After cleaning out a closet, the options for recycling old clothes are limited. Unlike bottles and cans, textiles lack a dedicated recycling process. On average, an American discards about 81 pounds of clothing annually, contributing to over 11 million tons of textile waste in landfills or incinerators. MIT engineers aim to reduce this waste with a newly designed recyclable yarn.
The team created a yarn using a type of plastic often found in milk bottles and grocery bags. This yarn feels like traditional thread and can be woven into stretchy, lightweight garments. At the end of its life, the yarn can be melted down and re-spun into new yarn or transformed into plastic accessories like buttons and belt buckles. To prove its recyclability, the researchers repeatedly melted and respun the yarn, finding it retained its strength and flexibility even after 10 cycles.
The new yarn could replace spandex-polyester or spandex-nylon yarns that cannot be recycled together. This yarn is crafted from a specific plastic combination that mirrors the properties of spandex while being recyclable. “Eighty percent of textiles in the U.S. contain nonrecyclable spandex,” notes MIT researcher Svetlana Boriskina. “Our yarn could change that.” The study was detailed in ACS Materials Letters with authors SeongHyeon Kim, Duo Xu, Volodymyr Korolovych, Domingo Flores-Hernandez, Kaniz Moriam, and Daniel Braconnier.
Spandex is a synthetic fiber known for its stretch but lacks strength. Elastic yarns combine a spandex core with a polyester or nylon sheath, making recycling difficult without chemical separation. “These processes are costly and environmentally harmful,” says Boriskina. Most garments end up discarded due to this.
In 2021, Boriskina’s team developed a polyethylene yarn, a thermoplastic widely used in products like bags and bottles. The yarn demonstrated properties like moisture wicking and stain resistance. Now, the team has adjusted it to mimic spandex’s strength and flexibility, focusing on its recyclability.
The team experimented with polyethylene-based copolymers for the yarn’s core and engineered a sturdy sheath. They evaluated different chemical formulations, finding polyethylene’s structure allows for varied properties. “Polyethylene offers diverse properties based on its production,” explains first author SeongHyeon Kim.
The yarn’s core uses a stretchier polyethylene resin, while a stiffer resin forms the sheath. After processing the resins into fibers, they created the final elastic yarn by winding the sheath fibers around the core. Since both parts are polyethylene-based, no separation is needed before recycling, unlike traditional spandex yarns. “They work well together,” Boriskina says, enhancing recyclability.
The team demonstrated the recycling process by re-spinning the yarn 10 times, confirming the recycled yarn’s strength matched the original. These recycled fibers are ready to be woven into new textiles. “We can now knit and weave with it,” Boriskina says. Scaling up production could lead to a sustainable textile economy where garments are recycled into new yarns.
Funding for this research came from the DEVCOM Soldier Center via the U.S. Army Research Office, the Office of Naval Research Global through Tecnologico de Monterrey, and the MIT Portugal Program. Boriskina hopes this innovation will reduce the need for new textile materials by enabling continuous recycling.
Original Source: news.mit.edu
