulfilled through measurements in steady shear flow, transient shear flow and oscillatory shear flow. The characterization of GO was performed using techniques such as: X-Ray Diffraction (XRD), Raman Spectroscopy, Fourier Transform Infrared (FTIR), Atomic Force Microscopy (AFM) and Thermogravimetric Analysis (TGA). The results will serve as a basis for understanding the interaction between the GO and the polymer, and the rheological behavior of GO-based polymer nanofluids.
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