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“There’s no widely-adopted technology now that recycles textiles into textiles. With our new yarn, we hope to change that,” says Svetlana Boriskina. These two SEM images compare a conventional elastic yarn made of PET-spandex (left) with a new type of recyclable made from two types of recyclable polyethylene.
Photo Credit: Courtesy of the researchers
(CC BY-NC-ND 3.0)
Scientific Frontline: Extended "At a Glance" Summary: Recyclable Polyethylene Yarn
The Core Concept: MIT engineers have developed a fully recyclable, elastic yarn constructed entirely from polyethylene, a thermoplastic polymer commonly found in everyday packaging. This novel material mimics the strength and flexibility of conventional spandex while eliminating the need for complex chemical separation during the recycling process.
Key Distinction/Mechanism: Traditional elastic threads utilize a springy polyurethane core wrapped in a tough polyester or nylon sheath, rendering them virtually impossible to recycle together due to their differing chemical properties. The newly developed yarn overcomes this barrier by pairing a highly stretchable polyethylene copolymer core with a stiffer polyethylene sheath, allowing the entire strand to be melted and extruded repeatedly without material degradation.
Major Frameworks/Components:
- Thermoplastic Extrusion: Pellets of the specific polyethylene resins are heated past their melting point (approximately 350°F) and drawn through micro-extruders to form hair-thin fibers.
- Polymer Tailoring: The physical properties of the yarn are manipulated by altering the arrangement of polyethylene's carbon backbone and its short molecular branches.
- Core-Sheath Architecture: An industrial yarn spinner is used to wind the rigid polyethylene sheath fibers around the elastic polyethylene core, providing both tensile strength and elasticity within a single chemical family.
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