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  • Chemistry  (15)
  • LUNAR AND PLANETARY EXPLORATION  (10)
  • Chemical Engineering  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 207-216 
    ISSN: 0887-624X
    Keywords: plasma polymerization ; thin films ; fluorocarbon ; surface tension ; breakdown strength ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Plasma polymerized (PP) fluoropolymer films have been synthesized by the plasma copolymerization of hexafluoropropylene (HFP) and a nonpolymerizable gas. Plasma etching was inhibited by fluorine scavenging and HF formation on the addition of hydrogen and was accelerated on the addition of oxygen. Nitrogen, oxygen, and hydrogen were incorporated into the deposited polymer molecules when added to the HFP plasma. The polar component of surface tension increased on nitrogen addition and the dispersive component on hydrogen addition. The higher surface tension drove the deposition and coalescence of smaller particles from the gas phase polymerization yielding smooth surfaces. The significant drop in breakdown voltage on the addition of nitrogen was attributed to a different conduction mechanism in the relatively polar PP fluoropolymer film. © 1996 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 733-744 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Macroscopic flow structures of gas-liquid and gas-liquid-solid fluidization systems are studied through flow visualization using a two-dimensional column under various operating conditions. The gas distributor in the column comprises multiple injectors which are individually regulated to generate desired gas flow rates, bubble injection frequencies, and bubble sizes. Colored bed particles and neutrally buoyant particles as solid and liquid tracers, respectively, are used for flow visualization through video photography. In a gas-liquid system operated under liquid-batch conditions, bubble streams injected near both sidewalls are observed to migrate toward bed vertical axis, and vortices appear along the sidewalls when gas velocity exceeds 4-6 mm/s. A considerable amount of liquid descends along the sidewalls in a vortical flow pattern. The gross circulation pattern occurring at high gas velocities is associated closely with induced liquid or liquid-solid flows resulting from rising bubbles and bubble wakes. When the gross circulation occurs, four flow regions can be distinguished. The formation of and mechanism for gross circulations can be interpreted in part based on two simplified flow conditions involving single bubbles rising in a stationary liquid and single chains of bubbles injected in a batch liquid. The effects of particle size, inlet liquid velocity and gas flow distribution on the macroscopic flow structure are also examined.
    Additional Material: 13 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 1093-1104 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Macroscopic flow structures of 3-D bubble columns and gas-liquid-solid fluidization systems under various operating conditions are studied using particle image velocimetry. Flow visualization is also conducted with the aid of a laser sheeting technique. The refractive index matching technique is used to eliminate the opaqueness of solid particles occurred in the visualization study of gas-liquid-solid fluidization. Three flow regimes (dispersed bubble, vortical-spiral flow, and turbulent flow) are identified. The flow structure is investigated for various operating variables including liquid velocity, gas velocity, and particle holdups. Four flow regions (descending flow, vortical-spiral flow, fast bubble flow, and central plume) can generally be characterized in the vortical-spiral flow regime where the gross circulation pattern occurs. A conceptual model for the flow structure in the vortical-spiral flow regime is discussed. The transition of the flow regimes and structure in the vortical-spiral flow regime is postulated to be related to the Taylor instability for flow between two concentric rotating cylinders. Similarities between the flow structures of 2- and 3-D beds are also discussed.
    Additional Material: 14 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 17 (1971), S. 747-749 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 5
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 1001-1007 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of random copolymers of methylmethacrylate and methacryloxypropyltris (trimethylsiloxy) silane were synthesized by free radical polymerization under ultraviolet light. The permeabilities of these copolymers to carbon dioxide, oxygen, and nitrogen were determined and correlated with the packing densities of the polymers. Correlation between the permeability and permselectivity of these copolymers is also addressed.
    Additional Material: 7 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 403-409 
    ISSN: 0887-6266
    Keywords: polyimides ; Kapton ; Upilex ; water absorption ; 1H, 2H and 17O NMR ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Commercial polyimide films containing up to ∼ 3 wt % water have been studied by proton, deuteron, and oxygen-17 nuclear magnetic resonance (NMR). Comparisons between NMR results and previous dielectric relaxation (DR) results for a variety of Kapton films show that there is a one-to-one correspondence between specific dielectric loss peaks and features of the 2H or 17O NMR spectra. It is concluded that water molecules, which interact only weakly with the polymer, reside in the polyimide matrix in two configurations, randomly oriented single molecules and chains of water molecules oriented perpendicular to the plane of the film. The correspondence between NMR and DR observed in water in Kapton extends to water in Upilex and to methanol and acetic acid in Kapton. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 471-483 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: “Row nucleated lamellar” structures are formed when highly crystalline polymers are melt-extruded and recrystallized under high stress. Polyethylene (PE) and polypropylene (PP) films with row lamellar structures have been utilized to produce microporous membranes. Birefringence measurements of melt-extruded PE films show that improved film orientation can be achieved by annealing, extruding at higher speed, and using higher molecular weight polymers. Images from scanning tunneling, atomic force, and field emission scanning electron microscopy (STM, AFM, and FESEM) clearly show the lamellar structures in the melt-extruded PE and PP films. Microscopy results also show that surface lamellar textures are more pronounced with thicker lamellae and are better aligned along the extrusion direction after annealing. X-ray diffraction results show that the increase in film orientation can be attributed to increased lamellar perfection and orientation during annealing and also to better crystallite alignment along the machine direction with higher extrusion speed or with higher molecular weight. High-resolution capabilities of STM, AFM, and FESEM prove to be very effective tools in elucidating lamellar structures in polymeric membrane precursors and can be used as an aid in establishing structure-process-property relationships in making microporous membranes. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 615-623 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Thin, pinhole-free, highly adhering films for advanced technology applications can be deposited through plasma polymerization, a low temperature, solvent-free process. This research studies the influence of plasma environment (power, pressure, and monomer mass flow rate (Fm)) on the plasma polymerization of hexafluoropropylene (HFP) using a common industrial parallel-plate plasma reactor. The deposition and structure of the transparent, yellow, and highly adhering plasma polymerized HFP (PPHFP) film are investigated. The rate of polymerization (Rp) increases with power (W) and reaches a plateau when the plasma changes from energy starved to monomer starved while the rate of etching (Re) continues to increase. The rate of deposition (Rd), the difference between Rp and Re, increases with W, reaches a maximum, and then decreases. In a monomer starved plasma Rd increases with Fm or pressure through a more efficient utilization of the energy supplied at a given W or even at a given W/Fm. The abstraction of F and the preferential scission of the C—CF3 bond can explain the F/C ratio of 1.5, the significant amount of double bonds, and the relative lack of CF3 in a PPHFP that consists of CF3, CF2, and CF groups. A gas phase dominated polymerization produces submicrometer particles some of which agglomerate into spheres. Both the particles and the spheres deposit on the surface and are incorporated into the film with further polymerization. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 25 (1980), S. 2211-2220 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Graftings of acrylonitrile and methyl methacrylate onto lignosulfonate were studied, respectively, with and without the lignosulfonate ozonized. Copolymerization was redox-initiated by peroxideferrous ions. Monomer conversion and grafting efficiency depended essentially on reaction medium and the maount of peroxide charged. Among the media employed, the magnitude of the medium effect on conversion was found to be in the following order: water, dioxane, and methanol. The conversions in water of acrylonitrile and methyl methacrylate were 55 and 90%, respectively, when using 3% hydrogen peroxide. Beyond this 3 % charge, both the grafting efficiency and the degree of lignosulfonate grafted approached certain limits. Ozonization appeared to be capable of stimulating the active centers in lignin macromolecules, whereon acrylic monomers could be grafted. Better grafting efficiency was obtained with the ozonized lignosulfonate.
    Additional Material: 6 Ill.
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