Design and Characterisation of a Co-Extruder

A co-extruder with three barrels was designed to produce trilayer tubes semi-continuously. A vital step in the design was to predict the required pressure to generate a sufficiently high extrudate velocity while being able to retain the extrudate shape. A physically based model was used to predict the pressure drops in the co-extrusion process at 3 different extrusion velocities for 5 pastes with different rheological characteristics. In general, predicted and measured values were in good agreement. Other important aspects in the co-extruder design, such as velocity and pressure matching of different flow streams are also highlighted.