After a closet cleanout, options for recycling old threads are limited. Besides donating used clothes, there is no effective recycling process for textiles like there is for bottles and cans. The average American discards about 81 pounds of clothing each year, resulting in over 11 million tons of textiles ending up in landfills or incinerators. MIT engineers aim to address this issue with a new recyclable yarn.
The team has developed a yarn made from a type of plastic commonly used in milk bottles and grocery bags. This new yarn, which feels similar to traditional sewing thread, can be woven into stretchy, lightweight clothing. Researchers claim that at the end of its life cycle, garments made from this yarn can be melted down and re-spun into new yarn, which can then be woven into new clothing or even formed into buttons and belt buckles.
To demonstrate the yarn's recyclability, the researchers spun a spool of yarn, melted it down, and respun it multiple times. They found that even after 10 cycles, the yarn remained as strong and flexible as conventional thread. They envision this new yarn as an alternative to elastic spandex-polyester or spandex-nylon yarns, which are made from fiber combinations that cannot be recycled together. In contrast, the new yarn is made from a specific combination of plastic materials that mimics the properties of spandex while being easily recyclable.
"Eighty percent of textiles on the U.S. market currently contain some amount of spandex, which makes them non-recyclable," says Svetlana Boriskina, a research scientist in MIT's Department of Mechanical Engineering. The core problem lies in the fact that spandex is a polyurethane-based synthetic fiber that is springy but not very strong. An elastic yarn thread consists of a spandex-based core surrounded by a tough polyester or nylon sheath, which gives the yarn its unique stretch and strength, but complicates recycling.
In 2021, Boriskina’s group developed a new type of yarn made from polyethylene, the most common plastic in the world. Polyethylene can be melted and remade, making it recyclable, but it had not been considered a textile material until now. The team aimed to tailor polyethylene yarn to mimic the strength and flexibility of spandex, while also showcasing its recyclability.
They explored formulations of stretchy polyethylene-based copolymers that resemble a spandex elastic core while engineering polyethylene yarns to act as the sturdier sheath. After evaluating various chemical variations of polyethylene, they proceeded to fabricate fibers from selected resins, which were then melted and drawn into fine fibers using an industrial yarn spinner.
Since both the core and sheath are derived from the same polyethylene family, they do not need to be separated before recycling. The new yarn can be melted down and reformed into new yarn or other plastic products. In their tests, recycled versions of the yarn showed equal strength to the original sheath yarn, allowing them to be used for new stretchy yarns.
The team believes their polyethylene yarn can be scaled up for industrial production, potentially enabling a more sustainable, circular fashion and textile economy. "Hopefully, it will prevent the need for making more and more textile materials, as a large portion can be recycled continuously," Boriskina states. This work was supported by various military and research organizations.
Blogger's Review: MIT's innovation addresses a critical recycling challenge in textiles and advances sustainable fashion. The use of polyethylene showcases its potential in the textile sector, providing a new approach to minimizing environmental impact. Looking forward to seeing this yarn in industrial applications!