A More Sustainable Recycling Of Plastics

November 2, 2021

Plastics belong to the most widely used materials and are vital components of all modern technologies. Until now, it has only been possible to recycle these valuable materials to a limited extent. To offer novel solutions, chemists in Professor Stefan Mecking’s group from the University of Constance developed a more sustainable method for chemically recycling polyethylene-like plastics. Researchers use “breakpoints” at the molecular level to disassemble plastic down to its molecular components. The new method works without extremely high temperatures, so it is more energy efficient and has a significantly higher recovery rate (approximately 96% of the starting material) than established processes.
Mechanical recycling vs. chemical recycling

‘The direct reuse of plastics is often hampered by the fact that in practice mechanical recycling only works to a limited extent, as plastics become contaminated and mixed with additives, which undermines the properties of recycled materials », Explains Stefan Mecking. “Chemical recycling” is an alternative: Using a chemical process, used plastic is broken down into its molecular components, which can be turned into a new plastic.

Limitations of chemical recycling of polyethylene

In the specific case of polyethylene – the most widely used plastic – chemical recycling is difficult. At the molecular level, plastics are made up of long molecular chains. “Polyethylene polymer chains are very stable and do not easily revert to small molecules,” explains Stefan Mecking. Temperatures in excess of 600º Celsius are required, which makes the procedure very energy consuming. At the same time, the recovery rate is limited (in some cases, less than ten percent of the starting material).

How to make chemical recycling of polyethylene more sustainable

Stefan Mecking and his team report on a method that enables more energy efficient chemical recycling of polyethylene-like plastics, along with a very high recovery rate of around 96% of the starting materials. To do this, chemists used “breakpoints” at the molecular level that allow the chain to be deconstructive into smaller molecular blocks. “The key to our method is polymers with a low density of predetermined breakpoints in the polyethylene chain, so that the crystalline structure and material properties are not compromised,” explains Stefan Mecking, adding: “This type of materials is also very suitable for 3D printing.

Stefan Mecking’s research team demonstrated this chemical recycling in vegetable oil-based polyethylene-like plastics. The recycling stage requires temperatures of only about 120 degrees. In addition, chemists also carried out this recycling method on mixed plastics as they are found in waste streams. The properties of the recycled materials match those of the starting material. ‘Recyclability is an important aspect for future plastics-based technologies. Reusing such valuable materials as efficiently as possible makes sense. With our research we want to contribute to making the chemical recycling of plastics more sustainable and efficient ”, sums up Stefan Mecking.

Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
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