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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 2 (1993), S. 75-106 
    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: The design of extrusion lines deals with the extruder and the die as well as with the down stream equipment, especially the cooling section. This paper aids in the design of these three units, regarding different aspects. The scale-up of extruders by means of the model theory is demonstrated in its practical use with examples. Emphasis is laid on the design of series of single screw extruders with mixing-pins and of twin-screw extruders (scale-up). There the adequate selection of the necessary restrictions for the compilation of model laws is discussed in detail. This is an approach to the safe machine design on the basis of model theory.The present standard of the calculation of threedimensional flow patterns in extrusion dies by means of the finite-element-method (FEM) is shown in order to point out how design-aids for the die-designer are derived from these calculations. After a discussion of application-criteria for the FEM, examples will show possible ways of using FEM-results.For the shaping of Y-branches in twin-screw machines the FEM-results point to possible plate-out areas and to their avoidance by geometrical modifications. The calculation of a die for a T-profile helps to design the passages between entry and exit sections. Finally, flow coefficients for the calculation of pressure losses in different cross sections are given.The design and optimization of cooling sections, as it can be done with the aid of the actual cooling models, is shown for some important extrusion processes. Heat transfer coefficients for practical cases (film-sheet-, pipe- and parison extrusion) are presented. Examples show, how diagrams for the design and optimization of cooling sections (for example the reduction of internal stresses and warping) can be made, using a microcomputer.
    Additional Material: 31 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    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: The processing of rigid-PVC is mainly performed on twin screw extruders. For a thermal sensitive material, such as rigid PVC, this implies certain advantages. They consist primarily in the fact that intermeshing counter-rotating twin screw extruders are axially closed pump systems, whereas single screw and co-rotating twin screw extruders represent axially open mixing systems, conveying by means of friction forces. This fundamental difference leads to totally different flow rate and shearing force distributions of the axial flow, which in turn affects the residence time distribution and the thermal dynamics of the process. Investigations have been carried out to determine the influence of screw speed, die resistances, barrel wall temperatures and different compounds on the melt temperature and its homogeneity. It could be shown that the melt temperature can be essentially influenced by heating the barrel wall and the screw. This even applies to the most diverging degrees of mechanical power consumption resulting from different compounds. The homogeneity of the melt temperature thus depends on the relationship between the barrel wall temperature and the melt temperature within the respective heating zone. The possibility is shown to establish a model theory based on energetic and rheological similarities, which can be employed in the construction of machines of different diameters. For this purpose the geometrical and operational data of an optimal operating machine serve as a basis.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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