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Biokemija : organski del
Črtomir Stropnik, 2005, other educational material

Keywords: biokemija, visokošolski učbeniki
Published: 01.06.2012; Views: 1256; Downloads: 57
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PEG modified poly(amide-b-ethylene oxide) membranes for CO2 separation
Anja Car, Črtomir Stropnik, Wilfredo Yave, Klaus-Viktor Peinemann, 2008, original scientific article

Abstract: In the present work, membranes from commercially available Pebaxr MH 1657 and its blends with low molecular weight poly(ethylene glycol) PEG were prepared by using a simple binary solvent (ethanol/water). Dense film membranes show excellent compatibility with PEG system up to 50 wt.% of content. Gas transport properties have been determined for four gases (H2, N2, CH4, CO2) and the obtained permeabilities were correlated with polymer properties and morphology of the membranes. The permeability of CO2 in Pebaxr/PEG membrane (50 wt.% of PEG) was increased two fold regarding to the pristine Pebaxr. Although CO2/N2 and CO2/CH4 selectivity remained constant, an enhancement of CO2/H2 selectivity was observed. These results were attributed to the presence of EO units which increases CO2 permeability, and to a probable increase of fractional free-volume. Furthermore, for free-volume discussion and permeability of gases, additive and Maxwell models were used.
Keywords: chemical processing, membranes, membrane separation, CO2, Pebax, gas separation, blend membranes
Published: 01.06.2012; Views: 1299; Downloads: 54
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Pebax©/Polyethlylene glycol blend thin film composite membranes for CO2 separation : performance with mixed gases
Anja Car, Črtomir Stropnik, Wilfredo Yave, Klaus-Viktor Peinemann, 2008, original scientific article

Abstract: The paper describes the performance of Pebax©/Polyethylene glycol (PEG) blend thin film composite membranes for CO2 separation from gas mixtures containing H2, N2 and CH4. Membranes were tested at different conditions; temperature andpressure dependence of gas flux and selectivity were explored. The temperature dependence was correlated with the Arrhenius equation to determinethe activation energy of single gas permeation. Single and mixed gas permeation was measured for different pressures at 293K up to 20 bar. Improvedpermeabilities and CO2/H2 selectivities were obtained in the newly developed composite membranes.
Keywords: chemical processing, membranes, membrane separation, CO2, Pebax, thin film composite membranes, gas separation
Published: 01.06.2012; Views: 1496; Downloads: 23
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Organska kemija : študijsko gradivo (verzija "dolgi tekst")
Črtomir Stropnik, 2004, other educational material

Keywords: organska kemija, visokošolski učbeniki
Published: 01.06.2012; Views: 1738; Downloads: 100
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Poly(styrene-co-divinylbenzene-co-2-ethylhexyl)acrilate membranes with interconnected macroporous structure
Urška Sevšek, Silvo Seifried, Črtomir Stropnik, Irena Pulko, Peter Krajnc, 2011, original scientific article

Abstract: A combination of doctor blading and emulsion templating was used to prepare macroporous poly(styrene-co-divinylbenzene-co-2-ethylhexylacrylate) and poly(styrene-co-divinylbenzene) membranes with an interconnected porous structure. Water in oil high internal phase emulsions including monomers in the oil phase were cast onto a glass plate and polymerised at elevated temperature. After purification porous polyHIPE membranes were obtained. The volume ratio of aqueous phase (75 % or 85 %) and the molar ratio of divinylbenzene (2 % or 4 %) were varied, while the addition of chlorobenzene to the oil phase influenced the viscosity of the emulsions. A comonomer, 2-ethylhexylacrylate substantially improved the flexibility of the membranes. All yielding membranes were characterized by measuring their cast thicknesses and flow densities for deionised water. Scanning electron microscopy was used to study the morphological features of the membranes.
Keywords: membrane, porous polymers, polyHIPE, emulsions
Published: 10.07.2015; Views: 1245; Downloads: 113
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Strjevanje polimera v sistemu polisulfon/N,N-dimetilacetamid/voda in njegova morfološka raznolikost
Vladimir Kaiser, Črtomir Stropnik, 2000, original scientific article

Abstract: Preučevali smo mokro fazno inverzijo ternaranega sistema polisulfon/N,N-dimetilacetamid/voda (PSf/DMA/voda) z namenom, poglobiti razumevanje mehanizma nastajanja polimernih asimetričnih poroznih membran. Morfologije presekov membran smo preučevali z vrstično elektronsko mikroskopijo, sam proces fazne inverzije pa smo opazovali z merjenjem motnosti membranotvornega sistema med procesom nastajanja membrane. Spreminjanje vsebnosti polimera v raztopini (PSf/DMA) in debeline njenega nanosa povzroči v procesu mokre fazne inverzije poleg nastanka polimernega lateksa formiranje morfološko različnih membran. Nastanejo membrane s celično, dvozvezno in krogličasto zrnatao morfologijo. Njihov nastanek lahko predstavimo s "potmi sestave" v ternarnem faznem diagramu polimer/topilo/netopilo in pojasnimo z različnimi načini fazne inverzije.
Keywords: polisulfonske asimetrične porozne membrane, mokra fazna inverzija, načini fazne inverzije, morfologija
Published: 10.07.2015; Views: 844; Downloads: 55
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Mehanizem nastajanja polimerne asimetrične porozne membrane z mokrim postopkom fazne inverzije
Črtomir Stropnik, Leonida Oberš, Vesna Lahovnik, 1997, original scientific article

Abstract: Kvalitativno je predstavljen mehanizm nastajanja polimerne asimetrične porozne membrane po mokrem postopku fazne inverzije. Nastanek morfoloških značilnosti membran iz celuloznega acetata, polisulfona, polimetilmetakrilata,termoplastičnega poliuretana in poliamida 4,6 je interpretiran s `potmi sestave` v ternarnem faznem diagramu polimer/topilo:netopilo ter podprt z evidencami pojavov motnosti med nastajanjem membrane, skrčitve ulite raztopine polimera v (proto)membrano in s permeabilnostjo nastalih membran z vodo.
Keywords: kemija, polimeri, membrane, nastanek membran, morfologija, motnost, skrčitev, pretok
Published: 10.07.2015; Views: 663; Downloads: 47
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Polimerne asimetrične porozne membrane
Črtomir Stropnik, 1994, original scientific article

Published: 10.07.2015; Views: 763; Downloads: 29
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Chemical modification and characterization of the surface of polysulfone membranes
Irena Kukovičič, Robert Šoster, Milan Brumen, Volker Ribitsch, D. Wiegel, K. Arnold, Črtomir Stropnik, 2000, original scientific article

Abstract: Asymmetric porous membranes were prepared from polysulfone by a wet-phase separation procedure. Different chemical modifications were applied to the upper membrane surface, i.e. the surface which was exposed to interaction with nonsolvent (water) in the coagulation bath during the membrane formation. The membrane surface was modified by the series of Friedel-Crafts electrophilic substitutions of aromatic rings in the polysulfone molecules. As a reagent 1-chlorodecane or propylene oxide dissolved in hexane and $AlCl_3$ as a catalyst were used. In the former case a hydrophobic and in the latter one a hydrophilic coating was achieved, respectively. The membrane surface was also modified by sulfonization with sulfuric (VI) acid water solution; in this way negative charges were introduced at the membrane surface. The membranes, unmodified and chemically modified, were characterized by measuring the membrane thickness, the deionized water flux through the membrane, the zeta potential and contact angle. The specific chemical modifications of the membrane surface affect the water flux, the zeta potential and contact angle values whereas the membrane thickness remains unchanged. These effects are interpreted in terms of hydrophilicity and hydrophobicity, changes of the membrane surface charge and the thickness of shear layer at the membrane surface, all with respect to the particular modification applied. Reaction with 1-chlorodecane gave a hydrophobic surface by nonpolar $–(CH_2)_9-CH_3$ groups and reaction with propylene oxide gave a hydrophilic surface with polar group $-CH(CH_3)-CH_2-OH$. The surface of sulfonized polysulfone membranes contained ionizable ($-SO_3H$) functional groups.
Keywords: polysulfone, chemical modification, Friedel-Crafts electrophilic substitution, sulfonization, hydrophylicity, hydrophobicity
Published: 17.08.2017; Views: 678; Downloads: 78
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