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Currently, only about 9% of plastics in the U.S. are recycled, in part because the chemical makeup of many plastics makes recycling difficult. When plastics are recycled, they often become weaker in their second life. But chemists at the University of North Carolina at Chapel Hill have found a way to break down plastics and recycle them into an even stronger, more durable material.
The method breaks down plastics and alters the carbon-hydrogen bonds found in plastic polymers to make them tougher than the original plastic. This not only recycles the plastic, but also makes it more valuable. The team published their findings in the journal Science.
“Our approach views plastic waste as a potentially valuable resource for the production of new molecules and materials,” said Frank Leibfarth, assistant professor of chemistry in the UNC College of Arts & Sciences. “We hope this method could drive an economic incentive to recycle plastic, literally turning trash into treasure.”
According to the researchers, a recently identified reagent can strip hydrogen atoms from polymers, and the chemists then used this to form new bonds in formerly unreactive areas.
“The versatility of our approach is that it enables many valuable transformations of carbon-hydrogen bonds on such a wide range of important compounds,” said Erik Alexanian, a UNC-Chapel Hill professor with expertise in chemical synthesis.
In their testing, the researchers were able to turn postconsumer polyethylene foam, often used for safely shipping electronics, made from low-density plastic into a high-value type of plastic known as an ionomer, which is often used for food packaging.
Typically, recycled plastics weaken during the recycling process, so they are used in other products, like carpets or clothing, and often still end up in landfills. The newly discovered method of creating stronger plastics through recycling could help make use of the millions of tons of plastic waste we generate each year.
“It could change the way we look at plastic,” Leibfarth said.
The Leibfarth Group at UNC-Chapel Hill is working in several ways to develop more sustainable plastic polymers. In addition to finding a method for recycling plastics into stronger plastics, Leibfarth and environmental engineer Orlando Coronell, also at UNC-Chapel Hill, were able to develop a polymer capable of absorbing PFAS, also known as “forever chemicals” with potential harmful impacts to health, from water in 2020.
“Fluorinated compounds will continue to be made because consumers will continue to demand them,” Leibfarth said of the PFAS-absorbing resin. “And it’s a problem that’s a product of our modern society, but we need modern solutions, then, to that problem.”