Elastane – also called Spandex – is an elastic material that is popular for use in clothing, as it allows the fabric to stretch and adapt to the wearers’ body. But, when these fibers are mixed with other fibers, the clothes become almost impossible to recycle as separating the different fibers is very difficult. This problem has led to clothes and other textiles being among the materials with the lowest recycling rates.
A team from Aarhus University’s Interdisciplinary Nanoscience Center has developed a technology that can separate the fibers 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 fibers are broken down in the process. But we believe that, with some minor adjustments, we can solve this problem,” said Assistant Professor Steffan Kvist Kristensen. “In other words, we can disassemble the fabric so that we can recycle far more textiles in the future.”
Textiles are often constructed by winding the main fibers – such as nylon or cotton – around the elastane fibers, which consist of long chains of molecules. These long chains must be broken apart in order to separate the fibers.
“The many links in the elastane chain are bound together by a small molecule called a diamine. 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,” explained Kristensen.
As harsh chemicals cannot be used, the team uses alcohol and adds a potassium hydroxide base.
“Potassium hydroxide is one of the main ingredients in ordinary drain cleaner. We found that adding this accelerated the process. It simply increases the speed of the chemical reaction,” said Kristensen.
To date, the technology is not ready for commercialization at an industrial scale. The team is hoping to work with large facilities in Germany in order to scale up the recycling process.