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Ibrahim Busuladzic
Abstract
Modeling of the mixing elements in extrusion by boundary element method
Ibrahim Busuladzic - 30 january 2004
In order to obtain new plastic materials, polymer mixing is a very
commonly used process.
Polymer processing using single-screw extrusion makes it possible by
modifying the screw of extrusion. For this reason, the Maddock mixing
head is used in order to study its effect on quality of the mixing. In
this work, the dispersive mixing is especially studied. The experimental
part of this project studies the dispersion of the secondary phase in
the polymer matrix. Beside the experimental study, the numerical methods
can be used to provide more detailed information on the mixing flows. In
this study the Boundary Element Method (BEM) is used. Whereas, the
polymer flows exhibits non-Newtonians behaviors and consequently
non-linear constitutive equation, the BEM simulations have take that
into account. The classical BEM enables to solve this type of
problems. Specific techniques have to be developed in order to adapt the
BEM resolution. For that, the technique of multi domain decomposition
together with the Dual Reciprocity Method (DRM) has been
developed. Software called "POLY_BEM" has been developed based upon BEM.
Newtonian and non-Newtonian computations have been performed in 3D and
2D respectively. The dispersion performances of mixing devices are
calculated using the flow number definition.
In order to validate these results, preliminary comparisons have been
carried out showing the beneficial effect of the mixing head.
The polymer flow in specific zones of the mixing head (the entry and the
exit of the passage between channels) exhibits elongational flows
improving dispersion more than in other zones.
Keywords:
Boundary element method, BEM, multi domain, DRM, single screw extrusion,
polymer blends, dispersion.
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