10. Dec 2024
Recycling of Polyurethane Foams through Reactive Extrusion
The Institut für Kunststofftechnik (IKT) of the University of Stuttgart (Germany) is researching on an innovative process for energyefficient recycling of polyurethane foams. This research project aims to determine whether these foams, at the end of their product life, might be used as fillers in new materials and can be integrated into them effectively.
The reintegration of used polyurethane components into the material cycle has so far been achieved mainly through energy-intensive chemical recycling. This raises the question of whether there is a more efficient way to close the cycle.
Conventionally, new polyurethane foams are produced using mixing heads, where the liquid base components are mixed and discharged. Solid materials, such as foam recyclates, can only be added to a limited extent in this process – typically less than five percent by mass. In the IKT project, the mixing of the reactive components is now intended to take place in a twin-screw extruder. This approach allows for significantly higher filler contents, compared to what isachievable with conventional mixing equipment (>75 percent by mass).
The main challenge lies in ensuring continuous extrusion with high reproducibility and mixing quality, despite variations during dosing and differences in foam particle sizes. Therefore, the prototype must be precisely adapted to the process. Additionally, experiments are required to identify optimal process parameters.
At IKT, the basic feasibility of this approach has already been demonstrated on a laboratory scale. The next step is to transfer the process into a continuous series production using a demonstrator. For this purpose, a twin-screw extruder specifically designed for this application is being constructed. One particular challenge is ensuring the sealing of the system, as the base components are more fluid than thermoplastic melts. Furthermore, very high screw speeds and cooling are required.
The goal is to produce insulation panels, typically used for buildings. The project will evaluate and assess the impact of different recyclate filler levels on both the processing conditions and the properties of the resulting polyurethane foam.
The project is funded under the program "Validierung des technologischen und gesellschaftlichen Innovationspotenzials wissenschaftlicher Forschung – VIP+ " with the grant number 03VP12070.