Sorting of black plastics for recycling

The recycling of plastic waste is a key factor for resource-friendly production. Techniques that are capable of sorting black plastics according to type play an important role here.

Black plastics cannot be recycled satisfactorily with the technology that is available today. The soot that is used to blacken plastics absorbs most of the electromagnetic radiation in the visible as well as in the infrared wavelength range. As a result, black plastics cannot be distinguished and separated according to type with conventional sensor technology. This not only reduces the quality of products made from recycled material but also lowers the per ton value of the recyclate. The separation of black plastics according to type therefore opens up new earnings potential for companies.

Terahertz technology offers a solution for this technical problem. The absorption behavior in the terahertz range allows the separation of recyclate and, in particular, black plastics according to type. To date, the high expenditure associated with the development of a full spectroscopic, imaging terahertz sensor system has hindered its application in the industrial sector.

Fraunhofer FHR, Fraunhofer IAIS and Fraunhofer IOSB decided to tackle these challenges jointly. The combination of a terahertz camera with optical sensors allows complete material characterization using selected frequency bands in the low terahertz range and the acquired data can subsequently be evaluated using new analysis algorithms. This facilitates the utilization of a cost-effective, realtime-capable multisensor suite.

Our solution offers:

  • a system with integrated sensors and algorithms
  • upgradeability
  • high separating preciseness
  • applicability on plastic flakes (in particular black flakes)
  • capacities of up to 5 tons per second
  • cost-effective, economic implementation

Thus, it is possible to recycle black plastics at an industrial scale thanks to clean separation according to type and increased economic efficiency. The participating Fraunhofer institutes and their industrial customers are therefore opening up new market segments.

We would be happy to provide you with information on our system and the materials that can already be distinguished today. We look forward to receiving material samples so that we can further expand our database.