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“Thermodynamic and physical properties for high pressure process design”
Maša Knez Marevci, 2014, doktorska disertacija

Opis: The thesis is comprised of three main categories. The first part of dissertation covers investigations of phase equilibria of compounds from natural materials in conventional and also non conventional supercritical fluids. In details, the impact of pressure and/or temperature on the system behaviour (miscibility, solubility, phase inversion) is investigated, quantitative and qualitative analyses to evaluate and identify compounds contained after performing preliminary extraction experiments from different natural tissues are presented. The impact of operating parameters (pre-treatment of the raw material with SFE; different extraction solvents: propane, CO2, non conventional SCFs; different extraction temperatures and pressures) on extraction kinetics is observed. Following substances were taken into consideration: vanillins, caffeine, carnosoic acid extract and lecithin. Second part of dissertation covers studies of phase equilibria of the systems bio oil/gas, which is crucial in biorefinery process design. In this part of dissertation, which covers studies of phase equilibria of binary and ternary systems, the impact of pressure and/or temperature on the system behaviour (miscibility, solubility, phase inversion) for binary system bio oil/supercritical fluid (bio oil/CO2) and (bio oil/H2) was studied. Additionally, phase behaviour of ternary systems of (bio oil/diesel/CO2) and (bio oil/tail water/CO2) under the impact of pressure and/or temperature is observed. These data are of a high importance for bio refineries as an important part of necessary sustainable development. In recent years, studies on biodiesel synthesis have focused on development of process intensification technologies to resolve some of these issues. Fundamental data to design fractionation process of components of bio oil are crucial for an efficient hydrogenation process of bio oil. In the third part of dissertation observation of phase equilibria and determination of the parameters like diffusion coefficient, density and viscosity for the systems polymer/CO2 at elevated pressures is investigated. An overview of different methods applied to determine the parameters like diffusion coefficient, density and viscosity of the systems polymer (PEG)/CO2 at elevated pressures is offered. Observation of phase equilibria of the binary system PEG/CO2, determination of the impact of pressure and/or temperature on the system behaviour (miscibility, solubility, phase inversion), determination of thermodynamically and physically properties of the system with new applicative methods and finally, comparison of the results obtained by different methods is provided. The interfacial tension (IFT) at the (PEG)/CO2 interface has been determined by using an experimental technique developed to study the interfacial interactions of the liquids in equilibrium with gas in a glass-windowed equilibrium cell by the means of Capillary Rise (CR) method. Advantages and disadvantages of methods that were applied are exposed and discussed.
Ključne besede: phase equilibria, natural materials, conventional and non conventional supercritical fluids, extraction, bio oil, data for biorefinery process design, systems polymer (PEG)/CO2, diffusion coefficient, density, viscosity, surface tension, Capillary Rise (CR) method.
Objavljeno: 28.10.2014; Ogledov: 1905; Prenosov: 261
.pdf Celotno besedilo (4,46 MB)

Electrokinetic investigation of polyelectrolyte adsorption and multilayer formation on a polymer surface
Stefan Köstler, Volker Ribitsch, Karin Stana-Kleinschek, Georg Jakopic, Simona Strnad, 2005, izvirni znanstveni članek

Opis: Self assembled polyelectrolyte layers of poly(sodium 4-styrenesulfonate) (PSS), and poly(diallyldimethylammonium chloride) (PDADMAC) were deposited on planar poly(ethylene terephthalate) (PET) substrates using the layer-by-layer technique. Charged functional groups were generated on the polymer substrates by means of a surface modification procedure prior to polyelectrolyte adsorption. The layers were characterised concerning their electrokinetic properties. The build-up of multilayer architectures could be followed by changes of the zeta-potential versus pH curves. An increase of coating density with increasing layer number was found. The electrokinetic properties of the PET substrates were not recognised anymore if more then four layers were applied. If PSS formed the outermost layer these assemblies were very stable against shear forces while if PDADMAC formed the outermost layer the films were partially destroyed by high shear forces.
Ključne besede: textile materials, polyelectrolyte multilayers, layer-by-layer assembly, zeta-potential, ellipsometry, polymer substrate, layer stability
Objavljeno: 01.06.2012; Ogledov: 1720; Prenosov: 66
URL Povezava na celotno besedilo

Use of AFM force spectroscopy for assessment of polymer response to conditions similar to the wound, during healing
Uroš Maver, Tina Maver, Andrej Žnidaršič, Zdenka Peršin, Miran Gaberšček, Karin Stana-Kleinschek, 2011, izvirni znanstveni članek

Opis: Force spectroscopy is a very promising technique for the evaluation of interactions within different environments. Knowledge about them is especially important during the design and preparation of those modern wound dressings in contact with a changing wound-environment over a prolonged time. Such exposure can cause a drastic decrease in the materialćs mechanical performance, and can lead to degradation, thus lowering the success of any healing process. Our study tries to establish a model system, which would enable us to assess the applicability of the mentioned technique for the evaluation of any interaction changes between polymer molecules and a chosen surface, after exposure to different environments. Our proposed experimental setup consists of two representative polymers, a model silicon surface, and two solutions of various pHs and ionic strengths, respectively. Within the chosen range of parameters, we are confident that we can prove the usefulness of force spectroscopy for further research into polymer suitability, for the development of novel wound dressings.
Ključne besede: force spectroscopy, AFM, wound dressings, polymer materials, model system
Objavljeno: 01.06.2012; Ogledov: 1471; Prenosov: 72
.pdf Celotno besedilo (316,48 KB)
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