Coating Extrusion Characteristics of Thin-Walled Tubes for Catheters Using Thermoplastic Elastomer

During the production of medical thin-walled tubes, a thin coating layer is required. This requirement reduces the cross-sectional clearance area of the straight section flow channel formed by the mandrel and the die, leading to excessive pressure of the polymer melt at the shaping section, elevated die pressure, and backflow of the material melt, all of which directly impact the quality of the coating layer. To address these issues, this study conducted a non-isothermal numerical simulation of coating models both with and without a shaping section. It analyzed the impact of the coating model without a shaping section on the coating layer's thickness and the stability of the coating flow field under varying drag velocities, inlet flow rates, and die temperatures. Furthermore, it compared these results with those of coating extrusion using shaping section runners and investigates how different flow channel parameters affect the extrusion characteristics of the coating layer. The results showed that the setting of the shaping section could not eliminate the extrusion expansion in wrap extrusion. In comparison to coating extrusion utilizing a shaping section die, the process without a shaping section die reduced die pressure drop by 35% to 40%, decreased energy consumption, and enhanced the quality of the coating layer. Finally, an amorphous segment-coating extrusion die was designed based on the simulation results, and coating extrusion experiments were carried out using the designed and fabricated die.