Anyone who has heard the snap of a rubber band breaking
knows it’s time to reach for a replacement. But now, a group of French
scientists have made a self-healing rubber band material that can
reclaim its stretchy usefulness by simply pressing the broken edges
back together for a few minutes.
The material, described on
Wednesday in Nature, can be broken and repaired over and over again. It
is made from simple ingredients – fatty acids like those found in
vegetable oils, and urea, a waste compound in urine that can be made
synthetically.
The material would be an asset to industry and
might even help shed light on the physics of elasticity, wrote Philippe
Cordier and colleagues from the Industrial Physics and Chemistry Higher
Educational Institution in Paris.
Researcher
Ludwik Leibler displays the self-mending rubber that heals itself in 15
minutes by simply pressing the damaged pieces together
Standard rubber bands, which can stretch up to several hundred per cent
then snap back into shape, are made from long chains of cross-linked
polymers.
The
new material is linked by short chains of a type of molecule called
ditopic, which can associate with two other molecules, and multi-topic
molecules, which can associate with more than two molecules. This
network of molecules is strengthened by hydrogen bonds that allow the
material to stretch up to several hundred per cent, then snap back into
shape.
If severed, the material mends itself when the ends are
pressed together at room temperature. This is because the molecules
re-partner with molecules on the other end of the break.
However,
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.
“Mended samples can sustain large deformations and recover shape and size when
stress is released,” the researchers wrote.
The
material can “withstand multiple fractures, and is otherwise
straightforward to produce,” Justin Mynar and Takuzo Aida of the
University of Tokyo wrote in an accompanying article.
“A final blessing is that it can be broken down with heat and easily recycled –
so it is environmentally friendly, too.”
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