Modification of polypropylene fibrous materials with ultradispersed polytetrafluoroethylene

The effects of narrowly and widely dispersed fractions of ultradispersed polytetrafluoroethylene on the structures of melt-spun polypropylene fibrous materials and the ultimate tensile half-cycle characteristics of polypropylene filaments and nonwoven materials have been studied via X-ray diffraction analysis, optical microscopy, and differential scanning calorimetry. It has been shown that the addition of 1–2% ultradispersed polytetrafluoroethylene, which exists as an individual phase in polypropylene, allows a significant increase in the relative tensile stress of the filament and its elastic modulus.     

Relationships of formation and characteristics of colloidal particles in tin-containing organosols intended for activation of the surface of fibrous polyester materials

Formation of colloidal particles in tin-containing alcoholic solutions was studied in relation to the SnCl₂ concentration, storage time, and kind of the solvent and stabilizing additive. The highest category of flame resistance and the highest resistance of the fireproofing coating to repeated launderings are reached when the poly(ethylene terephthalate) fabric is activated with alcoholic SnCl₂ solutions with high concentration of 10–15-nm colloidal particles prior to application of an inorganic fireproofing compound.     

Modification of polymeric matrix of polyester fiber-glass materials with powder polyamide and epoxy resin

The possibility of improving the quality of polyester fiber-glass products prepared by environmentally safe low-pressure procedures by modification of the polymeric matrix with moderate amounts of polycaproamide powder in combination with small amounts of epoxy resin was studied.     

Effects of discharge mode and gas composition for plasma-hydrophilized titanium surface on hydrophilic sustainability

Plasma hydrophilization under various conditions was carried out on Ti substrates to investigate the effect of the applied parameters on the hydrophilic sustainability. The plasma was discharged from gases comprising Ar and/or O₂ at various ratios using DC and RF modes. Notable differences in the surface morphology by the plasma conditions was hardly found, while the ratio of hydroxide on the surface was influenced by the discharge mode. The hydrophilicity was significantly improved regardless of the treatment conditions, that is, the gas composition and discharge mode. The deterioration of the hydrophilicity was occurred by storing in the ambient atmosphere or distilled water, wherein the deterioration in distilled water was suppressed when using DC as a discharge mode. The hydrophilicity was preserved when the specimens was stored in a physiological solution such as phosphate buffered saline solution due to the adsorption of Na⁺ and Cl⁻ in the solution; its effect was far superior to that contributed by the parameter settings. In conclusion, plasma discharge mode enabled to improve the deterioration of hydrophilicity only slightly.     

Breakdown of a gas gap in a surface barrier discharge

The processes that occur in a surface barrier discharge in oxygen at atmospheric pressure have been studied by numerical modeling. Modeling is performed assuming the existence of local equilibrium, and the dynamics of charged particles in the gas gap is calculated using continuity equations. The configuration of the electric field in the discharge zone is determined by integration of the Poisson equation. It turns out that the breakdown of the gas gap is determined by the photoemission from the cathode surface. The appearance and development of the microdischarge channel are sustained by the cathode layer that is formed at the conducting cathode. The parameters of the cathode layer obtained in oxygen at atmospheric pressure are virtually the same as for the ordinary cathode layer of the glow discharge.     

An open-source surface barrier discharge plasma pretreatment for reduced cracking of outdoor wood coatings

The development of a simple surface barrier discharge plasma device is presented to enable more widespread access to and utilization of plasma technology. The application of the plasma device was demonstrated for pretreatment of wood prior to application of protective coatings for outdoor usage. The coatings' overall performance was increased, showing a reduction or absence of cracking due to weathering on plasma-pretreated specimens. Moreover, after ten months of outdoor weathering, the plasma-pretreated specimens showed fewer infections with biotic factors and improved adhesion performance in cross-cut tests, while the surface gloss performed independently from plasma pretreatment. In contrast to that, plasma-pretreated specimens were slightly more prone to discoloration due to outdoor weathering, whereas the plasma pretreatment did not impact the initial color after coating application.

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Modification of gluing compositions around polychloprene with fibrous fillers

The influence of fibrous fillers on adhesive properties of glues around polychloroprene rubber is considered.     

Hydrophobization of polyester textile materials with telomeric tetrafluoroethylene solutions

Hydrophobic coatings formed on a polyester fabric by treatment with telomeric solutions prepared by a radiation-chemical procedure in acetone and butyl chloride were studied by IR spectroscopy (MATIR), energy-dispersive analysis, and atomic force microscopy. The hydrophobic properties of the textile material were evaluated by procedures traditional for textile chemistry. Conditions determining the formation of a thin, highly hydrophobic, uniform, and flawless coating resistant to the effect of operation factors were suggested.     

Sorption of cesium radionuclides with composite carbon fibrous materials

Sorption of composite sorbents produced by a combined method of thermal treatment and electrochemical and chemical deposition of transition metal ferrocyanides stabilized with latex emulsions onto a fibrous carbon matrix for cesium radionuclides was studied.     

Superhydrophobicity of PHBV fibrous surface with bead-on-string structure

A poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) fibrous surface with various bead-on-string structures was fabricated by electrospinning. PHBV was electrospun at various concentrations and then CF4 plasma treatment was employed to further improve the hydrophobicity of the PHBV fiber surfaces. The surface morphology of the electrospun PHBV mats was observed by scanning electron microscopy (SEM). The surface properties were characterized by water contact angle (WCA) measurements and X-ray photoelectron spectroscopy (XPS). The surface morphology of the electrospun PHBV fibrous mats with the bead-son-string structure varied with the solution concentration. The WCA of all of the electrospun PHBV mats was higher than that of the PHBV film. In particular, a very rough fiber surface including porous beads was observed when PHBV was electrospun from the solution with a concentration of 26 wt%. Also, its WCA further increased from 141 degrees to 158 degrees after CF(4) plasma treatment for 150 s. PHBV can be rendered superhydrophobic by controlling the surface morphology and surface energy, which can be achieved by adjusting the electrospinning and plasma treatment conditions.     

Optical coherence tomography image analysis of polymer surface layers in sound-absorbing fibrous composite materials

The material surface layer affecting sound absorption was identified by optical coherence tomography (OCT) image analysis. To characterise this layer, a special algorithm was developed to distinguish the polymer surface layer in thermoplastic composite materials, define its structure and thickness, and specify differences in these properties. The composite materials were obtained by thermal pressing of multilayer systems comprising viscose/polylactide and polylactide nonwoven fabrics, yielding thin polymer surface layers on the order of several hundred micrometres. The results of the measured sound absorption coefficient were analysed together with the OCT results. The use of OCT for the study of materials with specific acoustic characteristics was successfully demonstrated.     

Mixed oligonucleotides for random mutagenesis: best way of making them

The generation of proteins, especially enzymes, with pre-deliberated, novel properties is a big challenge in the field of protein engineering. This aim, over the years was critically facilitated by newly emerging methods of combinatorial and evolutionary techniques, such as combinatorial gene synthesis followed by functional screening of many structural variants generated in parallel (library). Libraries can be generated by a large number of available methods. Therein the use of mixtures of pre-formed trinucleotide blocks representing codons for the 20 canonical amino acids for oligonucleotide synthesis stands out as allowing fully controlled partial (or total) randomization individually at any number of arbitrarily chosen codon positions of a given gene. This has created substantial demand of fully protected trinucleotide synthons of good reactivity in standard oligonucleotide synthesis. We here review methods for the preparation of oligonucleotide mixtures with a strong focus on codon-specific trinucleotide blocks.     

Modification of surface properties of high and low density polyethylene by Ar plasma discharge

Structural changes induced by Ar plasma discharge in low and high density polyethylene (LDPE and HDPE) were studied by different techniques. AFM and SEM methods were used to determine surface morphology, the changes in chemical structure were followed using FTIR and UV-vis spectroscopy. The content and the depth profile of incorporated oxygen was determined by RBS method. The degree of polymer ablation was determined gravimetrically. Standard goniometry was used to determine contact angle and to follow aging of plasma modified polymer. As a result of plasma treatment a lamellar structure or spherulites appear on the surface of HDPE and LDPE, respectively. Pronounced increase of the surface roughness is observed on HDPE contrary to LDPE. Plasma treatment for 400 s leads to the ablation of the surface layer of about 0.6 and 1 μm thick for LDPE and HDPE, respectively. Plasma treatment results in oxidation of the polymer surface layer which is more pronounced in HDPE. Concentration maximum of incorporated oxygen lies 25 nm beneath the sample surface in both polymer types. After exposure to plasma discharge carbonyl, carboxyl and amide groups were detected in the polymer surface layer together with CC bonds either in aromatic or in aliphatic structures. Immediately after the plasma treatment strong decline of the contact angle is observed, the decline being larger in HDPE. Later, in aged specimens the contact angle increases rapidly. The increase, which may be due to rearrangement of degraded structures, is stronger in the specimens exposed to plasma for longer times.     

Modification of polyester binders for glass fiber-reinforced plastics with phosphorus-containing metacrylates for reduction of composite flammability

Synthetic procedures for methacrylic derivatives of phosphorus acids are developed. Their copolymerization with unsaturated polyesters gives binders for low-flammable composite materials. Novel fiberglass plastics for shipbuilding are presented.     

Oxidation of propylene and isobutylene in a reactor with barrier discharge

The oxidation of propylene and isobutylene in barrier-discharge plasma in the presence of octane was studied. The possible reaction mechanism was considered.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1922–1924.Original Russian Text Copyright © 2004 by Kudryashov, Ryabov, Sirotkina, Shchegoleva.     

Amorphous porous sulfides nanosheets with hydrophilic/aerophobic surface for high-current-density water splitting

The rational construction of electrocatalysts with desired features is significant but challenging for superior water splitting at high current density. Herein, amorphous CoNiS nanosheets are synthesized on nickel foam (NF) through a facile structure evolution strategy and present advanced performance at high current densities in water splitting. The high catalytic activity can be attributed to the sufficient active sites exposed by the flexible amorphous configuration. Moreover, the hydrophilicity and aerophobicity of a-CoNiS/NF promote surface wettability of the self-supporting electrode and avoid the aggregation of bubbles, which expedites the diffusion of electrolyte and facilitates the mass transfer. As a result, the optimized electrode demonstrates low overpotentials of 289 and 434 mV at 500 mA/cm² under alkaline conditions for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Impressively, an electrolytic water splitting cell assembled by bifunctional a-CoNiS/NF operates with a low cell voltage of 1.46 V@10 mA/cm² and reaches 1.79 V at 500 mA/cm². The strategy sheds light on a competitive platform for the reasonable design of non-precious-metal electrocatalysts under high current density.     

Computer simulations of a dielectric barrier discharge used for analytical spectrometry

A model developed for a dielectric barrier discharge (DBD) in helium, used as a new spectroscopic source in analytical chemistry, is presented in this paper. The model is based on the fluid approach and describes the behavior of electrons, He⁺ and ions, He metastable atoms, He atoms in higher excited levels, and He₂ dimers. The He ground-state atoms are regarded as background gas. The characteristic effect of charging/discharging of the dielectrics which cover both electrodes is also simulated. Typical results of the model include the distribution of potential inside the plasma (and the potential drop across the dielectrics), the electric current and gap voltage as a function of time for a given applied potential profile, the spatial and temporal number-density profiles of the different plasma species, and the relative contributions of the mechanisms of their production and loss. Figure Schematic diagram of the dielectric barrier discharge (left) and typical temporal profiles of voltage and current, as obtained from the simulations (right)     

Investigation of materials for making a carbon-support zinc-selective electrode

The usefulness of zinc orthophosphate and zinc mercuric thiocyanate to make a carbon-support electrode responsive to zinc was investigated. The best results were obtained with zinc orthophosphate, which produced a Nernstian response to zinc in the concentration range from 10(-5) to 10(-2)M. The electrode response was lowered by the formation of acidic oxides on the surface of the electrode. Different ways of minimizing this problem are discussed. Interference effects from copper(II) (K(pot)(Zn.Cu) = 1.0), cadmium (K(pot)(Zn.Cd) = 8.9) and lead (K(pot)(Zn.Pb) = 10) were observed.     

Operation modes of the helium dielectric barrier discharge for soft ionization

Among different applications of dielectric barrier discharge (DBD) plasma, the soft ionization ability is certainly one of the most interesting. In this paper the helium plasma jet, produced by a capillary DBD, penetrating in the ambient atmosphere, has been spectroscopically investigated in dependence on applied voltage and helium flow. It was found that the change of the applied voltage leads to different discharge modes. Based on the measurements of the emission spectra of atomic He and N₂⁺ and N₂ molecules in the capillary and in the plasma jet with high spatial resolution, it can be assessed in which mode, i.e. under which conditions the plasma jet is expected to be most effective for soft ionization of molecules.