Advanced engineered material technologies for a challenging environment

  • 06-Apr-2014 10:04 EDT
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Jeffrey H. Helms, Ph.D., Global Automotive Manager, Celanese Corp.

This is a time of both great challenge and great opportunity in the transportation industry. In February, President Obama directed the U.S. Environmental Protection Agency and Department of Transportation to set the next round of fuel efficiency standards for medium- and heavy-duty trucks by March 2016. The goal of this next round of fuel efficiency standards is to harness new technologies and drive innovation that can lower emissions, improve fuel savings, and deliver advanced vehicles.

Already transportation OEMs and Tier suppliers are working very hard to reduce the weight and emissions, and increase the fuel efficiency, of their vehicles to meet legislative mandates, or to reduce the cost of ownership where regulations on fuel economy are secondary to market development. A good example is the demonstration vehicle that is part of the Department of Energy’s SuperTruck initiative, which is intended to develop tractor-trailers that are 50% more efficient than baseline models by 2015.

Pressure to reduce tailpipe emissions and fuel consumption, and improve safety, is driving innovations in lighter weight components, powertrain technologies, aerodynamics, rolling resistance with high-efficiency tires, and anti-counterfeiting methods for components that are most sensitive to unapproved and non-validated material substitutions.

Leading the innovation will be several new technologies, materials, and processes that can play an important role in delivering new solutions that manufacturers and their suppliers can embrace for a new generation of clean, fuel-efficient vehicles.

Focus on thermoplastic composite materials

Interest is at an all-time high for thermoplastic composite materials and processes that can improve mechanical performance vs. weight and cost.

Several companies that have worked with the Energy Department since 2009 to develop SuperTrucks have come up with unique approaches that rely on thermoplastic composite solutions for aerodynamic technologies that reduce drag and improve vehicle fuel efficiency.

But the thermoplastics composites industry is also working with manufacturers to develop other innovative and lightweight applications based on fiber-reinforced plastics, including instrument panels, door modules, electronic boxes, seat panels, under body panels, noise shields, and bumper reinforcements. On the horizon are new structural components that combine traditional long-fiber glass reinforced thermoplastics with new continuous-fiber carbon reinforced thermoplastics, which are less expensive and faster to assemble than metal versions.

Nearly all types of semi-crystalline and amorphous thermoplastic polymers—polypropylene (PP), polyamides (PA), polyesters (PBT/PBT), polyphenylene sulfide (PPS), and polyetherimide (PEI)—are suitable as thermoplastic matrix materials that can be combined with a wide range of fibers and additives to make continuous fiber-reinforced thermoplastic (CFR-TP) unidirectional tapes, rods, and profiles that are particularly suited for highly stressed transportation components.

High-heat performance polymers

The internal-combustion engine will remain an important part of the powertrain, even as the push for lighter and more efficient vehicles accelerates.

As manufacturers push the limits of their engines, they are creating higher operating temperatures and more challenges under the hood, an environment in which high-performance polymers thrive.

Several families of fiber-reinforced, injection-moldable, high-temperature semi-crystalline thermoplastics—PPS, polyoxymethylene (POM), polyphthalamide (PPA), and high temperature nylon (HTN)—excel in extreme under-the-hood applications, and other applications exposed to road and engine chemicals. They can replace aluminum, steel, and die-cast metals and other materials in throttle body valves, crankshaft flanges, water pump housings and impellers, thermostat housings, and air management systems. In addition they can be used in alternative and biofuel applications and hybrid powertrain components.

High-performance engineered materials such as PPS offer impressive dimensional stability, inherent flame resistance, and broad chemical resistance—including automotive/aircraft fuels and fluids; strong acids and bases (pH 2 to 12), even at elevated temperatures up to 464°F (240°C); and shows notable stability in typical and alternative fuels.

Innovative developments by material scientists are leading to a next-generation of injection moldable PPS with improved improved productivity and properties that will open significant and new design spaces, as well as newly developed grades that can be used to blow mold complex shapes and contours.

Advanced fuel and air conditioning systems

Polymers for pipes and tubes used in fuel and air conditioning systems are being pushed to new levels of performance by several trends: higher operating temperatures, more demanding part geometries, weight reduction, lower emissions requirements, improved impact strength, and design-life standards.

Not the least of these trends is the ability of used fuel-system plastics—POM, PPS, PPA, aliphatic polyketone (PK), and polybutylene terephthalate (PET)—to withstand prolonged exposure to the new generation of more-reactive, oxygenated fuels.

POM provides high performance at thermal conditions found in fuel tanks and outside the engine compartment, while PPS is known for its performance at thermal conditions found under the hood. In general, these polymers show the least dimensional change and the highest retention of tensile strength when exposed to aggressive fuels.

These high-performance engineering resins are extremely versatile and typically find use in fuel system applications such as filler caps and necks, fuel sender modules, pumps, emissions control valves, and on-engine components.

In the area of pipes and hoses for use in fuel lines, pneumatic braking systems, clutch, air-conditioning, and power steering, material scientists have developed a new POM solution that delivers unique elastic mechanical properties that provide customers with a technical alternative to traditional thermoplastics, as well as low permeation and toughened POMs that deliver an unprecedented balance of impact and durability performance to meet EPA and CARB regulations.

High-strength materials that ensure safety

U.S. national regulations specifying design, construction, performance, and durability requirements for motor vehicles and regulated safety-related components, systems, and design features are putting new performance demands on materials as well as creating a need for technologies that can ensure applications contain components and parts that meet their material specifications.

To meet this demand, material scientists have developed enhanced performance packages for engineered materials that, when combined with anti-counterfeiting technologies, can assist manufacturers in avoiding a documented field failure, which could result in further investigation by companies and regulators and possibly require a recall for resolution.

Various traceability technologies, when combined with impact-modified POMs for injection molded parts that can absorb very high g forces or high-performance PPS used in head-up display bearing housings, optical rails, and mirror holders, can help customers avoid significant losses due to missed business opportunities, image-loss of brand, unwarranted claims for damages, and patent infringements.

The policy and regulatory environment is having, and will continue to have, a profound impact on how the materials the transportation industry uses.

Jeffrey H. Helms, Ph.D., Global Automotive Manager at Celanese Corp., wrote this article for SAE Off-Highway Engineering.

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