No description available.

Foam fractionation is an adsorptive bubble separation technology that has shown potential as a replacement to the more costly and non-sustainable traditional downstream processing methods such as solvent extraction and chromatography for biological systems. However biological systems mostly tend to be a mixture of surface active species that complicates the foam fractionation separation. In this thesis a detailed experimental study on the application of foam fractionation to separate a well-defined surfactant-protein mixture was performed with emphasis on the competitive adsorption behaviour and transport processes of surfactant-protein mixtures in a foam fractionation process. Surface tension and nuclear magnetic resonance (NMR) measurements showed that nonionic surfactant Triton X−100 maximum surface pressure, surface affinity and diffusivity were a factor of 2.05, 67.0 and 19.6 respectively greater than that of BSA. Thus Triton X−100 dominated the surface adsorption at an air-water surface by diffusing to the surface and adsorbing at the surface faster than BSA. This competitive adsorption behaviour was observed in foam fractionation experiments performed for Triton X−100/BSA mixtures for different feed concentration ratios and air flow rates. The recovery and enrichment of Triton X−100 were found to increase and decrease respectively with increasing air flow rate for all foam fractionation experiments as expected for a single component system. However the recovery and enrichment of BSA were both found to increase with increasing air flow rate for high feed concentrations of Triton X−100.Bubble size measurements of the foamate produced from foam fractionation experiments showed that at steady state conditions the bubbles rising from the liquid pool were stabilised by BSA. However at the top of the column the recovery of Triton X−100 in the foamate (75% to 100%) was always greater than the recovery of BSA (13% to 76%) for all foam fractionation experiments. In addition, for high feed concentrations of both components and at low air flow rates, the enrichment of BSA remained at almost unity for most experiments and only increased when the recovery of Triton X−100 reached 100%. Thus it was concluded that Triton X-100 displaced the adsorbed BSA from the surface. The foam drainage properties of Triton X−100/BSA mixtures were characterised using two methods; forced foam drainage and from pressure profiles of steady state foam fractionation experiments (pressure method). The drainage data from the forced foam drainage was found not to be compatible with experimental foam fractionation results, by indicating that stable foam was not produced during the foam fractionation experiments. However stable foam was repeatedly produced during foam fractionation experiments. The drainage data from the pressure method was found to be in close agreement to experimental foam fractionation experiments. The work in this thesis takes a significant step beyond the literature experimental foam fractionation studies for multicomponent systems. In addition to investigating the effect of foam fractionation process parameters on the separation of mixed systems, the results from the characterisation studies of surface adsorption and foam properties provided insight and deeper understanding of the competitive adsorption behaviour of surfactants and proteins in a foam fractionation process.

Since their discovery in the 1930s, polymeric foams have been widely used in the industry for a variety of applications such as acoustical and thermal insulation, filters, absorbents etc. The reason for this ascending trend can be attributed to factors such as cost, ease of processing and a high strength to weight ratio compared to non-foamed polymers. The purpose of this project was to develop an “indestructible” material made of polycarbonate (PC) for industrial applications. Due to the high price of polycarbonate, two foaming methods were investigated to reduce the amount of material used. Samples were foamed physically in supercritical CO2 or chemically with 5-phenyl-1H-tetrazole. After thermal characterization of the foams in differential scanning calorimetry (DSC), we saw that none of the foaming methods had an influence on the glass transition of polycarbonate. Micrographs taken in scanning electron microscopy (SEM) showed that foams obtained in physical and chemical foaming had different structures. Indeed, samples foamed in supercritical CO2 exhibited a microcellular opened-cell structure with a high cell density and a homogeneous cell distribution. On the other hand, samples foamed with 5-phenyl-1H-tetrazole had a macrocellular closed-cell structure with a much smaller cell density and a random cell distribution. Compression testing showed that polycarbonate foamed physically had a compression modulus a lot greater. Then, XLPE mesh 35 or 50 and wollastonite were added to the polymeric matrices to enhance the foaming process and the mechanical properties. DSC experiments showed that the addition of fillers changed the thermal properties of polycarbonate for both foaming methods by inducing a shift in glass transition. SEM revealed that fillers lowered the average cell diameter and increased the cell density. This phenomenon increased the compression modulus for polycarbonate foamed in supercritical CO2. However, mechanical properties decreased for samples foamed with 5-phenyl-1H-tetrazole due to their relative brittleness and the propagation of microcracks.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24647号 / 工博第5153号 / 新制||工||1984(附属図書館) / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 大嶋 正裕, 教授 佐野 紀彰, 教授 山本 量一 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

No description available.

Wildland fire services have successfully integrated compressed air foam systems (CAFS) into their fire suppression arsenal over the last few decades to effectively increase the firefighting ability of water. Many urban fire departments have done the same, but far more still rely on plain water to extinguish Class A fires. Many claims have been made about the advantages and disadvantages of firefighting foams, but only limited research has been conducted on the subject to date. Fire departments need more information, beyond that provided by foam suppliers and CAFS equipment manufacturers, to make an independent decision on whether or not to adopt the technology. This thesis is part of a larger project sponsored by the United States Department of Homeland Security Assistance to Firefighter Grant Program (grant ID: EMW-2010-FP-01369) to evaluate the capabilities and limitations of compressed air foam systems (CAFS) for use in structural firefighting applications. Large-scale tests comparing water and foam suppression, which includes aspirated foam and CAFS, in a variety of scenarios were performed to measure the ability of the hose streams to reduce the temperature of a hot gas layer within a structure. These temperature reductions were recorded with thermocouples and are analyzed to determine which suppression agent has a superior gas cooling ability.

<p><strong><em>Dedicated to the loving memory of my mother and father,</em></strong></p> <p><strong><em>Zohreh Hojati & Mostafa Emami</em></strong></p> / <p>Commercial interests in polymeric foams continue to increase due to their unique physical characters and the new emerging applications for foamed materials. This thesis investigates the foam development process under non-pressurized conditions as applicable to rotational molding to elucidate the underlying mechanisms in the bubble transformation process and provide an accurate basis for predicting the morphological structure and macroscopic properties of the foamed materials. It was found that the foaming mechanism is comprised of four distinct stages: two stages of bubble nucleation, primary and secondary nucleation, followed by bubble growth and bubble coalescence/shrinkage. Following the nucleated bubbles during the foaming process revealed that primary nucleation was the controlling stage in determining the final cellular structure. Growth and coalescence mechanisms were dynamically active and competed during both heating and cooling cycles.</p> <p>The influence of the rheological properties on the rate of nucleation and the bubble growth mechanism were investigated. Morphological analysis was used to determine the rheological processing window in terms of shear viscosity, elastic modulus, melt strength and strain-hardening, intended for the production of foams with greater foam expansion, increased bubble density and reduced bubble size. Visualization experiments and theoretical predictions showed that higher viscosity could impede the number of nuclei generated in the foaming system. A bubble growth model and simulation scheme was also developed to describe the bubble growth phenomena that occurred in non-pressurized foaming systems. It was verified that the viscous bubble growth model was capable of depicting the growth behaviors of bubbles under various processing conditions.</p> / Doctor of Philosophy (PhD)

Flotation is a complex, multiphase process used to separate minerals. Four problems central to the fundamentals of the flotation process were studied. A multiphase grid turbulence experiment was conducted to verify particle collision models. The slip velocities of solid particles and bubbles were measured using Digital Particle Image Velocimetry (DPIV). The experimental results were compared with the predictions from empirical and theoretical collision models. Time-resolved DPIV was used to measure the turbulent velocity field in a Rushton turbine around the impeller region. The turbulence quantities were found by removing the periodic component from the blade passing, which is a dominant part of the measured velocities near the impeller. We provide evidence that larger, biased dissipation and turbulent kinetic energy values are estimated in the vicinity of the impeller due to the periodic component of the blade passage. The flow was found to be anisotropic close to the impeller. Vortex detection revealed that the tip vortices travel in a nearly radial direction from the impeller for small Reynolds numbers and with a wider distribution for higher Reynolds numbers. The rise of a buoyant bubble and its interaction with a free liquid surface was experimentally investigated using Time-Resolved Digital Particle Image Velocimetry as a function of bubble size, and surfactant concentration of the fluid medium. It is shown that the presence of a surfactant significantly affected the characteristics of the velocity field during the rise and interaction with the free surface. This difference is attributed to the adsorption coverage of the surfactant at the bubble-fluid interface. Wake profiles were compared. The presence of large vortices were observed and found to play a significant role. Finally, Numerical and experimental results of stable and unstable foams are presented by comparing liquid fractions and bubble sizes. There was good agreement between the experiments and numerical modeling in free drainage and forced drainage experiments. In addition, foam coarsening was measured and characterized experimentally. Each of the problems investigated have added to the understanding in the underlying physics of the flotation process and can lead to more accurate modeling. The ultimate goal of this work is to contribute to the design of more effective and efficient flotation machines. / Ph. D.

Les mousses extinctrices sont utilisées sur les feux de catégorie B (solvants inflammables). L’efficacité des mousses actuelles contenant des agents moussants fluorés est apportée par la formation d’un film aqueux à la surface du carburant enflammé. Les entreprises recherchent et développent de nouveaux agents moussants sans fluor car ce type de tensioactif est nocif pour l’environnement et la santé. Des mousses très stables sont nécessaires pour qu'une couche épaisse de mousse résiste aux températures élevées et au démoussage par le solvant et évite ainsi la ré-inflammation.Dans ce travail, l’amélioration de la stabilité de la mousse a été réalisée en utilisant des épaississants dans une solution moussante avec des tensioactifs non fluorés. Des polysaccharides tels que la gomme xanthane ont été utilisés et ses interactions avec des tensioactifs ont été étudiés. Les complexes formés par ces interactions ont été utilisés dans le but d’améliorer la stabilité de la mousse et sa résistance aux flammes. Ceci engendre des mousses de plus faible moussabilité mais de plus grande stabilité. Des tests à échelle réduite ont été réalisés selon la norme EN1568 et ont montré l’efficacité de l’addition de gomme xanthane. Ces formulations innovantes associant des polysaccharides et des agents moussants sont de bonnes alternatives aux formules contenant des tensioactifs fluorés. Le mécanisme d’action des hydrotropes améliorant la moussabilité a aussi été étudié / Firefighting foams are used on class B fires (flammable solvents). The efficiency of currently used foams containing fluorinated foaming agents is ensured by the formation of an aqueous thin film on top of the burning solvent. The formation of such film requires the use of fluorinated surfactants that specifically adsorb at the water-air interface. Companies currently develop fluorine-free products for firefighting foams because this kind of surfactants is harmful for the environment and health. Very stable foams are necessary to the formation of a thick layer of foam that resists high temperatures and defoaming by the solvent, preventing fire re-ignition.In this work, improved foam stability was achieved by using thickeners in the foaming fluid together with the non-fluorinated surfactants. Polysaccharides such as xanthan gum were used and their interactions with surfactants were investigated. Complex species formed by such interactions were used in order to improve foam stability and resistance against flames. This causes a lower foamability but higher stability of foams. Small scale fires extinguishing experiments performed following the standard EN1568 showed the efficiency of xanthan gum addition. These innovative formulations combining polysaccharides and foaming agents are suitable alternatives to those containing fluorinated surfactants. The action mechanism of hydrotropes improving foamability has also been studied

No description available.