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The role of sonication of polyethyleneoxide solutions containing magnetic nanoparticles on morphology of nanofibrous mats
Peer, Petra ; Stěnička, M. ; Filip, Petr ; Pizúrová, Naděžda ; Babayan, V.
Properties of the resulting polymer nanofibers are often tailored by sonication technique applied prior or past an electrospinning process. The aim of this contribution is to evaluate morphology of nanofibrous mats formed by poly(ethylene oxide) with distributed magnetic nanoparticles (MNP) (about 20 nm in diameter) in dependence on time of sonication of the used polymer solutions. The solutions were exposed to sonication (intensity 200W, frequency 24 kHz) for 10, 30, and 60 minutes. It was shown that rheological characteristics (viscosity, storage and loss moduli) strongly depend on time of sonication (particularly phase angle) in contrast to electric conductivity and surface tension. For analysis of homogeneous distribution of MNP in polymer solution, the rheological measurements were carried out also in presence of external magnetic field. Magnetorheological efficiency (a relation of corresponding viscosities) was determined for 80, 170, and 255 mT. Consequently, changed rheological characteristics participate significantly in the process of electrospinning and resulting quality of the obtained nanofibrous mats. Qualitative changes were described by\nmeans of scanning electron microscopy (variance of mean diameter of nanofibers), transmission electron microscopy (distribution of MNP within nanofibrous mats). Static magnetic properties were determined by a vibration sample magnetometer. It was shown that even distribution of MNP in the mats can be achieved by mere sonication process without application of external magnetic field during an electrospinning process. However, time of sonication generates a degree of embedding of MNP into individual nanofibers.
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Molecular Simulation of Electrospinning.
Jirsák, Jan ; Moučka, F. ; Nezbeda, Ivo
Our recent attempts to apply standard molecular simulation techniques to the process of electrospinning are presented. We employ a molecular dynamics simulation to study phenomena involved in the electrospinning of polymer solutions, with particular attention to the formation of the Taylor cone and the development of a liquid jet. A molecular-based approach allows us to reveal the molecular structure and dynamics, which are inaccessible to continuum methods.
Plný tet: SKMBT_22317031713170 -  PDF
Plný text: content.csg - PDF
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Electrospinning of Modified Biopolymers for Medical Applications
Pavliňáková, Veronika ; Martinová,, Lenka (oponent) ; Zajíčková, Lenka (oponent) ; Vojtová, Lucy (vedoucí práce)
Proposed dissertation thesis is dedicated to the preparation and characterization of novel biocompatible nanofibers with both biological and medical potential applications. The main emphasis of this thesis was focused on the preparation of composite nanofibers respecting the principles of "green chemistry", meaning hard requirements of tissue engineering. The theoretical part summarizes knowledge about the electrospinning process and its parameters. The literature review also describes the electrospinning of proteins like collagen and gelatin, their blends with synthetic polymers and biopolymers as well as with inorganic fillers. One chapter deals with various kinds of crosslinking agents to improve nanofiber hydrolytic stability. The last chapter is aimed to halloysite inorganic nanotubes (HNT) gaining much attention for the use as drug carrier due to its remarkable physical (mechanical reinforcement) and biological (biocompatibility and low toxicity) properties. The experimental part is divided into two chapters, each of them examines issues of nanofibrous material preparation from different perspective. The first part is focused on novel hydrolytically stable antibacterial gelatin nanofibers modified with oxidized cellulose. The unique inhibitory effect of the nanofibers was examined by luminometric method using genetically modified Escherichia coli strain. Seeded adenocarcinoma lung cells proved good adhesion and proliferation. Second experimental part explores the effect of source and amount of natural tubular halloysite on the structure and properties of biocompatible amphiphilic nanofibers based on a polycaprolactone and gelatin. The addition of HNT improved the thermal stability, mechanical properties (both stiffness and elongation) and reduced the crystallinity of nanofibers. The HNT from different sources did not affect the cell behavior but slightly influenced the proliferation and viability of cells on nanofibers.
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Modul ohřevu elektrozvlákňovací elektrody
Lukesle, Václav ; Musil, Vladislav (oponent) ; Pokorný,, Marek (vedoucí práce)
Diplomová práce se zabývá principiálním návrhem ohřevu elektrozvlákňovací elektrody. Na tuto elektrodu se přivádí vysoké napětí (desítky kV), které je nezbytnou součástí zařízení pro výrobu nanovláken. V práci je uvedena rešerše možných řešení ohřevu a také jsou rozebrány některé principy výroby nanovláken. Dále jsou v práci uvedeny elektrická schémata a desky plošných spojů modulu ohřevu. Cílem je navrhnout takové řešení ohřevu, aby bylo zvlákňování z taveniny realizovatelné v přístroji pro výrobu nanovláken 4SPIN®.
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Influence of incorporated nanodiamond particles on mechanical properties of composite material based on multi-layer PVA nanofiber textiles
Prošek, Zdeněk ; Indrová, K. ; Rácová, Z. ; Ryparová, Pavla ; Nežerka, V. ; Topič, J. ; Tesárek, Pavel ; Kromka, Alexander
The present study investigates the influence of NDP on mechanical properties of multi-layer PVA nanofiber textiles. The particles of a diameter equal to 5 nm were incorporated into double- and triple-layer textiles, while the single-layer samples were prepared as the reference. The diameter of PVA nanofibers varied from 100 to 300 nm. We characterized the tensile strength, stiffness and ductility of fabricated nanofibers by using a conventional method – a tensile test. We found that the NDP-enriched nanofibers reveal antibacterial character. However, none or negligible influence of NDP additions on the tested mechanical properties was observed.
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Spinnability of PEO solutions with respect to their aging
Zelenková, Jana ; Peer, Petra ; Filip, Petr
Non - negligible portion of pol ymer commodity suffers from ageing that participates in sometimes significant changes of products attributes. Rheology represents a useful tool for a description of this process. The aim of this contribution is to evaluate possible ageing of PEO solution ( polyethylen e oxide ( M w =300,000 g/mol) dissolved in water at 10 wt.% concentration) based both on rheological characterization and on quality of electrospun fibres. Rheological measurements in steady shear and oscillatory modes were carried out using a rota tional rheometer MCR 501 (Anton Paar, Austria) equipped with the concentric cylinders geometry. The electrospinning measurements were executed with the help of a proposed laboratory device. The tip - to - collector distance attained 20 cm, applied voltage rang ed from 20 to 30 kV. The obtained electrospun fibres were analysed using a scanning electron microscope (VEGA 3, Tescan, Czech Republic). Both types of measurements were carried out in the period of several months during which the solution studied was plac ed in a dark and tempered box (25°C). The measurements indicate no ageing impact on rheological characteristics or quality of electrospun fibres. This guarantees more or less the identical quality of non - woven textiles prepared from PEO solutions regardles s of time period during which the solutions are deposited.
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Příprava a charakterizace nanovlákenných katalyzátorů pro environmentální aplikace
Soukup, Karel ; Topka, Pavel ; Hejtmánek, Vladimír ; Petráš, D. ; Šolcová, Olga
Cílem předložené práce bylo detailně popsat vliv přípravy palladiových a platinových katalyzátorů nanesených na polymerních nanovlákenných nosičích na bázi poly(2,6-dimethyl-1,4-fenylenoxidu) (polyfenylenoxid – PPO) na jejich katalytické vlastnosti. Katalytická aktivita připravených nosičových katalyzátorů byla ověřena pomocí modelové reakce založené na totální oxidaci metanolu. Příslušné nanovlákenné katalyzátorové nosiče byly připraveny technikou elektrostatického zvlákňování, přičemž tato technika představuje v současné době nejběžnější metodu vhodnou pro přípravu polymerních nanovlákenných útvarů. Principem elektrospiningu je dloužení vláken příslušného polymeru v elektrostatickém poli tvořeném dvěma opačně nabitými elektrodami, z nichž jedna měla podobu duté kapiláry a druhá byla ve formě desky.
Plný tet: SKMBT_C22013110613400 - PDF
Plný text: content.csg - PDF
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On the electrospinning of PVB solutions
Švrčinová, Petra ; Filip, Petr ; Lubasová, D.
Extension rheological characteristics belong to the principal description of polymer jet formation during a process of electrospinning. However, in spite of nearly absence of shear deformation of polymer solutions during the process of their spinnability, it seems that shear electrorheological characteristics can serve as an indicator of good or bad quality of an electrospun template. The experiments were carried out with four polyvinylbutyral (PVB) solutions in concentration of 10 wt%. Shear viscosities in absence (η0) and presence (η) of electric field were measured using a rotational rheometer equipped with an electrorheological cell. It was shown that the good solvents of PVB exhibit an almost constant curve of η/η0 vs. electric field strength, whereas the viscosity curves for the poor solvents exhibit enhancement. This enhancement corresponds to better quality of electrospun templates (obtained for polymer solutions of PVB with poor solvents).
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