Nanotubes boost shape recovery

Researchers from the University of Dayton, Miami University and the Air Force Research Laboratory have mixed carbon nanotubes with polymer to make a plastic that is good at springing back into shape when heated.

Carbon nanotubes are rolled-up sheets of carbon atoms that are stronger by weight than steel.

The material would be useful for making large area structures in space that need to be packaged for launch and then unfurled later, according to the researchers. It could also be used to make eyeglass frames that recover their shape and to make temperature-triggered switches.

Adding carbon nanotubes to plastic increases the material's rubbery modulus and electrical conductivity without changing the elongation and toughness properties of the plastic, according to the researchers.

Shape recovery occurs when these materials are heated, which melts polymer crystallites that form when the material is bent. The light-absorbing and electrical characteristics of the nanotubes enabled the researchers to heat the material by applying light or current directly to it rather than using an external heater.

The shape memory polymers could be used in practical applications in five years, according to the researchers. The work appeared in the January 25, 2004 issue of Nature Materials.