By contrast, most of today's stretchy fabrics blend spandex, a bouncy-but-weak polyurethane fiber, with a tougher fiber like polyester or nylon. For the yarn's stretchy core, the researchers created a soft, springy version of polyethylene akin to a rubber band. Around that core, they wound a second, stiffer polyethylene fiber, more like a fishing line, coiling it tightly the way a spring or a twisted phone cord is coiled. Each time, they tested its strength, and the recycled yarn performed just as well as the original in every case. Article Sources Kim, S., Xu, D., Korolovych, V., Flores-Hernandez, D. R., Moriam, K., Braconnier, D. J., & Boriskina, S. V. (2026).