Grafting vinyl monomers onto silk fibers IV. Graft copolymerization of methyl methacrylate onto silk using bromate-thiourea redox system

The use of a bromate-thiourea redox system to initiate graft copolymerization of methyl methacrylate onto silk has been investigated. The rate of grafting has been determined by varying the concentration of bromate ion, monomer, thiourea, the temperature and the solvent. The graft yield increases with increasing the bromate ion concentration up to 20 mmo1/1. With further increase of oxidant the graft yield decreases. The percentage of grafting increases with increase of hydrochloric acid up to 40 mmo1/1. Thereafter it decreases. The effect of increasing thiourea concentration up to 15 mmo1/1. is to bring about an increase in the graft yield. Above this concentration grafting decreases sharply. The rate of grafting increases with increase of temperature. The use of various water soluble solvents effects the percentage of grafting considerably. The alkali solubility of the grafted fiber has been investigated.     

Grafting vinyl monomers onto wool fibers,IX. Graft copolymerization of methyl methacrylate onto wool using peroxydiphosphate-cysteine redox system

The graft copolymerization of methyl methacrylate onto wool was studied at 50°C using peroxydiphosphate-cysteine redox system as initiator. The rate of grafting was determined by varying monomer, initiator, cysteine, acid and temperature. The grafting is considerably influenced by chemical modification prior to grafting. A suitable kinetic path has been pictured and a rate expression has been derived.     

Grafting vinyl monomers onto wool fibers. VIII. Graft copolymerization of methyl methacrylate onto wool using peroxydiphosphate–fructose redox system

The graft copolymerization of methyl methacrylate onto wool fibers was investigated in aqueous solution using the peroxydiphosphate–fructose redox system. The rate of grafting was determined by varying monomer, acidity of the medium, temperature, nature of wool, and reaction medium. The graft yield increases with increase in peroxydiphosphate concentration. With increase in concentration of fructose up to 7.5 × 10^?4 mole/l., there is a significant increase in graft yield; and with further increase in concentration of fructose the graft yield decreases. The graft yield increases with increase in monomer concentration up to 65.72 × 10^?2 mole/l. and decreases thereafter. The grafting is considerably influenced by chemical modification prior to grafting. The effect of acid, temperature, and solvent on the rate of grafting has been investigated and a suitable rate expression has been derived.     

DSC and TG Analysis of a Blended Binder Based on Waste Ceramic Powder and Portland Cement

Cement industry belongs to the business sectors characteristic by high energy consumption and high \(\hbox {CO}_{2}\) generation. Therefore, any replacement of cement in concrete by waste materials can lead to immediate environmental benefits. In this paper, a possible use of waste ceramic powder in blended binders is studied. At first, the chemical composition of Portland cement and ceramic powder is analyzed using the X-ray fluorescence method. Then, thermal and mechanical characterization of hydrated blended binders containing up to 24 % ceramic is carried out within the time period of 2 days to 28 days. The differential scanning calorimetry and thermogravimetry measurements are performed in the temperature range of \(25\,^{\circ }\hbox {C}\) to \(1000\,^{\circ }\hbox {C}\) in an argon atmosphere. The measurement of compressive strength is done according to the European standards for cement mortars. The thermal analysis results in the identification of temperature and quantification of enthalpy and mass changes related to the liberation of physically bound water, calcium-silicate-hydrates dehydration and portlandite, vaterite and calcite decomposition. The portlandite content is found to decrease with time for all blends which provides the evidence of the pozzolanic activity of ceramic powder even within the limited monitoring time of 28 days. Taking into account the favorable results obtained in the measurement of compressive strength, it can be concluded that the applied waste ceramic powder can be successfully used as a supplementary cementing material to Portland cement in an amount of up to 24 mass%.     

Assessment of the potential natural status of riparian zones in the Czech Republic

Riparian zones represent an important ecosystem providing a range of functions and services important to humans—for example, biodiversity support, a reduction in erosion risk, or the transport of pollutants from the surrounding landscape to watercourses. At the same time, it is an environment that has been often subjected to significant pressure during the agricultural cultivation of the landscape or the development of industrial and residential activities of human society. Thus, a large number of riparian ecosystems have been disappeared or degraded. The assessment of the overall ecological status of riparian habitats constitutes an important source of information for watercourse management and landscape planning, the aim of which should be to maintain good status or to improve the current unsatisfactory state of these habitats. However, in order to reliably evaluate the current ecological status of the landscape, it is necessary to have information on the reference status, that is, a potentially natural status that would prevail without human influence. For this purpose, a methodology that can determine the potential natural status of riparian zones for Central European conditions was developed. In this study, it was found that approximately a quarter (26%) of all river basins in the Czech Republic reach very low environmental values of the potential natural status of riparian zones and, conversely, approximately 29% of river basins are expected to develop significantly above average riparian zone quality.     

Fabrication of low-cost polydimethylsiloxane master from laminating foil for isotachophoresis separation on a chip

This article introduces use of laminating foils as the base for rapid polydimethylsiloxane master fabrication. The designs are punched directly to the foil structure with fabricated knife; therefore, the preparation time requires only a few minutes. This approach offers low-cost and variable possibility of master fabrication to produce microfluidic devices the size of dozens of microns. The resulting structures enable precise control of various device geometries, such as variable channel diameters and shapes in a single device. We describe the fabrication of microfluidic channels using these masters with polydimethylsiloxane polymer. The usability is demonstrated for the isotachophoretic separation of organic anionic dyes.     

Linear Distortion Analysis of 3D Double Gate Junctionless Transistor with High-K Dielectrics and Gate Metals

Silicon - The paper presents the investigation of linearity distortion analysis of double gate junctionless transistor with high-k gate dielectrics and gate metals. As double gate junctionless...     

Swelling and mechanical behavior of ionized poly(acrylamide-<Emphasis Type="Italic">co</Emphasis>-<Emphasis Type="Italic">N,N</Emphasis>’-diethylacrylamide) gels in water/acetone mixtures and in water at various temperatures

Summary Ionized networks of random copolymers of acrylamide (AAm) and N,N’-diethylacrylamide (DEAAm) (mole ratios of x_AAm/x_DEAAm=1/0,0.75/0.25,0.5/0.5,0.30/70,0.15/0.85,0/1) with various amounts of ionic comonomer-sodium methacrylate (MNa) (mole ratios to all monomers x_MNa=0.0,0.025,0.05) and crosslinker – N,N’-methylenbisacrylamide (MBAAm) were prepared at high dilution in water. Their swelling and mechanical behavior was investigated in water at various temperatures (from 10 to 90 °C) and in water/acetone (w/a) mixtures at room temperature. For some copolymers the transition region from expanded to collapsed state was observed at critical concentration of acetone, a_c, in w/a mixtures or at critical temperature, T_c, in water. It was found that with increasing content of DEAAm component in copolymers the a_c values increase; the similar increase was observed with increasing x_MNa. Neat PDEAAm and copolymers with the highest DEAAm content exhibit temperature transition; both increasing amount of AAm and charges bound on the chains (x_MNa) in copolymers shifts the T_c temperatures to higher values very efficiently (for more than 20 °C).     

Coupling of Phosphates on Alumina Surfaces for Bioactivation

This paper reports on a new surface treatment, coupling phosphates on alumina surfaces for bioactivation. Alumina samples were treated in monoaluminumphosphate solution at 1400°C. Strongly coupled aluminum phosphates due to the treatment were proved by X-ray diffraction and infrared spectroscopy. Contact angle measurements proved the hydrophilic nature of the treated surface. In vitro tests in simulated body fluid indicated a bioactive behavior by means of apatite-forming ability. Such functionalized alumina ceramics imply the potential for a new class of bioactive high-strength ceramic implant materials, due to a pronounced affinity of bioactive phosphate groups to particular amino acid sequences of proteins.     

Photo-induced graft copolymerization. XV. Graft copolymerization of methyl methacrylate onto nylon-6 using erythrosin as photoinitiator

The photo-induced graft copolymerization of methyl methacrylate onto nylon-6 was investigated using erythrosin as the photoinitiator. The systems were buffered with phosphate citrate buffer (Na₂HPO₄/citric acid). The graft copolymerization was carried out within the temperature range of 35–50°C and from the corresponding Arrhenius plot, the energy of activation was evaluated. The effect of monomer, initiator, ascorbic acid, etc. on the graft yield has been investigated. Further, the effect of solvent on the rate of grafting has been investigated and the chain transfer constant (C_s) of the solvent has been evaluated. The kinetic data and other events indicate that the overall polymerization takes place by a radical mechanism. A suitable mechanism has been suggested and rate expressions have been derived.