Pilot project: Audi works on physical recycling of automotive plastic waste

Today’s vehicles typically contain more than 200 kilograms of various plastics and plastic composites. The quality demands placed on the plastics are high. The same criteria apply to recycled components as to virgin materials. These include crash safety, heat resistance, and media resistance.

Also, there is dimensional stability and quality, feel, appearance, and smell throughout the vehicle’s entire service life. Environmental requirements also must increasingly be taken into account.

Mechanical recycling of plastics reaches its limits where different plastics are processed as a composite and various adhesives, coatings, and fillers such as glass fibers are used.

An added disadvantage is that the quality of the plastics decreases with each mechanical processing step. As a rule, plastics recycled in this way are no longer suitable for use in vehicle construction, especially not for safety-related components.

And together with the Karlsruhe Institute of Technology (KIT) and industry partners, Audi has developed on a chemical recycling method. Mixed plastic waste is processed into pyrolysis oil.

Pyrolysis oil can replace crude oil as a raw material in the production of high-quality plastics. The components produced in this way are just as valuable and safe as when they are made from virgin material.

In addition to research projects focusing on mechanical and chemical recycling, Audi is now conducting a feasibility study in cooperation with the Fraunhofer Institute for Process Engineering and Packaging IVV to investigate the possibilities of the physical recycling of automotive plastic waste and its reuse in vehicles.

This method makes it possible to work with plastics with significantly higher levels of contamination, meaning that simple and incomplete pre-sorting from on old vehicle is sufficient.

Unlike chemical recycling, plastic is not destroyed by physical recycling. Instead, it is dissolved with solvents. This means that no chemical degradation reaction takes place and the polymer chains remain undamaged.

“Only substances that are absolutely harmless are used as solvents,” explained Dr. Martin Schlummer of Fraunhofer IVV. “Other solids that could interfere with the new end product are separated”.

Dissolved substances such as flame retardants can also be dissolved from the plastic solution if necessary. The solvents used are then evaporated and also fed into the cycle. After drying, this results in a very pure plastic granulate that matches the quality of virgin material.

The aim is now to produce larger quantities of this granulate in order to ensure its technical feasibility and to test its cost-effectiveness.

In further testing, the “plastic with a past” will be transformed into add-on parts, such as the seat height adjuster. It is a small component, but it has to meet high standards in terms of emissions and odor.

Looking ahead, the company plans to use the various recycling technologies to complement each other in order to recover plastics from old vehicles for high-quality reuse.