Composites

Some of the carbon fiber shapes, created out of polyethylene using Oak Ridge's new technique
Thanks to research currently being conducted at the U.S. Department of Energy's Oak Ridge National Laboratory, our unwanted plastic bags may one day be recycled into carbon fiber. Not only that, but the properties of the fibers themselves could be fine-tuned, allowing different types of carbon fiber to be created for specific applications.

The Oak Ridge team, led by materials scientist Amit Naskar, start with polyethylene-base fibers – these could conceivably come from waste plastic sources, such as shopping bags and carpet backing scraps. Using a “a multi-component melt extrusion-based fiber spinning method,” the surface contours of these fibers can be customized, and their diameter can be manipulated with submicron precision. It is also possible to control their porosity.

Bundles of these fibers are dipped into a proprietary acid chemical bath. A process known as sulfonation causes the plastic molecules to bond with one another, transforming each bundle of fibers into one joined black fiber.

When subsequently exposed to very high temperatures, these fibers won’t melt. The heat does, however, cause many of their chemical components to turn to a gaseous state. After these have off-gassed, what’s left behind is a fiber composed mostly of carbon.

Many uses are envisioned for the plastic-derived carbon fiber – because of its tunable porosity, it may be particularly well-suited for applications such as filtration or energy harvesting. It is also hoped that the material could be used by the American auto industry, to make tough yet lightweight, inexpensive car parts.