Advanced measurement technology and modelling of the residence time-dependent molecular structures of polymers

• Applicant: Professor Dr.-Ing. Volker Schöppner
• Subject Area: Plastics Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 560248555

In a circular economy, plastics are processed multiple times. Although this makes it possible to avoid synthesising virgin material from crude oil, maintaining the material properties when recycling plastics poses a challenge. Every time plastics are processed, they are melted and subjected to high shear. This affects the molecular structure of the plastic and therefore also the mechanical properties of the plastic product. While in the case of polypropylene, for example, there is only a shortening of the polymer chains, which can be determined relatively easily by reducing the viscosity, other polymer groups can undergo more complex chemical reactions that influence recycling. In the case of polyethylene, for example, branching can occur and in the case of polycondensates (PC, PA, PET) hydrolytic degradation and post-polymerisation can occur due to the presence of water. All effects at the molecular level have an influence on the properties of a manufactured plastic product. In order to keep the product properties as constant as possible in a circular economy, the changes in the plastic at the molecular level must be minimised. The aim of the research project is therefore to model the residence time-dependent molecular structure of thermoplastics under the influence of temperature, shear rate and moisture. The change in shear viscosity, storage and loss modulus should allow conclusions to be drawn about a change in the average molecular weight as well as the degree of branching and cross-linking. Finally, a modelling should be carried out which can be used as a prediction model for single-screw extrusion and enables a material-saving process design.

• DFG Programme: Research Grants