Optimism reigns in the world of automotive design

Officials interviewed at this year''s Plastics in Automotive Design conference in Mannheim, Germany were noticeably upbeat about the chances for plastics to penetrate further into automotive applications.

This relatively small (about 1400 attendees) event, organized each spring by Germany''s plastics engineers association, punches an impact well above its weight. That''s no surprise since the paychecks of one-seventh of the country''s workers are tied to the automobile industry, with OEMs including DaimlerChrysler, BMW, Volkswagen, and Porsche calling the country home. Plastics experts from these and other OEMs, and the processors, plastics suppliers, and moldmakers who hope to work with them, all flock to Mannheim.

Leading plastics suppliers discussed developments that seem sure to boost plastics use in automotive. For instance, Greg Adams, newly crowned VP plastics (automotive) at GE Advanced Materials (GEAM; Europe HQ Bergen op Zoom, Netherlands), says the firm is set to commercially introduce materials technologies it calls High Modulus Ductile (HMD) and High Performance ThermoPlastic Composites (HPPC).

HMD and HPPC make use of current GE materials-Noryl PA/PPE, Cycoloy PC/ABS, and Xenoy PC/PBT-but improve them using unidentified nanofillers. Mark Kingsley, GM global automotive marketing, explains, "We didn''t just look at this [improving our materials] as a filler problem-we looked at this as a fundamental chemistry issue" to be dealt with at the molecular level.

Peter Stahl, GEAM''s global body panels technology manager, says the new HMD products help GE to "cut CTE [coefficient of thermal expansion] in half" compared to currently available plastics. All the new materials "incorporate nanomaterials but keep very good ductility," he says; the nanofillers used, which Kingsley says are unlike others in use, do not alter the base materials'' densities much from unfilled ones.

The HMD grades of Cycoloy and Xenoy will be injection moldable and suitable for molding offline paintable substrates. In addition, "We''re working on a Noryl HMD for online e-coating," says Stahl. The offline paintable materials will handle baking at 90_C for 30 minutes. HPCC materials are thermoformable and suitable for use in horizontal body panels. "We''ve a material [HPPC] that has a CTE between aluminum and steel," says Stahl. These parts will have Class A finishes with "no pretreatment required, just apply paint."

Plastic plus metal equals synergy

Talks in Mannheim indicate that the technologies for injection molding hybrid metal/plastic parts are making headway. At Lanxess, Ralf Zimnol, head of application development (transportation), says the firm is developing materials specifically for these hybrid parts. With Durethan Easy Flow and 30% glass-fiber-reinforcement (GFR), "we can reduce wall thickness of some areas [of a hybrid part] up to 12 mm," he says. Plastics comprise most of the cost of these parts, so reducing plastics use is a big issue.

Soon, says Zimnol, Lanxess will offer a polyamide with 60% GFR for hybrids. The higher loading gives it a stiffness at room temperature of 20,000 MPa, about double that of 30% GFR-PA. Lanxess is also working with an aluminum manufacturer to determine whether aluminum sheet could replace steel sheet in hybrid parts.

Hybrid parts are not limited to front ends, notes Zimnol. Lanxess worked on a hybrid side-door project for an Audi sedan that he says "is developed all the way to production," though not yet commercial. "These doors offer much more parts integration [opportunities] than front ends," he says.

Last year Dow Automotive (Schwalbach, Germany) displayed a prototype hybrid front end for the VW Golf 4. It was made using Dow''s Low Energy Surface Adhesive (LESA) technology, and this year ramp-up for a commercial LESA-manufactured hybrid front end is underway, says Roland Janssen, market manager plastics, Europe for Dow Automotive. Non-disclosure agreements prevent him from naming the car. "The OEM is seeing weight reduction of 25% versus the hybrid technique they had been using," he says.

The trick to LESA is that the molding includes a closed-box design, with the box "closed" by a metal insert. "The closed box gives a highly stiff structure, so you can reduce weight without losing stiffness," explains Janssen. Long-glass-fiber-reinforced polypropylene (LGF-PP) is used, with no pretreating (flaming or priming) of the PP required; metal inserts are applied with adhesives marketed by Dow. Dow also supplies the LGF-PP used.

The firm also is working on LESA-manufactured instrument panels (IP). Janssen says these can eliminate the need for an aluminum, magnesium, or steel crossbeam. Plus, the molded-in U-shaped box can serve as an air duct, negating the need for an additional part. Dow developed and "completely validated" an IP with a European OEM; series production is awaited. Dow also has LESA-made tailgates in its crosshairs. "Using adhesives in the Tier community is not a common thing," he admits, "but those now doing so are very enthusiastic about it."

Still, with hybrid parts, it''s horses for courses, notes Karsten Guse, marketing director at Tier supplier Decoma, with European headquarters in Altbach, Germany. The firm molds the hybrid front-ends for the Mercedes A-Class vehicles using an unidentified hybrid molding technology, but also molds front ends for the VW Golf A5 with metal supports ultrasonically welded to the LGF-PP moldings. Welding won out for cost reasons. "Molds for hybrid parts are very, very expensive," he explains.

Hard news on software developments

Work at BASF continues on the firm''s collar molding technology for joining molded parts to metal. Plastics and metal parts are joined postmold by mechanically pressing a collar protruding from the metal component into the plastic assembly. Postmold assembly of a hybrid part provides more design freedom, allows for the use of less costly molds, and can reduce cycle times, according to BASF.

The supplier has worked with Visteon, already a leading supplier of hybrid front ends, to further develop collar molding, and it says it''s also working with other processors, and not only for front ends. BASF also says finite element analysis has proven that the performance of parts made using collar molding can be accurately predicted, which should help speed commercial acceptance.

"Immense" interest in CBT

Dow Automotive is working with Cyclics Corp. (Schenectady, NY) to develop and market the latter''s cyclic polybutylene terephthalate (CBT) for the automotive market. "We''re the exclusive outlet to the mobility industry for Cyclics," is how Peter Cate, European market development manager, CBT resins, explains the relationship. (CBT melts to a water-like viscosity when heated and with the use of a catalyst polymerizes into PBT; for more on CBT, see Notable Materials on p. 46.)

The Dow/Cyclics relationship reaches back to 2002. Cate says Dow is in the "last stages of formulation" for development of injection moldable CBT pellets, working with two partners to validate the material. Dow polymerizes the material so that the pellets are readily processable. CBT is a Cyclics'' trademark; Dow calls its pellets pCBT ("p" for polymerized).

Dow''s work is a long-term project, but one Cate predicts will, by 2010 or sooner, explode like a bombshell on the automotive market. "The interest in structural automotive components has been immense," he says. It arises because the material will process essentially the same as standard PBT, but parts will withstand the 205_C e-coat baking that carmakers use for metal parts.

The material also-and Cate says most importantly-will absorb practically no moisture, meaning that there is no postmold shrinkage, "so OEMs don''t need to leave large gaps between metal and plastic parts," he explains.

TPU keeps its color

In Mannheim, Bayer MaterialScience announced new developments including grades of thermoplastic polyurethane (TPU) that remain lightfast over a car''s lifetime, even when dyed in light colors. The TPUs are suitable for coextrusion onto thermoformed ABS parts to give these a soft-touch surface, or can be used to coat industrial fabrics, non-wovens, and interlaced yarns.

Jens Uferman, automotive segment manager in Bayer''s TPU business unit, predicts the material will see use in trunk floor mats, rear shelves, and door and other trims. For instance, a fabric/TPU composite could be rear injection molded onto a substrate. Coated ABS could see use in instrument-panel components. Bayer says TPU coatings realize better mechanical properties and scratch and abrasion resistance than ones of PVC or polyolefins.

Matthew Defosse [email protected]