Pramod D. Patil, James J. Feng & Savvas G. Hatzikiriakos
AIChE J. 52, 4028-4038
(2006).
Abstract - An approximate mathematical model
for polytetrafluoroethylene (PTFE) paste extrusion through annular dies
is developed. The model takes into account the elastic-plastic (strain
hardening) and viscous nature of the material in its non-melt state due
to the creation of fibrils and presence of lubricant, respectively. The
radial flow hypothesis has been used to describe the flow kinematics of
PTFE paste in the conical annular section of the die. The validity of
the radial flow hypothesis is demonstrated by performing numerical
simulations using a model recently developed for PTFE paste extrusion
(Patil et. al.1). Model predictions are presented for various cases and
are found to be consistent with experimental results of macroscopic
pressure drop measurements in rod and tube extrusion.