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  • AERODYNAMICS  (2)
  • Polymer and Materials Science  (2)
  • 1975-1979  (4)
  • 1979  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Comparisons of the cure of phenol-formaldehyde novolac and resol systems by differential scanning calorimetry (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 1973-1985 
    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: Comparisons were made of differential scanning-calorimetric (DSC) thermograms of both liquid and powdered commercial phenol-formaldehyde resins. By a combination of the results from analyses under a variety of conditions, such as ambient pressure, high pressure, using freeze-dried samples, and also by direct observation of the resin-curing process in wood-veneer assemblies, the curing reactions of phenol-formaldehyde resins were found to differ for resol and novolac systems. At a heating rate of 10°C/min, the resol resin showed endothermic curing reactions at temperatures of about 150°C, while the novolac-type resin showed an exothermic peak maximum at about 160°C. Results are presented to show how DSC can be used to differentiate between a resol and novolac system.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1979.070230708
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A water-sensitive thermomechanical transition in a polyimide (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 1189-1201 
    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: The effect of water vapor on a polyimide has been investigated in the temperature region of -190 to 325°C using an automated torsion pendulum. A damping peak, TH2O developes at -122°C (1 Hz) in the thermomechanical spectra of the polymer which is due to water-polymer interactions. The peak intensifies as the humidity of the conditioning atmosphere, at both 30° and at 325°C, increases and attains a limiting value at about 3000 ppmv H2O. The process is reversible. It is concluded that the number of sites in the polymer for interaction with water is low and limited (〈0.3 molecule H2O per polymer repeat unit) and, assuming direct proportionality between the intensity of the loss peak and the amount of water adsorbed, that the adsorption of water vapor follows the Langmuir isotherm.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1979.070230422
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    Paper (German National Licenses)
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  • 3
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    Unknown
    Base pressure associated with incompressible flow past wedges at high Reynolds numbers (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A model is suggested to study the viscid-inviscid interaction associated with steady incompressible flow past wedges of arbitrary angles. It is shown from this analysis that the determination of the nearly constant pressure (base pressure) prevailing within the near wake is really the heart of the problem and this pressure can only be determined from these interactive considerations. The basic free streamline flow field is established through two discrete parameters which should adequately describe the inviscid flow around the body and the wake. The viscous flow processes such as boundary-layer buildup along the wedge surface, jet mixing, recompression, and reattachment which occurs along the region attached to the inviscid flow in the sense of the boundary-layer concept, serve to determine the aforementioned parameters needed for the establishment of the inviscid flow. It is found that the point of reattachment behaves as a saddle point singularity for the system of equations describing the viscous recompression process. Detailed results such as the base pressure, pressure distributions on the wedge surface, and the wake geometry as well as the influence of the characteristic Reynolds number are obtained. Discussion of these results and their comparison with the experimental data are reported.
    Keywords: AERODYNAMICS
    Type: ASME PAPER 79-APM-31
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Calculations of transonic boattail flow at small angle of attack (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A transonic flow past a boattailed afterbody under a small angle of attack was examined. It is known that the viscous effect offers significant modifications of the pressure distribution on the afterbody. Thus, the formulation for the inviscid flow was based on the consideration of a flow past a nonaxisymmetric body. The full three dimensional potential equation was solved through numerical relaxation, and quasi-axisymmetric boundary layer calculations were performed to estimate the displacement effect. It was observed again that the viscous effects were not negligible. The trend of the final results agreed well with the experimental data.
    Keywords: AERODYNAMICS
    Type: NASA-CR-158471 , ME-TN-395-6 , UILU-ENG-79-4001
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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