Sunlight heals scratches in paintwork

It’s annoying when the paint job of a car gets scratched. And it’s not just because it impairs the vehicle’s appearance, as scratches can enable moisture to get through the paint job and cause rust to form. A research team led by Dr. Jin Chul Kim at the Korea Research Institute of Chemical Technology (KRICT) has now found a way to make scratches disappear before the car owner even notices them—in less than 30 minutes and simply with the help of the sun. This is made possible by a novel coating resin that has a polymer network of dynamic chemical bonds. If damage causes the bonds to dissolve, they will resume their original order when stimulated by heat. This is achieved using urea and an organic photothermal dye in the coating. Urea causes the polymer structures to repeatedly decompose and rearrange, while the dye ensures that the compounds in the coating react to heat. When sunlight hits a scratched paint job, the surface temperature rises, triggering the self-healing process of the broken chemical bonds so that they seemingly recombine on their own. The coating is transparent and can be easily mixed with a variety of paints.