Engineers at MIT have developed a two-resin polyethylene yarn that matches the stretch and strength of conventional spandex fabrics, but unlike spandex blends, it can be melted down and reprocessed up to ten times without losing its properties.
Stretch fabrics have long posed a sustainability paradox: the same elastic blends that deliver comfort and freedom of movement are also among the hardest textiles to recycle. When spandex is combined with polyester or nylon, the differing chemical compositions of the fibers make mechanical separation nearly impossible, meaning most such garments cannot be reclaimed and instead head to landfill or incineration. The scale of the problem is significant — the average American discards roughly 81 lb of clothing a year, contributing to an estimated 11 million tons of textiles disposed of annually in the US alone.
MIT’s yarn addresses the problem at the material level rather than through better sorting or collection. It combines two polyethylene-based resins with complementary properties: a softer, more elastic resin forms the core, while a stiffer, tougher resin forms the outer sheath. Because both components share the same base chemistry, they can be melted and processed together at end of life, rather than requiring the kind of separation that makes spandex blends unrecyclable in practice.
To produce the yarn, MIT engineers heated pellets of each resin to roughly 350°F and extruded the molten plastic through fine dies to form hair-thin fibers. In testing, the resulting yarn matched the strength and flexibility of conventional elastic thread, and showed a higher maximum load capacity than standard spandex-polyester yarns.
The standout property is durability through repeated reprocessing: the yarn can be melted and respun up to ten times while retaining its mechanical performance, a sharp contrast to spandex blends, which cannot be meaningfully recycled at all. MIT researchers now plan to weave the recycled yarn into finished fabrics to evaluate whether performance holds up against textiles made from virgin material, a step that will help determine how close the innovation is to commercial-scale readiness.
