MIT engineers have created a new recyclable yarn that mimics the stretch and strength of spandex.
The yarn is designed to be woven into fabric for stretchy, lightweight clothing.
In a demonstration, researchers showed that melting the thread down and respinning it 10 times left the yarn equally strong.
The researchers believe the fabric woven from this yarn could present an alternative to other stretchy, lightweight fabrics.
The engineers then use an industrial yarn spinner to wind the sheath fibers around the core to make the final product.
MIT engineers have created a new recyclable yarn that mimics the stretch and strength of spandex.
The yarn is constructed entirely from polyethylene, the type of plastic often used in packaging and containers, such as milk bottles and grocery bags. The yarn is designed to be woven into fabric for stretchy, lightweight clothing.
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The material can also be recycled, enabling a more circular textile industry. Polyethylene is a thermoplastic, which means it can be melted down and made into a new item. Clothing made from this yarn could be dropped off in a recycling bin at the end of its life, melted, and then spun into new yarn or cast into plastic accessories like buttons. In a demonstration, researchers showed that melting the thread down and respinning it 10 times left the yarn equally strong.
The researchers believe the fabric woven from this yarn could present an alternative to other stretchy, lightweight fabrics. The issue with spandex—which is used in the majority of textiles on the U.S. market—is that it is nonrecyclable, meaning that most garments made with it end up in landfill. Spandex is a polyurethane-based fiber that is then covered with a sheath of polyester or nylon. The combination of these two materials gives the fabric its stretch, but in order to separate them, one would have to use a chemical treatment.
"Even though chemical separation technologies exist, they add extra cost and complexity and usually require toxic chemicals that are harmful to the environment," said Svetlana Boriskina, a research scientist in MIT's Department of Mechanical Engineering.
Since MIT's elastic yarn is made up of a core and sheath that are both made of polyethylene, this material does not have the same issue when it comes to reuse.
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"Because they are exactly the same chemistry, they play nicely together," says Boriskina. "That's what makes this yarn very recyclable."
The new yarn consists of two resins: one that creates a stretchy core and a second, stiffer resin for the sheath. In order to convert the resins to fibers, the pellets are heated to about 350 degrees Fahrenheit and extruded. The engineers then use an industrial yarn spinner to wind the sheath fibers around the core to make the final product.
"You just melt it in a barrel with a heater, and then you extrude and spin it into fibers," said SeongHyeon Kim, one of the MIT engineers. "It's like a spaghetti machine."
Boriskina explained that the next stage is knitting and weaving the yarn. The recipe that this team has developed is ready to be taken to an industrial scale. Like spandex, the weaving process for this yarn requires a lot of material, but this product has the added feature of possible recycling and respinning.
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"Hopefully it will prevent the need for making more and more textile materials, because you can keep recycling a large portion of it," Boriskina said. "There's no widely adopted technology now that recycles textiles into textiles. With our new yarn, we hope to change that."
