December 21, 2007
New Plastic Decomposes Faster
A new biodegradable plastic could decompose much faster than existing ones, safely breaking down in the environment instead of polluting the world for centuries.
The novel material is a modified form of a plastic with the tongue-twisting name of polyhydroxybutyrate, or PHB for short. This bacteria-produced compound is found in everything from soft drink bottles to medical implants, and was widely hailed as a clean alternative to petroleum-based plastic for use in packaging, agricultural and biomedical applications.Although PHB has been commercially available since the 1980s, it has seen only limited use because of its brittleness and unpredictable rates of biodegradation. Now scientists at Cornell University in New York have designed a new form of the plastic that at first glance is paradoxically both stronger and decomposes faster.
The key is the addition of particles of clay only nanometers — billionths of a meter — in diameter. These "nanoclays" help the PHB crystallize, enhancing its strength. At the same time, the nanoclays act as catalysts, eventually helping the plastic decompose.
The scientists found their hybrid PHB could break down almost completely in a compost chamber after seven weeks, while its traditional counterpart showed almost no decomposition. They could modify the rate of degradation by adjusting the amount of added nanoparticles.
The researchers suggest their work could lead to wider use of PHB. Such plastics, which are renewable since they are created by bacteria, "will be more and more important as we move away from petroleum-based economy," researcher Emmanuel Giannelis, a materials scientist at Cornell, told LiveScience.
Giannelis and his colleagues detailed their findings in the November issue of the journal Biomacromolecules.
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