Number of found documents: 304
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Antibacterial electrospun membrane prepared from poly(vinylidene fluoride)-co-hexafluoropropylene with lauric acid monoacylglycerol
Zelenková, Jana; Peer, Petra; Pleva, P.; Janalíková, M.; Sedlaříková, J.; Filip, Petr
2020 - English
The aim of this study was to prepare an antibacterial nanofibrous membrane using electrospinning technique. The nanofibrous membranes were spun from polymer solution of poly(vinylidne fluoride)-co-hexafluoropropylene (PVDF-co-HFP) dissolved in N,N´-dimethylformamide. Monoacylglycerol of lauric acid (MAG C12) was used as an antimicrobial agent at the concentrations ranging from 1 to 3 wt%. The impact of MAG C12 incorporation on the rheological, structural and antibacterial properties was investigated. The rheological tests of polymer solutions, as steady shear and oscillatory shear, proved that addition of MAG C12 changed marginally rheological quantities such as viscosity, elastic (storage) and viscous (loss) moduli. Measurement of mean nanofibres diameter indicated a slight decrease with increasing MAG C12 concentration. Antimicrobial activity of PVDF-co-HFP nanofibre membranes with incorporated MAG C12 against Gram-positive bacteria Staphylococcus aureus and Gram-negative Escherichia coli was studied. An antibacterial activity was revealed for the samples containing MAG C12 at all concentrations against Gram-positive bacteria Staphylococcus aureus by the disk diffusion method. Keywords: nanofibres; electrospinning; antibacterial memrane; rheology; polymer solution Available in digital repository of the ASCR
Antibacterial electrospun membrane prepared from poly(vinylidene fluoride)-co-hexafluoropropylene with lauric acid monoacylglycerol

The aim of this study was to prepare an antibacterial nanofibrous membrane using electrospinning technique. The nanofibrous membranes were spun from polymer solution of poly(vinylidne ...

Zelenková, Jana; Peer, Petra; Pleva, P.; Janalíková, M.; Sedlaříková, J.; Filip, Petr
Ústav pro hydrodynamiku, 2020

Magnetic properties of electrospun polyvinyl butyral/Fe2O3 nanofibrous membranes
Peer, Petra; Cvek, M.; Urbánek, M.; Sedlačík, M.
2020 - English
In this contribution, magnetic Fe2O3 nanoparticles (MNPs) were successfully incorporated into the polyvinyl butyral (PVB) nanofibrous membranes using the electrospinning process. The effects of the MNP concentration on the morphology of the nanofibres and their magnetic properties were investigated. Scanning electron microscopy and transmission electron microscopy confirmed their concentration-dependent, yet uniform diameter, and the presence of well-embedded MNPs inside the PVB nanofibres. The magnetic properties of the PVB/MNP membranes were studied using the vibrating-sample magnetometry. The saturation magnetization increased from 6.4 to 45.5 emu/g as the MNP concentration in the feedstock solution increased from 1 to 15 wt%. The fabricated PVB/MNP nanofibrous membranes possessed the ability to respond to the external magnetic fields, which determines their potential in the development of the advanced smart textiles. Keywords: electrospinning; polyvinyl butyral; nanofibres; magnetic properties Available in digital repository of the ASCR
Magnetic properties of electrospun polyvinyl butyral/Fe2O3 nanofibrous membranes

In this contribution, magnetic Fe2O3 nanoparticles (MNPs) were successfully incorporated into the polyvinyl butyral (PVB) nanofibrous membranes using the electrospinning process. The effects of the ...

Peer, Petra; Cvek, M.; Urbánek, M.; Sedlačík, M.
Ústav pro hydrodynamiku, 2020

Preparation and characterization of fibrous non-woven textile decorated by silver nanoparticles for water filtration
Peer, Petra; Polášková, M.; Mosnáček, J.; Sedlařiková, J.; Masař, M.
2019 - English
The environmentally friendly preparation of silver nanoparticles was proposed for the production of antibacterial non-woven textile used in water filtration. The silver nanoparticles were prepared by chemical reduction of silver nitrate using two environmentally friendly reducing agents, such as fructose or ascorbic acid. For comparison also commonly used reducing agent-sodium borohydride was used. The silver nanoparticles in various size and yield were produced by immersion of the plasma pre-treated polypropylene (PP) nonwoven textile in the colloidal solutions for different periods (35, 45 and 135 min). The morphology of the silver nanoparticles was characterized by SEM and EDX analysis. Additionally, the antibacterial activity of the silver decorated PP non-woven textile was evaluated by an agar diffusion test using both Gram-positive Staphylococcus Aureus and Gram-negative Escherichia coli. The results suggest that the type of the reducing agent has major effect both on the morphology of silver nanoparticles and the antibacterial activity. Keywords: silver nanoparticles; reducing agent; non-woven textile; antibacterial activity Available on request at various institutes of the ASCR
Preparation and characterization of fibrous non-woven textile decorated by silver nanoparticles for water filtration

The environmentally friendly preparation of silver nanoparticles was proposed for the production of antibacterial non-woven textile used in water filtration. The silver nanoparticles were prepared by ...

Peer, Petra; Polášková, M.; Mosnáček, J.; Sedlařiková, J.; Masař, M.
Ústav pro hydrodynamiku, 2019

Flow behaviour of sand-water mixture in horizontal and inclined pipes
Vlasák, Pavel; Chára, Zdeněk; Matoušek, Václav; Kesely, Mikoláš; Krupička, Jan; Konfršt, Jiří; Mildner, Michael
2019 - English
Pipelines transporting slurries in different industrial applications often contain inclined sections. The effect of pipe inclination, slurry concentration and mean velocity on the flow behaviour, deposition\nlimit velocity, and internal structure of a settling slurry was studied in an experimental pipe loop of inner diameter D = 100 mm. The slurry consisted from water and a narrow particle size distribution sand of mean diameter d50 = 0.55 mm. The experiments focused on the effects of the pipe inclination on solids distribution and deposition limit velocity. The concentration distribution in pipe cross-section was studied with application of a gamma-ray densitometer. The study revealed the stratified flow pattern of the medium sand-water mixture in inclined pipe sections. Experimental results show that the degree of the slurry stratification decreased with an increasing angle of inclination in the ascending pipe sections. The slurry stratification affected the deposition limit velocity. Mean in situ concentration for the descending flow was always lower than that for the ascending flow. The deposition limit in ascending pipe, in comparison with that in a horizontal pipe, slightly increased up to inclination angle about +25°, and then remained practically constant. For negative pipe inclination over – 30° no deposition limit was observed. Keywords: slurry flow; inclined pipe; deposit limit velocity Available at various institutes of the ASCR
Flow behaviour of sand-water mixture in horizontal and inclined pipes

Pipelines transporting slurries in different industrial applications often contain inclined sections. The effect of pipe inclination, slurry concentration and mean velocity on the flow behaviour, ...

Vlasák, Pavel; Chára, Zdeněk; Matoušek, Václav; Kesely, Mikoláš; Krupička, Jan; Konfršt, Jiří; Mildner, Michael
Ústav pro hydrodynamiku, 2019

Effect of pipe inclination on local concentration and flow behaviour of settling slurry
Vlasák, Pavel; Chára, Zdeněk; Matoušek, Václav; Kesely, Mikoláš; Konfršt, Jiří; Mildner, Michael
2019 - English
Settling slurry, consisted from narrow-graded sand of mean particle diameter 0.87 mm and water, was investigated on an experimental pipe loop of inner diameter 100 mm. The investigation was focused on the effect of the pipe inclination, slurry concentration, and velocity on concentration distribution, and deposition limit. The settling slurries tend to stratify; a layered structure is typical for a settling slurry flow. Slurry stratification is sensitive to pipe inclination, and differs for the positive and negative pipe inclination. Deposition limit increases with pipe inclination up to about 25°, and then remain nearly constant. Keywords: sand-water slurry; pipe inclination; concentration distribution; deposition limit Available at various institutes of the ASCR
Effect of pipe inclination on local concentration and flow behaviour of settling slurry

Settling slurry, consisted from narrow-graded sand of mean particle diameter 0.87 mm and water, was investigated on an experimental pipe loop of inner diameter 100 mm. The investigation was focused on ...

Vlasák, Pavel; Chára, Zdeněk; Matoušek, Václav; Kesely, Mikoláš; Konfršt, Jiří; Mildner, Michael
Ústav pro hydrodynamiku, 2019

Local velocity scaling in upward flow to tooth impeller in a fully turbulent region
Šulc, R.; Ditl, P.; Fořt, I.; Jašíková, D.; Kotek, M.; Kopecký, V.; Kysela, Bohuš
2018 - English
The hydrodynamics and flow field were measured in an agitated vessel using 2-D Time Resolved Particle Image Velocimetry (2-D TR PIV). The experiments were carried out in a fully baffled cylindrical flat bottom vessel 400 mm in inner diameter agitated by a tooth impeller 133 mm in diameter. Distilled water was used as the agitated liquid. The velocity fields were investigated in the upward flow to the impeller for three impeller rotation speeds – 300 rpm, 500 rpm and 700 rpm, corresponding to a Reynolds number in the range 94 000 < Re < 221 000. This means that fully-developed turbulent flow was reached. This Re range secures the fully-developed turbulent flow in an agitated liquid. In accordance with the theory of mixing, the dimensionless mean and fluctuation velocities in the measured directions were found to be constant and independent of the impeller Reynolds number. On the basis of the test results the spatial distributions of dimensionless velocities were calculated. The axial turbulence intensity was found to be in the majority in the range from 0.4 to 0.7, which corresponds to the middle level of turbulence intensity. Available at various institutes of the ASCR
Local velocity scaling in upward flow to tooth impeller in a fully turbulent region

The hydrodynamics and flow field were measured in an agitated vessel using 2-D Time Resolved Particle Image Velocimetry (2-D TR PIV). The experiments were carried out in a fully baffled cylindrical ...

Šulc, R.; Ditl, P.; Fořt, I.; Jašíková, D.; Kotek, M.; Kopecký, V.; Kysela, Bohuš
Ústav pro hydrodynamiku, 2018

Droplets breakage in flow conditions of an agitated tank
Kysela, Bohuš; Konfršt, Jiří; Chára, Zdeněk; Šulc, R.; Kotek, M.
2018 - English
Production of two immiscible liquid dispersions used in chemical or metallurgical industry is usually performed by a mixing process. The droplets of secondary liquid are predominantly dispersed by the shear flow forces to the primary liquid. It is well known, that the real droplet size distribution is limited by the physical properties of both liquids, the acting forces and residence time. This phenomenon is investigated experimentally or numerically simulated by several methods. In this study, the simplified mixing test case was studied. The single droplet dispergation was simulated using finite volume method and multiphase VOF (Volume-of-Fluid) model. The capability of the local remeshing method was investigated. The increase of calculation performance and the phases mass imbalance during automatic mesh refinement is summarized. Keywords: immiscible liquid dispersion; mixing process; droplet size distribution Available at various institutes of the ASCR
Droplets breakage in flow conditions of an agitated tank

Production of two immiscible liquid dispersions used in chemical or metallurgical industry is usually performed by a mixing process. The droplets of secondary liquid are predominantly dispersed by the ...

Kysela, Bohuš; Konfršt, Jiří; Chára, Zdeněk; Šulc, R.; Kotek, M.
Ústav pro hydrodynamiku, 2018

Modelling of non-monotonous course of shear viscosity
Filip, Petr
2018 - English
A number of parameters appearing in the 'classical' empirical constitutive equations usually oscillate between two and five. With the onset of new rheologically more complex materials exhibiting non-monotonous behaviour of flow curves this range (2-5) is no longer tenable and more additional parameters are required for a proper description of the flow curves. An 8-parameter model is presented and testified. Keywords: viscosity; flow curve; constitutive equation; empirical modelling Available at various institutes of the ASCR
Modelling of non-monotonous course of shear viscosity

A number of parameters appearing in the 'classical' empirical constitutive equations usually oscillate between two and five. With the onset of new rheologically more complex materials exhibiting ...

Filip, Petr
Ústav pro hydrodynamiku, 2018

The role of solvents in the preparation of hydrophobic nanofibrous membrane containing fumed silica
Peer, Petra; Polášková, M.; Musilová, I.; Filip, Petr
2018 - English
It is well-known that a type of used fumed silica nanoparticles plays a dominant role in wettability of the corresponding nanofibrous mats. As a result, the desired contact angle can be approximately achieved by a choice of adequate fumed silica nanoparticles. However, less attention has been hitherto paid to an active role of solvents in connection with the tailoring this contact angle. For analysis we used poly(vinyl butyral) representing electrospun-friendly material, various types of fumed silica nanoparticles and two solvents - methanol and ethanol. It is demonstrated that a choice of polymer solvents plays a significant role in contact angle changes. Hence, in combination of the type of fumed silica nanoparticles and the type of solvent it is possible to achieve a finer partition of the required contact angles. Keywords: PVB solution; solvents; fumed silica; electrospinning; rheology Available at various institutes of the ASCR
The role of solvents in the preparation of hydrophobic nanofibrous membrane containing fumed silica

It is well-known that a type of used fumed silica nanoparticles plays a dominant role in wettability of the corresponding nanofibrous mats. As a result, the desired contact angle can be approximately ...

Peer, Petra; Polášková, M.; Musilová, I.; Filip, Petr
Ústav pro hydrodynamiku, 2018

Thermal induced morphological changes of poly(ethylene oxide) nanofibrous webs
Polášková, M.; Peer, Petra; Ponížil, P.; Čermák, R.
2018 - English
The crystallinity of fibres prepared by electrospinning shows lower level in comparison with samples processed by common technologies such as moulding or film casting. Thus, the attempts to improve the structure of electrospun fibres in order to increase physical and mechanical properties of nonwoven webs are obvious. Post-process thermal treatment is one of the possibilities of the crystallinity enhancement that can be easily included to the finishing operation of final products. For the experiment we used poly(ethylene oxide) representing electrospun-friendly material and two solvents - methanol and water, both ensuring good electrospinnability. It is demonstrated that a choice of polymer solvents plays a significant role in fibre diameter and their capabilities to resist applied heat. However, in all cases the enhancement of crystallinity is detected at the short time of thermal exposure. Keywords: PEO nanofibres; degree of crystallinity; electrospinning Available at various institutes of the ASCR
Thermal induced morphological changes of poly(ethylene oxide) nanofibrous webs

The crystallinity of fibres prepared by electrospinning shows lower level in comparison with samples processed by common technologies such as moulding or film casting. Thus, the attempts to improve ...

Polášková, M.; Peer, Petra; Ponížil, P.; Čermák, R.
Ústav pro hydrodynamiku, 2018

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