Published on March 28th, 2012 | by Tina Casey1
Plastic Bag Recycling Gets a New Spin from Science
It looks like plastic bag knitters the world over are going to have to make room for a new recycler in town. Scientists from the Oak Ridge National Laboratory have figured out how to recycle plastic bags by extracting the polyethylene to make carbon fibers, which can be fabricated into new strong, lightweight components for – well, for practically anything that can be made out of plastic.
Spinning carbon fiber from a plastic bag, with science
The ORNL process is a far cry from simply cutting plastic bags into strips. Using a high-tech spinning process combined with another step called sulfonation, the researchers produced polyethylene-based fibers with surfaces that can be customized “down to the submicron scale.” So, in addition to being used in products like lightweight car parts, the fibers can be used in advanced devices used for filtration and electrochemical energy harvesting, among others. The interior structure of the fiber can also be manipulated, depending on how the processing is conducted.
So, what is sulfonation?
Sulfonation is a reaction in which a bundle of fibers is dipped into a chemical bath, bonding the plastic molecules together. The result is a single black fiber that cannot melt into a puddle, as ordinary plastic does.
And carpet recycling, too
Aside from having the kind of extraordinary weight-to-strength ratio demanded of new materials in a more energy efficient economy, the new carbon fibers are also made from an inexpensive, seemingly endless feedstock. But if the world ever bans plastic bags (ha!), not to worry. Recycled carpeting – of which there are untold millions of tons in the U.S. alone – also contains plastics that can get a second life, quite possibly in those new electric vehicles we’ll all be driving some day.
Follow Tina Casey on Twitter: @TinaMCasey.