An analytical flow model for PTFE paste through annular dies

An approximate mathematical model for polytetrafluoroethylene (PTFE) paste extrusion through annular dies is developed. The model takes into account the elastic–plastic and viscous nature of the material in its nonmelt state arising from the formation of fibrils and the presence of lubricant. 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 this hypothesis is demonstrated by performing numerical simulations using a model recently developed for PTFE paste extrusion. 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. © 2006 American Institute of Chemical Engineers AIChE J, 2006

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