Liquid-crystalline main-chain polymers with a poly(p-phenylene terephthalate) backbone. 3. Drawing, structure development and ultimate mechanical properties of films of the polyester with dodecyloxy side chains

Soln.-cast films of poly(p-phenylene 2,5-didodecyloxyterephthalate) were characterized by x-ray diffraction, DSC and mech. measurements. Three different structures, in which the main chains are arranged in layers sepd. by the interdigitating side chains, could be distinguished. In the as-cast films these layers are parallel to the film surface. Upon drawing, the backbones of the chains orient parallel to the drawing direction, while most of the parallel orientation of the layers with respect to the film surface is maintained. At room temp. the Young's moduli of the less-ordered phases, termed A and Lf, are approx. 15 GPa, which is rather low in comparison with the value of almost 30 GPa found for the third modification, termed B. However, below the b-relaxation at .apprx. -20 Deg the moduli of all three phases are of the same order of magnitude. At -175 Deg they are in line with the theor. predicted modulus of 50 GPa. [on SciFinder (R)

AutoReaGas - A CFD-Tool for gaz explosion hazard analysis

Gas explosions constitute a major hazard for offshore gas and oil producing installations. A gas explosion is the consequence of an accidental release of a flammable gas, the mixing with air and a subsequent ignition. Under appropriate boundary conditions the resulting flame propagation process may develop explosive combustion and damaging blast loadings. In spaces containing a lot of equipment, this is a particular problem and a small quantity of fuel may be sufficient to give rise to the development of high explosion overpressures. If such overpressures are not anticipated in the design they may have fatal consequences for both crew and rig

Carbon-covered alumina as a support for sulfide catalysts

Carbon-covered alumina carrier materials (10–35 wt.% carbon deposited) were prepared via pyrolysis (873–973 K) of cyclohexene or ethene on the surface of a ¿-alumina and evaluated for their use as supports for cobalt sulfide hydrodesulfurization catalysts. Promising textural properties were obtained for the samples prepared: BET surface areas up to 334 m2 g-1, meso- and macropore surface areas reaching values of 190–270 m2 g-1, and narrow pore size distributions in the 2.5–10 nm pore radius range. XPS measurements showed that the alumina surface was not uniformly covered, probably due to diffusion limitations of the carbon forming hydrocarbons. The coverage could be improved (maximum value reached was 77%) by increasing the amount of carbon deposited as well as by an additional high-temperature (1073 K) treatment. The thiophene hydrodesulfurization activity of Co sulfide supported on the prepared carbon-covered aluminas was found to increase linearly with increasing alumina surface coverage by carbon. A threefold increase in activity compared to Co/Al2O3 catalysts was obtained, demonstrating the effective shielding by the carbon layer which reduces or eliminates the strong metal-alumina interactions. Oxidizing the carbon surface prior to the introduction of cobalt led to a further improvement of the catalytic activity