New research supported by the National Science Foundation's Center for Sustainable Polymers showcases a novel kind of plastic that has all the strength of regular plastic but decomposes in the sun. Called isotactic polypropylene oxide, or iPPO, this plastic was developed originally in 1949, but chemists from the laboratory of Geoff Coates at Cornell University have updated its isotacticity (enchainment regularity) and polymer chain length to give it mechanical strength.
A strong material on the ocean is important for fisheries around the world. Fishing nets and ropes are made from mostly three polymers that get the job done: isotactic polypropylene, high-density polyethylene, and nylon-6,6. The problem with these polymers is that they don’t degrade easily and contribute vastly to plastic pollution in the ocean. In fact, Bryce Lipinski, a doctoral candidate working on this study, commented that commercial fishing accounts for about half of all floating plastic waste that ends up in the oceans.
"While research of degradable plastics has received much attention in recent years," said Lipinski, "obtaining a material with the mechanical strength comparable to commercial plastic remains a difficult challenge."
According to the researchers, iPPO could be part of the solution. "We have created a new plastic that has the mechanical properties required by commercial fishing gear. If it eventually gets lost in the aquatic environment, this material can degrade on a realistic time scale," Lipinksi. "This material could reduce persistent plastic accumulation in the environment."
Aside from its mechanical strength, the most important property of iPPO is its ability to photodegrade under UV light. As the chemists showed in the laboratory, the polymer chain lengths degraded to a quarter of their original length after 30 days of exposure. Of course, the ideal goal is for the polymer to degrade completely, without any trace on the oceans. Though that level of degradation, says Lipinski, is still in the works.
This research was published in the Journal of the American Chemical Society.