The various die designs that have been proposed for the manufacture of sheets and flat films from polymeric materials are reviewed, along with the corresponding flow analysis and derived design equations. Successively, the T-die, the linearly tapered coat-hanger die, the curvilinearly tapered coat-hanger die (with manifold of circular or rectangular cross-section), and the fishtail die are examined. In each case, care is taken to outline the assumptions used to derive the equations, and to state the advantages and disadvantages of each design. The limits of these mentioned assumptions are explained and illustrated. Particular attention is paid to the aspects of the design which affect the processing of sensitive or reactive materials (i.e., residence time distribution and wall shear stress).
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