Molding the future of Auto Exteriors

According to one estimate, North American vehicle production currently consumes about 700 million pounds of exterior plastics, and is expected to grow to 900 million pounds by the year 2002. This upward trend in use of plastics in automotive exterior design is being driven by market conditions faced by the car companies. These have dictated continuing efforts to reduce costs, create more stylish, distinctive models and cut vehicle weight in order to meet increasingly stringent fuel efficiency standards. The pressure to meet all these objectives is leading to new ground-breaking technical developments, as well as new business opportunities and responsibilities within the supply base, says Al Power, president and CEO of Decoma International Inc. (Concord, Ont.).

The Tier 1 heavyweight, with 1998 sales of Cdn $656 million, has averaged about 25 percent growth in sales over the past two years. A large factor contributing to that growth has been several contracts that have given Decoma complete responsibility for engineering and supplying the entire exterior appearance of the vehicle. Having sole responsibility for a vehicle’s exterior allows Decoma to capitalize on economies of scale that reduce cost in comparison to single-sourcing each component of the exterior, Power notes.

“The amount of emphasis placed on cost has gone up,” says Power. “Our customers are getting more and more aggressive in terms of their expectations for cost reduction actions. The amount they’re mandating has gone up.”

Power says while the systems approach for supplying the interior of a vehicle has been used successfully for a number of years, the industry has been slower to adopt systems sourcing for the exterior, which is more logistically and aesthetically challenging.

“You can’t assemble the exterior of a vehicle and drop it into an assembly plant,” notes Power.

Nonetheless, Power sees the newer trend to systems sourcing of the entire exterior of a vehicle as a logical extension of the approach car companies have used in recent years of sourcing, for example, bumpers or trim as a system. Complete vehicle sourcing is a huge benefit to a company like Decoma, Power says, because, unlike smaller companies, it has the financial and technical resources to manage the entire exterior of the vehicle.

As a source supplier of a vehicle’s complete exterior, Decoma’s involvement in a project begins after clay models have been made and scanned. Decoma handles all aspects of part design and development, including material specification and testing. In a bumper system, for example, Decoma will be responsible for developing everything from the radiator support forward, which would perhaps include support brackets, a cooling module, grilles, bumper beams, electronics and other parts. The new responsibilities have required Decoma to add significantly to its design and engineering staff, says Power. It has also affored Decoma’s supply base ample opportunity for growth.

“A bumper today may sell for $75 (Canadian) whereas a front end module could sell for anywhere from $500 to $700,” notes Power. “Much of this could be purchased, so there’s plenty of potential for new business for our suppliers.”

PAINTLESS OPTIONS GROWING

Extending the use of thermoplastics on the vehicle exterior has involved a host of on-going material and process refinements. The hottest trends include molded-in color, the use of in-mold films and resins that increase the transfer efficiency of paint on plastic parts.

DuPont Automotive’s (DuPont Canada Inc., 75) Surlyn Reflection Series molded-in-color supergloss alloy is getting its debut use as the material for the front and rear bumper fascias of the model-year 2000 Dodge and Plymouth Neon. The supergloss alloy is an engineered alloy of ionomer and polyamide resins. John Wahl, executive marketing manager, DuPont Automotive, calls the Surlyn Reflection Series the successor to DuPont’s Bexloy W molded-in-color ionomer alloy first used for the front and rear bumper fascias of the 1994 Chrysler Neon.

Wahl says the Surlyn supergloss alloy offers scratch and mar resistance equal to or better than painted plastic, excellent color and gloss matching and good moldability. While the alloy is more costly than a TPO, those costs are recouped by savings on paint and investment costs for paint equipment, Wahl claims. The alloy also allows reduction of VOC emissions associated with a paint operation and is more readily and economically recyclable than painted plastic, says Wahl.

Decoma’s Power says the North American consumer’s long-term acceptance of molded-in color, such as that used in MMC’s all-plastic-exterior Smart Car, recently introduced in Europe, remains to be seen. Two traditional concerns with molded-in color material has been its gloss retention and scratch resistance. At this year’s Society of Automotive Engineer’s (SAE) conference and exhibition in Detroit, however, a paper presented by DuPont’s Michael Day and William Johanson gave evidence that gloss retention and scratch and mar resistance of Surlyn supergloss alloy met performance standards most commonly accepted by the North American automotive industry (see Table 1).

Avery Dennison recently announced that its Avloy formable paint film laminate (66) has been selected by General Motors for use on thermoplastic bumper caps for the GMT 800 Series of trucks. Avloy paint-film laminate is an OEM approved dry-paint film specifically formulated and designed for use with injection molded parts. The dry paint-film laminate is supplied in roll form to the molder and is thermoformed and precision trimmed into shape of the finished part. This preform is then inserted into the injection mold cavity causing a melt bond to form between the film and the final molded part.

Another type of paintless film was introduced at K’98 by BASF (67) and featured at the company’s booth at this year’s SAE show. The paintless film process is being used to produce body panels and other components in a new all-plastic vehicle, the Paradigm, manufactured by Huatong Motors in China. Automotive Design & Composites, Ltd., San Antonio, TX (68) developed and built the Paradigm prototype.

According to BASF senior account manager Donald McLean, the paintless film process starts with co-extruding a three-layer sheet consisting of a top layer of clear acrylic, a second layer of pigmented Luran S ASA, and a third layer of either ASA or ABS. Next, the co-extruded sheet is thermoformed and trimmed to the shape of the desired panel. In the final step, says McLean, the thermoformed film can be placed in the cavity of a mold and injection or compression molded with base resin backing. McLean says one ideal application for the process is outside mirror housings. Often, McLean notes, up to 80 percent of mirror housings are made in one color, for instance black. With the paintless film, additional colors can be made with the same tool simply by inserting the film into the mold.

While acknowledging that in-mold film processes have improved, Decoma’s Power expresses caution about the technology: “In-mold films have some merit, but still they’ve been in the development stage for 15 years. There’s still a lot of work to be done.”

Power notes that the advantages of in-mold films are largely related to the economics of painting.

“Where we do see a place for in-mold film is in places like emerging markets, where you don’t necessarily want to make a $100 million dollar investment in a paint plant,” says Power.

THERMOPLASTIC BODY PANELS LOOKING MORE CERTAIN

The exterior body panels of a typical passenger car account for as much as 35 percent of the total mass of a vehicle. Making body panels from thermoplastic instead of steel could reduce this portion of a vehicle’s mass by as much as 55 percent, according to one estimate.

Chrysler, with its recently announced plans to build body panels out of PET, is one of several car companies that have made it a goal to extend lessons learned on concept cars and make production vehicles with all-plastic body panels.

While car companies have had
their sights set on making exterior body panels out of lightweight, corrosion-resistant, recyclable thermoplastic resins for some time, actual production applications, though growing, have been held in check by a number of factors. Most significant of these is the need for a thermoplastic resin to provide suitable stiffness, modulus and strength, while still providing good moldability characteristics and a class A surface finish along the entire length of the finished part.

A new materials development using “nanocomposites” may soon result in thermoplastic body panels that meet all of these requirements and pave the way for widespread use of the material on production vehicle lines, says Al Power.

Still in the development stage, the new technology uses small amounts of a nanocomposite filler in a base resin to achieve significant increases in various structural properties. A nanocomposite in this case means a clay-reinforcing particle with dimension at the nanometer level (10(-9)m). The improvement occurs without loss of Class A finish or melt flow properties. The materials development project, which involves Decoma and Dow Chemical Co., is a year and a half ahead of schedule, according to Power. The project is apparently similar to one announced recently by Montell North America and GM.

“We’re damn optimistic (about this material) at this time,” Power says.

Power describes the process as essentially taking traditional fillers and peeling all the layers off microscopically. The microscopically engineered filler is mixed into the base resin and injection molded by conventional means. He says that for a typical bumper system, the material will improve flex modulus by a factor of three to four, with no decrease in impact strength or no decrease in melt flow.

Power says they’re looking at using the new material in a host of automotive applications which include, but are not limited to, fascias and body panels. “If this is successful, it’s a breakthrough for the plastics industry,” says Power. CPL