An Approximate Analytical Flow Model for Polytetrafluoroethylene (PTFE) Paste through Annular Dies

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.