MIT's polyethylene yarn survives 10 melt-and-respin cycles

The average American throws out around 81 pounds of clothing each year, and there are few ways to recycle it. MIT engineers want to change that with a yarn that can be melted down and spun again into new thread.

Stretchy garments usually rely on elastic yarns that combine spandex with polyester or nylon. Those fibers would have to be separated before the garment could be recycled, a process that isn't practical.

The MIT team took a different route. It built a comparably stretchy yarn from two variations of polyethylene, the plastic used in milk jugs and grocery bags. Both variations belong to the same chemical family, so the yarn can be melted as it is, without first pulling its components apart. The melted material can then be spun into new yarn for a next generation of clothing.

In the team's tests, the yarn held up through 10 cycles of melting and respinning. After all of them, it stayed as strong and flexible as conventional thread. Svetlana Boriskina, who led the work, said the team now has something that “can be knitted and woven”, and called that “the next stage”.

The benefit would reach the collection bin first. The researchers hope that one day a polyethylene garment could be dropped into a bin and sent to a recycling facility, supporting a more circular textile economy. The MIT report gives no date for that, and the yarn has not yet been made into a garment.