New recycling process can sort black plastic for the first time

Kim Muntinga

9.3.2026

Translation: machine translated

Black plastic is omnipresent. But it is almost impossible for current recycling machines to sort. Researchers have now succeeded in solving this problem.

Black plastics are everywhere: in electronic housings, household products, toys, sports equipment and packaging. All of these products end up in the yellow bag or recycling bin at some point. This is where the problem begins: black plastic is largely invisible to conventional sorting technologies.

The core problem lies in the physics. Conventional near-infrared spectroscopy (NIR) works by analysing the light reflected by a material. Each type of plastic - whether polyethylene, polypropylene or PET - has a characteristic reflection pattern, a kind of molecular fingerprint.

In the case of black plastic, however, the soot it contains absorbs a large proportion of the incident light before it can be reflected. The fingerprint remains invisible. As a result, a large proportion of black plastic ends up in thermal utilisation rather than in the recycling loop.

A new approach for sorting black plastics

Researchers at the Fraunhofer Institute for Non-Destructive Testing IZFP have now taken a fundamentally different approach to this problem. Instead of spectral methods, they rely on a thermography-based system that utilises the different thermal reactions of different types of plastic.

The method combines brief heating of the objects with thermal imaging, which is then analysed by an AI model, enabling the identification of black plastics that remain invisible to conventional NIR scanners.

First successes in the identification of black plastics

A key result of the research to date: the demonstrator can currently reliably distinguish between polyamide (PA) and polypropylene (PP) in particular. This differentiation is considered an important step forward because these two black plastics are usually not detectable in existing NIR sorting systems.

Further types of plastic are to follow in future project phases. However, the expansion to a wider range of materials is currently still under development.

From research to the plant

For a sorting technology to find its way out of the laboratory and into industrial practice, it must be robust, fast and economical. The demonstrator developed at the Fraunhofer IZFP already shows what such a process could look like in principle:
Black plastic parts are briefly heated on a conveyor belt, then captured by a thermal imaging camera and analysed by an AI in real time. A sorting arm automatically separates the materials according to the recognised type.

When the process will be used in real sorting plants is still open. The researchers are working on incorporating other types of plastic, increasing the processing speed and optimising the overall system for continuous industrial operation. The technological foundation for reliable sorting of black plastics has thus been laid, but still needs to mature further.

Kim Muntinga

Editor

Kim.Muntinga@galaxus.de

My interests are varied, I just like to enjoy life. Always on the lookout for news about darts, gaming, films and series.

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