NPE: toward the plastic car

Automotive Design & Production, Sept, 2003

The plastics industry makes no secret of the fact that it would like to replace as much of the steel on vehicles as possible with its injection molded wares. And at the recently concluded National Plastics Exposition (NPE) plastics companies showed the products that together Form the latest attacks on traditional materials. With plastics formulations and processing becoming increasingly sophisticated, problems associated with exterior applications like consistently achieving Class A surfaces and withstanding high paint booth temperatures are being solved. At the same time, plastics developers are targeting structural components like front end modules and other mainstays of stamped steel like seat Frames. Whether the plastics industry can succeed in eating the lunch of their Ferrous Foes is still an open question, but it won't be for lack of trying.

GE Plastics' latest automotive development, a weatherable polymeric film dubbed Lexan SLX has already found its way onto a current application, albeit one available only in Europe. The new Smart Roadster-Coupe will come equipped with a roof module that will have a Class A molded-in-color surface of Lexan SLX film that has been co-extruded with two other layers of plastic. GE Plastics says that the hard surface thermoplastic film retains 95% of its gloss in testing that simulates ten years of Florida sun exposure, and performs as well as current exterior painted surfaces. It doesn't require a clear coat and can be applied over various thermoplastic and thermoset substrates.

Dupont's latest attempt to replace stamped steel exterior panels with plastic is its new Shine-E Rynite thermoplastic polyester. The material can withstand temperatures as high as 200[degrees]C for 30 minutes, and can be run through dip tanks and paint ovens right along side its stamped steel counterparts. "On-line painting overcomes a major hurdle in plastic exterior panels because it greatly simplifies color matching and cuts total costs," says Dave Ritchey, Rynite global business manager. Other thermoplastics have been able to take paint oven temperatures, but Rynite's new twist is that it has minimal moisture gain. That means that unlike panels made with sheet molding compound (SMC), it produces no moisture "pops" in the paint baking process. It also means that its dimensional stability is not affected by humidity, so it can meet the high fit and finish requirements of exterior panels. Dupont says it has provided samples of the material to several OEMs and is targeting its use for vertical exterior panels like fenders and doors.

BASF has targeted structural steel applications with its Ultratect thermoplastic structural foam (derived from the high-temperature Ultrason E resin). The first application is the rear seat backrest for the BMW M3 CSL which consists of a 25 mm core of Ultratect sandwiched between two 1 mm sheets of polypropylene reinforced with continuous glass filament. The part is made in a 1.5 minute single step operation that heat-forms the polypropylene sheets onto the cold foam in the mold. BASF says that the 5.5 kg. part is half the weight of the steel structure that it replaces.