Effects of grooves on processing conditions within grooved plasticizing units in single screw extrusion

• Applicant: Professor Dr.-Ing. Christian Bonten
• Subject Area: Plastics Engineering
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 346097498

Single-screw extrusion is an important production process for large-scale plastic product manufacturing at low cost. Conventional single-screw extruders are a combination of a conveying screw with three processing zones and a smooth barrel. Today, variants with grooved feed zones and/or barrier screws are the state of the art and widely used. Due to the typical occurrence of wear in the feed zone, low melting rates and poor mixing performance when using grooved feed extruders, the use of continuously grooved barrels in combination with barrier screws has gained momentum within the last years. Extruders with a grooved plasticizing zone have since proved to feature uniform pressure profiles, little wear, energy efficient operation and low melt temperatures.Whereas melting and flow models are well established for conventional extruders, their validity and application for grooved plasticizing zones so far has not been investigated. The existing model concepts are based on assumptions and experience only, which lack scientific validation. Thus, the aim of this project is a detailed examination of the grooves influence on the process. A model will developed, enabling an analytical or simple numerical description (e. g. with finite differences) of what happens within a grooved plasticizing unit. First, experimental studies with a dividable extrusion barrel as well as a screw simulator will give insight to which extent the grooves affect the melting and flow behavior. Inline measurements based on ultrasound technology will be used in order to investigate the temperature and residence time distribution. The results will help to revise and adjust the current model concepts. Subsequently, the newly improved model will then be described mathematically and implemented into a simulation tool. A final set of reference experiments is used to conclusively validate the model. Therefore, the result to be achieved within this project is a deepened and improved understanding of the melting and flow processes within grooved plasticizing zones. The application within a computational model will allow describing and predicting these processes for improved design of continuously grooved single-screw extruders.

• DFG Programme: Research Grants