Analysing and modelling the melting behavior of planetary roller extruders

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Extrusion and compounding are fundamental steps in the production process of plastic products. Due to increased quality requirements and the trend to cost reduction by process optimization, the compounding process is outstandingly important. The major aim of this process step is the optimal mixing of additives with the polymer matrix. In this context, the planetary roller extruder is a machine concept that is well suited for these tasks. Reasons for this are the excellent homogenization and dispersion abilities t with a low shearing of the material as well as a narrow residence time distribution.Models that describe the process behavior of single and twin screw extruders have been discussed in the scientific and engineering literature for several years. For planetary roller extruders, first process models were published. However, these models neglect the melting process and thus they are only applicable for melt transportation.The aim of this research project is the analysis of the melting behavior of planetary roller extruders and the first time development of physical mathematical models, which describe the melting processes. Based on the successes in modeling the transport mechanism of melt fed planetary roller extruders, the approaches that are used to describe the melting process of single and twin screw extruder are adjusted to the conditions in the planetary roller extruder. The adjusted models shall make it possible to calculate the pressure, filling degree, melting degree, temperature and power consumption along the extruder length for planetary roller extruders that run as melting extruders.Because of the complexity of the topic, in the first two years only the melting behavior of unfilled polymer pellets was observed. With this simplified system the fundamentals of the modeling were created. At first an experimental setup, which enabled the analyses of melting behavior with dead stop experiments, was build. The following experiments showed, that a disperse melting model is suitable for describing the melting. This model was adapted for the planetary roller extruder and integrated in the simulation tool SimPla. First comparisons between simulations done with SimPla and experiments showed a good agreement. In the requested research project, the melting model shall be extended for powder shaped and filled materials, so that at the end of the project, a comprehensive process model for planetary roller extruders will be available.