New Scientist reveals the latest breakthrough in paint technology, coatings that 'self-heal' in sun. You might never have to fear for your car's paintwork again if a new kind of polyurethane that is able to heal its own surface scratches makes it to market.
Small scratches to the surface of the material close up in only a few minutes when the material is exposed to the ultraviolet light in sunlight. This life-like healing occurs because the damaged polymer molecules around the edges of a scratch use the energy from the UV to form new cross-links and recreate the network that makes up the material.
The material could make a good top coat for an automobile, says Marek Urban, a polymer scientist at the University of Southern Mississippi, Hattiesburg, who led the study.
The secret of the material lies in using molecules made from chitosan, which is derived from the shells of crabs and other crustaceans.
In the event of a scratch, ultraviolet light drives a chemical reaction that patches the damage.
The work by University of Southern Mississippi researchers is reported in the journal Science.
They designed molecules joining ring-shaped molecules called oxetane with chitosan.
The custom-made molecules were added to a standard mix of polyurethane, a popular varnishing material that is also used in products ranging from soft furnishings to swimsuits.
Scratches or damage to the polyurethane coat split the oxetane rings, revealing loose ends that are highly likely to chemically react.
In the ultraviolet light provided by the sun, the chitosan molecules split in two, joining to the oxetane's reactive ends.
"In essence you create a scratch, and that scratch will disappear upon exposure to the sun," said Professor Marek Urban, director of the university's school of polymers and high-performance materials.
Professor Urban and graduate student Biswajit Ghosh found that their coatings were able to fully heal themselves in just 30 minutes.
Source: New Scientist and BBC News
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