A huge hurdle in recycling clothes is elastane – a fabric often used in running tights and clothes that people wear to gyms. It’s made to fit comfortably as the elastic material allows the fabric to stretch and adapt to the body. However, when it is mixed with other fabrics, these clothes become almost impossible to recycle.
It’s extremely difficult to separate the different fibres, and hence, clothes are often not recyclable. Due to reasons like this, clothes pose a significant hurdle in recycling. However, a new study suggests that this might change. Researchers from Aarhus University have developed a new technology that can separate fibres in mixed fabrics.
“We’ve developed a method to remove elastane completely from nylon. We’re not quite there yet with cotton, because some of the cotton fibres are broken down in the process. But we believe that, with some minor adjustments, we can solve this problem,” study author Steffan Kvist Kristensen said in the university’s press statement. The new method can disassemble the fabric so that more textiles can be recycled in the future, he added.
However, it is not easy to separate elastane and other fibres after they have been woven together. Clothes are made by winding the main fibres, such as nylon or cotton, around the elastane fibres, which comprise long chains of molecules, the statement explains. If these chains of molecules break, only then can the fibres break apart.
The many links in the elastane chain are bound together by a small molecule called a diamine, Kristensen explains. The researchers have found that when clothes are heated to 225 degrees Celsius and specific alcohol is added, the bonds in elastane can be broken. When this happens, the chains break and the materials separate.
The entire process takes place in equipment that is like a large pressure cooker into which the textiles are added. To this, a little alcohol and potassium hydroxide base are added. This is heated up for about four hours, and by the end of it, the different fibres will have been separated, the statement explained.
“Potassium hydroxide is one of the main ingredients in ordinary drain cleaners. We found that adding this accelerated the process. It simply increases the speed of the chemical reaction,” Kristensen added in the statement.
Although they are unsure how potassium hydroxide breaks the bonds, they have guessed that either it increases the reactivity of our alcohol or the bonds are broken down slightly by the potassium hydroxide, so it is easier for the alcohol to break them completely.
They have used this method on only two nylon stockings till now and aim to expand it to more fabrics in the future.