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  • 1
    Digitale Medien
    Digitale Medien
    Fourier representation method for electronic structures of linear polymers (1978)
    Springer
    Theoretical chemistry accounts 48 (1978), S. 127-141 
    Details
    ISSN: 1432-2234
    Schlagwort(e): Polymers, linear ∼
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The Fourier representation method described in the previous paper of this series is used to make electronic structure calculations for a linear chain of equally spaced hydrogen atoms. The electronic wavefunction is assumed to be a determinant of doubly-occupied crystal orbitals of modulated-plane-wave type, built from one 1s Slater-type orbital of screening parameter ζ centered on each atom. The energy is calculated from the electrostatic zero-order Hamiltonian with exact evaluation of all Coulomb and exchange contributions, and is optimized with respect to the lattice spacing and ζ value. Good agreement with work by others is noted, indicating a near-equivalence of modulated-plane-wave and tight-binding wavefunctions for this half-filled-valence-band system. The linear chain is calculated to be far more stable than cubic three-dimensional hydrogen crystals. This fact sheds light on the unusually large calculated nearest-neighbor distances in the cubic crystals, and is related to a suggestion that under certain conditions the most stable structure for solid atomic hydrogen may be of lower symmetry than cubic.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00554175
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  • 2
    Digitale Medien
    Digitale Medien
    Fourier representation method for electronic structures of linear polymers (1978)
    Springer
    Theoretical chemistry accounts 48 (1978), S. 127-141 
    Details
    ISSN: 1432-2234
    Schlagwort(e): Polymers, linear ∼
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The Fourier representation method described in the previous paper of this series is used to make electronic structure calculations for a linear chain of equally spaced hydrogen atoms. The electronic wavefunction is assumed to be a determinant of doubly-occupied crystal orbitals of modulated-plane-wave type, built from one 1s Slater-type orbital of screening parameter ζ centered on each atom. The energy is calculated from the electrostatic zero-order Hamiltonian with exact evaluation of all Coulomb and exchange contributions, and is optimized with respect to the lattice spacing and ζ value. Good agreement with work by others is noted, indicating a near-equivalence of modulated-plane-wave and tight-binding wavefunctions for this half-filled-valence-band system. The linear chain is calculated to be far more stable than cubic three-dimensional hydrogen crystals. This fact sheds light on the unusually large calculated nearest-neighbor distances in the cubic crystals, and is related to a suggestion that under certain conditions the most stable structure for solid atomic hydrogen may be of lower symmetry than cubic.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02399023
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Compatible glassy polyblends based upon poly(2,6-dimethyl-1,4-phenylene oxide): Tensile modulus studies (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 519-524 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The mechanical behavior of compatible glassy polyblends based upon poly(2.6-dimethyl- 1,4-phe nylene oxide) (PPO) was investigated. In particular, the influence of composition, molecular weight, and molecular weight distribution upon the tensile modulus of the blend was assessed. Various possible correlations between the experimentally determined moduli and theory are considered. Included are correlations with density, packing density, composite theory, and lattice fluid theory. The modeling of the properties of mixtures via Simplex lattice design is also presented. Finally, attention is given to the development of compatibility criteria based upon tensile modulus and density measurements.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760190710
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Curing and heat transfer in polyurethane reaction moldingPresented in part at the AiChE Annual Meeting, Chicago, 1976. (1978)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 382-387 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Temperature measurements were made on the adiabatic polymerization of three urethane systems; two casting formulations, one thermoplastic and the other thermosetting, and a commercial reaction injection molding (RIM) formulation with a 10 second gel time. The data were found to fit a simple nth order overall kinetic expression. These kinetic and heat of reaction results were used to model heat transfer in a 3.8 cm diameter cylinder with an isothermal wall. Experimental temperature profiles for the two casting urethanes were in good agreement with predictions. The kinetic data on the RIM material was used to model temperature profiles1 in 3 and 6 mm thick plaque molds. Experimental measurements of temperature near the mold center agreed with the model. Temperatures measured near the wall were higher due to failure of the isothermal wall assumption.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760180509
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