March 13, 2009

Special Coating Clears Scratches On Cars

Scratches on an otherwise perfect looking vehicle can be a real annoyance for car owners, but scientists have developed a polyurethane coating that heals its own scratches when exposed to sunlight.

"We developed a polymeric material that is able to repair itself by exposure to the sun," said Marek Urban of the University of Southern Mississippi in Hattiesburg.

The findings are published in the journal Science.

The report says the self-healing coating uses chitosan. It's a substance found in the shells of crabs and shrimp.

"In essence, you create a scratch and that scratch will disappear upon exposure to the sun," Urban said in an interview on the Science website.

The process works like this: when a scratch damages the chemical structure, the chitosan responds to ultraviolet light by forming chemical chains that begin bonding with other materials in the substance.

The special coating eventually smooths the scratch.

The coating also uses readily available materials, offering an advantage over other self-repairing coatings, which Urban said were "fairly elaborate and economically unfeasible."

He said the polymer can only repair itself in the same spot once, and would not work after repeated scratches.

"Obviously, this is one of the drawbacks," he said, adding that the chances are slim of having two scratches in exactly the same spot.

Howell Edwards, who leads the chemical and forensic sciences division of the University of Bradford in Britain, said the findings were groundbreaking.

"Clearly, there are future applications of this work in the repair of automotive components, which extensively use polyurethane polymers, that have suffered minor damage," Edwards said.

Researchers point out, that the special coating could be used for anything that requires a high-performance type of coating.

"You can dream up anything you desire," he said.

Urban said his team is considering commercialization.