A new elastic yarn built entirely from polyethylene matches spandex blends for strength and stretch — and survived ten rounds of melting and respinning without losing performance.

Somewhere in your closet there is almost certainly a pair of leggings, a T-shirt, or a pair of jeans with a little give to it. That stretch comes from spandex, and it carries a hidden environmental cost. Once a garment containing spandex wears out, there is essentially nowhere for it to go but the landfill.

“Eighty percent of textiles on the U.S. market currently contain some amount of spandex, which makes them nonrecyclable,” said Svetlana Boriskina, a research scientist in MIT’s Department of Mechanical Engineering.

Boriskina and her colleagues think they have found a way out. In a study published in ACS Materials Letters, the MIT team describes a stretchy yarn made entirely from polyethylene — the same plastic used in milk bottles and grocery bags — that performs much like conventional elastic yarns but can be melted down and spun again and again.

A mountain of discarded clothing

The scale of the problem is enormous. The average American throws away about 81 pounds of clothing each year, and more than 11 million tons of textiles end up in landfills or incinerators annually. Aside from donating clothes, there is no widespread textile recycling system comparable to the ones that handle bottles and cans.

“There’s no widely adopted technology now that recycles textiles into textiles,” Boriskina said. “With our new yarn, we hope to change that.”

Part of what makes stretchy fabrics so hard to recycle is the way elastic yarn is built. Spandex, a polyurethane-based synthetic fiber, is springy but not especially strong. To make it durable enough for clothing, manufacturers wrap a spandex core in a sheath of polyester or nylon. The result works well on the body but is a recycling nightmare, because the core and sheath are made of chemically different materials that cannot be processed together.

Separating them is possible, but “even though chemical separation technologies exist, they add extra cost and complexity,” Boriskina said, “and usually require toxic chemicals that are harmful to the environment. That’s why most stretchy garments go to the dump.”

One plastic, two personalities

The MIT team’s solution was to build both parts of the yarn from the same base material. Polyethylene is the most common plastic in the world, and it turns out to be surprisingly versatile.

“Polyethylene can give us a wide range of properties, depending on how you make it,” said SeongHyeon Kim, the study’s first author.

Boriskina offers a vivid image for why. “The chemical structure of polyethylene is like Christmas garland — a backbone of carbon, carbon, carbon,” she said. “How these chains are arranged can change the properties of the whole structure.”

By choosing different polyethylene-based resins, the researchers could make one version stretchy and another stiff. They used the stretchier resin for the yarn’s core and the stiffer one for its sheath, mimicking the architecture of conventional elastic yarn while keeping everything within a single chemical family.

“Because they are exactly the same chemistry, they play nicely together,” Boriskina said. “That’s what makes this yarn very recyclable.”

Like a spaghetti machine

The manufacturing process is refreshingly simple. Polyethylene pellets are heated to about 350 degrees Fahrenheit, past their melting point, and then drawn through small extruders into hair-thin fibers. An industrial yarn spinner then wraps the sheath fibers around the stretchy core.

“You just melt it in a barrel with a heater, and then you extrude and spin it into fibers,” Kim said. “It’s like a spaghetti machine.”

The finished yarn feels much like ordinary sewing thread and can be woven into lightweight, stretchy fabric.

Ten lives and counting

The real test was recyclability. The team spun the yarn, melted it, and respun it ten times in succession. After each cycle, they stretched the threads and measured the force at which they broke.

After all ten cycles, the yarn remained as strong and flexible as conventional thread. The recycled material proved as strong as the original sheath yarn and could be used to make new elastic yarn — demonstrating a genuine textile-to-textile loop rather than downcycling into lower-grade products.

That is a crucial distinction. Much of what passes for plastic recycling degrades the material with each round, eventually turning it into products that can’t be recycled again. A yarn that maintains its performance through repeated cycles could, in principle, stay in circulation far longer.

From lab to closet

The work builds on earlier efforts by Boriskina’s group, which in 2021 spun polyethylene into yarns designed for moisture wicking, stain resistance, and cooling. The new stretchy version extends that approach to one of the most stubborn categories of textile waste.

The team says the process can be scaled up to industrial spools, which matters because weaving even a single textile requires kilometers of yarn. “Now we have something that can be knitted and woven,” Boriskina said. “That is the next stage.”

The researchers envision a future in which worn-out garments go into recycling bins, get melted down, and are respun into new textiles — or into other plastic products such as buttons and belt buckles.

“Hopefully it will prevent the need for making more and more textile materials,” Boriskina said, “because you can keep recycling a large portion of it.”

There are hurdles ahead. Recycling only works if collection systems exist to gather old clothing and if garments are made purely from compatible materials, without the blends and trims that complicate sorting. And polyethylene, for all its versatility, is still a fossil-fuel-derived plastic. But in an industry where stretch has long meant a one-way trip to the dump, a yarn that can be melted down and spun anew offers a rare glimpse of a closed loop.

The research was funded by the DEVCOM Soldier Center through the U.S. Army Research Office, the Office of Naval Research Global via Tecnológico de Monterrey, and the MIT Portugal Program.

Featured image: Photo by Brett Jordan on Pexels.com

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Notes

1. Kim, S., Xu, D., Korolovych, V., Flores-Hernandez, D., Moriam, K., Braconnier, D., & Boriskina, S. “Polyethylene-Based Thermo-Mechanically Recyclable Stretchable Yarns for Circular Sustainable Textiles.” ACS Materials Letters, 2026. DOI: 10.1021/acsmaterialslett.6c00337.
2. Massachusetts Institute of Technology. “MIT engineers design recyclable elastic yarn.” News release via EurekAlert!, July 27, 2026. https://www.eurekalert.org/news-releases/1137757