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  • Chemistry  (40)
  • Instrumentation and Photography
  • 1995-1999  (8)
  • 1975-1979  (33)
  • 1
    Electronic Resource
    Electronic Resource
    Irregularities in steady flow for non-newtonian fluids between cone and plate (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 953-965 
    Details
    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: Flow irregularities have been visually observed in solutions of polyacrylamide of high molecular weight on shear in a cone-and-plate rheometry (gap angle 2.3°). This anomalous flow was found to depend on molecular weight, concentration, and solvent. The onset of flow irregularities were generally at shear rates 〈 5 sec-1. A dimensional analysis shows that the elastic component of the fluid is responsible for the anomalous flow. The onset of flow irregularities has been predicted from measurements of recoverable strain as a function of shear stress.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1979.070230401
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  • 2
    Electronic Resource
    Electronic Resource
    The preparation and tensile properties of polyethylene composites (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 22 (1978), S. 3249-3265 
    Details
    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: Single polymer composites have been prepared using different morphologies of polyethylene as matrix and as the reinforcement. Depending on annealing conditions, the ultraoriented fibers used as reinforcement can have higher melting points (ca. 139°C) than the matrix made from the same conventionally crystallized high-density polyethylene (ca. 132°C) or from low-density polyethylene (ca. 110°C). The optimum temperature has been assessed for bonding to occur by growth of transcrystalline regions from the melt matrix without considerable modulus reduction of the annealed ultraoriented and reinforcement fiber or film. Pullout tests have been used for determining the interfacial shear strength of these single polymer composites. The interfacial shear strength for the high-density polyethylene films embedded in a low-density polyethylene matrix is 7.5 MPa and for high-density polyethylene self-composites is 17 MPa. These values are greater than the strength for glass-reinforced resins. The strength is mainly due to the unique epitaxial bonding which gives greater adhesion than the compressive and radial stresses arising from the differential shrinkage of matrix and reinforcement. The tensile modulus of composites prepared from uniaxial and continuous high-density polyethylene films embedded in low-density polyethylene obeys the simple law of mixtures and the reinforced low-density polyethylene modulus is increased by a factor of 10. High strength cross-ply high-density-polyethylene - low-density-polyethylene laminates have also been prepared and the mechanical properties have been studied as the film orientation is varied with respect to the tensile axis.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1978.070221119
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  • 3
    Electronic Resource
    Electronic Resource
    Radiative transfer in photocatalytic systems (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 532-537 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Radiation absorption at the surface of catalytic particles is the initial step of photocatalytic oxidation reactions currently considered for their potential effectiveness in the treatment of polluted water with traces of highly toxic organics. Owing to the presence of catalyst particles within the fluid phase, the radiation field within a photocatalytic reactor results from the absorption and scattering within the participating medium. An annular reactor with a coaxial central lamp was considered, and the resulting 2-D radiation field was analyzed using a Monte Carlo technique to solve the radiative transfer equation. Results are discussed based on the relevant optical parameters, and a heuristic is derived for the design and rating of a photocatalytic reactor. To exploit the reaction volume effectively, the order of magnitude of the optical thickness should be close to unity, and for a given value of the absorption coefficient the catalyst with the lowest albedo should be selected; however, a precise evaluation of the phase function is not crucial to a relable representation of the radiation field.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420222
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  • 4
    Electronic Resource
    Electronic Resource
    Bethe-Bloch stopping power parameters for polystyrene, kapton, and mylar (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 65 (1997), S. 997-1003 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Values of several parameters appearing in the modified Bethe-Bloch theory must be known if one is to calculate the stopping power for a given projectile-target combination within the energy interval of applicability of the theory. In the course of the past several years, the author has established values for kapton and mylar target materials through fits of experimental data with the modified Bethe-Bloch theory. During the past year, several sets of measurements of polystyrene stopping powers for light projectiles have been studied so as to extract values of Bethe-Bloch parameters also for this target material. Results of these studies, including uncertainties in the parameter values that reflect the number and accuracy of the measurements analyzed, are summarized in this presentation.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 997-1003, 1997
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Bethe-Bloch stopping-power parameters for GaAs and ZnSe (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 70 (1998), S. 919-924 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: If one is to calculate the stopping power for a specified projectile-target combination within the energy interval of applicability of modified Bethe-Bloch theory, values of several parameters appearing in the formulation must be ascertained. In the past, the author has established such values for numerous target materials through fits of stopping-power measurements with modified Bethe-Bloch theory. However, the semiconductor materials ZnSe and GaAs have not yet been thus characterized. A set of very recent measurements of the stopping powers of each compound for low-energy protons and alpha particles, reported by members of the Helsinki group, has been analyzed in order to remedy this dearth of parameter values. Moreover, some corresponding measurements for 7Li ions traversing ZnSe have been analyzed for the purpose of obtaining the value of a single effective charge parameter. Results of these studies are reasonably consistent with expectations, and values are recommended for the mean excitation energy and the Barkas-effect parameter for each compound.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 919-924, 1998
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Einfluß von Verschiebungsreagentien auf NMR-Kopplungskonstanten (1978)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 90 (1978), S. 51-52 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19780900112
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  • 7
    Electronic Resource
    Electronic Resource
    A latent entanglement model for the draw of semicrystalline polymers (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 16 (1995), S. 813-819 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A novel molecular model, the latent entanglement, is proposed to explain the relationships between ductilities of polyethylene reactor powders and different conditions of synthesis. According to Hoffman's variable cluster model, irregularities in the crystallite fold surface increase as the synthesis temperature is decreased. The concept of latent entanglement stems from the potentiality of these defects to convert into active entanglements when the involved chain segments are drawn out of the crystals.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1995.030161106
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  • 8
    Electronic Resource
    Electronic Resource
    Viscoelastic properties of linear chain macromolecular gels. Growth of stress at the onset of steady shear flow (1979)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 76 (1979), S. 191-208 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Das Anwachsen von Zugspannung und Scherung zu Beginn einer konstanten Scherung wurde an Lösungen linearer Makromoleküle untersucht, um Aussagen über nichtlineare Viskoelastizität zu machen. Die Polyacrylamide (PAAm)…wurden in Wasser, Formamid und Ethylenglycol gelöst. Die Polymeren wurden in diesem Labor hergestellt. Sie waren unverzweight und initiatorfrei. Die Polystyrolproben (PS) von der Pressure Chemical Company wurden in Dekalinlösung untersucht. PAAm zeigt mit steigendem Molekulargewicht und steigender Konzetration zunehmend typischen Gelcharaketer in allen drei Lösungsmitteln. für homogene Systeme wurde Gelbruch und ein „undershoot“ beob-achtet. Zum ersten Ma1 konnten „overshoot“ aufgrund von verhakten Ketten und auf-grund von energetisch assoziierten Ketten voneinander unterschieden werden. Dies Ver-halten zeigt einen grol3en Gegensatz gegenuber dem PS/Dekalin-System und zeigt die Starke der Nebenvalenzbindungen in den PAAm-Systemen.
    Notes: The growth of stress (shear stress and normal stress) at the onset of steady shear flow was investigated for linear chain macromolecular fluids to determine nonlinear viscoelasticity. The polyacrylamides (PAAm) were dissolved in H2O, formamide and ethyleneglycol. The polymers were prepared in this laboratory. They were unbranched and free of initiator. The polystyrene (PS) samples from Pressure Chemical Company were studied in decalin solutions. PAAm shows increasingly typical gel character - in all 3 solvents - with increasing molecular weight and polymer concentration. For homogeneous systems gel fracture and undershoot were observed. Further for the first time overshoot due to entangled molecules and overshoot due to energetically associated chains have been distinguished. This behaviour is a strong contrast to the PS/decalin system and demonstrates the strength of the second valence bondings in the PAAm-systems.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1979.050760111
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  • 9
    Electronic Resource
    Electronic Resource
    Scanning force microscopy and effective medium theory study of free-standing polyaniline thin films (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 2167-2173 
    Details
    ISSN: 0887-6266
    Keywords: scanning force microscopy ; electric conductivity ; polyaniline ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The technique of scanning force microscopy was used to study the nanometer-scale structure of NMP cast films of polyaniline. Noncontact mode images provide direct evidence that polyaniline prepared in this form is a granular conductor. The films were found to consist of micrograins whose size and density were determined by the pH of the acid solution used to protonate the films. At pH 7, the polyaniline films exhibited a mostly disordered structure, with small 2-10 nm particles visible. Protonation at pH 5 to pH 3 resulted in partial agglomeration of the primary particles into larger bundles, with sizes up to 75 nm. Treatment in solution pHs of 2 or less resulted in films consisting of close-packed bundles of dimension 20-30 nm. The conductivity of the films exhibited a sharp rise beginning with protonation at pH 2 or less. Effective medium theory (EMT), was used to model the macroscopic conductivity of these films based on the SPM measured microscopic film structure. Using the size and size distribution of polymer micrograins or bundles in a modified EMT, we are able to obtain predicted conductivities that are close to the measured values for these films. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090331508
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  • 10
    Electronic Resource
    Electronic Resource
    Rheology of concentrated solutions of poly(γ-benzyl-glutamate) (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2271-2289 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Steady shear viscosity, dynamic viscosity, dynamic modulus, and normal force were measured via rotational rheometry for concentrated solutions of racemic mixtures of poly(benzyl-glutamate) and poly(benzyl-D-glutamate) in m-cresol. A transition from the isotropic state to liquid-crystalline order with increase in concentration was indicated by optical anisotropy and maxima in all four material functions. This occurred at a critical concentration higher than the Flory prediction. Over a well-defined range of concentrations and shear stresses, some of the liquid-crystalline solutions exhibited negative first normal-stress differences that were not due to inertial effects.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1996.938
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