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'Self-healing' car paint developed
A car paint that heals itself like human skin may in future make prangs a lot less painful.
Scientists have developed a polyurethane coating that mends its own scratches with the help of sunlight.
The material can repair itself in less than an hour when exposed to ultraviolet radiation.
The US researchers believe it could be used in packaging, clothing and biomedical products as well as on vehicles.
Dr Marek Urban and Biswajit Ghosh, from the University of Southern Mississippi in Hattiesburg, created the material using a natural substance found in the shells of crabs and shrimps.
The coating consists of a network of ring-shaped "oxetane" molecules which split open when damaged, exposing two reactive ends.
Sunlight causes a chemical reaction which allows the material's crab-shell element, chitosan, to fix the broken rings. Chains of chitosan form cross-links with the reactive oxetane ends to close the rings and repair the network.
In human skin, wounds are healed by a cross-link network of the scar protein fibrin.
The scientists wrote in the journal Science: "An ideal automotive coating would mend itself while a vehicle is driven."
Tests showed that brighter sunlight speeded up the repair process. During summer, scratch healing would be three to four times faster in the sunny southern United States compared with the same level of exposure in the north. "Because cross-linking reactions are not moisture sensitive, dry or humid climate conditions will not affect the repair process," the researchers wrote.