Substance retains its stretchiness and can be repaired many times
By Andrea Thompson
LiveScience
February. 20, 2008
It sounds likes something from a sci-fi movie: a
rubber-like material that can fuse itself back together after being snapped in
two.
As anyone who's shot a rubber band across a room knows, standard
rubbers are very flexible — they can stretch by several hundred percent.
But if you've pulled just a little too hard on that rubber band, you also know
it can suddenly (and painfully) snap in two.
Ludwik Leibler of the Industrial Physics and Chemistry Higher Education
Institution in Paris and his colleagues have solved the broken rubber band
problem by creating a material that stretches like rubber, snaps like rubber,
but then will mend itself if its two broken ends are brought back together.
The new material, made from fatty acids and urea, is translucent and can have a
yellowish tint, Leibler says.
The bonds between the molecules in the material, called
hydrogen bonds, are what give the new rubber its self-healing ability. They
form linear links, called chains, between some molecules, as well as cross-links
between those chains, creating a "supramolecular" network of smaller molecules.
When the material is broken, the molecules on each side of the break lose their
partners, and "so they look for partners to make these hydrogen bonds," Leibler
explained. If the two ends of the broken piece are brought back together, the
molecules will re-partner with molecules on the other end of the break. But if
they aren't brought together within several hours of the break, the molecules
will just pair up with other molecules on their respective end, and the material
can no longer be repaired.
If the material does re-fuse, it retains the same amount of stretch as it did
before and, "you can repair it many times," Leibler said.
The rubber material is currently being produced on a test basis by a company
called Arkema, Leibler told LiveScience. His team envisions the material being
used in toys, which children are prone to breaking, perpetually closed bags, or
as an
adhesive .
URL: http://www.msnbc.msn.com/id/23258630/