|
ABSTRACT
The objective of this study is an attempt to develop a possible
strategy for effective die design in profile extrusion for
forming a polymeric extrudate with a desired shape by
considering the die swell behavior of a polymer melt and taking
into account the most important physical and rheological
phenomena involved in the process. The three-dimensional flow
and heat transfer through the die, as well as within the free
surface downstream the die exit, is analyzed using finite
element CFD code by considering the non-Newtonian behavior of
the polymer. Two extrudate profiles with the required shapes, a
rectangular cross section of 1 cm ´ 2 cm
with a circular hole of 1.1 mm diameter at its center and a
rectangular cross section of 10 cm
´ 0.5 cm with ten
equally spaced centerline circular holes of 1.1 mm diameter, are
considered for the design of dies. The material used is a
commercial-grade, general-purpose polystyrene, Styron 663, mixed
with scintillator dopants. The objective of the CFD simulation
is to compute the pressure, temperature, velocity, stress, and
shear rate distributions over the entire simulation domain and
to investigate the effect of different sections on mass flow
balance at the die exit and finally to determine the optimum die
shape including the die land and pin(s) profile to obtain the
desired dimensions of the extrudate profile.
|
