Flow Characteristics of Polymer Melt for Die Shapes for the Extrusion of Catheter Tubing

The plastic tubing in catheter is manufactured by extrusion. In this study, computer simulation was performed and results were compared for two types of dies, specifically, straight die and crosshead die for the extrusion of catheter tubing. A spider leg supports the mandrel in the straight die and this die is attached to the extruder in the same line. For the crosshead die, mandrel contains helical grooves and the die is attached to the extruder at an angle of 90 degrees. The pressure, velocity, streamline, wall shear stress, and residence time in the two types of dies were analyzed and compared through computer simulation. The velocity difference in the die land region where the size of catheter tubing is determined between the two types of dies was large whereas the pressure drops in the two dies were similar. A complex flow pattern was observed in the crosshead die and subsequently, the residence time in the crosshead die was three times longer that of the straight die. Wall shear stress in the crosshead die was much smaller than that of the straight die. Thus, more stable extrusion of catheter tubing is expected for the crosshead die.