Solar-powered coating repairs car scratches in just 30 minutes of sunlight

ULSAN, South Korea — A new clear coat can actually get rid of those nasty scratches on your car after just 30 minutes, scientists reveal. A team in South Korea claims that the protective material “self-heals” damaged surfaces using only sunlight!

Until now, researchers say it has been difficult for manufacturers to create a coating that is colorless, transparent and has a high level of durability. The new material meets all these needs, according to Dr. Jin Chul Kim, Dr. Young il Park and Dr. Ji-Eun Jeong of the Korea Research Institute of Chemical Technology (KRICT).

“The technology developed is a platform technology that synthesizes self-healing coating materials using both inexpensive commercial polymeric materials and photothermal dyes. It is expected to be widely used not only in automotive varnishes but also in various applications,” says Dr. Jin Chul Kim in a Press release.

To examine the performance of their invention, the researchers coated a lab scale model of a car using a spray coating machine. The team then exposed the scratched car to the midday sun for half an hour. The results reveal that the scratches have completely disappeared, with the surface of the coating material being fully restored.

Self-healed surface of a car model after scratching when exposed to focused sunlight with a magnifying glass (top) or direct sunlight (bottom). CREDIT: Korea Research Institute of Chemical Technology (KRICT)

How does the coating work?

When the material absorbs sunlight, its surface temperature increases as the light energy is transformed into thermal energy. The higher temperatures allow self-healing to begin with the dissociation and recombination of chemical bonds in surface polymers.

The study authors combined a commercial coating resin with a dynamic chemical bond (congested urea structure) that allows this process to occur. They also mixed it with a transparent photothermal dye, so the chemical bonding begins after exposure to sunlight.

Although this is not the first time that scientists have experimented with photothermal dyes, previous studies have mainly used inorganic materials that are difficult to apply industrially while maintaining a clear and transparent color. Additionally, the study authors claim that inorganic materials need more light energy to trigger a photothermal effect than their urea coating.

The team also used transparent organic photothermal dyes that absorb near-infrared light. This type of light consists of long wavelength energy and represents less than 10% of natural sunlight.

The researchers add that there are several advantages to using organic photothermal dyes in commercial coatings. These include not affecting the color of the product, mixing easily with various types of paints, and generally being inexpensive to use.

In addition to repairing the surface of cars, the study authors claim that this new coating can become a protective material for public transport vehicles, electronic devices like smartphones and even buildings in the future. Since the material uses fewer harmful organic solvents, the team says their invention would likely be carbon neutral, unlike repainting a scratched vehicle.

car scratch
Self-healing mechanism of an environmentally friendly protective coating material for vehicles comprising a dynamic polymer network and a photothermal dye.
CREDIT: Korea Research Institute of Chemical Technology (KRICT)

The study is published in the journal ACS Applied Polymer Materials.

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