How to turn old plastic bags into racing cars

Jeff Hecht, consultant

(Image: James W. Pearce)

At last, something useful to do with plastic bags. Chemists at the Oak Ridge National Laboratory in Tennessee have found out how to turn the plastic into carbon fibres. So today's plastic rubbish might wind up in tomorrow's carbon-composite racing cars, or in sophisticated filters for chemical processing.

Environmentalists detest plastic bags and some governments have banned or taxed them. Municipal recycling programs generally won't take plastic bags because the chemicals used to make them into films are incompatible with the recycling of plastic bottles. Although stores collect and recycle some plastic bags, most end up being thrown away.

The Oak Ridge team, led by Amit Naskar, has found a way to recycle the polyethylene used in bags and other plastic rubbish into carbon fibres in a wide ranges of sizes and shapes. They mix polyethylene with a compound derived from cornstarch or sugar cane called polyactic acid, heat the mixture, and spin it into bundles of fibres 0.5 to 20 micrometres thick. Each bundle is dipped into an acid-containing chemical bath where it reacts and forms a black fibre that won't melt.

This bonds the plastic molecules so they can't melt or flow when the fibres are heated to very high temperatures, driving off all elements but carbon, which remains behind as a fibre. The shapes can be quite complex.

Varying the details of the process allows the Oak Ridge group make fibres with different cross-sections, such as hollow-circles or gear shapes, which can be used for a variety of applications. They also can tailor porosity. The gear-shaped fibres could be assembled into filters for water desalination or other chemical processing, they write in Applied Materials. Other shapes can be used in lightweight composite materials for cars bodies, reducing the vehicle's weight and improving its fuel efficiency without impairing safety, Oak Ridge says.

Source: http://feeds.newscientist.com/c/749/f/10897/s/1df01c3e/l/0L0Snewscientist0N0Cblogs0Conepercent0C20A120C0A30Cturning0Eold0Eplastic0Ebags0Einto0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

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