A newly developed yarn out of MIT could chip away at one of activewear’s most stubborn sustainability problems: fabrics that stretch well but can’t be recycled.
Detailed in a July 25 study published in ACS Materials Letters, the yarn is made entirely from polyethene rather than the spandex-polyester or spandex-nylon blends that dominate stretch fabrics today. The MIT team engineered a soft, springy polyethene core, functioning much like a rubber band, and wrapped it in a second, more rigid polyethene fibre coiled tightly around it, similar to a twisted phone cord. Because both parts are chemically identical, they can be recycled together without the separation step that makes blended fabrics so difficult to process.
That separation step is precisely where conventional stretch fabrics fail. Spandex, a flexible but comparatively weak polyurethane fibre, is typically paired with stronger fibres like polyester or nylon to give fabric both give and durability. But those chemically different fibres are costly to separate for recycling, and the chemicals involved in doing so can be toxic. The result, according to study co-author Svetlana Boriskina of MIT’s Department of Mechanical Engineering, is that around 80% of textiles sold in the US contain spandex — and most of that ends up incinerated or in landfill rather than recycled.
In lab testing, researchers melted a spool of the new yarn and respun it into fresh yarn ten times over, checking strength after each cycle. The recycled material held up as well as the original. In direct comparisons, it also outperformed commercially available spandex-polyester yarn on maximum load — meaning it could withstand greater force before breaking.
The team, building on earlier work with polyethene-based wearable fabrics, has also shown that lightweight polyethene fibres can be engineered for added functions such as cooling, moisture-wicking and stain resistance. The researchers see potential to extend the approach beyond fabric altogether: buttons, zippers and buckles made from compatible plastics could, in theory, allow an entire garment to be melted down and remade without dismantling it first.
