A Multi-Rheology Design Method of Sheeting Polymer Extrusion Dies Based on Flow Network and the Winter–Fritz Design Equation

Abstract

In the polymer sheet processing industry, the primary objective when designing a coat-hanger die is to achieve a uniform velocity distribution at the exit of the extrusion die outlet. This velocity distribution depends on the internal flow channels of the die, rheological parameters and extrusion process conditions. As a result, coat-hanger dies are often designed for each polymer based on its individual rheological data and other conditions. A multi-rheology method based on a flow network model and the Winter–Fritz equation is proposed and implemented for the calculation, design and optimization of flat sheeting polymer extrusion dies. This method provides a fast and accurate algorithm to obtain die design geometries with constant wall-shear rates and optimal outlet velocity distributions. The geometric design when complemented and validated with fluid flow simulations could be applied for multi-rheological fluid models such as the power-law, Carreau–Yasuda and Cross. This method is applied to sheet dies with both circular- and rectangular-shaped manifolds for several rheological fluids. The designed geometrical parameters are obtained, and the associated fluid simulations are performed to demonstrate its favorable applicability without being limited to only the power-law rheology. The two such designed dies exhibit 32.9 and 21.5 percent improvement in flow uniformity compared to the previous methods for dies with circular and rectangular manifolds, respectively.

Effects of Melt Temperature and Non-Isothermal Flow in Design of Coat Hanger Dies Based on Flow Network of Non-Newtonian Fluids

“…In our previous work [ 6 ], we proposed simplifying the die into a series of segments where fluid flows in each segment can be described analytically or numerically. As a result of segmentation, two continuous geometrical parameters reduce to two sets of discrete parameters.…”

“…Thus, introduction of simplified methods with low computational cost with efficiency is necessary. Different design methods based on analytical [ 3 , 4 , 5 ], semi-analytical [ 6 , 7 ] and numerical optimization were developed [ 8 ]. Winter and Fritz [ 3 ] proposed the first analytical design method for rectangular and circular-shaped sheeting extrusion dies.…”

“…To the authors’ best knowledge, no analytical or semi-analytical design method of a coat hanger die which takes into account the effects of temperature exists in literature. In our previous study, a new isothermal design method based on constant shear rate and uniform velocity assumptions was proposed [ 6 ]. It is known that the design of a coat hanger dies depends on wall shear rate, temperature and heat dissipation of polymer melt [ 15 ].…”

Optimization of Polymer Processing: A Review (Part I—Extrusion)

“…The Taguchi method was used to optimize the geometry of dies with different widths, the solutions being evaluated with an analytical model, and flow rate was also appended as design variable. Recently, Razeghiyadaki et al [ 98 , 99 ] used a response surface method to optimize the geometry of a coat hanger die in order to obtain uniform velocity at the die lips. The response surface was generated from computations using a commercial package, and a central composite DOE defined the conditions for the calculations.…”

An Iterative Approach for the Parameter Estimation of Shear-Rate and Temperature-Dependent Rheological Models for Polymeric Liquids

“…Experimental measurements of polymeric liquids (solution and melt) are routinely carried out to obtain the necessary data on their rheological properties. Then, various numerical methods were used to find a suitable set of parameters for the rheology model to facilitate efficient flow simulations [ 2 , 3 , 4 , 5 , 6 , 7 , 8 ].…”