Automotive: High Class
Composites are making inroads on 2002 model cars and trucks, and not only in their traditional role as body panels. Parts molded of bulk molding compound (supplied by Premix Inc.) include headlight re...
Composites are making inroads on 2002 model cars and trucks, and not only in their traditional role as body panels. Parts molded of bulk molding compound (supplied by Premix Inc.) include headlight reflectors for the Honda Accord; the sunroof frame on Toyota’s Avalon; and Ford Explorer cam covers.
In their traditional niche as low-volume body panels, sheet molding composite, (SMC) and reinforced reaction injection molding (RRIM) are also growing. The Automotive Composites Alliance estimates 2002 models will see a 9% rise in the volume of composites used, compared with 2001 usage. Most of that growth is in the trucks, SUVs and “crossovers” segment which now accounts for half of all U.S. light-vehicle sales (see sidebar, p.15).
In niche-vehicle and medium-volume applications, composites have advantages that other materials can’t match: rust-free durability, lower tooling costs, lighter weight, and styling freedom to quickly customize vehicles.
The 2002 Ford Thunderbird stands out for its high SMC content. Sixty percent of the car’s exterior panels are made of thermoset composites. The Thunderbird’s roof is the first production use of SMC for a full roof module that integrates the inner and outer panels, headliner, framework for the porthole windows and all seals, lighting, hatches and hinges.
Although composites are a well-established alternative for certain parts, the challenge now is to move them into other areas of the vehicle, and to move them into higher volume applications.
“With reaction injection molding (RIM), we’re asking, How do we grow the product in the front fender applications? That’s an area we want to work on,” says Allan James, senior R&D leader with Dow Automotive. The first foray into front fenders has already been made on trucks.
LFI HOLDS PROMISE
Higher expectations of composite materials have prompted process innovations that may open new doors for polyurethane RIM.
Polyurethane materials supplier Bayer Corp. reports that each of the major polyurethane processing machinery manufacturers has developed competing technologies to process long glass fibres along with the polyurethane system as a one-step process.
In the long-fibre injection (LFI) process, a glass chopper gun is attached to the mixhead, which is mounted to a robot. The robot is programmed to move over the mold cavity while dispensing both the long glass fibres and the polyurethane SRIM formulation in an open-pour method. The mold is then closed.
The primary benefit of this technology, according to Bayer, is the automation of the structural reaction injection molding (SRIM) process, making glass-fibre reinforced parts more economical to produce.
The LFI method also makes it possible to have varying amounts of reinforcement throughout the part. It is suitable for either foamed or solid SRIM formulations, and can be used with two-component in-mold paints.
Both Bayer and Dow Automotive have installed LFI machines in their labs to further investigate this process.
In May, Dow Automotive installed a LFI molding machine manufactured by Krauss Maffei at its automotive research and development facility at Modeland Centre in Sarnia, ON.
“We think this will be one of the big growth areas for polyurethanes once the economy turns around,” says James. Early development work will be focused on large structural components and pick-up truck end gates. Future developments are expected to include instrument panels, interior trim components and noise, vibration and harshness (NVH) applications for the global automotive industry.
This equipment is capable of producing full size parts, which can be used to more accurately demonstrate production molding capability and part performance, facilitating smoother production launches.
One of the possible limitations of this process, says James, will be the ability to cover large vertical surfaces of the mold, because the polyurethane formulation is sprayed in an open mold.
In addition to the new machine, Dow Automotive capabilities at Modeland Centre include full-scale RIM molding for component testing and development, and several foaming machines for application development and testing.
Similarly, Bayer created last fall a fully-automated Long Fiber Technology Lab at its Polyurethane Application Development Center in Pittsburgh. Bayer will use the lab for internal development programs and to assist customers with applications development.
The lab includes the first Class I, DIV2 robot of its type in the world to handle the polyurethane mixhead and glass chopper. It is rated to work in close proximity to combustible materials, which includes some polyurethane in-mold coatings. The LFI injection press is a 150-ton model, with a 4 ft. by 6 ft. platen. The lab also includes in-mold coating equipment.
Bayer cites significant opportunities to use LFI technology in automotive, agricultural and construction equipment markets.
“We also see long-fibre technology as one alternative for composites fabricators that must comply with styrene emission limits (announced in 2001 by the U.S. government),” says Harry George, manager of Bayer Specialty RIM business. “Long-fibre technology with polyurethane RIM engineering resins does not produce styrene emissions, and it can be used to produce many of the composite parts now produced with polyester resin.”
George notes that the roof of the DaimlerChrysler Smart Car is produced with the LFI process. Prior to injection, a sheet of thermoplastic material and the headline material for the interior of the roof are placed in the mold. Thus, a complete roof is produced in each molding cycle.
In automotive interiors, equipment supplier Cannon reports that RIM skin molding is gaining popularity for producing thin-walled interior parts (less than 1 mm thick), such as door panels, consoles, arm rests and dashboards. Cannon displayed a lab line for RIM skin molding at K 2001. The company says RIM skin molding of imitation leather achieves improved part quality, reduced costs and process advantages compared with conventional PUR-based systems.
THE NATURAL ALTERNATIVE
Soy-based polyurethanes have reached commercial status in the past year. John Deere tractors are believed to be the first commercial application of a soy-based polyurethane RIM. Beginning with 2002 models, the entire line of John Deere Harvester Works combines will include body panels molded with HarvestForm composite, some of which will use Bayer’s Baydur structural foam polyurethane RIM system incorporating a soybean-based polyol component.
“When the program received a green light from John Deere, Bayer set to work to develop a Baydur structural foam formulation that would produce physical properties and processing parameters equivalent to our conventional Baydur formulation,” explains Harry George of Bayer.
G.I. Plastek is molding a 52-lb. Class A rear wall of the John Deere 9650 and 9750 STS model combines. The part measures 7 ft., 10 in. wide by 5 ft. 9 in. high.
“We are excited by using a renewable resource for our products,” says John Cerny, an engineer for John Deere, who was responsible for this program. “Deere is committed to using crop-based materials because it directly benefits our customers. In terms of performance, the parts are comparable, or in some areas, improved.”
John Deere expects that the long-term cost of molding with soybean and corn could be less than the traditional petroleum-based compounds used in the past, and estimates that it will use approximately 600,000 of the RIM-based panels on production models.
Because oils and fats from soybeans are chemically similar to petroleum, it is speculated that bio-based polymers can be used to replace petroleum-based plastics. Urethane Soy Systems, for example, produces bio-based polyols. The company’s SoyOyl brand polyols are used to produce rigid and flexible polyurethane foams.
Various U.S. universities are currently researching bio-based plastics. The United Soybean Board has identified urethane foams, urethane binders and agricultural film as three market segments that offer the b
est opportunity for soy-based plastics.
APPEARING ON A TRUCK NEAR YOU
The use of composites to differentiate vehicles in the same model line is particularly evident in the Ford Expedition and Lincoln Navigator that will debut in December 2002, says Mike Dorney, chairman of the Automotive Composites Alliance, and vice-president sales and marketing for The Budd Company’s Plastics Division. “The Navigator has an SMC hood, front fenders and grille opening reinforcement, that allows Ford to differentiate the vehicles at lower cost for tooling than steel.”
In the Chevrolet Avalanche, the tailgate and mid-gate are made of an SMC/SRIM hybrid sandwich. The tailgate is 15 lb. lighter than a comparable steel assembly.
For Toyota, The Budd Company Plastics Division will mold a pick-up truck inner box of SMC. Budd will build a new facility in the Tijuana area of Mexico to supply Toyota’s new truck bed facility planned for that region. Budd-made SMC pick-up boxes are also featured on the Ford Sport Trak.