Clothes are mostly made by winding the main fibers, such as nylon or cotton, around elastane fibers, an elastic material that allows the fabric to stretch. However, it’s almost impossible to separate them once woven together, making recycling difficult. Most end up in landfills. Now, a team of researchers has created a new method that can remove elastane from other fibers and reduce waste.
When Japan attacked Pearl Harbor in 1941, the US didn’t only lose soldiers, aircraft and warships but also access to about 90% of the natural rubber it depended on. So, they started to produce synthetic rubber. After the war, the production of synthetic rubber led to the discovery of many synthetic fibers — including elastane, or Spandex.
The fiber was invented by chemist Joseph Shivers in 1958 and, since then, has been used in many of our clothes, from sportswear to trousers. While comfortable, elastane has created a recycling problem. As separating elastane from other fibers isn’t currently feasible, clothes usually end up in landfills. Only 15% of the material used for clothes is recycled.
“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,” Steffan Kvist Kristensen, one of the study authors, said in a news release.
A hot new approach
Elastane fibers consist of long chains of molecules called polymers. The fibers can only be broken apart by breaking these chains, explains Kristensen. “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,” he added.
The process takes place in a large pressure cooker that the researchers feed the textiles into. They then add alcohol and potassium hydroxide and heat it up, letting it cook for about four hours. When they open the lid again, the fibers are separated. As the resulting materials need to be recycled, using harsh chemicals wasn’t an option.
Potassium hydroxide is one of the main ingredients in ordinary drain cleaners. The researchers don’t fully understand why, but adding it accelerates the process. “It increases the reactivity of our alcohol. Either that, or the bonds are broken down slightly by the potassium hydroxide, so it’s easier for the alcohol to break them,” Kristensen said.
So far, the researchers have tried their method with two nylon stockings at a time. This suggests that it’s not yet ready for industrial-scale use, which would be required to decompose larger amounts of clothing. “We can only scale things up a little because of the limitations in our equipment,” Kristensen said, still hopeful for its future expansion.
For the technology to take off, large chemical plants would have to be involved. Kristensen said it’s more likely for Germany to take the lead as it has some of the largest plants in the world. Theses production companies will need to see a valuable business model in buying recycled materials and using them in the production of new fibers. Hopefully as the method is further studied, we can scale up to reduce pollution.
The study was published in journal Green Chemistry.
