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  • 1
    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: Coat-hanger dies are commonly used for the extrusion of plastic sheets and films. To describe the flow of a molten polymer through a coat-hanger die, a two-dimensional approach is necessary. Moreover, the thermal effects, which play an important role in the flow distribution, have to be taken into account. In this paper, two numerical models for the simulation of coat-hanger dies are described and compared. These models differ mainly in the simplifying assumptions used and in the treatment of the thermal problem. The simulations obtained with the two models were compared with each other and with experimental data. The discrepancies between the two models can be explained by the different theoretical treatments.
    Additional Material: 17 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 30 (1990), S. 1544-1550 
    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: Plastic profile die design is a complex task because of cross section area and shape changes occurring after die exit. Dimensions of the profile are increased by the extrudate swell phenomenon and decreased by drawdown and shrinkage. An experimental study on the effect of processing conditions on extrudate swell and on the shape of a rectangular profile was done for rigid poly(vinyl chloride), PVC, and high density polyethylene, HDPE, resins. Extrudate swell was found to be a strong decreasing function of residence time in the die and also, for short dies, of entrance geometry. For PVC, equilibrium swell increased with melt temperature. The differences in swelling for the two polymers are explained with the help of creep/recovery data obtained on a stress rheometer. Drawdown, die land length, and melt temperature were shown to have an important effect on the shape of a rectangular profile. Decreasing the die land and increasing the melt temperature had the effect of increasing preferably the thickness while drawdown, by inhibiting the swelling, decreased the thickness.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0193-7197
    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 , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this paper, we investigate the effects of processing aids, impact modifiers, inorganic fillers, and resin molecular weight on the postextrusion swelling of rigid PVC compounds. Rotational rheometry measurements of the loss tangent in dynamic mode and of the recoverable shear in creep mode are made to evaluate PVC's elasticity. Long elastic relaxation times are found for rigid PVC. This apparent contradiction, i.e., relatively low swell but very high elastic relaxation time, is explained by taking into account the two-phase flow behavior of PVC.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6956-6972 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Macroscopic systems composed of particles whose time evolution is governed by the rigid body dynamics are called rigid body fluids. Such fluids could be, for example, macromolecular fluids composed of rigid macromolecules. Kinetic theory and hydrodynamics of these systems are introduced by using the method of Hamiltonian modeling. The physical basis of this method is the requirement that solutions to the governing equations agree with results of the experimental observations that constitute the empirical basis of equilibrium thermodynamics. The advantages of the Hamiltonian method are best displayed on the level of extended hydrodynamics, i.e., hydrodynamics with state variables composed of classical hydrodynamics fields and some extra fields characterizing the rigid body motion of the particles. Both the time evolution equations and the formula for the extra stress tensor are obtained without the need of closure approximations. Moreover, the formula for the extra stress tensor is guaranteed to be compatible with the rest of the time evolution equations. Qualitative properties of solutions of the governing equations derived in the paper lead to the conclusion that rigid body fluids possess a nonsymmetric stress tensor and exhibit elastic behavior. Both of these features have been seen in simulations. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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