Advanced Polymers Drive Automotive Lightweighting

July 10, 2020

When it comes to reducing weight of both electric and conventional automobiles, advanced polymers are changing the game.

According to Machine Design:

“Automakers are committing significant resources to develop electric, autonomous, and hybrid vehicles. These OEMs also need to meet rising demand for greater connectivity in every class of car, including vehicles with internal combustion engines. Automotive lightweighting, a design strategy that seeks to reduce vehicle weight, isn’t new. It has, however becoming more important for reasons beyond fuel efficiency and emissions reductions. Today, engineers want lightweight materials that improve design, manufacturability, and the performance of molded and machined parts.

“For decades, automotive designers have been replacing heavier metal components with engineering plastics and fiber-filled composite versions. This practice is now broadening as automakers look beyond exterior components and interior fixtures. Thanks to advances in polymer technology, engineers have a wider range of new and lighter options for drivetrain and underhood components. Importantly, these materials offer greater design freedom and fit in well with the lightweighting strategies that go beyond replacing metal with plastic.

“Designers who take a system-level approach in all automotive segments are discovering new possibilities. For example, the unique combination of advanced polymers’ properties are improving the slot liners and magnet wire insulation in electric (EVs), hybrid electric (HEVs), and plug-in hybrid electric vehicles (PHEVs). In turn, non-metal materials reduce the weight and size of traction motors while improving their efficiency. In all types of cars, replacing several metal parts with a single plastic part reduces vehicle weight while reducing the amount of assembly needed.

“Recent advances in polymers let automotive designers consider different manufacturing methods. Most plastic parts are injection molded, but plastic coolant tubing is extruded, thermoformed, and spin welded onto connectors. Plastic thermoforming also makes exterior components such as hoods and spoilers. In addition, advanced polymers work well with adhesives and can be machined from stock shapes or printed via additive manufacturing (aka 3D printing) during prototyping. Plastic composites with significant glass, mineral, or carbon fiber content can be precision machined with tight tolerances.

“Automotive designers may appreciate the design flexibility and manufacturing benefits advanced polymers provide, but high temperatures and exposure to chemicals or fluids might make metals seem like the only choice for especially demanding applications. This isn’t the case, however, as demonstrated by recent innovations in polymers for automotive electrical systems and electronics, internal combustion engines, fuel injection systems and assemblies, transmissions, EV batteries and cooling, and electrified drivetrains.

“These newer materials might seem like just the latest chapter in the history of automotive lightweighting, but polymers aren’t just replacing metals. They’re replacing other plastics, too. When selecting materials, then, designers need to think beyond plastics vs. metals and compare the performance profiles of high-performance specialty polymers.

Machinedesign Com Sites Machinedesign com Files G2 Ppa Spider Graph

Spider graphs like this one let designers compare and contrast characteristics of related materials. This one looks at polyphthalamide (PPA), polyamide 66 (PA66), and polyphenylene sulfide (PPS).

Plastics in Vehicles

“In Plastics and Polymer Composites in Light Vehicles, a report from the American Chemistry Council, the industry trade association explains that in 1960, the average light vehicle contained just 20 lb of plastics and polymer composites. By 1990, this had climbed to 191 lb, and by 2018, non-metal materials averaged 342 lb for 8.6% of total vehicle weight. Today, plastics typically make up 50% of the volume of a light vehicle but less than 10% of its weight.

“Since the 1960s, plastics have changed auto body designs and let OEMs adopt modular assembly practices while lowering production costs. Plastic parts for automotive interiors promoted not only comfort and styling, but also ergonomics and noise control. When car buyers became more concerned about auto safety, plastics were added to door modules to strengthen side-impact resistance and plastic foams added to automotive cavities to increase occupant safety and reduced noise, vibration, and harshness (NVH).

“Today, automotive plastics are used with brake pistons, wheel speed sensors, and parts such as the solenoids and plungers in the hydraulic control units of anti-lock brakes. Automotive plastics in the chassis provide strength and rigidity while absorbing energy that can cause NVH. In addition, specialty polymers are used in powertrains, which include the internal combustion engines, batteries, and motors.

“Many automotive fuel systems and engine components also use plastics instead of metal. During the last several decades, in fact, plastics have helped transform automotive electrical systems. For example, plastic components support the operation, interconnection, and housing of printed circuit boards, connectors, sockets, switches, wires, and cables. As computer chips regulate and monitor automotive subsystems, specialty polymers can be found  in everything from global positioning systems for navigation to audio systems for entertainment.

“Today’s cars contain electrical and electronic components that perform many important functions, but sensors are especially critical. For instance, anti-lock brake sensors monitor wheel speed, oxygen sensors determine how much fuel is needed to run the engine efficiently, and other sensors monitor coolant levels. Advanced polymers support these and other automotive sensors while withstanding the high temperatures and harsh environments associated with such systems.

“As automotive electronics become smaller and more densely packaged, advanced polymers have started to replace more traditional engineering ones such as standard polyamides. For example, Solvay produces a polyphthalamide (PPA) that provides an attractive balance of properties compared to polyamide 66 (PA66) and polyphenylene sulfide (PPS). PPA maintains its properties in humid environments, offers superior dimensional and thermal stability, and provides greater resistance to a broad range of chemicals, including brake fluid.

“Advanced polymers also improve fluid monitoring in electrified drivetrains. Some of these materials are inherently heat stable and do not require additives to inhibit or prevent thermal degradation. There are also polymers with non-metal heat stabilizers that can prevent thermal degradation if needed. For example, Solvay’s PPA contains an organic stabilizer that’s free of migrating metal that could short-circuit an electrical system.

“Designers rely on advanced PPS in vehicle electrical systems and electronics applications because they have long-term resistance to temperatures up to 392°F (200°C) and short-term resistance to temperatures up to 500°F (260°C). PPS offers the broadest resistance to chemicals of any high-performance plastic and can combine dimensional stability and inherent flame retardancy with support for precision molding to tight tolerances with high reproducibility. With its combination of properties, PPS is an excellent candidate for electrical and electronic components in coolant systems and for oil and fuel system components.

“Specialty polymers, such as Solvay’s high-performance polyetheretherketones (PEEK), are often specified for electric water and oil pumps. They reduce weight while offering excellent chemical resistance for durable, long-term performance. They also have dimensional stability needed for tight tolerances that can maintain high pumping efficiencies.”

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