Back in the 1980s, PU was a very specialised material in automotive paints: now it is used in all layers of a car paint system, says Bayer expert
Polyurethane is now used somewhere in the coating of each and every car. The various body coating layers use polyurethane to different extents, with the trend towards high performance and water-borne materials favouring wider use of urethane resins.
PU is especially widely used in plastics coatings, and since more and more plastics components are used internally and externally in the car, more and more PU coating materials are being used.
Not all of a car’s plastics parts are coated, but when they are, then PU is usually involved.
A metal car body is protected in the majority of cases by four paint layers, as pictured in the diagram on p34: first is the electrodepositon coat (EDC) for corrosion protection. Next comes the primer surfacer layer for levelling out the surface structure and for stonechip resistance before the third layer, the base coat, containing the colour, is applied. Finally a clear top coat is applied to protect the colour coat and for long-term brilliance of the whole car.
This piece is based on a 1 Aug 2012 telephone interview with Lothar Kahl, head of industrial marketing for the automotive coatings raw materials business at the Coatings, Adhesives and Specialities unit of Bayer MaterialScience. Kahl explained the purpose of these layers, and gave some insight into how trends in the coatings…