Self-healing tires perhaps?

Here's something new and different (I think?) ..

New rubber mends itself when broken
Last Updated: Wednesday, February 20, 2008 | 1:38 PM ET
CBC News
French scientists have created a rubber that mends itself when broken.

The new "Material B" stretches to several times its original length like regular rubber, but once broken, the pieces "self-heal without the need to heat or press strongly" at room temperature, about 20 C.

Time improves the healing, but even after 15 minutes, a sample can be stretched up to about 200 per cent without breaking, the Paris-based researchers reported in an article published in the journal Nature on Wednesday.

"You can feel the material mending itself when you hold the fractured sides together," inventor Ludwik Leibler told New Scientist.com. "It's a very strange feeling."

The material could be used to make rubber products that take a lot of wear and tear, such as children's toys.

The healing scars are not visible, but the rubber will break at the same point unless it heals for a very long time.

"The cycle of stretching, breaking and healing can be repeated many times," said researchers from the Ecole Supérieure de Physique et Chimie Industrielles in Paris.

Leibler and three colleagues noted that elasticity in rubber results from very big molecules linked in a lattice or a network, using covalent, ionic or hydrogen bonds.

Using only hydrogen bonds, the researchers developed the stretchy material from vegetable oils and urea, which comes from urine.

They believe that the hydrogen bonds' ability to reconnect is the mechanism that enables the rubber to heal, however it makes the material somewhat weaker than conventional rubber.

It will reconnect up to 18 hours after it's broken, they reported.