PU coating heals itself

According to Marek Urban at the University of Southern Mississipi in the USA, "We developed a polymeric material that is able to repair itself by exposure to the sun." The self healing coating uses chitosan, which is found in the shells of crabs and shrimp. This is incorporated into traditional polymer materials, such as those used in coatings on cars to protect paint. 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, eventually smoothing the scratch. The process can take less than an hour. Urban said the new coating uses readily available materials, offering an advantage over other self-repairing coatings, which he said were "fairly elaborate and economically unfeasible." The team tested the compound's properties using a razor-blade-thin scratch. "We haven't done any of the tests to show how wide it can be," He said that 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 low 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: "Clearly, there are future applications of this work in the repair of automotive components, which extensively use polyurethane polymers, that have suffered minor damage," Urban said the coating could be used in packaging or furniture or anything that requires a high-performance type of coating, adding that his team has patents pending and is considering commercialization.