Advance Could Lead to a New Era in Recycling Plastics

In an advance toward a new era in recycling of plastics, scientists in Japan are reporting development of a process that breaks certain plastics down into their original chemical ingredients, which can be reused to make new, high quality plastic.

That approach fostered recycling of beverage cans, scrap steel and glass containers, which are melted to produce aluminum, glass and steel. However, no process has emerged to depolymerize, or break down, the long chains of molecules that make up millions of pounds of polymer, or plastic, materials that are trashed each year. Instead, recycling of certain plastics involves melting and reforming into plastic that is less pure than the original.

According to June 25 announcement by the American Chemical Society (ACS), Akio Kamimura and Shigehiro Yamamoto will report invention of an efficient new method to depolymerize polyamide plastics -- which include nylon and Kevlar -- in an article in ACS Organic Letters, a bi-weekly journal. The technology, still at the laboratory-scale stage, does not require costly pressure chambers, extreme temperatures, or high energy inputs. Rather, it uses ordinary laboratory glassware.

The method relies on ionic liquids, liquids that contain only ions (atoms with an electric charge) and are powerful solvents. Researchers used an ionic liquid that changed nylon-6 into its component compound, captrolactam, and could be recycled and reused multiple times.

"This is the first example of the use of ionic liquids for effective depolymerization of polymeric materials and will open a new field in ionic liquid chemistry as well as plastic recycling," the report states.

The report, "An Efficient Method to Depolymerize Polyamide Plastics: A New Use of Ionic Liquids, can be accessed in HTML format at http://pubs.acs.org/cgi-bin/sample.cgi/orlef7/2007/9/i13/html/ol070886c.html. It also can be accessed in PDF format at http://pubs.acs.org/cgi-bin/sample.cgi/orlef7/2007/9/i13/pdf/ol070886c.pdf.

This article originally appeared in the 07/01/2007 issue of Environmental Protection.

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