More than surface

Wolfgang Schaefer from Freie Anwendungstechnik (FAS) has many years of experience in surface coating in the automotive industry. He sees three core topics that will become increasingly important in the coming years: autonomous driving, car sharing and new functional elements.

Image: Kunststoffinstitut Lüdenscheid

Focusing on the first he gives insights in coming trends for the coating industry. In the course of autonomous driving, a car is increasingly equipped with complex sensor technology, the signals of which the protective outer skin ideally transmits without interference. Plastic covers, so-called radomes, protect these sensors and integrate them inconspicuously into the exterior design.

“And that`s where things get complicated, because on the one hand you want signals not to be absorbed, broken or scattered, and on the other hand you want radomes to shield external interference,” says Schaefer. Even the slightest angular error of 1° caused by radar reflection results in a lateral error the width of a motorway lane in 100 m, as experts from BASF’s Coatings division reported at the Plastics Painting Conference organized by the Kunststoff Institut Lüdenscheid. Investigations have shown that not only the substrate thickness, but also each individual layer thickness and its composition have a relevant influence on the signal attenuation during paint build-up. A higher number of layers tends to lead to a higher proportion of reflections. “Black is generally well transparent to radar radiation, white in multilayer structures and metallic paints, especially silver shades, are still problematic in some cases,” adds Schäfer. In addition, various sensor systems are used for autonomous driving, which are based on both sound and electromagnetic waves and operate in different frequency ranges. These different signal types and frequencies also play a role in transmission, reflection and absorption by the radome. The reflection minimum should be in the range of the respective signal frequency in interaction with the respective substrate thickness. In addition to the layer thickness of the clear coat, basecoat and primer, possible influencing factors include the primer conductivity as well as the pigmentation and application of the basecoat.

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