Synthetic hydrogels 3. Solvent effects on poly(2-hydroxyethyl methacrylate) networks

Poly(2-hydroxyethyl methacrylate) networks were synthesized in aqueous solutions of propylene glycol, ethylene glycol, ethylene glycol monomethyl ether, or ethylene glycol dimethyl ether and the influences of solvent on phase separation during the polymerization process studied. Results from conversion-phase diagrams, turbidity measurements, swelling studies, and viscosity measurements show that the phase separation process is dependent upon the solubility parameter of the organic solvent, the instantaneous monomer concentration at each stage of the gel formation process, and the crosslinker content of the reaction mixture.     

SOLUBILITY OF CO2 AND H2S IN A HINDERED AMINE SOLUTION

The solubility of H₂S and CO₂ in aqueous solutions of the sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP), was determined at 40 and 100°C. Partial pressures of C)₂ ranged from approximately 2 to 6000 kPa and of H₂S from 2 to 2200 kPa. The solubility results were compared with previously reported acid gas solubilities in aqueous monoethanolamine (MEA) solutions.     

Synthesis and Microstructure of Highly Oriented Lead Titanate Thin Films Prepared by a Sol-Gel Method

Thin films of PbTiO₃ were deposited on fused silica, resistor-grade alumina, and single-crystal (100) MgO by a sol–gel processing method. Whereas the films deposited on silica and alumina substrates were randomly oriented and polycrystalline, highly {100} oriented PbTiO₃ films were grown on the MgO single crystals. The perovskite-type structure was observed with films deposited on the single-crystal MgO and annealed at temperatures as low as 470°C, whereas a pyrochlore-type strcuture was observed with films on fused silica and alumina processed in a similar manner. All films heat-treated at temperatures in excess of 570°C showed significant formation of a second PbTi₃O₇ phase. The films were characterized by electron microscopy and glancing-incidence-angle X-ray diffraction.     

Analysis of nonvolatile material in solvent hexane

The amount and composition of the nonvolatile residue in solvent hexane are important quality criteria. These residue characteristics are particularly significant in the hexane extraction of foods because of the possibility of contaminating edible products. A laboratory evaluation of the residue from a typical hexane was made to find if there was any trace of multi-ring aromatics which might be potential carcinogens. Samples of hexane directly from a refinery and after storage and transportation to two solvent extraction plants were analyzed. All residues were separated by paper chromatography and analyzed by ultraviolet spectrophotometry. In no case, were they found to contain polynuclear aromatic carcinogenic materials. The test method is sensitive to less than 0.01 ppm. In order to verify the accuracy of the test, an analysis was made for the quantitative recovery of a known carcinogen. For this purpose, 0.01 ppm of 3,4 benzpyrene was added to the hexane as an internal standard and the analysis conducted as before. In these tests, the benzpyrene was recovered quantitatively.     

A New Indole Synthesis Promoted by Metal Triflates

A new synthesis of 4- and 7-carbon-substituted indoles is described. The overall sequence involves the addition of a nitrile oxide to 1 carboethoxy-2-(or 3-) allylpyrrole, hydrogenation of the intermediate isoxazoline to β-hydroxy ketone and cyclization of the ketol using magnesium or zinc triflate to the substituted indole. This new indole-forming strategy can also accommodate the introduction of oxygen functionality into the indole 6-position. Possible mechanistic aspects of the reaction are detailed.     

In situ polymerization and nano‐templating phenomenon in nylon fiber/PMMA composite laminates

Supercritical Carbon Dioxide (SC CO₂) is used as a reaction/processing medium in the fabrication of fiber‐reinforced composite materials. SC CO₂ allows resin (reactive monomer), to penetrate inside the fibers themselves, partitioning into the amorphous regions of the fiber. The crystal structure then templates polymerization of matrix within the fiber. This process produces a composite that exhibits ultralong‐range order from the nanoscale reinforcement of crystals to the macroscale fiber reinforcement of matrix. In addition, SC CO₂ lowers resin viscosity and aids in wetting out Nylon 6,6 fiber reinforcement in a process similar to reaction injection molding (RIM) or resin transfer molding (RTM). This article will discuss the fabrication technique in detail, including process parameters and the structure of resulting composites and morphology of modified fibers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1600–1607, 2003     

Microstructure and ultimate properties of injection molded amorphous engineering plastics: Poly(ether imide) and poly(2,6-dimethyl-1,4-phenylene ether)

Specimens of two engineerig plastics i.e., poly(ether imide), PEI, and poly(2,6-dimethyl- 1,4-phenylene ether), PPE, were injection molded employing a 40t Van Dorn injection molding machine and industrial practices. The mold and melt temperatures and the injection speed were varied in a limited range which furnished acceptable samples. The density, birefringence, residual stress distributions, flexure and tensile properties, and crack development of the injection molded specimens were studied. Vacuum compression molded samples were also prepared to investigate the role played by the cooling rate in shaping microstructural distributions. The results revealed significant differences in the development of microstructure of the molded specimens of the two resins, which was related to rheology and molding conditions on one hand and to development of cracks and ultimate properties on the other hand.     

Designing for reportability: sustainable gamification,public engagement,and promoting environmental debate

There is a growing emphasis in many countries on matters such as participation in e-government, e-democracy, the provision of forums for online debate, and so on. A critical issue in all of these cases is one of encouraging engagement across a broad spectrum of potentially interested parties and stakeholders. In this paper, we use an ethnographic study of an online event, designed to encourage debate, to explore some critical issues in how the mechanisms productive of debate have shifted in company with the Web 2.0 phenomenon. By contrasting this with a prior study of how players managed their gameplay in a multiplayer pervasive game, we focus upon how different ways of constructing games and events can have serious implications for their ordinary everyday reportability in routine face-to-face interactions. We conclude that designing for reportability should be an active consideration when designing the resources for online debate and consider some ways in which that might be accomplished.     

Kinetic Study of the Steam Reforming of Isobutane Using a Pt–CeO2–Gd2O3 Catalyst

Steam reforming of isobutane on a 0.5% Pt–Ce_0.8Gd_0.2O_1.9 catalyst was carried out from 300 to 700 °C under integral conditions with a gas hourly space velocity (GHSV) of 12,000 h⁻¹. The major products were H₂, CO₂, CO and CH₄. The other products produced were ethane, ethylene, propane and propylene with a total molar composition of less than 1.5%. A complete conversion of isobutane was achieved at 700 °C, Kinetic data was obtained by changing the partial pressure of the reactants and the temperature under differential conditions with a GHSV of 55,400 h⁻¹. This was done after observing stable isobutane steam reforming for 160 h and under conditions where the mass transfer limitations were insignificant. An empirical Langmuir–Hinshelwood type model that best fit the kinetic data available was developed.     

Analysis of wide-angle X-ray diffraction patterns of aligned glassy polymers with particular references to polystyrene

Improvement of WAXD patterns from aligned glassy polymers by a numerical desmearing technique is reported. This gives a fibre type diffraction pattern that can be more easily interpreted than radial or cylindrical distribution functions. Application to atactic and quenched isotactic polystyrene shows that the molecular conformations that are found are in agreement with those deduced from i.r. and n.m.r. spectroscopy. For isotactic polystyrene there is significant agreement between the fibre pattern of the aligned glassy polymer and that of the drawn crystalline polymer.