The effect of fumed silica aggregates on fat crystal networks is studied using a combination of rheology, differential scanning calorimetry and polarized light microscopy. We probe a model system for fat-structured foods with the aim of reducing the amount of fat whilst retaining the desirable mechanical and thermal properties. We begin with oscillatory rheology to investigate the effect of added silica and different fat concentrations on the resulting gel networks. The addition of silica is shown to increase the linear viscoelastic region, without significantly changing the storage modulus within this region. Differential scanning calorimetry measurements show that the presence of silica slightly increases the crystallization temperature but does not act as a seed for nucleation or significantly affect the melting profile of the system. We propose the formation of a composite gel network structure with a layer of silica on the surface of the fat crystal chains. We demonstrate that it is possible to create reduced-fat alternatives with similar rheological behaviour and thermal properties as the full-fat systems through the addition of colloidal silica. Next, we look at the effects of silica concentration, surface area and surface chemistry on the model system. In particular, we focus of the storage modulus, the length of the linear viscoelastic region and the rate of network breakdown after the linear region. We interpret these results in terms of hydrogen bonding between the silica aggregates and its role in reinforcing the fat crystal networks. Then, we study the time-dependent rheological behaviour of this system using the three interval thixotropy test. We measure the deformation under an applied stress and the recovery of structure once the applied stress is removed. We show that, under certain conditions, both fat and silica networks are thixotropic, leading to a full recovery after an applied deformation. We observe a synergistic effect leading to much stronger gel networks when fat and silica are present together. We use polarized light microscopy to gain a more direct insight into the effect of silica aggregates on the fat crystal microstructure. In particular, we study the effects of different fat concentrations, cooling rates, silica concentrations and silica surface chemistries. We use various image analysis techniques to quantify the fat crystal microstructure and find no significant difference in the presence of silica, at low concentrations.

Orientador: Hermes Pretel / Resumo: O objetivo desse estudo foi realizar a caracterização morfo-fisicoquimica e avaliar a resposta histopatológica e a biodegradação de AH indicados para preenchimento dérmico: DMC-Facial 12,5% (D12) e RennovaFill (RF) e aumento volumétrico de tecido: DMC-Facial 15% (D15) e RennovaLift (RL). A caracterização foi realizada por microscopia eletrônica de varredura (MEV), espéctroscopia dispersiva de raios X (EDX) e infra vermelha com transformada de Fourier (FT-IR) e reometria dinâmica oscilatória. Para avaliação da resposta histopatológica e da biodegradação foi implantado 0,1 mL de cada AH no plano sub-dérmico do dorso de 25 ratos Hostsman, aleatóriamente distribuidos em 5 grupos (n=5), de acordo com o tempo de implantação dos AH (7, 14, 30, 60 e 120 dias). Um examinador experiente (HP), calibrado e cego para os AHs utilizados analisou os cortes. Modelo loglinear e teste de quiquadrado (χ2) foram utilizados para avaliar a associação entre os AH e a intensidade da resposta histopatológica e biodegradação para p<0,05. A hipótese nula (H0) foi rejeitada pois tanto na caracterização morfo-fisicoquimica quanto na avaliação da resposta histopatológica e da biodegradação mostraram diferenças signficatica entre os Ahs testados. Pode-se concluir que: 1) AH com a mesma indicação clínica diferem tanto nas características morfo-fisicoquimica com na resposta inflamatória provocada e no padrão de biodegradação. 2) O nível de resposta histopatológica depende do AH utilizado. 3) Uma morfologia es... (Resumo completo, clicar acesso eletrônico abaixo) / The aim of this study was to perform the morpho-physicochemical characterization and to evaluate the histopathological response and biodegradation of AH indicated for dermal filling: DMC-Facial 12.5% (D12) and RennovaFill (RF) and tissue lifting: DMC-Facial 15% (D15) and RennovaLift (RL). The characterization was performed by scanning electron microscopy (SEM), X-ray dispersive (EDX) and Fourier transform infra red spectroscopy (FT-IR) and oscillatory dynamic rheometry. To evaluate the histopathological response and biodegradation, 0.1 mL of each HA was implanted in the dorsal subdermal plane of 25 male Hostsman rats, randomly distributed in 5 groups (n = 5), according to the time of implantation of AH: 7, 14, 30, 60 and 120 days). Slides were analyzed by a experienced examiner (HP), calibrated and blinded for the AH used. Loglinear model and chi-square statistical test (χ2) were used to evaluate the association between AH and the intensity of histopathological response and biodegradation for p <0.05. Results: The null hypothesis (H0) was rejected because both the morpho-physicochemically characterization and the histopathological analysis showed significant differences between the tested AHs. It can be concluded that: 1) AH with the same clinical indication differ in the morpho-physicochemical characteristics, in the inflammatory response and in the biodegradation pattern. 2) The level of histopathological response depends on the AH used. 3) A structural morphology characteristic of D12 and D15, formed by chambers separated by thin septa, with sharp and irregular borders, causes a greater inflammatory response, 4) All HA tested stimulated the fibroblast and collagen neoformation. 5)...(Complete abstract electronic access below) / Mestre

A abóbora se destaca como uma hortaliça de grande potencial nutritivo e tecnológico. Para que se possa aumentar a variabilidade dos produtos de origem vegetal disponíveis no mercado, a abóbora deve ser submetida a processos térmicos que visam prolongar a sua vida de prateleira, além de realizar as modificações necessárias para a sua comercialização. Neste contexto, o objetivo principal da presente pesquisa foi avaliar a aplicação da tecnologia de aquecimento ôhmico em diferentes etapas a serem realizadas durante o processamento da abóbora híbrida Tetsukabuto. Na primeira etapa do trabalho, objetivou-se investigar os efeitos do branqueamento convencional e ôhmico (realizados a 80 ºC durante 4 minutos e 163 V no aquecimento ôhmico) sobre a inativação da enzima peroxidase e sobre a cor das abóboras. Para o ajuste dos dados relativos à inativação enzimática, diferentes modelos cinéticos foram avaliados, sendo o modelo de distribuição de Weibull o escolhido para descrever a cinética de inativação da peroxidase. Com este estudo, foi possível observar que o branqueamento com campo elétrico afetou significativamente os parâmetros cinéticos de inativação enzimática, tornando esse processo mais rápido. A aplicação de ambas as tecnologias não causou modificações significativas dos parâmetros de cor da abóbora. Na segunda etapa do trabalho, creme de abóbora foi pasteurizado via tratamento térmico convencional e ôhmico realizados a 90 ºC por 2 horas e 47 V no aquecimento ôhmico. O objetivo dessa etapa foi avaliar os efeitos de ambas as tecnologias sobre a variação de cor, degradação de carotenoides totais e mudanças nos parâmetros reológicos do creme. Foi possível observar que a cor do creme foi levemente afetada durante a aplicação dos processos, tornando-se ligeiramente mais escura e perdendo o tom amarelado. Além disso, foi verificada perda no teor de carotenoides totais presentes no creme. Ainda, não foi observado um efeito não-térmico adicional do campo elétrico sobre a cor e os carotenoides presentes no produto. O creme de abóbora apresentou comportamento pseudoplástico e que se ajustou satisfatoriamente ao Modelo da Lei da Potência. Com a aplicação dos tratamentos, foi observado um aumento significativo no índice de consistência do creme, sendo que ambas as tecnologias não apresentaram diferenças representativas entre si. O conjunto de resultados obtidos pelo presente trabalho sugere que o aquecimento ôhmico é uma tecnologia promissora a ser aplicada em diferentes operações envolvidas durante o processamento de alimentos. / Pumpkins stand out as vegetable of great nutritional and technological potential. In order to increase the variability of vegetal products available on the market, pumpkins must be subjected to thermal process which can prolong its shelf life, and imposing also the necessary modifications for its commercialization. In this context, the main objective of the present research was to evaluate the application of ohmic heating technology in different stages carried out during the processing of the hybrid pumpkin Tetsukabuto. In the first part of the work, the objective was to investigate the effects of conventional and ohmic blanching (performed at 80 ºC during 4 minutes and 163 V in the ohmic heating) on the inactivation of peroxidase enzyme and on the color of the pumpkins. In order to adjust the data related to enzyme inactivation, different kinetic models were evaluated, being the Weibull distribution model chosen to describe the inactivation kinetics of peroxidase. With this study, it was possible to observe that the electric field blanching significantly affected the kinetic parameters of enzymatic inactivation, turning this process faster. The application of both technologies did not cause significant modifications of pumpkins color parameters. In the second part of the work, pumpkin cream was pasteurized via conventional and ohmic thermal treatment carried out at 90 ºC for 2 hours and 47 V in the ohmic heating. The objective of this stage was to evaluate the effects of both technologies on the color variation, the degradation of total carotenoids and the changes in rheological parameters of the cream. It was possible to observe that the color of the cream was slightly affected during the application of the processes, becoming slightly darker and losing its yellowish tone. In addition, it was verified loss of total carotenoid content in the cream. Furthermore, no additional non-thermal effect of the electric field on the color and on carotenoids present in the product was observed. The pumpkin cream presented a shear thinning behavior and was satisfactorily adjusted to the Power Law Model. It was observed a significant increase in the consistency index of the cream after the application of both treatments, and both technologies did not present significative differences between them. The overall results obtained in the present work suggests that ohmic heating is a promising technology to be applied in different operations involved during food processing.

A particulate suspension under shear is a classic example of a system driven out of equilibrium. While it is possible to predict the equilibrium phase behaviour of a quiescent suspension, linking microscopic details to bulk properties under flow remains an open challenge. Our current understanding of sheared suspensions is restricted to two disparate regimes, the colloidal regime, for particle sizes d < 1 μm and the granular regime, for d > 50 μm. The physics of the industrially-relevant intermediate size regime, 1 μm ≲ d ≲ 50 μm, is unclear and has not been explored previously. In this thesis, we use conventional rheometry on a range of model spheres to develop the foundations of a predictive understanding of suspension flow across the entire size spectrum. In the first part of the thesis, we show that in repulsive particulate systems the rheology is characterised by two viscosity "branches" diverging at different volume fractions φRCP and φm, which represent states of flow with lubricated (frictionless) and frictional interactions between particles. In the intermediate size regime, there is a transition between these two branches above a critical onset stress σ* which manifests as shear thickening. This σ* is related to a barrier (invariably due to the charge or steric stabilisation) keeping particle surfaces apart. Our data are quantitatively fit by the Wyart and Cates theory for frictional thickening [1] if we assume that probability distribution of forces in the system is similar to in dry granular media. The onset stress for shear thickening is found to decrease with the inverse square of the particle size σ* / d ̄ 2 for diverse systems. We show that it is the competition between the scaling of σ*(d) and the size dependence of the entropic stress scale (~ d ̄ 3) that controls the crossover from colloidal to granular rheology with increasing size. Granular systems are "always shear thickened" under typical experimental conditions, while colloidal systems are always in a frictionless state. In the second part of the thesis, we explore the validity of the frictional framework for shear thickening. Although it quantitatively predicts our steady-state rheology, the frictional framework contradicts traditional fluid-mechanical thinking and has yet to be rigorously tested experimentally. In fact, there is a large body of literature that attributes thickening to purely hydrodynamic effects. Using dimensional analysis and simple physical arguments we examine possible physical origins for thickening and show that previously-proposed mechanisms can be subdivided into three types: two-particle hydrodynamic thickening, many-particle hydrodynamic thickening ("hydroclusters") and frictional-contact driven thickening. Many of these mechanisms can are inconsistent with the experimental two-branch phenomenology and can be disregarded. We further narrow down possible causes of thickening using the technique of flow reversal, which disentangles the relative contributions of contact and hydrodynamic forces to the viscosity. Consistent with recent simulations [2] and theory [1], we find that in each case thickening is dominated by the formation of frictional contacts and that hydrodynamic thickening, if present, is subdominant.

La formation d’émulsions stables eau/huile lors des processus de récupération et de raffinage du pétrole peut impacter défavorablement l’efficacité de ces opérations. Bien que résines et asphaltènes soient généralement tenus pour responsables de la stabilité des émulsions, la composition exacte des molécules présentes à l’interface eau/huile est en réalité assez mal connue. L’identification de ces molécules et la connaissance de leur influence sur la propriété des interfaces est une étape nécessaire pour mieux prédire les problèmes de stabilité des émulsions dans l’industrie pétrolière. Cette thèse présente des résultats de caractérisation analytique par GPC-ICP-HRMS et FTMS du matériel interfacial (IM) extrait de quatre bruts différents et des espèces transférées dans la phase aqueuse lorsque ces bruts contactent l’eau, ainsi que des propriétés rhéologiques en cisaillement et en dilatation des interfaces eau/huile en présence de ces composés. Les bruts ont été choisis en raison de leur capacité à former des émulsions eau-dans-huile de stabilités différentes. Les mesures d’élasticité de cisaillement ont montré que la majorité des interfaces eau/huile étudiées formaient une structure élastique susceptible de fausser la mesure du module dilatationnel de Gibbs par la méthode d’analyse du profil de goutte. Néanmoins, nous montrons à l’aide de simulations numériques que le module apparent Eapp mesuré dans un tel cas est proche de la somme du module de Gibbs et du module de cisaillement (G) multiplié par 2 du réseau interfacial dès lors que G reste petit (G < 10 mN/m), ce qui est très souvent le cas puisque nous observons que le réseau interfacial formé se rompt lors des expériences de dilatation. Une équation phénoménologique a été développée permettant d’attribuer un temps de relaxation unique aux processus de relaxation qui ont lieu aux interfaces eau/huile, ce qui nous permet de classer les différents systèmes entre eux. Nous avons également étudié les IM extraits des bruts selon la technique chromatographique dite « wet silica method » récemment développée par Jarvis et al. (Energy Fuels, 2015). Les expériences de rhéologie interfaciale confirment que cette méthode permet d’extraire les composés les plus tensioactifs présents aux interfaces eau-brut. Les analyses chimiques montrent que les IM sont partiellement composés d’asphaltènes et suggèrent que les composés contenant du soufre jouent un rôle important dans la stabilité des émulsions. Enfin, nous avons trouvé que les composés hydrosolubles transférés du brut à l’eau ont un comportement bénéfique, dans le sens où leur présence rend les émulsions eau-dans-brut moins stables. L’analyse FTMS de ces composés montre qu’ils appartiennent aux classes d’hétéroatomes suivant : O2, O3, S1, OS et O2S2 et qu’une partie de ces composés appartient à la classe des asphaltènes. / Crude oil recovery and refining operations rely on high consumption water processes, which may induce the formation of stable water-in-oil emulsions. Although asphaltenes and resins are known to influence the stability of crude oil emulsions, much is still unknown about the real composition of the w/o interfacial layer. Therefore, identifying these molecules and understanding their impact on the w/o interfacial properties are key points for better predicting emulsion problems in the petroleum industry. This thesis presents results on water/oil (w/o) interface characterization using shear and dilatational interfacial rheology as well as results on molecular characterization (GPC-ICP-HRMS and FTMS) of the crude oil interfacial material (IM) and of the amphiphilic crude oil species, which are transferred to the aqueous phase during the emulsification process. Four crude oils forming w/o emulsions of different stability were used in this study. Shear interfacial rheology experiments showed that most of the studied w/o interfaces were capable of forming an elastic interfacial network exhibiting shear elasticity G. A non-null G value interferes on drop deformation and thus on drop shape analysis (DSA) results. Nevertheless, the dilatational elasticity modulus measured by DSA (Eapp) was found to be representative of the sum of the Gibbs modulus plus 2 times G, as long as G  10 mN/m. This condition is generally satisfied since the asphaltene network is broken during dilatational experiments. Consequently, Eapp gives a good approximation of the real Gibbs modulus of the interface. A new phenomenological equation was proposed to fit the dilatational Eapp experimental data, allowing the assignment of a unique characteristic time to describe the w/o interfacial relaxation process and thus sample comparison. The IM of the crude oils was extracted using the “wet silica method” recently developed by Jarvis et al. (Energy Fuels, 2015). Results showed that this method collects the most-surface active compounds that adsorb in the time frame of the extraction procedure. Successive extractions collected species that were larger and less concentrated in the crude oil, but with higher adsorption energies. Molecular characterization revealed that the IM was partially composed of asphaltene compounds, and suggested that sulfur-containing compounds may play a major role in emulsion stability. Lastly, the oil-to-water transferred species were proven to impact the w/o interfacial properties and emulsion stability. Interestingly, concentrating these water-soluble species led to more efficient crude oil dehydration. FTMS analysis of the transferred species revealed that part of the compounds belonged to O2, O3, S1, OS and O2S2 heteroatom classes, and some of them have an asphaltene-type of molecules classification.

Une étude numérique des suspensions diluées à base d'un fluide à matrice non newtonienne et de particules sphéroïdales rigides est réalisée. Un fluide de Carreau décrit la matrice non newtonienne. Le cas particulier des particules sphériques rigides est pris en compte. Ici, on simule un écoulement élongationnel uniaxial autour d'une sphère et on utilise l'homogénéisation numérique pour obtenir la viscosité apparente de la suspension diluée pour différents taux de déformation appliqués et différents exposants de dilution. Dans le régime newtonien, on obtient le fameux résultat d'Einstein pour la viscosité d'une suspension diluée de particules sphériques rigides. Dans le régime de la loi sur la puissance, on constate que la viscosité intrinsèque ne dépend que de l'exposant d'amincissement. En utilisant les résultats de la simulation, une modification du modèle de Carreau pour les suspensions diluées avec un fluide de matrice non newtonienne est proposée. Pour étudier l'influence de la forme des particules, une autre étude numérique est réalisée. En particulier, différents écoulements autour de particules sphéroïdales de différentes orientations sont simulés et une homogénéisation numérique est utilisée pour obtenir la viscosité intrinsèque de la suspension en fonction de la vitesse de déformation appliquée, de l'exposant d'amincissement et du rapport de forme. A partir des résultats, il est possible d'extraire les coefficients rhéologiques du modèle Lipscomb. Dans le régime newtonien, les résultats de simulation coïncident avec les prévisions de Lipscomb. Dans le régime de la loi de puissance, les coefficients rhéologiques dépendent fortement de l'exposant d'éclaircie. De plus, les résultats de la simulation indiquent que les coefficients rhéologiques dépendent en outre de l'orientation des particules en régime non linéaire. / A numerical study of dilute suspensions based on a non-Newtonian matrix fluid and rigid spheroidal particles is performed. A Carreau fluid describes the non-Newtonian matrix. The special case of rigid spherical particles is considered. Here, a uniaxial elongational flow around a sphere is simulated and numerical homogenization is used to obtain the bulk viscosity of the dilute suspension for different applied rates of deformation and different thinning exponents. In the Newtonian regime the well-known Einstein result for the viscosity of a dilute suspension of rigid spherical particles is obtained. In the power-law regime it is found that the intrinsic viscosity depends only on the thinning exponent. Utilizing the simulation results a modification of the Carreau model for dilute suspensions with a non-Newtonian matrix fluid is proposed. To investigate the influence of the particle shape another numerical study is performed. In particular, different flows around spheroidal particles with different orientations are simulated and numerical homogenization is used to obtain the intrinsic viscosity of the suspension as function of applied rate of deformation, thinning exponent and aspect ratio. From the results it is possible to extract the rheological coefficients of the Lipscomb model. In the Newtonian regime the simulation results coincide with Lipscomb’s predictions. In the power-law regime the rheological coefficients depend strongly on the thinning exponent. Furthermore, simulation results indicate that the rheological coefficients additionally depend on the particle orientation in the non-linear regime.

Made available in DSpace on 2014-06-11T19:25:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-11-24Bitstream added on 2014-06-13T20:53:20Z : No. of bitstreams: 1 matos_fc_me_arafcf.pdf: 1148382 bytes, checksum: acb5e1bbfbec2e34aa0311d72ae2a142 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / Os polissacarídeos naturais vêm sendo extensamente usados no desenvolvimento de formas farmacêuticas sólidas para liberação prolongada de fármacos, fato demonstrado na literatura por inúmeros estudos de utilização de polissacarídeos como quitosana, pectina, sulfato de condroitina, ciclodextrinas, dextranas, inulina, amilose e galactomananas de goma de guar e de alfarroba. Neste trabalho, os polímeros de galactomananas de flamboyant (Delonix regia) e de Carolina (Adenanthera pavonina), que são vegetais pertencentes à família Leguminosae, foram estudados após serem reticuladas por reação com trimetafosfato de sódio, um agente reticulante adequado para o uso farmacêutico e alimentício e avaliou-se os diferentes graus de reticulação das gomas em função da variação do tempo de reação (30 min. a 4 horas) e da concentração de base no meio reacional( 2% e 4%). As técnicas analíticas empregadas mostraram-se úteis na avaliação do grau de reticulação das amostras, exceto a espectroscopia na região do infravermelho, que não permitiu estabelecer diferenças entre as estruturas obtidas com diferentes graus de reticulação. A técnica da reologia apresentou-se como uma ferramenta importante na análise dos polímeros. Através das análises de viscoelasticidade foi possível observar mudanças significativas no comportamento viscoelástico dos polímeros reticulados quando comparados aos polímeros não-reticulados, oriundos do flamboyant ou da carolina. Para todos os tempos de reticulação, o módulo G’ apresentou valores maiores para os polímeros reticulados em comparação aos polímeros não reticulados, para todos os tempos de reticulação. A análise do grau de intumescimento das partículas aliada à reologia mostrou ser útil para a caracterização dos polímeros, permitindo observar que os produtos reticulados de ambas as origens tiveram sua capacidade... / The natural polysaccharides have been extensively used in the development of solid dosage forms for sustained release of drugs, a fact demonstrated by countless studies in the literature about the use of polysaccharides such as chitosan, pectin, chondroitin sulphate, cyclodextrins, dextran, syrup, starch and gum galactomannans of guar and carob. In this work, the polymers of galactomannans of Flamboyant (Delonix regia) and Carolina (Adenanthera pavonina), which are plants belonging to the family Leguminosae, were studied after a cross-linked reaction with sodium trimetaphosphate, which is a cross-linked agent suitable for pharmaceutical and food use. Then, from this study, the different cross-linked degrees of gum depending on the variation of the reaction time (30 minutes to 4 hours) and the concentration of base in the middle reaction (2% and 4%) were analyzed. The analytical techniques employed have proved useful in assessing the cross-linked degree of the samples, except in the infrared spectroscopy, which failed to establish differences between the structures obtained with different degrees of cross-linkage action. The rheology technique presented itself as an important tool in the analysis of polymers. Through the viscoelasticity analysis it was possible to see significant changes in the viscoelastic behavior of cross-linked polymers when compared to non-cross-linked polymers, from the Flamboyant or the Carolina. For all times of reticulation, the module G had higher values for the cross-linked polymers when compared to non-cross-linked polymers, for all times of cross-linkage actions. The analysis of the degree of swelling of the particles combined with rheology has shown to be useful for the characterization of polymers, enabling the observation that the cross-linked products of both origins had their ability to absorb water increased significantly in relation to non-cross-linked... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:26:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-06-29Bitstream added on 2014-06-13T20:14:58Z : No. of bitstreams: 1 rocha_rr_me_rcla.pdf: 995687 bytes, checksum: 64dced64ef9283bbde42a317d3cac1c0 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O estudo do comportamento reológico de barbotinas com argilas da Formação Corumbataí, surgiu da necessidade das indústrias cerâmicas do Pólo de Santa Gertrudes se adaptarem às mudanças do comportamento mercadológico e ao aumento das exigências dos órgãos ambientais em relação aos riscos causados pela geração de poeira pelo processo de moagem via seca. Foram selecionadas três áreas geograficamente distantes, mas dentro do pólo, e foram feitas caracterizações mineralógicas e reológicas. Para o estudo reológico foram feitas medidas de viscosidade, tensão de cisalhamento e taxa de cisalhamento com viscosímetro rotacional, tendo como parâmetros de controle, o teor de sólidos da barbotina e a granulometria. Desta forma, foram obtidas curvas de defloculação e foram medidas variações nas suspensões, tais como o comportamento pseudoplástico e a tixotropia. Também foi analisada a dependência do comportamento reológico com a mineralogia das argilas, obtida por difração de raios X. Os resultados das curvas de fluxo e de viscosidade mostraram-se muito coerentes com a mineralogia determinada, indicando uma piora do comportamento reológico no sentido da base para o topo da Formação, bem como lateralmente, na dependência de alteração supérgena, permitindo avaliar o uso destas argilas no processo de preparação de massa via úmida. / The study of rheological behavior of clay slips at Corumbataí Formation, arose from the need for the ceramic industries of Santa Gertrudes Pole to adapt to the changes of the market behavior and the demands of the environmental organs regarding the risks caused by the generation of dust, by the dry milling mass preparation. Three geographically distant regions were selected inside the area of the pole, mineralogical and rheological characterization were made. Viscosity measurements, shear stress and shear rate have been made with rotational viscometer, by having the solid content of the slip and particle size as control parameters. Therefore defloculation curves were made and variations of the suspensions have been verified, like the pseudoplastic behavior and the tixotropy. The dependence of the rheological behavior on the clay mineralogy has also been analyzed and it was obtained by X-ray diffraction. The results of the rheological curves appeared to be very coherent with the determined mineralogy, indicating a worsening of the rheological behavior from the bottom to the top of the formation, as well as laterally, in dependence on the superficial alteration, permitting to evaluate the use of these clays in the wet milling process.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O estudo do comportamento reológico relacionando a interação entre as partículas do solo com o fluido é de grande importância para o desempenho e aplicação em obras de engenharia A reologia é mais utilizada na Engenharia Civil para avaliar a interação entre as partículas sólidas e a água em pasta, argamassa e concreto. Saibro é um material incoerente, originado pelo intemperismo incipiente de rochas graníticas, contendo grande quantidade de fragmentos pequenos de feldspatos e quartzo, além de outros minerais acessórios da rocha e é utilizado em argamassa. A presente pesquisa tem por objetivo caracterizar e avaliar o comportamento reológico de cinco Solos com diferentes consistências e de nove Saibros da Região Metropolitana do Recife (RMR) usados em argamassas, através de métodos convencionais de avaliação da consistência dos solos, como limites de liquidez e plasticidade e comparar com o comportamento obtido em ensaio com o Squeeze-Flow. O ensaio para o estudo da reologia consiste na compressão da amostra por meio de duas placas paralelas, medindo-se, simultaneamente, a carga aplicada e o deslocamento resultante. Foram obtidos os valores dos limites de consistências obedecendo às recomendações da Associação Brasileira de Normas Técnicas. As amostras foram moldadas, no formato cilíndrico com diâmetro de 101 mm e altura de 10 mm, nas mesmas umidades utilizadas para a obtenção do limite de liquidez no aparelho de Casagrande e nas umidades correspondentes ao limite de liquidez e de plasticidade e posteriormente comprimidas com medidas de deslocamento e carga. Os resultados mostram que os materiais mais argilosos apresentam maiores valores dos limites de liquidez e dos índices de plasticidade. Os dados obtidos nos ensaios com o Squeeze-Flow mostram a influência da quantidade de água na mistura com o solo e a curva carga versus deslocamento que apresenta comportamento elástico, plástico e plástico com endurecimento dependendo da quantidade de água, de finos e da consistência dos materiais. O estudo da interação entre as partículas e a água utilizando o Squeeze-Flow mostrou que a técnica é capaz de aferir e avaliar, com sensibilidade a forma da curva carga versus deslocamento dos materiais estudados para análise do comportamento utilizado. / The study of the rheological behavior relating the interaction between the soil particles with the fluid is of great importance for the performance and application engineering works The rheology is most used in Civil Engineering to evaluate the interaction between the solid particles and water paste, mortar and concrete. Clay is a material inconsistency, caused by the incipient weathering of granitic rocks, containing large amounts of small fragments of feldspar and quartz, and other accessory minerals of the rock and is used in mortar. This research aims to characterize and evaluate the rheological behavior of five soils with different consistencies and nine grit of the Metropolitan Region of Recife (RMR) used in mortars, through conventional methods of assessing the consistency of the soil, such as limits on liquidity and plasticity and compare with the behavior obtained in the test with the Squeeze-Flow. The test for the study is the compression rheology of the sample by means of two parallel plates, measuring both the applied load and resultant displacement. We obtained the values of consistency limits of complying with recommendations of the Brazilian Association of Technical Standards. The samples were molded in a cylindrical shape with a diameter of 101 mm and height 10 mm, the same water content used to obtain the liquid limit of the apparatus Casagrande and moisture corresponding to the liquid limit and plasticity and subsequently compressed by measures load and displacement. The results show that the more clayey materials present higher liquidity limits and plasticity indexes. The data obtained in tests with the Squeeze Flow show the influence of the amount of water to mix with the ground and the load versus displacement curve which has elastic behavior, plastic and plastic hardness depending on the amount of water, and the consistency of fine material . The interaction between particles and water using the Squeeze-Flow showed that the technique is able to assess and evaluate, with sensitivity to the shape of load versus displacement curve of the studied materials used for the analysis of behavior.

Coating flows can be defined as a laminar free surface flows, whereby a liquid layer is applied onto a solid substrate. A typical industrial application consists of co-rotating cylindrical rollers, which are used to apply a liquid coating (paint) onto a moving substrate, and depending on the direction of the rollers, can be configured in either forward or reverse mode. These types of coating solution flows are industrially important applications, and convey viscoelastic aspects due to their polymeric content and unsteady polymeric behaviour. The process often possesses localized regions of high shear and extension rates (narrow nip and wetting-line zones), which may cause instabilities on the coated substrate (ribbing, leveling, striping). These non-Newtonian and viscoelastic studies for industrial reverse roll coating focus on the use of computational techniques to model these types of coating flows, alongside the analysis of the fluid flow behaviour and under varied rheological properties. Two flow problem configurations have been considered, a model benchmark problem of mixed combined-separating flow, and the industrial application of reverse roll coating flow. Predictions and corresponding solutions are reported for viscous, inelastic and complex viscoelastic fluid properties. The numerical formulation adopts a Taylor-Galerkin pressure-correction (TGPC) scheme, using a finite element method for viscous, inelastic flows and a hybrid finite element/finite volume method for their viscoelastic counterparts. The research plan is centered around computational fluid dynamics and rheological studies, with the main target focused on industrial roll-coating operations. From simple theory, Newtonian and non-Newtonian coating flows possess specific, yet disparate characteristics. This may lead to distinct and significant differences in their detailed flow behaviour, and in the stressing levels generated, dependent upon the nature of the flow configuration. The study is segmented into several stages: initially, solution was sought for a benchmark flow problem, where a semi- implicit time stepping finite element procedure was employed to simulate a mixed combined- separating flow. Here, both viscous and viscoplastic material approximations have been introduced. Secondly, the industrial application of reverse roll coating flow was addressed for viscous inelastic coating fluids. This incorporated scenarios of inclusion and not of a dynamic wetting line and consideration of the effects of a rubber elastomer-cover upon the applicator roll. Thirdly, viscoelastic paint coatings were addressed for the industrial reverse roll coating flow. Here, a hybrid finite element/finite volume sub-cell method was utilized, and with inclusion of a dynamic wetting line. Of the various viscoelastic material models available, use has been made of the Phan-Thien Taimer (PTT) network class of models, in both linear and exponential variety, and of the FENE class of models, with FENE-CR and FENE-P versions. This has offered a richness in capacity over variation of rheological properties. The choice of computational methods has been justified and the TGPC algorithm was deemed suitable for problem solution. The methodology tested on combined-separating flow provided high-quality numerical results, which compare favorably against experiments, literature and theory. When applied to the reverse roll coating problem, the TGPC algorithm has been coupled to a time-dependent free-surface update procedure, to determine the dynamic movement of the meniscus and the wetting line. Around the nip-region, the flow problem manifests strong flow features, which have been investigated for a range of rheological properties of varying shear and extensional response. The direct impact these have on localized peak nip-pressures and distributional lift levels has been observed, where several relief mechanisms have been successfully identified (important to optimize process control). The influence of solvent fraction, extensional viscosity and increasing elasticity, up to critical stress states have been analysed in considerable detail. In summary, the success of this work indicates optimal flow process settings and preferential Theological coating properties to employ, with respect to this industrial coating process. As such, it lays the foundation and guide towards achieving a stable and consistent coating application - specifically, as high-speed high-gain production is of current demanded.