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  • 1990-1994  (3)
  • Polymer and Materials Science  (2)
  • contraction and expansion flow  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Two-dimensional planar flow of a viscoelastic plastic medium (1993)
    Springer
    Rheologica acta 32 (1993), S. 181-191 
    Details
    ISSN: 1435-1528
    Keywords: Two-dimensional flow ; viscoelastic plastic medium ; yield surface ; contraction and expansion flow ; pressure drop
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The present study is concerned with finite element simulation of the planar entry flow of a viscoelastic plastic medium exhibiting yield stress. The numerical scheme is based on the Galerkin formulation. Flow experiments are carried out on a carbon black filled rubber compound. Steady-state pressure drops are measured on two sets of contraction or expansion dies having different lengths and a constant contraction or expansion ratio of 4:1 with entrance angles of 90, 45 and 15 degrees. The predicted and measured pressure drops are compared. The predicted results indicate that expansion flow has always a higher pressure drop than contraction flow. This prediction is in agreement with experimental data only at low flow rates, but not at high flow rates. The latter disagreement is possibly an indication that the assumption of fully-developed flow in the upstream and downstream regions is not realistic at high flow rates, even for the large length-to-thickness ratio channels employed. The evolution of the velocity, shear stress, and normal stress fields in the contraction or expansion flow and the location of pseudo-yield surfaces are also calculated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366681
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Blends of thermotropic polyester with poly(phenylene oxide) (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 2923-2932 
    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: A thermotropic liquid crystalline polymer (LCP) based on wholly aromatic copolyesters based on hydroxynaphthoic and hydroxybenzoic acid was melt-blended with a thermoplastic poly(phenylene oxide) by corotating twin screw extruder. Rheological properties, temperature transitions, dynamic and mechanical properties, and electron microscopy study have been performed. Rheological study indicated significant viscosity reductions with increasing LCP content leading to ease of processing. From the differential scanning calorimeter (DSC) and dynamic mechanical thermal analyzer results, these blends showed incompatibility for the whole range of concentrations. Mechanical properties were found to be slightly improved at low LCP and dramatically improved at above 50% LCP contents. In addition, impact strength was significantly increased up to two times after adding 10% LCP into the matrix. The morphology of blends was affected by composition. Droplets and stubby fibrils structures caused lower tensile strength, whereas fibrillar structure improved this property.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070421109
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of oscillations during extrusion on rheology and mechanical properties of polymers (1990)
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 10 (1990), S. 31-45 
    Details
    ISSN: 0730-6679
    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
    Notes: An experimental study associated with the applications of sound and ultrasonic waves to extrusion is conducted. Two laboratory setups are developed for these purposes incorporating orthogonal and parallel superposition of oscillations on pressure flow during extrusion. The orthogonal superposition of sound oscillations is imposed in an annular die. The parallel superposition of ultrasound oscillations is imposed in a circular die. Several materials including unfilled and filled thermoplastics, thermoplastic elastomer, and elastomer are tested. Die characteristics, power consumption, and die swell are determined during extrusion. The rheological properties, molecular weight, tensile properties, and impact strength of materials with and without sound and ultrasound treatment are investigated, indicating permanent changes in these properties. The observed effects are found to depend on melt temperature, flow rate, nature of polymer system, and oscillating parameters such as frequency and deformation amplitude.
    Additional Material: 23 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adv.1990.060100104
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    Paper (German National Licenses)
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