In the near future, tyres might be able to heal themselves on the road thanks to a major new breakthrough in materials science research.
A team of engineering researchers at Harvard has produced a new type of rubber that is as tough as natural rubber, but can also repair itself, giving hope for the development of self-healing tyres for vehicles.
In a paper published to Advanced Materials, the team wanted to improve upon existing self-healing properties found in hydrogels and apply them to dry materials, which has, up until now, proven incredibly difficult.
This is because rubber is made of polymers often connected by permanent, covalent bonds, and, while these bonds are incredibly strong, they will never reconnect once broken.
So, in order to make self-healing rubber, the team needed to make the bonds connecting the polymers reversible, so that they could break and reform.
Until this major breakthrough, it remained just a theory proposed by one of the paper’s corresponding authors, Liheng Cai, especially since covalent and reversible bonds don’t like to mix, similar to how water and oil react together.
Using some ‘molecular rope’
With the addition of some ‘molecular rope’ known as randomly branched polymers, the researchers were able to tie the two types of bond together, allowing them to be mixed homogeneously on a molecular scale, thereby creating the new rubber.
Unlike typical rubber, which cracks at particular stress points, this new hybrid develops ‘crazes’ instead, a feature similar to cracks but connected by fibrous strands.
This redistributes stress across the rubber, meaning there are no focus points for tearing and, when released, the material snaps back to its original form and the crazes heal.
“Imagine that we could use this material as one of the components to make a rubber tyre,” said Jinrong Wu, one of the authors of the paper.
“If you have a cut through the tyre, [it] wouldn’t have to be replaced right away. Instead, it would self-heal while driving enough to give you leeway to avoid dramatic damage.”
The team said it will now try to figure out why exactly this hybrid rubber exhibits crazes when stretched, as little is understood about it in the field of materials science.