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  • Chemical Engineering  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 372-377 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 viscosity-shear rate functions for polysulfone (PSF) condensates ranging from 0.4RV to 0.95RV were determined using capillary rheometry, The most probable distribution of molecular weights of these resins allowed facile comparison with the polydisperse Bueche theory for viscosity, The agreement in shape of the viscosity function with theory was good but the data were displaced by a factor of 3 to 4 to higher reduced shear rate, a fairly common occurrence for melts. The high absolute value of PSF viscosity was explained with existing empirical correlations as a combination of low critical molecular weight and strong intermolecular interactions. The temperature dependence of viscosity was found to be close to that for polystyrene in the temperature range, Tg + 90 to Tg + 190°C. The die swell, end corrections, and melt fracture characteristics were also determined. The latter was found to occur at a constant wall shear stress of about 6 × 106 dynes/cm2 while the die swell and end corrections were found to be small.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 1098-1103 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Neck-in and maximum stress were studied in a tape-drawing experiment using a 3.5 MI low density polyethylene at 300°C. The conditions of the experiment were designed to reproduce closely those found in extrusion coating lines. The maximum stress was found to increase roughly with the 1.6 power of the drawdown ratio and the 1.0 power of the extrusion speed over a stress range of 4 × 103 to 5 × 105 Pa produced by drawdown ratios ranging from 2 to 22 and extrusion speeds of 2.3 to 6.1 cm s-1. The neck-in decreased weakly with drawdown ratio at low extrusion speed and with extrusion speed at constant drawdown ratio. After carefully characterizing the test resin in shear and extension, the similarities between predicted pure-shear (planar extension) transients and the tape experiments were studied. It was found that the trends, but not the magnitude of the experimental maximum stress were quite similar to the calculated longitudinal stress in pure shear. The behavior of the transverse to longitudinal stress ratio in pure shear was similar in behavior to the neck-in results, but considerable improvement was achieved by adding in a decayed stress from a simple-shear transient to simulate the conditions produced by the extrusion die. The philosophy of purposefully studying similarities between transient, pure or simple deformations and steady, complex processes is discussed.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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