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  • 1995-1999  (6)
  • Polymer and Materials Science  (6)
  • contraction and expansion flow
  • 1
    Electronic Resource
    Electronic Resource
    Ultrasonic devulcanization of rubber vulcanizates. I. Process model (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 59 (1996), S. 803-813 
    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: Tire and rubber waste recycling is an important issue facing the rubber industry. In addressing this issue, the present article describes the first attempt to formulate a model and to simulate a novel continuous ultrasonic devulcanization process. The proposed model is based upon a mechanism of rubber network breakup caused by cavitation, which is created by high-intensity ultrasonic waves in the presence of pressure and heat. Dynamics of bubble behavior is described by the Notlingk-Neppiras equation with incorporation of an additional term based upon elastic strain-energy potential. Acoustic pressure arising in the ultrasonic field is related to void formation. Their concentration is calculated based upon nucleation and growth of gas bubbles in crosslinked elastomers under negative driving pressure. The breakup of a three-dimensional network in crosslinked rubbers is combined with flow modeling. The viscosity function required for this modeling is based upon a power-law model which includes temperature, shear rate, and gel fraction dependence. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Ultrasonic devulcanization of rubber vulcanizates. II. Simulation and experiment (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 59 (1996), S. 815-824 
    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 simulation results based on the devulcanization model presented in Part I of this study are described for devulcanization of SBR vulcanizates. The vulcanizates are conveyed by a single-screw extruder to a thin gap between a stationary die and a vibrating horn. Gapwise velocity, temperature, and shear-rate distributions along the die length are calculated. Predictions of the model for changes of various structural characteristics including gel fraction, fraction of various broken bonds, rate of their breakup, and void formation along die length are given. Devulcanization energy consumption and energy dissipated by ultrasonic waves are calculated. Comparison of these energies indicates that the devulcanization energy represents only a small fraction of the dissipated energy. The predicted results for gel fraction, crosslink density, die characteristics, and “mixing cup” temperature are compared with the experimental data. These predicted results are found to be only in qualitative agreement with experimental observations. The theoretical and experimental results indicate that the rubber is partially devulcanized and the devulcanization process is accompanied by some degradation of the macromolecular chains. © 1996 John Wiley & Sons, Inc.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Percolation simulation of the network degradation during ultrasonic devulcanization (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2409-2418 
    Details
    ISSN: 0887-6266
    Keywords: devulcanization ; modeling ; network ; percolation ; recycling ; rubber ; ultrasound ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The percolation model of network degradation during rubber devulcanization is presented. The model is based on a random crosslink scission and molecular chain breakup. The obtained results indicate that the primary model parameter characterizing the network degradation is the ratio of the probabilities of backbone breakup to crosslink scission. The predicted dependences of the gel fraction of devulcanized rubber on crosslink density are in excellent agreement with experimental data for styrene-butadiene rubber and ground rubber tire. The estimated critical exponents indicate that the process of devulcanization for the vulcanizate without filler appears to belong to the universality class of standard 3D bond percolation while devulcanization for the vulcanizate with filler appears to belong to its own new universality class. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Injection molding of semicrystalline polymers. II. Modeling and experiments (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 821-838 
    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 injection molding of an isotactic polypropylene was computer-simulated with both quiescent and shear-induced crystallization taken into account. A one-dimensional finite difference model was used to simulate the filling, packing, and cooling stages of the injection-molding cycle. The Spencer-Gilmore equation was used to relate the density variations to the pressure and temperature traces in the packing simulation. The quiescent crystallization kinetics was modeled by the differential form of the Nakamura equation. The theory developed by Janeschitz-Kriegl and co-workers was used to model the shear-induced crystallization kinetics. The pressure traces during the filling and packing stages of the molding cycle, the thickness of the shear-induced crystallization layer, and the crystallinity profile throughout the thickness of the part were measured and compared with predicted values. © 1995 John Wiley & Sons, Inc.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070550519
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  • 5
    Electronic Resource
    Electronic Resource
    Injection molding of semicrystalline polymers. I. Material characterization (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 807-819 
    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: Various material data for an isotactic polypropylene were acquired for the simulation of the injection molding of this material. Viscosity as a function of shear rate and temperature was measured using a capillary rheometer at high shear rates and a cone-and-plate rheometer at low shear rates. Heat-flow properties, characterizing kinetics and induction time of quiescent crystallization, were obtained from DSC measurements. Material data characterizing shear-induced crystallization were obtained from extrusion experiments through a slit die with subsequent quenching of the material in the die after various rest times. The thickness of the shear-induced crystallization layer was measured along with the birefringence in this layer. A model of shear-induced crystallization developed by Janeschitz-Kriegl and co-workers was used to fit the kinetic data. Thus, kinetic parameters such as the limiting shear rate below which no shear-induced crystallization can occur and the characteristic time for the relaxation of birefringence were obtained. © 1995 John Wiley & Sons, Inc.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070550518
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Blends of a PPO-PS alloy with a liquid crystalline polymer (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 1117-1129 
    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: Blends of a PPO-PS alloy with a liquid crystalline polymer have been studied for their dynamic properties, rheology, mechanical properties, and morphology. This work is an extension of our previous work on PPO/LCP blends. The addition of the LCP to the PPO-PS alloy resulted in a marked reduction in the viscosity of the blends and increased processibility. The dynamic studies showed that the alloy is immiscible and incompatible with the LCP at all concentrations. The tensile properties of the blends showed a drastic increase with the increase in LCP concentration, thus indicating that the LCP acted as a reinforcing agent. The tensile strength, secant modulus, and impact strength of the PPO-PS/LCP blends were significantly higher than that of PPO/LCP blends. Morphology of the injection molded samples of the PPO-PS/LCP blends showed that the in situ formed fibrous LCP phase was preserved in the solidified form. A distinct skin-core morphology was also seen for the blends, particularly with low LCP concentrations. The improvement of the mechanical properties of the blends is attributed to these in situ fibers of LCP embedded in the PPO-PS matrix. The improvement in the properties of PPO-PS/LCP over PPO/LCP is also attributed to the addition of the PS which consolidates the matrix. © 1995 John Wiley & Sons, Inc.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070550715
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    Paper (German National Licenses)
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