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  • Chemistry  (4)
  • 1970-1974  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 14 (1970), S. 79-88 
    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: Measurements of melt viscosity on samples of polytetrafluoroethylene of different molecular weight were carried out at 360°C by means of tensile creep tests in the linear viscoelasticity range. The apparent activation energy for viscous flow in the range between 330° and 380°C was estimated to be 20 kcal/mole. A value of about 7,500 was also determined for the average molecular weight between entanglement points (Me), from the equilibrium compliance (De). Melt viscosity data were compared with zero strength time (ZST) values and a linear correlation was found on a bilogarithmic scale. The dependence of ZST on the applied stress and temperature was also studied and the results are discussed on the basis of Bueche's theory on the creep at rupture above the glass transition temperature.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    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 dynamic-mechanical properties as a function of temperature and the low- and high-speed tensile properties at 23°C have been determined on specimens of conventional suspension-polymerized PVC and of low-temperature-polymerized PVC roll milled and then compression molded at different temperatures. It has been found that the main transition α and the shear modulus above Tα depend on the thermal history and are strongly affected by crystallinity, whereas the dynamic-mechanical spectrum below Tα is not influenced by these parameters. Room-temperature tensile modulus and yield properties are very little affected by processing history and crystallinity. The elongation at break and the fracture energy, on the contrary, increase, at any fixed strain rate, for conventional PVC with milling temperature. The same trend has been found for low-temperature PVC, but the elongation at break-versus-temperature curve is shifted, as a whole, toward higher temperatures by approximately 50°C. Such results are discussed in terms of homogeneity of the specimens, which is controlled by the melting process of the crystallites. Stereoscanning electron micrographs of fracture surfaces appear to substantiate these conclusions.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 15 (1971), S. 2487-2512 
    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 dynamic-mechanical properties as a function of temperature and frequency were measured for five samples of polycaprolactam (nylon 6) containing different amounts of hydrosoluble products. Low- and high-speed tensile properties and Izod impact strength were determined between -190° and 100°C for the same samples by using autographic methods. The influence of the mechanical relaxation processes on moduli, yield strength σy, yield strain εy, tough-brittle transition temperature, elongation at break εR, and tensile and Izod fracture energies was investigated. It has been found that some mechanical properties, such as modulus and yield properties, can be directly related to specific relaxation phenomena, whereas as far as other properties, such as the ultimate properties, are concerned, the existing correlation can be concealed by the interference of purely mechanical phenomena which depend on the testing technique used, the testing conditions, and the previous history of the material.
    Additional Material: 27 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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