Machines can now distinguish 12 different types of plastic

Contrary to popular beliefs, plastic is by no means close to a single material. Rather, it is a combination of many materials (polymers) with different chemical compounds and additives such as pigments or fibers, depending on its use. It is very difficult to tell the difference between different types of plastics, and this is what makes it difficult to separate and recycle them.

Together with Vestforbrænding, Dansk Affaldsminimering Aps and PLASTIX, researchers from the Department of Biological and Chemical Engineering at Aarhus University have now developed a new camera technology that can see the difference between 12 different types of plastics (PE, PP , PET, PS, PVC, PVDF, POM, PEEK, ABS, PMMA, PC and PA12). Together, they make up the vast majority of types of household plastics.

The technology allows plastics to be separated on the basis of a purer chemical composition than is possible today, and this opens up whole new opportunities for recycling plastics. The technology has been pilot tested and is expected to be implemented at PLASTIX and Dansk Affaldsminimering Aps in spring 2022.

“With this technology, we can now see the difference between all types of consumer plastics and several high-performance plastics. We can even see the difference between plastics that are made up of the same chemical building blocks, but are structured slightly differently. . We use hyperspectral camera in the infrared domain, and machine learning to analyze and categorize the type of plastic directly on the conveyor belt. The plastic can then be separated into different types. This is a breakthrough that will have a huge impact on separation of all plastics, ”says associate professor Mogens Hinge, who heads the project at Aarhus University.

The study was published in the scientific journal Vibrational spectroscopy.

Plastics are currently separated using near infrared (NIR) technology or through density testing (floats / sinks in water). These methods make it possible to separate certain plastic fractions (for example PE, PP and PET), but not with the same precision as the new technology, and therefore not with the chemical purity of the composition, which is vital in order to be able to increase the rate of recycling of plastic waste.

“The technology we have developed in collaboration with the university is nothing less than a breakthrough in our ability to recycle plastics. We look forward to installing the technology in our processing hall and seriously starting the long journey to 100% waste utilization. plastic ”, says Hans Axel Kristensen, CEO of PLASTIX.

Plastic must be at least 96% pure by polymer type to be recycled in conventional industry. This means that the plastic must be separated into an almost pure product in terms of chemical composition.

Thanks to the new technology, we have now taken an important step forward, says Associate Professor Mogens Hinge, who points out that the technology is constantly evolving and the data indicates that it may be possible to differentiate even more between types of polymers. and additives before long.

The hyperspectral camera technology was developed in an interdisciplinary collaboration, with BSc and MSc engineering students and researchers from the Department of Biological and Chemical Engineering at Aarhus University, as well as experts from the participating companies.

The research is part of the Re-Plast project, which is funded by the Innovation Fund Denmark with DKK 22.7 million. The project is led by the Department of Biological and Chemical Engineering at Aarhus University. The other participants are the Department of Electrical and Computer Engineering at Aarhus University, Vestforbrænding, Dansk Affaldsminimering and PLASTIX.

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Material provided by Aarhus University. Original written by Jesper Bruun. Note: Content can be changed for style and length.