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  • 1
    Electronic Resource
    Electronic Resource
    Simulation of two-dimensional planar flow of viscoelastic fluid (1986)
    Springer
    Rheologica acta 25 (1986), S. 80-94 
    Details
    ISSN: 1435-1528
    Keywords: Streamwise integration ; abrupt contraction ; Leonov model ; birefringence ; Weissenberg number ; Deborah number
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract A numerical scheme based on the Finite Element Method has been developed which uses a relaxation factor in the momentum equation with the stresses being evaluated via a streamwise integration procedure. A constitutive equation introduced by Leonov has been used to represent the rheological behavior of the fluid. The convergence of the scheme has been tested on a 2 : 1 abrupt contraction problem by successive mesh refinement for non-dimensional characteristic shear rates, of 5 and 50 for polyisobutylene Vistanex at 27 °C. The recirculation region is shown to increase in size with non-dimensional characteristic shear rate. Theoretical predictions have been compared with the experimental data which include birefringence and pressure loss measurements. In general, the comparisons have been reasonably good and demonstrates the usefulness of the present numerical scheme and the Leonov constitutive equation to describe real polymer flows.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01332127
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  • 2
    Electronic Resource
    Electronic Resource
    Orthogonal superposition of small and large amplitude oscillations upon steady shear flow of polymer fluids (1989)
    Springer
    Rheologica acta 28 (1989), S. 176-189 
    Details
    ISSN: 1435-1528
    Keywords: Shear flow ; orthogonalsuperposition ; largeamplitudeoscillations ; harmonicanalysis ; Leonov model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The orthogonal superposition of small and large amplitude oscillations upon steady shear flow of elastic fluids has been considered. Theoretical results, obtained by numerical methods, are based on the Leonov viscoelastic constitutive equation. Steady-state components, amplitudes and phase angles of the oscillatory components of the shear stress, the first and second normal stress differences as functions of shear rate, deformation amplitude and frequency have been calculated. These oscillatory components include the first and third harmonic of the shear stresses and the second harmonic of the normal stresses. In the case of small amplitude superposition, the effect of the steady shear flow upon the frequency-dependent storage modulus and dynamic viscosity has been determined and compared with experimental data available in literature for polymeric solutions. The predicted results have been found to be in fair agreement with the experimental data at low shear rates and only in qualitative agreement at high shear rates and low frequencies. A comparison of the present theoretical results has also been made with the predictions of other theories. In the case of large amplitude superposition, the effect of oscillations upon the steady shear flow characteristics has been determined, indicating that the orthogonal superposition has less influence on the steady state shear stresses and the first difference of normal stresses than the parallel superposition. However, in the orthogonal superposition a more pronounced influence has been observed for the second difference of normal stresses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01356978
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  • 3
    Electronic Resource
    Electronic Resource
    Self-Reinforced melt processible polymer composites: Extrusion, compression, and injection molding (1987)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 8 (1987), S. 158-175 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Rheological properties, extrusion, fiber spinning, compression, and injection molding of blends of polycarbonate and two thermotropic liquid crystal polymers based on wholly aromatic copolyesters have been studied. Blends were prepared using an internal Banbury mixer and static Koch mixer. Based upon differential scanning calorimetry and dynamic mechanical measurements, these blends have been shown to be incompatible in the entire range of concentrations. During extrusion and injection molding at high strain rates, it has been observed that thermotropic liquid crystal polymer at concentrations 2.5, 5, and 10 percent by weight in situ forms high modulus and high strength fibers within the polycarbonate matrix leading to self-reinforced polymer composites. The tensile strength of the composite containing 10 percent of liquid crystal polymer exceeds that of the pure components. In addition, anisotropy of properties of the injection molded parts has been found to substantially reduce in a comparison with that of liquid crystal polymer. The processing conditions and technique for the production of self-reinforced polymer composite during processing of the blends have been identified. This has been done by measurements of mechanical properties, direct observation of morphology, and by theoretical calculation using simplified composite theory for the unidirectional continuous fiber-reinforced composites. At the high concentrations, 25 and 50 percent by weight, thermotropic liquid crystal polymer forms large spherical droplets inside polycarbonate leading to highly brittle material. This is in distinction from the fibrous, high modulus tough composites formed at the lower concentrations.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750080305
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  • 4
    Electronic Resource
    Electronic Resource
    Flow of polymeric melts in short tubes (1985)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 25 (1985), S. 264-270 
    Details
    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: In an attempt to further understand the flow of polymeric melts through gates in injection molding, the present investigation deals with measurement of pressure drops during isothermal extrusion of fiber-filled and unfilled polystyrene, polypropylene, and polycarbonate melts in short tubes with sudden contraction at high shear rates typical of injection molding. Flow curves for these materials have been determined over a wide range of shear rates at various temperatures by using a capillary rheometer and extruder. Measurements indicate that rheological properties of fiber-filled melts after injection molding differ from those of fresh samples. Moreover, it has been found that decreasing the tube length increases the slope of the curve for pressure drop vs. Volumetric flow rate. Extra pressure losses due to end effects have been determined which show that at high shear rates these losses can reach levels as high as 100 bar, with the effect being higher for the fiber-filled melts. By using a viscoelastic consitutive equation, the extra pressure losses have been separated into entrance and exit losses. Model parameters required for this calculation have been determined from viscosity-shear rate curves for the melts. For various polymers, master curves useful for industrial applications have been constructed for the extra pressure losses.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760250503
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  • 5
    Electronic Resource
    Electronic Resource
    Volumetric effects in the injection molding of polymers (1985)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 25 (1985), S. 271-278 
    Details
    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: Density and shrinkage measurements have been performed in quenched and molded slabs from polystyrene (PS) and poly (methylmethacrylate) (PMMA). Various processing conditions have been employed and their effect on density and shrinkage variation in the final parts, as well as volumetric aging vs. Elapsed time at room temperature, have been elucidated. A numerical simulation of the density variation in quenched parts and their aging has been performed by using first-order rate theory for volumetric changes in conjunction with solving the transient one-dimensional heat-conduction equation with a convective heat-transfer boundary condition at surface. A numerical simulation of the shrinkage in molded parts has been carried out by using the equation of state with a simultaneous solving of the governing equations for one-dimensional mold filling during the cavity filling stage followed by transient one-dimensional conduction during packing and cooling stages. Predicted results for density and shrinkage are compared with experimental data.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760250504
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  • 6
    Electronic Resource
    Electronic Resource
    Parallel superposition of small- and large-amplitude oscillations upon steady shear flow of polymer fluids (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 2303-2327 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The parallel superposition of small- and large-amplitude oscillations upon steady shear flow of elastic fluids has been considered. Theoretical results, obtained by numerical methods, are based upon the Leonov viscoelastic constitutive equation. Steady-state components, amplitude, and phase angle of oscillatory components of the shear stress, the first and second normal-stress differences as a function of shear rate, deformation amplitude, and frequency have been calculated. These oscillatory components include the first harmonic of the shear stresses and the first and second harmonic of the normal stresses. In the case of small-amplitude superposition, the effect of the steady shear flow upon frequency-dependent storage and loss moduli has been determined and compared with experimental data available in the literature for polymeric solutions and melts. In the case of large-amplitude superposition, the effect of oscillations upon the steady shear flow characteristics has been determined and compared with our experimental data for a polymeric melt. The experimental results for shear stress components have been found to be in good agreement with theoretical predictions, although there are some deviations for storage modulus at high shear rates. The deviations seem to be dependent on material. Moreover, the theory is unable to describe experimental data available for the first harmonic of normal stresses.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1988.090261110
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  • 7
    Electronic Resource
    Electronic Resource
    Unsteady flow of rubber compounds at injection molding conditionsThe work was supported by Grant MSM 8514952 from the National Science Foundation, Division of Engineering. (1989)
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 9 (1989), S. 167-180 
    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 automated rheometer is developed for an evaluation of the processability of rubber compounds at injection molding conditions. The rheometer utilizes a screw injection molding machine in order to push rubber compounds through a thermostated slit die at controlled flow rates. Three pressure transducers are flush-mounted along the die length and a displacement transducer is installed to measure the screw motion. Signals generated by the pressure and displacement transducers and thermocouple are supplied to an A/D converted and the IBM PC/AT computer. Unsteady character of flow of rubber compounds is observed. The obtained data are compared with predictions from modeling of flow, using the viscoelastic plastic constitutive equation.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adv.1989.060090301
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