The Greening of Plastics

Article excerpt

Landfills are clogged with the detritus of unusable or just unwanted plastic consumer goods. Why not, asked fiber scientist Anil Netravali, make a plastic that decomposes? A plastic that, in fact, could end up in the compost heap instead of the landfill?

By early next century, if Anil Netravali has his way, we may be putting broken or outmoded pieces of the family car - the cracked tape deck holder, the broken window handle - out on the compost pile, along with last night's onion peels and apple cores. Netravali, an associate professor in the Department of Textiles and Apparel, is investigating the properties of several natural fibers that, when imbedded in a moldable, degradable matrix, may become the reinforced plastic of the future - one that's biodegradable, or a "green" composite.

Remember the scene from The Graduate when a winking uncle advised the graduate that plastics were the future? To a large extent that fictional uncle was right. Plastics did become a large part of the history of the second half of the twentieth century, both for consumers and scientists. Without plastics and other new lightweight composites, the space program would have been all but impossible. In fact, much of the research leading to the new materials and fibers of the twentieth century focused on flight and space exploration and eventually filtered down to more mundane consumer items.

The problem is that those now ubiquitous plastics tend to hang around a very, very long time, even after the product is defunct. Landfills are clogged with the detritus of unusable or just unwanted plastic consumer goods. Recycling is one way of reducing this stream of solid waste, though recycling plastic brings its own problems and environmental issues.

Why not, asked Netravali, make composites that decompose? Plastics that, in fact, could end up in the compost heap instead of the landfill? Enter green composites, as Netravali terms this new and needed material for the manufacture of consumer goods. While small groups of scientists in Europe are also investigating more environmentally friendly plastics, Netravali probably is the only researcher whose ultimate goal is a totally biodegradable plastic.

"Green composites could eventually become inexpensive composites for mass-produced items," Netravali says. "And they would be environmentally friendly because they would biodegrade."

Netravali came to Cornell, "for one year," he explains, as a postdoctoral associate in 1984, and he has been here since then as a faculty member in the college's Fiber Science Program. The green composite program began officially in 1996.

The substance that nonscientists call plastic is part of a larger group of manufactured substances technically known as polymers. Polyurethane foam, nylon, polyester, and spandex are examples. Reinforced polymer composites are versatile and provide a high strength-to-weight ratio, making them invaluable in, for instance, the space program and aviation. Voyager, the first aircraft to circle the globe without refueling, was made of a high-strength, lightweight composite. Green composites, made of biologically and chemically active rather than inert materials would, of course, be weaker and less durable. But there are many other applications for such products that are noncritical, where a biodegradable composite could be as feasible as a tougher, nonbiodegradable alternative.

"You wouldn't use a green composite in an application where, if it broke, it would be a significant loss," Netravali says. "You don't want an airplane wing to break, for instance. 'But there are many other instances of use when if a piece of plastic breaks, it is just inconvenient, not critical. Those uses would be suitable for green composites."

Current research in the fiber science laboratory at Cornell focuses on finding the most advantageous combination of fiber and resin - one that would provide a finished product that is as strong as possible, durable, affordable, and biodegradable - and the most efficient method of combining the two substances. …