Materials

Coating highlights microscopic cracks, before they lead to disaster

Coating highlights microscopic...
The polymer incorporates yellow dye, that changes color to red when released from microcapsules by structural damage
The polymer incorporates yellow dye, that changes color to red when released from microcapsules by structural damage
View 1 Image
The polymer incorporates yellow dye, that changes color to red when released from microcapsules by structural damage
1/1
The polymer incorporates yellow dye, that changes color to red when released from microcapsules by structural damage

Whether they're on airplanes, bridges or pipelines, even the tiniest of cracks can fast lead to catastrophic failures. That's why it's important to identify them as early as possible, before they get out of hand. With that in mind, scientists at the University of Illinois have created a new polymer coating that can be applied to a wide variety of structural materials. When those materials crack – even a little – the polymer changes color to let inspectors know that something's up.

Designed by a team led by professors Nancy Sottos and Scott White, the polymer contains epoxy resin microcapsules filled with a light-yellow pH-sensitive dye.

As long as no damage occurs, those capsules remain intact. However, should a crack form (as small as 10 micrometers in width), the capsules in that area burst and release the dye. That dye chemically reacts with the epoxy, changing from yellow to bright red in color. The larger the crack, the greater the amount of dye reacts, and the more pronounced the color-change.

According to the researchers, the polymer has been successfully tested on materials including metal, glass and other polymers. It's also reasonably inexpensive, as it only needs to be composed of five percent microcapsules in order to work effectively.

Along with other possible applications, they're now looking at incorporating the polymer into a self-healing plastic that they previously created. In that case, an initial color-change would indicate that a crack had formed, while a secondary change would indicate that it had subsequently healed.

The research is described in a paper that was recently published in the journal Advanced Materials.

Source: University of Illinois

1 comment
Bob
This sounds great at first but--- what if the coating is the only thing that cracked? What if temperature changes stretching and contracting break the capsules. Many structural items are made to flex if only a little. Cracking paint is always a problem because it is the first to fail even if the underlying structure is sound. I could see something like this coating giving enough false indications that it was no longer taken seriously. If you were looking at a bridge and saw cracks everywhere, how much time would it take to investigate them all looking for the real structural failure? What happens when a new coat of paint is applied over it? Will all the old paint need to be removed first? That said, there are indoor applications where this coating would be useful.