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  • Physics  (70)
  • SOLAR PHYSICS  (55)
  • Chemical Engineering  (38)
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  • 1980-1984
  • 1975-1979  (163)
  • 1965-1969
  • 1977  (163)
  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 973-981 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Linear D2-m-carborane-siloxanes with one, two, and three trifluoropropyl moieties per repeat unit were prepared by the condensation reaction between bisureidosilanes and carborane disilanol. Molecular weights between 100,000 and 220,000 were obtained. Compared to fluorosilicones, the trifluoropropyl-modified carborane-siloxanes exhibited greater thermal and oxidative stability and in certain cases comparable solvent resistance. The swelling index for carborane-siloxane elastomers decreased with increasing trifluoropropyl content, although this fluorocarbon moiety did compromise the thermal stability of the carborane system.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 2673-2684 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The zinc chloride-catalyzed polymerization of 2-vinylnaphthalene (VN) with both photoinitiation and electronitiation methods was examined. Good yields were obtained with both methods, the electroinitiated process being somewhat faster. The mechanism for polymerization initiation was investigated through a detailed comparison of the kinetics. Both initiation methods show a similar response to increasing input energy and to change in salt to monomer mole ratio. Both methods indicate formation of a ZnCl2-(2-VN)2 complex as intermediate with the formation of the species being rate-determining. These results, together with other similar investigations, are then used to deduce a mechanism that involves the formation of an electronically excited donor-acceptor complex. It is argued that in certain salt-stabilized, electron-delocalized, aromatic systems, such excitation is possible in electroinitiation.
    Additional Material: 10 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 1563-1571 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As part of a program to extend the range of donor-acceptor-initiated polymerization processes, the electroinitiation of 2-vinylnaphthalene in a zinc chloride-sulfolane solution has been studied. Good conversion yields of well-characterized (NMR, IR, GPC, elemental analysis) poly(vinylnaphthalene) were obtained with the process showing several mechanistic similarities to other donor-acceptor salt electropolymerization systems.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 1555-1562 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrochemically initiated polymerization of styrene in methylene chloride solvent with the use of platinum electrodes and tetraalkyl and -aryl group VA halides (i.e., quaternary ammonium, phosphonium, and arsonium compounds) as electrolyte has been investigated. The order of reactivity of the electrolytes with respect to polymerization rate and initiation efficiency was found to be: arsonium 〉 phosphonium 〉 ammonium. Mechanisms involving the electroreduction of the group VA quaternary halides to species capable of electroinitiating polymerization are postulated. The observed losses in solution conductivities during polymerization with the quaternary phosphonium and arsonium electrolytes indicate possible interaction between the initiating radical-ionic species and the supporting electrolyte. In an attempt to further elucidate the mechanism of initiation in these systems, a separate series of experiments, employing the nonpolymerizing monomer, 1,1-diphenylethylene, has been carried out.
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 23 (1977), S. 319-326 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The dual enzyme sequential reactions that decompose arginine to ammonia were investigated experimentally to determine appropriate rate equations and to test predictions of optimal distribution of the two enzymes (arginase and urease) immobilized in a packed-bed reactor.The kinetics of this system were experimentally found to be of the kind that calls for a bang-band control with a well-defined switching point between the two immobilized enzyme catalysts. At low values of reactor residence time, the optimum switching point is shown to approach a limiting position which depends on the kinetic order of the second reaction. In the higher ranges of residence time, the switching point moves into the latter half of the reactor, but exceptions to this generalization are found when Michaelis-Menten kinetics are applicable to both reactions. For the special circumstance where the two reactions are of zero and first order, respectively, the optimal distribution of the two catalysts is independent of the first rate constant. The experimental results are, in general, consistent with these expectations, and secondary deviations are discussed. A suboptimal policy alternative is also treated analytically and tested by experiment.
    Additional Material: 14 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 23 (1977), S. 679-685 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rate of pyrite oxidation in aqueous ferric chloride was determined for two distinct solid particle systems: industrial grade pyrite and coal particles containing pyrite. The oxidation rate for the pyrite particle system was found to increase significantly with increasing temperature (40° to 100°C), ferric chloride concentration (0.1 and 1.0 M), and pyrite loading (2 to 20 g/l); the rate decreased with increasing particle size (-325 to 140 mesh). Agitation did not have a significant effect, and a kinetic model was developed and fit to the experimental data.For the coal particle system used in this study, the most important variable was particle size. The oxidation rate of pyrite in coal smaller than 325 mesh was much greater than in larger coal particles. The effect of temperature (80° to 100°C) on the oxidation of pyrite in coal was not significant, nor was the effect of pretreatment with 0.1N hydrochloric acid. Approximately half of the detected ferric iron reduction was attributable to pyrite oxidation; the balance arises from other coal reactions.
    Additional Material: 10 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 17 (1977), S. 560-562 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: The molecular theory of Rouse-Bueche-Zimm has been modified to predict the viscoelastic behavior of homogeneous block copolymers. The model consists of beads and springs whose magnitudes correspond to the types of blocks in the polymer. Maximum relaxation times can be computed by this model. Viscoelastic data for poly(styrene-b-α-methyl styrene-b-styrene), poly(α-methyl styrene-b-styrene-b-α-methylstyrene) and poly(styrene-b-α-methyl styrene) were determined by stress relaxation methods. The results compare favorably with those predicted by the theory.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 17 (1977), S. 598-605 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: The basic theory of X-ray scattering is applied to various hypothetical models for the bulk state of block polymers in order to explain the angular dependent scattering. The intensity of scattering is calculated for a rnicellar model, a zone model, and a molecular dumbbell model. The molecular dumbbell model, in contrast to the micellar and zone models, assumes that a block copolymer containing domains may be treated as one giant molecule and that, therefore, the locations of the domains are not random but are governed by the statistics of the segments which interconnect them. Experimental and calculated scattering curves are compared for several different types of block polymers.
    Additional Material: 16 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 15 (1977), S. 2013-2026 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The tensile properties of highly oriented polypropylene (PP) filaments are markedly dependent on their fabrication drawn history. Highly oriented filaments prepared by drawing at 〈100°C were capable of appreciable plastic deformation after passing through a marked yield point. This deformation process was very rate dependent, transforming to essentially brittle behavior at deformation rates 〉500%/min. Filaments produced by drawing at a higher temperature, or by annealing above 100°C of those produced at 100°C, had a slightly lower modulus, greatly reduced residual elongation to break, and showed no yield point. A model for the plastic deformation is proposed involving localized fibrillation to produce craze-like structures. This model is consistent with the observed filament susceptibility to chromic acid etching. Electron micrographs of highly drawn then etched samples show that just prior to fracture only small plastes of the acid resistant (presumably original, unvoided) structure remain.
    Additional Material: 8 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 15 (1977), S. 723-732 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: D2-m-decacarborane dimethylsiloxane has unusual thermal stability and resistance towards reversion, however, this material exhibits a crystalline phase, Tm at 68°C. To obtain an elastomeric material, this crystallinity is disrupted by replacing 30 to 50% of the m-carborane with p-carborane moieties or by the incorporation of phenyl moieties on the polymer backbone. The latter approach is preferred since improved thermo-oxidative stability accompanies this modification. Correlation of the glass transition temperature and thermo-oxidative stability with the polymer structure are presented.
    Additional Material: 5 Ill.
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