MIT Engineers Create Recyclable Elastic Yarn for Sustainable Textiles

MIT engineers have developed a recyclable elastic yarn designed to tackle the growing problem of textile waste. With most stretchy garments containing spandex, end-of-life recycling is notoriously difficult—typically requiring chemical separation of different polymer layers. The new approach replaces that mixed-material problem with a yarn built from polyethylene, a widely produced plastic.

The researchers’ material strategy mimics spandex’s mechanical behavior using a polyethylene-based core-and-sheath architecture. Instead of a polyurethane spandex core wrapped in polyester or nylon, both the flexible core and the sturdier sheath come from related polyethylene formulations. Because the chemistry is the same family, the yarn can be melted and reshaped without isolating layers first.

Polyethylene matters because it is a thermoplastic: it can be repeatedly melted and remade. In this work, MIT shows that polyethylene can be engineered into hair-thin fibers and assembled into a stretchable yarn using an industrial spinning process. The core is produced from a resin composition optimized for extensibility, while the sheath uses a stiffer resin that contributes tensile strength and durability.

To manufacture the yarn, pellets of each resin are heated well above their melting point and drawn through small extruders, forming microscopic fibers. These sheath fibers are wound around the core fiber to yield an elastic composite thread with the hand-feel associated with conventional sewing or textile yarns.

The key recyclability test is intentionally straightforward: the team melted a spool of the elastic core–sheath yarn and respun it into new yarn repeatedly. Mechanical testing after each cycle—measuring the force required for a thread to break—showed that even after 10 recycling cycles, the yarn retained strength and flexibility comparable to the starting material.

Beyond the lab demonstration, the researchers envision a circular workflow. Polyethylene-based garments could be dropped into recycling streams, melted at scale, respun, and remade into new textiles or simpler plastic products such as buttons and belt accessories.

The work is positioned as a direct alternative to spandex-containing elastic blends, which dominate the market and remain largely unrecyclable at scale. By reducing chemical separation requirements and avoiding toxic, high-cost processing, the team aims to make recycling into new textiles more practical.

In their study, published in ACS Materials Letters, MIT presents a thermo-mechanically recyclable yarn recipe intended for scaling into industrial spools. Viral takeaway: a spandex-like stretch without spandex-like recycling dead ends.

Keywords

recyclable yarn, polyethylene, thermoplastic recycling, elastic fibers, circular textiles, spandex replacement, polymer engineering, fiber spinning, mechanical testing
Subject of Research: Recyclable stretchable yarns for circular sustainable textiles
Article Title: Polyethylene-Based Thermo-Mechanically Recyclable Stretchable Yarns for Circular Sustainable Textiles
News Publication Date:
Web References: http://dx.doi.org/10.1021/acsmaterialslett.6c00337
References: ACS Materials Letters (DOI: 10.1021/acsmaterialslett.6c00337)
Image Credits: Felice Frankel