Wire Coating Dies

Spiral mandrel die - Central feed -Star-shaped melt distribution - Radial boreholes - Spiral channels 

Ring spiral distribution - Central borehole for internal air exchange - Ring-shaped melt distribution - Axial boreholes 

FIGURE 7.37 Two spiral mandrel die designs. (Reprinted with permission of the publisher from Michaeli, 1984.) 

FIGURE 7.38 Basic features of a wire coating die. (Data from Michaeli, 1984.) 

FIGURE 7.39 Two mandrel designs commonly used in wire coating dies. In the upper figure the wire is coated under pressure inside the die while in the lower figure the wire is coated outside the die. 

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Annular flow is encountered in pipe extrusion dies, wire coating dies and film blowing dies. In the problem under consideration, a Power law fluid is flowing through an annular gap between two coaxial cylinders of radii kR and R, with k < 1 as schematically depicted in Fig. 5.15. The maximum in the velocity profile is located at r = j3R, where / is a constant to be determined. Due to the geometrical characteristics and ignoring entrance effects, the flow is unidirectional, i.e., u = (ur,ue,uz) = (0,0, wz(r)). 

The flow in a wire coating die can be modeled using a combination of drag and pressure flow. Derive an expression for the velocity field inside the die. 

Z. Tadmor and R. B. Bird, Rheological Analysis of Stabilizing Forces in Wire-Coating Dies, Polym. Eng. 

A general equation for the isothermal pressure flow of an incompressible Newtonian fluid in a die (without moving parts like, e.g., wire coating dies), can be written as... 

Fig. 12.46 Detailed schematic representation of the pressure type of wire-coating die.

Wire Coating Die A wire coating-die, with the wire velocity of V and annular thickness of II, results in a coating thickness h at a given pressure drop. Develop an... 

It was determined that the shear rate in PVC passing through a copper wire coating die was in excess of 4000000 Is. This resulted in volatilisation of the dioctyl phthalate plasticiser and changes in the polymer molecular structure, as determined by infrared spectroscopy. The flow was studied using capillary rheometry with a die of a 0.15 mm diameter. It was concluded that the change in... 

Profile, pipe, blown-film, and wire-coating dies are examples of dies generally constructed of hot-rolled steel for low-pressure melt applications. The high-pressure dies can be made of certain steels such as 4140 steel. Chrome plating is generally apphed to the flow surfaces, particularly when processing certain plastics such as EVA. Stainless steel is used for any die subject to corrosion. The steel... 

Figure 5.52 Wire-coating dies (a) pressure-coating die and (6) tubing tool...

Calculated streamlines in a coextrusion wiring-coating die. (a) viscosity ratio of 0.2 (b) viscosity ratio of 2.0 (c) thickness ratio of 0.3333... 

The design of wire-coating dies has been studied empirically by Hammond [34] and Ferrari [35], and through simple theoretical models by Bernhardt [36], McKelvey [15], and Middleman [3]. Bagley and Storey [37] have given an exact solution for shear rates and velocity profiles in Newtonian... 

Next, the posttorpedo section may be analyzed. The solution to the generalized annular Couette flow problem may be profitably used for wire-coating dies with appropriate modifications to account for the taper in the different sections (i.e., the variation of k with axial distance z). On eliminating A from Eqs. (7) and (10), the following equation for the determination of n, x) is obtained ... 

Fenner, R. T. and Williams, J. G., Analytical methods of wire-coating die design, Trans. Plast. Inst. London. i5(119) 701 (1967). 

Figure 4.32 Schematic representation of flow in a wire-coating die [88].

Figure 4.33 Simulated flow patterns of (a) Newtonian and (b) shear-thinning polymer melts (LDPE) in a wire-coating die. The Newtonian fluid exhibits a big vortex, while in the same geometry the LDPE melt flows without recirculation [88].

Figure4.34 Simulated flow patterns of an LDPEmelt in an industrial wire-coating die. The polymer melt flows smoothly in a streamlined flow both (a) inside and (b) outside the die, verifying the good die design [37].

Tadmor, Z. and Bird, R.B. (1974) Rheological analysis of stabilizing forces in wire-coating dies. Polym. Eng. Sci., 14, 124-136. 

Fig. 19.32. Basic design of a wire coating die. (Reprinted from Extrusion Dies, W. Michaeli. by courtesy of Carl Hanswer Veriag, 8 Munchen 80, VHshafener Str. 10.)...

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