Metal to Plastic Under the Hood

Plastics makers are moving into what has long been metal territory with applications that can reduce weight.

Several plastic makers are now producing components and subsystems once considered the sole domain of steel and-yes-even aluminum. Thermoplastic can mean up to a 30 to 40% weight reduction over equivalent metal components in many under hood applications, but cost reductions have gained the most attention. That's right: plastic components being cost competitive with metal.

To hear the plastic engineers and executives tell it, it wasn't long after the latest Corporate Average Fuel Economy (CAFE) standards were signed into law that Tier 1 suppliers and OEMS suddenly began returning phone calls and replying to long-dormant emails. In some cases, the classic cost versus lower weight calculations required serious recalibration given the long-term implications of both CAFE and Euro V emissions regulations. As a result, several plastic makers are now producing components and subsystems once considered the sole domain of steel and-yes-even aluminum. Thermoplastic can mean up to a 30 to 40% weight reduction over equivalent metal components in many under hood applications, but cost reductions have gained the most attention. That's right: plastic components being cost competitive with metal. It's being achieved through the use of increasingly sophisticated integrated designs and because of the lower machining costs associated with some polymers.

Here's a look at some of the materials developed for under-hood use.

 

BASF

Ultramid B3ZG7 OSI (optimized for stone impact) from BASF Corp. was designed specifically to take a pounding from rocks and stones in North American vehicles which, unlike their European counterparts, usually don't have protective underbelly pans. The Ultramid PA material is made of a polyamide 6 (nylon 6) material that is 35% glass reinforced. It has been subjected to 3,000 hours of hot oil testing and is shown to keep 94% of its original impact properties. An oil pan module produced with the polymer reduces weight by 2.2 kg, or 50%, over the steel pan it is benchmarked against. It is designed for light-duty, as well as 1-, 2- and 3-Class vehicles. The material also is suitable for molding into oil pan subsystems, such as oil pickup tubes and windage trays.

BASF's A3WG7 HP Ultramid is a new material for cylinder head covers designed for a richer, glossier appearance. Marianne Morgan, Powertrain sector leader for BASF, says some Asian OEMs are using the material to better color match the engine shroud. It is a higher flow material than previous generations, so it requires smaller injection molding equipment, and thus lowers production costs, Morgan says. It also cuts weight by more than 40% compared to die-cast aluminum (1.2kg per cylinder head cover), and is slated to debut in a 2009 calendar year North American program.

"OEMs have seen that a thermoplastic air intake can have even better NVH results because they are not as stiff as cast aluminum and, therefore, don't transfer as much noise," says Morgan. BASF is using a new grade of polymer, B3WG6 HPX, a 30% glass-reinforced polymer, for these applications. It has been approved for a calendar year 2010/model year 2011 large volume North American program.

 

DuPont

According to DuPont Automotive, the thermoplastic oil pan found on the 2009 Euro-spec. Mercedes-Benz C Class is the first-of-its-kind in a production volume vehicle. Made of DuPont's Zytel 70G35 HSLR resin, the oil pan is semi-structural-it is attached to the gear box and designed to handle the impact loads of a high-torque four-cylinder diesel engine. The lower shell includes a separate injection-molded oil deflector of the same resin welded to the flat portion of the pan. Internally, the high-placed ribs act as oil-calming baffles in the six-liter sump. Compared to the all-aluminum module that preceded it, the thermoplastic oil pan shaves 1.1kg (2.4 lbs) off the part. DuPont says the pan can withstand 1,000 hours of 150°C oil. Future versions of the Zytel oil pan likely will increase parts integration by including oil pick-up pipes, oil level switches, oil filters, and even the oil pump itself.

DuPont also anticipates a broader market for thermoplastics with the increased spread of high-pressure direct-injection engines. "I think the industry will continue to look for metal-to-plastic components in places they've never looked before," says Gianluigi Molteni, global marketing director, Powertrain Systems, DuPont Engineering Polymers.

In the near-term, DuPont is pursuing applications that include timing chain tensioners, cylinder head covers, and air ducts for turbocharger and supercharger components. A little farther out sit applications made from its "Metafuse" material, a nano-metal polymer hybrid created in alliance with Integran Technologies Inc. (www.integran.com; Toronto, ON) and PowerMetal Technologies Inc. (www.powermetalinc.com; Carlsbad, CA). It mimics the strength, stiffness and lightweight properties of magnesium or aluminum by bonding polymers in a metal coating that encases the thermoplastic substrates. Automotive applications include high-pressure fuel rails, timing chain tensioners, cylinder covers and in turbo- or superchargers where temperature and pressure conditions are too extreme for thermoplastics alone. DuPont and Integran are testing nanometal alloys, including nickel, copper, cobalt and phosphorus.

 

Ticona

Walt Maruszczak, Ticona Automotive Market Development Engineer, is in charge of finding metal components in powertrain and electrical systems to replace with one of the company's Ticona's two main polymers: Fortron linear PPS and Vectra LCP polymers. His list of possible component candidates is growing.

Fortron polyphenylene sulfide (PPS) is targeted to replace aluminum, steel and even thermoset plastics because of its rigidity, flame retardant composition and temperature resistance of up to 200°C. Maruszczak says the polymer can achieve a 25% to 35% reduction in weight over comparable steel designs. Ticona is using Fortron as a substitute for metals in throttle valves and bodies, crankshaft flanges, water pump housings and impellers, and thermostat housings.

Another 2009 engine application is shaping the Fortron into a liner into the air duct between the turbocharger and the air cooler. "Whether it's gears or other surfaces, where there's continuous motion or rubbing, it can replace harder materials, metals or machine diecast metals," he says. "The presence of this polymer will eliminate galling and wear." Areas with temperatures exceeding 200°C are the territory of Ticona's other under-hood polymer, Vectra, a liquid crystal polymer (LCP). It handles high service temperatures, up to 240°C. What's more, the highly crystalline thermoplastic has a higher chemical resistance and is designated for thin-walled applications (0.2-mm thickness), such as electronics. Without revealing specific customer programs, Ticona engineers are replacing metal components in cylinder deactivation electronics, solenoid modules, electrical bobbins, sensors and electrical terminals.