A network theory based approach modeling barrier screws in combination with grooved plasticizing barrels.

Extrusion is one of the most important technologies to process polymeric materials. Hence, describing the flow behavior of polymer melt in single-screw-extrusion is of high relevance. Over the last decades several modeling approaches describing the extrusion process were developed and introduced. Nevertheless, depicting flow behavior for grooved plasticizing extruders did not receive much attention. However, the Helibar concept, combining barrier screws and grooved plasticizing barrels, provides several benefits in comparison to other extruder systems. With its enhanced pressure build-up behavior required energy by cooling the feeding section and wear is reduced. Additionally, a in general more stable process is achieved, and the control of melt temperature and homogeneity improved. Therefore, such extruder systems become more and more important in industrial applications. The objective of this work is to develop a modeling approach which is considering grooved plasticizing barrels. Hence, a network-theory based approach in combination with a three-dimensional melt conveying model is used. The modeling approach is implemented in a calculation tool which allows to calculate axial pressure profiles for several screw and barrel geometries, as well as various polymeric materials at different processing parameters. The modeling approach is validified by experiments performed for different materials and screw types at a Helibar extruder. The results of the work proved a good accuracy of the modeling approach. Using the easy-to-handle calculation tool experimental pressure data were simulated. A deviation of calculated and experimental data of 8.1 % along the extruder was achieved. The deviation in the barrier section of the screw was 5.7 %. The calculation results using the novel modeling approach considering grooved plasticizing barrels was also compared to determinations of smooth barrel geometries and further compared to experimental data, showing the improvement of predicted axial pressure profile. However, the calculations also showed that the deviation increases with increasing ratio of solid material. Therefore, the accuracy along the screw increases with higher melt ratio based on the melt conveying model implemented in the modeling approach. The combination of modeling approach and calculation tool enhance modeling of single-screw-extruders by additional possibility to determine pressure profiles of plasticizing grooved barrels.