VW discusses plastic body panels

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LAS VEGAS — A Volkswagen AG engineer described research the German automaker has done into production of finished, colored exterior body panels made from polycarbonate blends with ABS and polybutylene terephthalate (PBT).

Joerg Hain said at Antec 2014 the PC blends expand like metal and offer good temperature resistance. Foamed injection molded plastic is lighter than aluminum — an attractive quality as carmakers try to shave off pounds to increase fuel economy.

Hain is an engineer specializing in plastics at VW’s research group for materials and manufacturing in Wolfsburg, Germany.

He said VW has looked at thermoplastic foaming technology to further reduce weight. Foaming also can reduce material costs by up to 30 percent compared to solid PC/ABS, he said. Injection and mixing happens inside the barrel, and after the part is injected, the mold is opened.

“The open time of the mold, it’s important for stiffness,” Hain said.

An in-mold polyurethane coating system gives the body panels a high gloss. The coating process also can give special color combinations, and three-dimensional graphics, Hain said. He showed a video of another unusual benefit: after a key scratches the car door, the scratch gradually disappears under high temperatures, or even under normal sunlight, in what Hain called a “reflow effect.”

VW got help from Germany’s Ostfalia University of Applied Sciences.

Answering an audience question, Hain said that so far, he has made some small parts using the foamed plastics process.

He displayed a slide showing the comparative cost of body panels from different resin blends versus steel and aluminum.