Morphology of nano and micro fiber structures in ultrafine particles filtration

Selected procedures permitting to prepare homogeneous nanofibre structures of the desired morphology by employing a suitable combination of variables during the electrospinning process are presented. A comparison (at the same pressure drop) was made of filtration capabilities of planar polyurethane nanostructures formed exclusively by nanofibres, space polycarbonate nanostructures having bead spacers, structures formed by a combination of polymethyl methacrylate micro- and nanofibres and polypropylene meltblown microstructures, through which ultrafine particles of ammonium sulphate 20-400 nm in size were filtered. The structures studied were described using a new digital image analysis technique based on black and white images obtained by scanning electron microscopy. More voluminous structures modified with distance microspheres and having a greater thickness and mass per square area of the material, i.e. structures possessing better mechanical properties, demanded so much in nanostructures, enable preparation of filters having approximately the same free volume fraction as flat nanofibre filters but an increased effective fibre surface area, changed pore size morphology and, consequently, a higher filter quality. © 2011 American Institute of Physics

Study into oxidative changes of butter with protective coat

The contribution deals with employing starch-protein hydrolysate of amaranth flour to produce protective edible coatings on butter. Tests were run on 3 types of coating solutions. The first was made in such manner that to hydrolysate of 40-% dry matter content, 30-% (w/w) plasticiser (glycerol) was added and also 3-% (w/w) emulsifying agent (lecithin). The second and third contained an extra 2-% (w/w) antioxidant (ascorbic acid) and the third an extra 2-% (w/w) cross-linking agent (dialdehyde starch). Protective layers on butter were produced by coating with coat solutions. Butters were stored for a total of 96 days in refrigerator at a temperature of 7±1.5°C and relative humidity of 36±3%. The objective was to investigate the oxidation course of butter with protective coatings, butter wrapped in original wrapping and butter without wrapping/coat. Determined values were peroxide value, acid value and anisidine value. Results of butters with protective and edible polymer coatings displayed a similar oxidation course to that of butter in standard wrapping. Butter with a coat containing antioxidant exhibited slightly lower levels of peroxide value during storage than butter in original wrapping, which confirms good barrier properties to oxygen of the coating thus prepared

Dispergation of vermiculites in polymer matrix and elected property characterization of prepared nanocomposites

Clay minerals in the form of nanofillers in polymer matrices are usually studied with the aim to improve mechanical properties, thermal and chemical stability and flame retardancy of nanocomposites. Clay mineral vermiculite was treated mechanically and chemically as a nanofiller and its exfoliation in polyolefins was studied. Effects of jet and ball milling and of chemical modification of vermiculite by means of intercalation with hexadecyl trimethyl ammonium bromide, modification with HCl and different homogenisation procedures including electrospinning of solution dispersions on exfoliation of vermiculite in a polymer matrix were studied in composites. Dispersion and content of nanoparticle in the matrix were characterized by X-ray diffraction analysis, scanning electron microscopy, light optical microscopy and thermogravimetric analysis. Effect of dispersion of vermiculite nanofiller particles in polyethylene on processing, mechanical and service properties of the composite was demonstrated by determining melt strength, by tensile and creep

Morphologically optimized non-woven fabrics based on nanofibers

Morfologicky optimalizované netkané textilie na bázi nanovláken, vykazující zejména zvýšený filtrační efekt, obsahují nanovláknitou strukturu s morfologicky oddělenými nanovlákny, jako je: a) nanovláknitá struktura s nanovlákny fyzicky oddělenými kapkovitými distančními útvary a/nebo nanočásticemi dispergovanými v nanostruktuře, vytvářející pravidelné struktury s kapkovitými distančními útvary a/nebo nanočásticemi dispergovanými v nanostruktuře, kumulovanými ve sloupcích, propojených nanovlákny do pravidelných morfologických uspořádání, b) nanovláknitá struktura s nanovlákny fyzicky oddělenými kapkovitými distančními útvary a/nebo nanočásticemi dispergovanými vnanostruktuře, vytvářejícími nepravidelné struktury s kapkovitými distančními útvary a/nebo nanočásticemi dispergovanými v nanostruktuře, c) nanovláknitá struktura na bázi vláken se širokou distribucí průměrů z neohebných polymerů s vysokými moduly pružnosti, skládaných s mechanicky udržovanými distancemi v objemných morfologických uspořádáních, a/nebo d) struktura s bimodální distribucí průměrů vláken na bázi kombinace mikro- a nanovláken vytvářejících objemná morfologická uspořádání. Tyto prostorové objemnější struktury vykazují ve srovnání s plošnými útvary větší tloušťku a plošnou hmotnost filtračního materiálu, tedy požadované zlepšení mechanických vlastností a manipulovatelnosti s filtračním nanomateriálem

Effect of morphology of nanostructures to filter ultrafine particles

Selected procedures permitting to prepare homogeneous nanofibre structures of the desired morphology by employing a suitable combination of variables during the electrospinning process are presented. A comparison (at the same pressure drop) was made of filtration capabilities of planar polyurethane nanostructures formed exclusively by nanofibres and space nanostructures having bead spacers or structures formed by a combination of micro- and nanofibres, through which ultrafine particles of ammonium sulphate 20 - 400 nm in size were filtered. The structures studied were described using a new digital image analysis technique based on black and white images obtained by scanning electron microscopy. More voluminous structures modified with distance microspheres and having a greater thickness and mass per square area of the material, i.e. structures possessing better mechanical properties, demanded so much in nanostructures, enable preparation of filters having approximately the same free volume fraction as flat nanofibre filters but an increased effective fibre surface area, changed pore size morphology and, consequently, a higher filter quality

Polyolefin composite with enhanced processing properties

Polyolefinický kompozit se zlepšenými zpracovatelskými vlastnostmi obsahuje vedle základní polymerní složky tvořené polyolefinem přídavek multifunkčního aluminosilikátového aditiva se synergickými účinky taveninu ztužujícího plniva a nukleačního činidla na bázi jílu upraveného vyluhováním v HCl, přičemž toto aditivum je v kompozitní směsi obsaženo v množství 0,5 až 10 % hmotnostních a velikost jeho částic nepřesahuje 50 .mi.m. Je vhodný zejména pro výrobu lehčených polyolefinů se zjemněnou lehčenou strukturou a zlepšenými mechanickými vlastnostmi v energeticky úspornějším režimu.In the present invention, there is disclosed a polyolefin composite with enhanced processing properties comprising in addition to the base polymer component formed by polyolefin addition of multifunctional alumosilicate additive exhibiting synergistic properties, a melt of stiffening filler and a clay-based nucleation agent treated by leaching in HCl, whereby the additive is comprised in the composite mixture in an amount in the range of 0.5 to 10 percent by weight and particle size thereof is not greater than 50 microns. The so prepared polyolefin composite is particularly suitable for the preparation of lightweight polyolefins with finer expanded structure and enhanced mechanical properties in energy-saving mode

Application of nanofibres in filtration processes

Mechanisms of capture of dust particles, two- and three dimensional modelling of properties of filtration materials and effect of selected variables on electrospinning of polyurethane (PU) solutions are discussed with the aim to prepare a nanofibre structure capable of capturing ultrafine particles. The two-dimensional modelling is used to gain an idea of the effect of mass per square area, thickness of nanofibre layers and nanofibre diameter on filtration efficiency of ultrafine particles. Values of filtration efficiency calculated at the three-dimensional modelling of the filtration process are compared with experimental measurements for sets of filtered particles 100 nm in diameter or bigger. The most important characteristics affecting quality of nanofibre materials are nanofibre diameter, porosity and homogeneity of nanofibre layers. The method making possible to achieve the required diameter of the nanofibres is demonstrated on the influence of relative humidity and solvent type on the fibre-forming process taking place in an electrostatic field. The effect of homogeneity of the nanofibre deposition on the collecting substrate is assessed employing images from scanning electron microscopy (SEM) and tests of filtering abilities of the nanofibre layers. Also, some measurements obtained when nanofibres were used in filtration of air, liquids and dispersions of carbon nanotubes in a liquid are presented

Oxidative tissue injury in multiple sclerosis is only partly reflected in experimental disease models

Recent data suggest that oxidative injury may play an important role in demyelination and neurodegeneration in multiple sclerosis (MS). We compared the extent of oxidative injury in MS lesions with that in experimental models driven by different inflammatory mechanisms. It was only in a model of coronavirus-induced demyelinating encephalomyelitis that we detected an accumulation of oxidised phospholipids, which was comparable in extent to that in MS. In both, MS and coronavirus-induced encephalomyelitis, this was associated with massive microglial and macrophage activation, accompanied by the expression of the NADPH oxidase subunit p22phox but only sparse expression of inducible nitric oxide synthase (iNOS). Acute and chronic CD4(+) T cell-mediated experimental autoimmune encephalomyelitis lesions showed transient expression of p22phox and iNOS associated with inflammation. Macrophages in chronic lesions of antibody-mediated demyelinating encephalomyelitis showed lysosomal activity but very little p22phox or iNOS expressions. Active inflammatory demyelinating lesions induced by CD8(+) T cells or by innate immunity showed macrophage and microglial activation together with the expression of p22phox, but low or absent iNOS reactivity. We corroborated the differences between acute CD4(+) T cell-mediated experimental autoimmune encephalomyelitis and acute MS lesions via gene expression studies. Furthermore, age-dependent iron accumulation and lesion-associated iron liberation, as occurring in the human brain, were only minor in rodent brains. Our study shows that oxidative injury and its triggering mechanisms diverge in different models of rodent central nervous system inflammation. The amplification of oxidative injury, which has been suggested in MS, is only reflected to a limited degree in the studied rodent models