An innovative method that removes elastane completely from nylon, and ongoing experiments with cotton is awaiting adoption at industrial scale and necessary funds to further the project.
- Researchers led by Assistant Professor Steffan Kvist Kristensen from the Interdisciplinary Nanoscience Center at Aarhus University have devised a way to separate fibres from blended fabrics which can then be recycled.
- The researchers are not quite there yet with cotton, because some of the cotton fibres are broken down in the process. With some minor adjustments, they hope to solve this problem.
The method: The many links in the elastane chain are bound together by a small molecule called a diamine, and it is not easy to separate them.
- Clothes are made by winding the main fibres, such as nylon or cotton, around the elastane fibres, which consist of long chains of molecules. And the fibres only break apart if the long chains of molecules are broken.
- This is done by heating the clothes to 225 degrees Celsius and adding a specific alcohol, we have found a method to break down the bonds in elastane. When this happens, the chains fall apart and the materials separate.
- The whole process takes place in—what is in effect—a large pressure cooker that the textiles are fed into. Then a little alcohol is added with some base and the mix is heated up.
- It is then “cooked” for just over four hours, and when the lid is opened again, the different fibres will have been separated.
- Potassium hydroxide is one of the main ingredients in ordinary drain cleaner. Adding this accelerated the process of the chemical reaction.
- So far, the researchers have experimented with only two nylon stockings at a time.
- However, this work does open up new opportunities for the recycling of certain blended textiles.
Funding: The study has received funding from Innovation Fund Denmark, the Carlsberg Foundation, the Danish National Research Foundation and the Novo Nordisk Foundation CO2 Research Center (CORC).
What they said:
We can only scale things up a little because of the limitations in our equipment. So, it's up to industry to embrace the technology and scale it up in earnest. The chemical industry in Denmark is small, but Germany has some of the largest plants in the world. They will most likely be able to use our method to recycle large amounts of fibres from elastane-containing clothes.
— Steffan Kvist Kristensen
Assistant Professor, Interdisciplinary Nanoscience Centre
Aarhus University
