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91.
Kuzhikalail M. Abraham Rebecca Schiff 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):177-181
Abstract Some reactions of the aliphatic amides, CH3CONH2, CH3CONHCH3, CH3CON(CH3)2 and CH3CON(C2H5)2 with elemental S and sodium sulfides, Na2S n , n ≥ 1, have been studied. The initial reaction product with elemental sulfur appears to be a substituted polysulfane, CH3COS n NR, formed by the insertion of the sulfur chain into the C[sbnd]N bond. This product decomposes on further heating, forming COS as the major gas product. In solutions of Na2S n in the amides, the reactive material appears to be elemental S, present in equilibrium with S n ?2. In the N-dialkyl substituted amides, CH3CON(CH3)2 and CH3CON(C2H5)2, the tetrasulfide is uniquely stabilized by solvent coordination so that solutions of Na2S4 in these amides are stable for long periods of time at 130°C. 相似文献
92.
Environmental stress cracking resistance (ESCR) is an important indicator of performance for high density polyethylene (HDPE) in structural and polymer pipe applications. The commonly used test for determining ESCR of HDPE can be time consuming and rather imprecise. A tensile strain hardening test was recently proposed to offer a faster way to characterize ESCR of polyethylene. In this paper, a practical approach is adopted whereby the test is extended to room temperature and shown to relate reliably to the ESCR of HDPE. Several HDPE resins (including pipe‐grade resins) are analyzed at strain rates of 0.5 mm/min and 7 mm/min to compare the effect of strain rate. Comparisons between the conventional ESCR test method and the strain hardening test show that strain hardening can be used to rank ESCR of HDPE in a reliable fashion. In our study the more direct measure of “hardening stiffness” is used to compare resins instead of strain hardening modulus. Because no true stress‐strain measurement is needed, this is a much simpler test method than other methods previously suggested. In addition, the use of the natural drawing ratio (NDR) as ESCR ranking indicator is examined. Results show that NDR can also be employed as a strain rate‐independent indicator of ESCR of HDPE. The test proposed herein is practical, simple and precise, and hence a more reliable indicator of ESCR performance of HDPE. 相似文献
93.
Abraham Warshawsky 《Separation & Purification Reviews》2013,42(2):95-130
A process for concentration and separation of platinum group metals (PGM) by a combination of ion exchange and liquid-liquid extraction is presented. First the PGM metals are dissolved by HC1/C11 and then passed through an isothiouronium anion exchange resin, where specific absorption occurs. The thiourea eluate from the resin is converted to the chloride complexes. Further hydrolysis (conditioning) yields an aqueous feed to a liquid-liquid extraction step, with Alamine-336. Platinum and palladium are very well extracted, while most of the other PGM are rejected in the aqueous phase. The liquid-liquid extraction can be used by itself, if the level of the base metals does not exceed the concentration of the PGM ions. Platinum and palladium are now separated from each other by the selective stripping of palladium with thiourea, and platinum with thiocyanate. The paper discusses the extraction chemistry of all the steps, and provides also experimental pilot-plant results. 相似文献
94.
The introduction of electron rich and sterically hindered ligands has made otherwise inert aryl chlorides and hetero aryl chlorides viable coupling partners in palladium-catalyzed Suzuki-Miyaura, Sonogashira, Stille and other types of cross-coupling reactions. This review gives highlights of cross-coupling of aryl chlorides employing in situ generated palladium catalytic systems. 相似文献
95.
Pamela Twu Jared L. Anderson Timothy W. Stephens Anastasia Wilson William E. Acree Jr. Michael H. Abraham 《Journal of solution chemistry》2013,42(4):772-799
Chromatographic retention data were measured for a wide range of organic solutes on 1-butyl-1-methylpyrolidinium tris(pentafluoroethyl)trifluorophosphate ([BMPyrr]+[FAP]?), 1-butyl-1-methylpyrrolidinium triflate, ([BMPyrr]+[Trif]?), and 1-methoxyethyl-1-methylmorpholinium tris(pentafluoroethyl)trifluorophosphate, ([MeoeMMorp]+[FAP]?), stationary phases at (323, 353 and 383) K. The measured retention factors were combined with published infinite dilution activity coefficient and gas-to-water partition coefficient data to yield gas-to-anhydrous ionic liquid (IL) and water-to-anhydrous IL partition coefficients. The three sets of partition coefficients were analyzed using the Abraham model. The derived Abraham model correlations describe the observed gas-to-IL (log10 K) and water-to-IL (log10 P) partition coefficient data to within average standard deviations of about 0.11 and 0.15 log10 units, respectively. 相似文献
96.
Axel Benichou Abraham Aserin Nissim Garti 《Journal of Dispersion Science and Technology》2013,34(1-3):93-123
Proteins, polysaccharides and their blends, as examples of natural biopolymers, are surface active materials. Biopolymers may be considered as amphiphilic macromolecules that play an essential role in stabilizing food formulations (foams, emulsions and dispersions). Under specific conditions (such as protein-to-polysaccharide ratio, pH, ionic strength, temperature, mixing processing), it has been stated that proteins and polysaccharides form hybrids (complexes) with enhanced functional properties in comparison to the proteins and polysaccharides alone. Different protein-polysaccharide pairs are reviewed with particular attention to the emulsification capability of their mixtures. In the case of uncomplexed blends of biopolymers, competitive adsorption onto hydrophobic surfaces is generally reported. Conversely, electrostatic complexation between oppositely charged proteins and polysaccharides allows better anchoring of the new-formed macro-molecular amphiphile onto oil-water interfaces. Moreover, improved thermal stability and increased resistance to external treatment (high pressure) involved in food processing are obtained. This review presents basic and applied knowledge on protein-polysaccharide interactions in aqueous medium and at the oil-water interface in food emulsion systems. Electrostatic interactions and thermodynamic incompatibility in mixed biopolymer solutions are correlated to the functional properties (rheology, surface hydrophobiciry, emulsification power) of these interesting blends. Basic and industrial selected systems of different families of hydrocolloids (as gum Arabic, galactomannans, pectins) and protein (caseins, whey, soya, gelatin) mixtures are reviewed. 相似文献
97.
Celecoxib belongs to a new NSAID family specifically inhibiting cyclooxygenase‐2 (COX‐2). The present formulations require high dosage since the transmembrane transport fluctuates and is very difficult to control. We solubilized celecoxib in micelles of nonionic microemulsions and hydrophilic surfactant. The supersaturated solubilized drug was precipitated from the nano‐droplets to form a new solid structure with improved dissolution properties. The selected microemulsion systems loaded with celecoxib were characterized by SAXS, SD‐NMR, viscosity, and electrical conductivity techniques. Precipitation was conducted from W/O as well as from O/W U‐type microemulsions. The crystals obtained by the precipitation were characterized by x‐ray powder scattering, differential scanning calorimetry, FTIR measurements, and microscopic scans. 相似文献
98.
The inhibition of mild steel corrosion in aerated acid mixture of 0.5 N H2SO4 and 0.5 N HCl solution was investigated using potentiodynamic polarization studies, linear polarization studies, electrochemical impedance spectroscopy, adsorption, and surface morphological studies. The effect of inhibitor concentration on corrosion rate, degree of surface coverage, adsorption kinetics, and surface morphology is investigated. The inhibition efficiency increased markedly with increase in additive concentration. The presence of PEG and PVP decreases the double-layer capacitance and increases the charge-transfer resistance. The inhibitor molecules first adsorb on the metal surface following a Langmuir adsorption isotherm. Both PEG and PVP offer good inhibition properties for mild steel and act as mixed-type inhibitors. Surface analysis by scanning electron microscopy (SEM) and atomic force microscopy (AFM) shows that PVP offers better protection than PEG. 相似文献
99.
Amino acids have been widely used as green corrosion inhibitors for an array of metals. Considering its importance in corrosion chemistry, studies were undertaken with the objective to discovering the inhibitory effect of a sulfur-containing amino acid, l-cysteine, on copper in different concentrations of sulfuric acid (0.5, 1.0, and 1.5 M) at different temperatures. Techniques like the weight loss method, electrochemical impedance spectroscopy, potentiodynamic polarization (Tafel), and adsorption studies were employed. Results revealed that l-cysteine do offer an attractive inhibition efficiency. However, with an increase in the concentration of the inhibitor, corrosion rates decreased irrespective of the temperature gradients. This is due to surface adsorption of the inhibitor molecules on the metal which has contributed to a decreased double-layer capacitance and increased polarization resistance. With the increase in the concentration of the medium, the corrosion rate was also enhanced and this is due the liberation of a high quantum of H+ ions. Based on the results of Tafel polarization studies, it is evident that the amino acid, l-cysteine, could act as a mixed type inhibitor. The importance of l-cysteine in the corrosion of copper metal has been highlighted in this paper. 相似文献
100.
Physicomechanical properties of nanocomposites based on cellulose nanofibre and natural rubber latex 总被引:1,自引:0,他引:1
Eldho Abraham B. Deepa L. A. Pothan Maya John S. S. Narine S. Thomas R. Anandjiwala 《Cellulose (London, England)》2013,20(1):417-427
Cellulose nanofibres (CNF) with diameter 10–60 nm were isolated from raw banana fibres by steam explosion process. These CNF were used as reinforcing elements in natural rubber (NR) latex along with cross linking agents to prepare nanocomposite films. The effect of CNF loading on the mechanical and dynamic mechanical (DMA) properties of NR/CNF nanocomposite was studied. The morphological, crystallographic and spectroscopic changes were also analyzed. Significant improvement of Young’s modulus and tensile strength was observed as a result of addition of CNF to the rubber matrix especially at higher CNF loading. DMA showed a change in the storage modulus of the rubber matrix upon addition of CNF which proves the reinforcing effect of CNF in the NR latex. A mechanism is suggested for the introduction of the Zn–cellulose complex and its three dimensional network as a result of the reaction between the cellulose and the Zinc metal which is originated during the composite formation. 相似文献