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Self-healing coating uses sunlight to fix scratches on car surfaces

Professional Engineering

Stock image. The transparent car coating uses sunlight to self-heal scratches (Credit: Shutterstock)
Stock image. The transparent car coating uses sunlight to self-heal scratches (Credit: Shutterstock)

A new coating for car surfaces can self-heal scratches in just 30 minutes, its developers have said.

Developed by researchers at the Korea Research Institute of Chemical Technology (KRICT), the transparent material uses energy from sunlight to heal.

Automotive coatings need to be highly durable and transparent to protect the car surface and show the colour of the paint, but the researchers said it is difficult to provide self-healing functions with those criteria – materials with free molecular movement have high self-healing efficiency but low durability, while materials with excellent durability have “remarkably poor self-healing performance”, they said.

The team developed a coating that met all of the required conditions by combining an existing commercial coating resin with a hindered urea structure, a type of dynamic chemical bond that can repeat the decomposition and recombination of the polymer structure. They mixed it with a transparent photothermal dye so that dynamic chemical bonding occurs during exposure to sunlight.

The material has similar performance to commercial protective coatings and self-heals using near-infrared light in sunlight, the researchers said. When it absorbs sunlight, the coating’s surface temperature rises as light energy converts into thermal energy. The increased surface temperature self-heals surface scratches by repeating the dissociation and recombination of chemical bonds in the polymer structure.

To demonstrate the self-healing, the research team coated a model car using a spray-coating machine. When it was exposed to midday sunlight for about 30 minutes, a scratch in the surface completely disappeared and the surface of the material was restored.

“Although self-healing functions using photothermal dyes have been studied, previous studies were mainly based on inorganic materials that are difficult to apply industrially as the coating material should be transparent,” the researchers said. “In addition, inorganic materials require a large amount of light energy to produce a photothermal effect.”

The material could be used as a vehicle coating, on electronic devices such as smartphones and computers, or even on building materials, the team said.

This research was published in ACS Applied Polymer Materials.

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