SHEAR RATE COAT-HANGER DIE USING CASSON VISCOSITY MODEL
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Date
2020-11-24
Authors
Igali, Dastan
Perveen, Asma
Zhang, Dichuan
Wei, Dongming
Journal Title
Journal ISSN
Volume Title
Publisher
MDPI
Abstract
Coat-hanger die design aims for optimization of the die geometry of the body and the flow
distribution manifold, such that through the exit at the die lip homogeneous distribution of the polymer
melt is achieved. This paper proposes a novel methodology for deriving the design equations of the
coat-hanger die geometry for some specific extrusion materials and provides fluid–solid interaction
simulations for validations. The basis for the calculations is the Casson rheological model, analytic
velocity profiles for the pseudoplastic flow through circular pipe and slit, and the constant shear rate
coat-hanger die design methodology developed by Winter and Fritz. The geometry obtained was then
evaluated using the fluid-structure interaction numerical simulation approach. The sensitivity of the
outlet velocity uniformity and die body deformation due to the material and mass flow rate change
were investigated using the finite element software, Ansys. It was found that the homogeneity of the
outlet velocity is very sensitive to the extrusion materials. The structural analysis of the solid die
body also resulted in higher deformations when using some other extrusion materials different from
the initial design. Mass flow rate increase only resulted in large zones of stagnation, which occurred
around the melt as it passes from the manifold to the slit region. Therefore, it is recommended to
define the required range of mass flow rate to prevent the formation of stagnation zones.
Description
Keywords
polymer extrusion, coat-hanger dies, uniform wall shear rate, power-law, Casson model, Research Subject Categories::TECHNOLOGY
Citation
Igali, D., Perveen, A., Zhang, D., & Wei, D. (2020). Shear Rate Coat-Hanger Die Using Casson Viscosity Model. Processes, 8(12), 1524. https://doi.org/10.3390/pr8121524