Plastics vs Automobile Industry

Ford considers its Prodigy prototype to be an interim step toward an affordable production hybrid in 2003. Ford's TH!NK city uses polyethylene body panels with an ABS plastic roof. The Precept from GM, unveiled at the 2000 NAIAS, features RRIM-composite parts, panels with Kevlar reinforcement, carbon-fiber components, and expanded polypropylene. DaimlerChrysler's ESX3 concept car is 46% lighter and 15% less costly to manufacture than a comparable metal body. The main structure of the ESX3 has only 12 pieces, compared with up to 100 metal pieces in a conventional car. Thermoplastic elastomer materials from E-A-R Specialty Composites. The underside and top of the roof module that Meritor manufacturers for the Smart car. The Quantum Group has chosen DuPont Hytrel thermoplastic polyester elastomer as a key element in its "future fabric" designs for automotive seating.

Ford became the first of the three PNGV-affiliated automakers to deliver a fully functional hybrid electric family sedan research vehicle to the DOE in October. Called the Ford P2000 LSR (low storage requirement), the five-passenger vehicle's powertrain is 40% lighter than that of a Taurus sedan. Aluminum is used extensively for the engine and body, with carbon fiber, magnesium, and titanium used in a variety of parts for further weight saving. The P2000 is powered by a proton exchange membrane (PEM) fuel cell, with each cell having an anode and cathode electrode separated by a compressed polymer electrolyte.

At the NAIAS, Ford unveiled the Prodigy prototype, what the company considers an interim step between the P2000 and its plans for an affordable production hybrid in 2003 (AEI March 2000). The Prodigy uses the same lightweight material mix as the P2000, having a mass of 1080 kg (2390 lb) and achieving a 3.02-L/100 km (78-mpg) diesel fuel economy, a gasoline equivalent of better than 3.36 L/100 km (70 mpg). Ford relied much more on plastics for its battery-powered TH!NK city electric vehicle that is currently for sale in Norway. The two-seat vehicle has a mass of 940 kg (2075 lb) and features polyethylene body panels and an ABS roof.

GM unveiled its answer to the PNGV program at the NAIAS, the Precept, a fully functional hybrid electric five-passenger sedan that achieves 2.94 L/100 km (80 mpg) (AEI January 2000). The Precept uses a light, stiff spaceframe body structure constructed of aluminum stampings, extrusions, and castings. Exterior panels are made of aluminum and composite materials. The front and rear fascia and rocker covers are RRIM composite parts, and the roof is a structural composite panel with Kevlar reinforcement. Carbon-fiber components total 20 kg (44 lb) and include front and rear bumper beams, headlamp and taillamp mounting panels, front storage tub, and select belly pans. The rear package shelf and headliner are made of expanded polypropylene, as is the substrate for the instrument panel and door trim pads. Total mass for the expanded polypropylene is 35 kg (77 lb). Overall, the mass is 45% less than a comparable steel body design.

In late February DaimlerChrysler unveiled its Dodge ESX3 concept car that depends on technology developed through PNGV. At only 1020 kg (2250 lb), it uses DaimlerChrysler's injection-molded thermoplastic technology first shown in the fall of 1997 in the four-piece Composite Concept Vehicle (CCV). The main structure of the Dodge ESX3 has only 12 pieces, compared to up to 100 metal pieces in a conventional car. But what DaimlerChrysler executives consider the most impressive technical feat is that its lightweight body costs less than a conventional steel body-and much less than other lightweight material options such as aluminum, titanium, or thermoset composites.

The low-cost, lightweight material also helps offset the weight and cost of the mild hybrid ("mybrid") electric powertrain that consists of a three-cylinder, 1.5-L, all-aluminum direct-injected diesel engine and 15-kW (20-hp) peak-power electric motor. The body is estimated to weigh 46% less and cost 15% less to manufacture than a comparable metal one, while contributing to an average 3.27-L/100 km (72-mpg) gasoline equivalent. A patent is pending on DaimlerChrysler's proprietary mix of thermoplastic, aluminum, and lightweight structural foam that make up the ESX3 body. The concept car was actually built with hand-made thermoset materials that match the properties of the injection-molded thermoplastic design. It was also hand-painted, as the technology does not yet exist to mold this particular material with a glossy finish. A combination of aluminum, magnesium, steel, and composites make up the powertrain and chassis of the ESX3.

Computer-simulated crash tests show that the ESX3 concept car stands up to all required federal tests. Data gained from actual crashes of CCV prototype vehicles, in temperatures varying from -40° to +100°C (-40° to +210°F), helped provide the necessary input to get accurate computer test results. Aluminum tubular sections are combined with the injection-molded thermoplastic body sections to provide body stiffness and crisp ride and handling characteristics. The company refers to the thin aluminum sections as the "sparseframe" to distinguish it from currently available vehicles that simply hang plastic body panels over a conventional, metal spaceframe.

While the varying types of composites and plastics used in vehicles today are sometimes difficult to recycle, DaimlerChrysler estimates at least 80% of the ESX3 could be recycled, which could increase in the future as the market for recycled materials evolves. Continued testing and improvements in generating a high-gloss surface color without conventional paint are required before DaimlerChrysler can produce vehicles made with the thermoplastic material. The company first introduced the ESX3's new material technology on Jeep Wrangler hardtops for the 2001 model year (AEI January 2000), a project that includes Husky Injection Molding Systems, Decoma International, Montell, Ashland Chemical, and Paragon Die & Engineering.

Suppliers have also been busy, and will continue to be, developing new materials to enable automakers to achieve PNGV goals. Owens Corning and DSM Automotive Polymers developed a new, patented material system called StaMax P compound, a thermoplastic that compounds PP with longer glass fibers than was possible using traditional composite compounding processes. The firms estimate that the StaMax P compound could replace up to 60 kg (132 lb) of metal on a typical vehicle. The material bridges the gap between traditional short-fiber composite systems and more expensive glass mat thermoplastics (GMTs). This makes it possible to be both cost effective and continue to provide replacement of semi-structural metal parts. The material system uses readily available molding processes, with typical applications including integrated front-end systems, splash shields, and door cassette systems. It is currently being considered by European automobile manufacturers for about 30 individual parts, with active development work under way on about 15 of those potential applications. The first application reached commercial production at the end of last year, with several more expected this year.

VersaDamp is a new family of vibration- and shock-isolation thermoplastic elastomer (TPE) materials from E-A-R Specialty Composites whose formulations can be adjusted to optimize damping performance or durometer, or both. The materials are injection-molded into isolators and other equipment components with limited isolator sway space. Applications include those with wide-ranging operating temperatures, such as small motors, fans, and electrical relay boxes. The materials contain no free sulfur, carbon, or plasticizer.

Roof module technology developed by Meritor Automotive is expected to find its way onto a European passenger car as early as model year 2004, offering a roof module with a 40% weight savings. The technology is currently under active review by several major automakers in North America and Europe, and a version is already in low-volume production for the Smart car. The ready-to-install module is produced through a process where a polyurethane composite is layered between the vehicle's outer roof skin and its interior headliner. The roof exterior-which can be constructed of steel, aluminum, or plastic-is delivered to Meritor pre-formed and painted. Polyurethane foam is injected between the exterior skin and interior fabric.

During the process, aluminum or steel coils are pre-painted to match the vehicle color, then formed using a Meritor-developed "floating" deep draw process that allows the material to move, or "flow," so that the material does not stretch, and in turn the paint is not broken or marred. During the application of the polyurethane foam, resin and fiberglass combinations can be varied throughout the roof, enabling softer areas above passengers and stiffer locations for mounting handles and light housings.

Meritor is also using a polyurethane foam for the vehicle headliner. The foam can be folded to fit through an assembly car/truck roof opening, then affixed to cover the entire interior surface. The company is now testing and validating the encapsulation of various components during module construction and has already successfully integrated wiring harnesses and roof-mounted grab handles. The second-generation modules will integrate a number of other components or systems, including antennae, sensors, sunroofs, telematics, and rollover protection airbags.

DuPont Dow Elastomers introduced two new types of Viton fluoroelastomers at the SAE 2000 World Congress, Viton TBR and Viton IBR, for aggressive powertrain applications. Viton TBR offers improved base resistance and processing characteristics, in addition to the high-temperature performance and chemical resistance of Viton A and B types. Viton TBR is recommended for use in applications with very aggressive lubricants and greases, such as wheel bearing and differential seals, as well as engine crankshaft, camshaft, and valve stem seals when total base resistance is required. For applications in less aggressive lubricants and additive packages, but still requiring better resistance than standard fluoroelastomers, Viton IBR offers improved base resistance and a good balance of properties.

Montell-JPO Co. (MJC), Montell's joint venture with Japan Polyolefins Co., is involved in a cooperative project with Toyota to develop a single PP-based material resin that could be used for automotive applications from dashboards to bumpers. Creating such a material will mean expanding the polyolefin property envelope along every relevant parameter from mechanical performance and processability to appearance and weathering. It would also provide advantages in terms of supply and manufacturing logistics, as well as recycling potential. The projected material will be known as TSOP-6 (Toyota Super Olefin Polymer) and is intended to replace four existing TSOP grades currently supplied to Toyota by MJC and other Japanese producers.

Therban hydrogenated nitrile rubber (HNBR) from Bayer already plays an important role as a base polymer for high-performance elastomers. In automobile engines it reliably withstands both extreme temperatures and exposure to oils and fuels. At SAE 2000 World Congress, Bayer introduced two new grades it says have even better resistance.

HNBR rubber grades are ideal raw materials for elastomer formulations expected to perform even under extreme conditions. This is the case, for example, with fuel hoses and technical rubber goods in cars. Fully and partially hydrogenated Therban grades bridge the gap between oil-resistant nitrile rubber grades and the extremely heat-resistant but very expensive fluoroelastomers. Therban FT (fluoropolymer technology) extends the performance profile of Bayer HNBR grades. These products are also resistant to oxygen-containing fuel components such as methanol, ethanol, and MTBE (methyl-tert-butylether). Therban's usual rubber properties, in particular its low temperature flexibility, are naturally retained. The product can be easily processed in an internal mixer, extruder, or injection-molding machine.

Bayer's development scientists have also responded specifically to the increasingly high long-term temperatures encountered in practice with Therban HT. Compounds that contain this component as well as standard grades can resist long-term temperatures of up to 165°C (329°F), an improvement of about 15°C (26°F). Under such extreme conditions, Therban HT retains its property profile twice as long as previous HNBR grades. This means that the service life of a timing belt, for example, can be doubled. In addition, the HT elastomer is able to resist the aggressive lubricant additives that are being used more and more frequently in high-performance engines.

DuPont and The Quantum Group announced at SAE 2000 World Congress that the two firms will be working together to develop future fabrics for automotive interior seating applications in response to and in anticipation of future trends in reduced foam seats. A fabric made of DuPont Hytrel thermoplastic polyester elastomer provides mass and space savings, while improving driver and passenger comfort. Conventional automotive seats have an estimated 13.6 kg (30 lb) of foam, which the companies believe could be dramatically reduced using Hytrel polyester. New elastomeric fabrics based on Hytrel technology can also replace springs in foam-based seat systems.

The fabric features resistance to creep, impact, and flex fatigue, while also providing flexibility at low temperatures, and good retention of properties at elevated temperatures. It also resists deterioration from numerous chemicals, oils, and solvents. These properties have made Hytrel successful in other automotive applications including airbag deployment doors, air-intake ducts, and constant velocity joint boots.

DaimlerChrysler announced in mid-March that it has developed a cost-effective, fiber-reinforced ceramic for use in brakes. Ceramic brakes have several advantages over conventional materials. They are heat and rust resistant, while having one-third the mass of steel. They are also not subject to wear or warping, thus being essentially maintenance free. However, fiber-reinforced ceramics, which overcome the problem of brittleness of traditional ceramic materials, have been too expensive for large-scale use. With a combination of carbon and silicon developed by DaimlerChrysler researchers, brake discs made from fiber-reinforced ceramics can be produced on a large scale.

Initial field studies have shown that ceramic brakes perform still reliably after about 300,000 km (180,000 mi) of use. Brake disk changes are not needed, saving the time and expense of maintenance. To produce the fiber-reinforced ceramics, short carbon fibers, carbon powder, and resin are first compressed and then heated to and held at about 1000°C (1830°F). During this process, the carbon bonds to form a stable framework similar to when pieces of ice fuse together. When cooled, this material can be shaped into the desired form. After grinding the brake disk blank to size, the finished blank is reheated together with silicon, causing the pores in the carbon framework to absorb the silicon. This fiber-reinforced ceramic material cools overnight, and the dark gray brake disc is ready for use.

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