Stretchy, self-healing paints and other coatings recently took a step closer to common use, thanks to research being conducted at the University of Illinois. Scientists there have used "off-the-shelf" components to create a polymer that melds back together after being cut in half, without the addition of catalysts or other chemicals.
The material is made from a proprietary mixture of inexpensive commercially-available compounds, including a polyurea elastomer – polyurea is commonly found in a wide variety of products such as paints and plastics. The researchers reportedly "tweaked" the structure of its molecules, making the bonds between them longer. As a result, the molecules are easier to pull apart from one another, but they're also better able to bond back together.
When samples of what is being called "dynamic polyurea" are cut and then left for a day with the severed ends touching, they will heal back together with almost the same strength that they had before cutting. The process works at room temperature, although raising the ambient temperature to 37ºC (98.6ºF) will speed it up.
Some other experimental self-healing materials incorporate liquid-filled micro-capsules that break open when the material is cut or cracked. This means that they will only heal as long as there are unruptured capsules present. By contrast, dynamic polyurea can reportedly heal over and over again, as it relies solely on its molecular structure.