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  • 1
    Digitale Medien
    Digitale Medien
    Transport processes in narrow (capillary) channels (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 473-482 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Rates of mass and momentum transport in narrow flow channels (gaps 0.2-0.5 mm) have been determined over a wide range of flow velocities, 220-7,700 cm/sec (Re 1,300 to 22,000). Existing correlations that apply to smooth channels of much larger hydraulic diameter were found to be valid for the narrow channels as well. However, in the turbulent regime the condition of hydraulic smoothness could be satisfied only when the walls were optically smooth. Transport rates to rough walls were also measured. The ratio of the mass transport to the momentum transport in the form of jD/(f/2) - a measure of the improved mass transfer compared to the increased pressure drop - is given for the smooth and rough-wall cells over the Re range studied.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690310315
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  • 2
    Digitale Medien
    Digitale Medien
    Tensile stress measurements on linear and branches low-density polyethylene melts. Interpretation of results with a generalized Maxwell model (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 33 (1987), S. 289-303 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Dynamic shear experiments in the linear range of deformation and extensional tests at constant strain rate have been carried out on a linear low-density polyethylene (LLDPE) melt and on two branched low-density polyethylene (LDPE) melts with different amounts of long-chain branching. Both the dynamic shear moduli and the tensile stress obey the time-temperature superposition principle. A simple model based on a nonaffine generalized Maxwell model with two relaxation times is proposed to describe the rheological behavior in elongation of these melts. Close agreement between the model and the experimental data can be obtained by adjusting the two relaxation times and the “slip parameter” of entanglements. The variations of these parameters with strain rate and their relationship with molecular structure are discussed.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1987.070330203
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  • 3
    Digitale Medien
    Digitale Medien
    Etude du couplage 2J(N15—H) en série hétérocyclique. Application à la détermination des constantes d'équilibres prototropiques rapides (1974)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 6 (1974), S. 224-225 
    Details
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: The fast tautomeric equilibrium of (N15)-4-phenylisoxazolin-5-one (2) has been investigated by a study of 2J(N15—H3) coupling. Comparison of the observed values for 2 and for the two fixed forms (N15)-2-methyl-4-phenylisoxazolin-5-one (3) and (N15)-4-phenyl-5-methoxyisoxazol (4) indicates a considerable amount of enolic type structure for 2 in basic media.
    Notizen: La comparasion des constantes de couplage 2J(N15—H3) présentées par la (N15)-4-phénylisoxazoline-5-one (2) et par deux de ses formes fixes, la (N15)-2-méthyl-4-phénylisoxazoline-5-one (3) et le (N15)-4-phényl-5-méthoxyisoxazole (4), indique une participation élevée de structure énolique (et/ou ionique) dans les milieux basiques.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1270060408
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  • 4
    Digitale Medien
    Digitale Medien
    Relationship between structure and rheological properties in the melt of polymers containing spherical inclusions (1995)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 6 (1995), S. 301-308 
    Details
    ISSN: 1042-7147
    Schlagwort(e): polymer blends ; melt rheology ; crosslinked rubber ; structured latex ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: The linear viscoelastic behavior of model rubbertoughened polymer melts has been studied. The most significant influence of the dispersed crosslinked rubber phase on the melt rheology of the blends is the existence of a secondary plateau for the storage modulus G′ at low frequencies. This behavior was ascribed to a percolation phenomenon, leading to the formation of a threedimensional network of inclusions, and contributing to the elasticity at low frequencies of the blend. Two different systems were investigated: (a) a polystyrene matrix with crosslinked and structured latex particles and (b) silicon oil matrices with homogeneous crosslinked PMMA particles. An initial shearing history was found to influence the dynamic mechanical properties of the molten blends and in particular to lower the lowfrequency plateau value for G′. During a subsequent annealing, the plateau modulus increases again. These results are in agreement with the assumption of a particle network.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pat.1995.220060508
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  • 5
    Digitale Medien
    Digitale Medien
    Viscoelastic properties of styrene-co-methyl methacrylate random copolymers (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 933-943 
    Details
    ISSN: 0887-6266
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Viscoelastic properties of styrene-co-methyl methacrylate random copolymers have been determined over a temperature range covering the glass transition, the rubbery plateau, and the terminal zone and compared with polystyrene and polymethyl methacrylate homopolymers. Nonlinear behavior was observed in the variations of most of the physical and rheological characteristics with the methyl methacrylate content in the copolymer. Results are interpreted in terms of the rupture of polar-polar intermolecular interactions between ester groups due to the presence of styrene units.
    Zusätzliches Material: 18 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/polb.1991.090290804
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  • 6
    Digitale Medien
    Digitale Medien
    Tensile stress and recoverable strain measurements on polystyrene melts. Interpretation of results in terms of rubberlike elasticity (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 295-310 
    Details
    ISSN: 0887-6266
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Extensional tests at constant strain rate \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document} have been carried out on polystyrene melts with different molecular weight distributions at various temperatures and strain rates. The true tensile stress is found to be well approximated by the sum of two contributions: (1) a neo-Hookean expression involving the recoverable strain and (2) a contribution rapidly reaching a steady-state value. Two experimental parameters can be defined: an elasticity modulus \documentclass{article}\pagestyle{empty}\begin{document}$ G(\dot \varepsilon ) $\end{document} from (1) and a viscosity \documentclass{article}\pagestyle{empty}\begin{document}$ \eta _{\rm v} (\dot \varepsilon ) $\end{document} from (2). It is further shown that time-temperature equivalence applies not only to the stress but also to the recoverable strain and to G and ηv. The dependence of G and ηv on strain rate is then discussed. For high strain rates, G is close to the linear viscoelastic plateau modulus of PS melts and decreases with decreasing strain rate. The value of ηv is found to a good approximation to be equal to three times the shear viscosity taken at a shear rate equivalent to the elongational strain rate.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/polb.1987.090250204
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  • 7
    Digitale Medien
    Digitale Medien
    Investigation of prototropic equilibria by carbon-13 relaxation time analysis (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 16-20 
    Details
    ISSN: 0749-1581
    Schlagwort(e): 13C NMR ; 13C Relaxation Times ; Prototropic equilibria ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Quaternary 13C dipole-dipole spin-lattice relaxation times are used to analyse prototropic equilibria of 2-acetylbenzimidazole (1) and 4-azabenzimidazole in DMSO-d6 solutions. For the first compound, fast exchange between the two chelated structures prevails for 13C relaxation times, whereas proton and 13C chemical shifts characterize a slow exchange. For 4-azabenzimidazole, 13C and 1H spectra do not exhibit absorptions from structures in slow exchange. Analysis of the T1 values of carbons 8 and 9 before and after isotopic exchange of the labile amino hydrogen clearly show that the major component of the equilibrium is the 3H structure.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260250105
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