Still, it would be disingenuous to report that all is well in the world of reinforced thermoset plastics, and especially in the all-important automotive end-use market. Thomas Schuh, manager, polymer and composite applications at carmaker DaimlerChrysler, said of reinforced thermoset parts, "It''s difficult to integrate a glass-fiber-reinforced part into a car full of thermoplastic and metal parts." He said the composites industry, and especially that portion processing thermosets, needs to develop a more vertically integrated, automobile-experienced process chain if it wants to catch and keep carmakers'' attention.
In other bad news for thermosets, German truck maker MAN Nutzfahrzeuge, which, like DaimlerChrysler has for years been on the leading edge in its use of sheet molding compound (SMC), plans to shift a number of parts from SMC to thermoplastics or back to steel or aluminum. Hartmut Häberle, in charge of MAN''s use of plastics parts in drivers'' cabs, noted the A-pillar, wind screen, battery box cover, step assist and some other SMC parts on MAN trucks all are now transitioning to molded thermoplastics. "The smaller the part, the better chance that thermoplastics perform better in inline painting, that they more resemble steel, and that they have lower costs," he explained.
Reinforced plastics, both thermoplastics and thermosets, have made huge strides, of course. "When we discuss bumpers, we don''t even bring up what material will be used; plastics are a given now," noted Schuh, who added, "But when we discuss fenders, then we discuss the choice of material to death."
The use of natural fibers in automotive parts was a common thread running through many of the 54 submissions for three awards given during the conference. Awards are in three categories-industrial, environmental, and for best university work-and MPW had the good fortune to serve as one of the judges.
Taking home prizes
Automotive interiors specialist Johnson Controls won in the environmental category for its innovative process for re-using scrap wood fibers. The processor stamps wood-fiber sheet (impregnated with epoxy resin) to form seatbacks for the front seats on the current DaimlerChrysler S-class sedan. Trimmings from the stamping process are collected, granulated, and-using a process developed by FiberGran (Oderwitz, Germany)-mixed into polypropylene (PP).
Additives added to the shredded scrap help inhibit smells, often a problem with natural fibers. The outcome is injection moldable 50/50 wood/PP pellets which Johnson Controls uses to mold hooks that are vibration welded to the back of the stamped wood sheet; these hooks affix the backrest to the rear of the front seats.
The firm will not stop at seatbacks. Eugene Prömper, director of materials and process engineering at Johnson Control''s Grefrath, Germany facility, noted that car door liners of natural-fiber-reinforced thermoplastics are increasingly common, but armrests attached to these liners typically are molded of PC/ABS. The dissimilar materials can expand or contract at different rates at extreme temperatures and humidity, with the result being cracks between armrest and panel. Mixing wood scrap into the thermoplastic could alleviate the problem.
A novel metal replacement application was presented by Composite Materials GmbH (COMAT; Kaiserslautern, Germany), in which fiber-reinforced, pultruded PP profiles from COMAT are used to replace metal/rubber straps now employeed as stretch bands wrapped around truck fuel tanks. The thermoplastic solution, reinforced with continuous glass fibers supplied by Johns Manville (Denver, CO), includes the same type of fastening system as the metal/rubber ones it hopes to replace, so OEMs see no change in their assembly process.
What OEMs do get are bands that weigh about 1 kg less, never rust (so no need for lacquer), and are easily recyclable. Cost is equivalent or less than that of steel bands. Markus Ringeisen, COMAT''s automotive market manager, estimates the global market for these bands at about 6 million/yr, of which 1.2 million are used in Europe. Ralf Funck, COMAT director, says three leading European truck manufacturers-DaimlerChrysler, MAN, and Iveco-are testing the bands, and he expects commercial use starting next year.
Matthew Defosse [email protected]
