Automotive Plastics Play Key Role as Automakers Seek to Build Fuel-Efficient Vehicles

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Use of lightweight yet strong materials has become the order of the day for auto manufacturers that are constantly seeking ways to reduce the weight of cars and trucks in order to improve fuel efficiency, safety and design for consumers.

Striving for Better Fuel Efficiency

A study conducted by the Department of Energy found that reducing a vehicle’s weight by 10 percent could increase its fuel economy by 5-7 percent. Not only is this a significant number for consumers seeking ways to save money at the pump, but it’s also an important figure to manufacturers.

Carmakers are counting on lightweight materials such as plastics and plastic composites to reduce the weight of autos so they can meet the Corporate Average Fuel Economy (CAFE) standard of 54.5 miles per gallon by 2025. This significant improvement in the fuel efficiency of new vehicles will go a long way towards lightening our environmental footprint.

Increasing Role of Plastics in the Auto Industry

Due to plastics’ favorable strength-to-weight ratio, today’s vehicles on average are made up of 50 percent plastics by volume but only 10 percent by weight. The average car today incorporates about 200 kilograms of plastics, and that figure is expected to jump by 75 percent to 350 kg by the year 2020.

In today’s automobiles, plastics can be found in windows; headlamps and tail lamps; fuel lines and fuel tanks; housings for electronics and braking systems; body panels and bumpers; and foam fill material for hollow structures such as areas between windows, door panels, bumpers and frames. Plastics even can be found in lithium polymer car batteries that power some hybrid and electric vehicles.

The driving force behind the increase in the use of plastics and plastic composites such as carbon fiber-reinforced plastics (CFRPs) may be the desire to make cars lighter and thus more fuel efficient, but it is not the only benefit gained from such a move.

Plastics Contribute Significantly to the Safety of a Vehicle

Modern plastics can be made to be resilient and flexible, soft and cushioned, or tough and shatter-resistant. This allows them to contribute to vehicle safety in a substantial way.

Plastics’ ability to absorb and distribute energy in a car crash via crumple zones in the front and sometimes the rear end of vehicles helps protect the passengers inside the reinforced cabin area. Crumple zones featuring reinforced plastic can absorb six to 12 times the energy of steel, and at considerably less weight.

Crumple zones featuring reinforced plastic can absorb six to 12 times the energy of steel, and at considerably less weight.

The National Highway Traffic Safety Administration also estimates that today’s seat belts made with industrial strength plastics can reduce auto fatalities by as much as 45 percent and serious injury by 50 percent, compared to not being buckled in. Engineers also are developing a new “smart fiber” plastic belt designed to hold the occupant in position at impact and then stretch to limit the force of the crash and absorb its energy, reducing the impact on the body.

Beginning in 2011, Ford began offering the industry’s first inflatable seat belts on some models. In the event of a crash, a sensor inflates the tubular air bag along the belt by sending gas up through a plastic seat belt buckle into the belt itself. The inflated belt cushions the passenger, reducing the potential for traumatic injuries.

Plastics and the Environment

Beyond additional safety features, vehicle lightweighting and increased fuel efficiency through the use of plastics, another growing trend with automakers is to manufacture vehicle parts using recycled plastics to help reduce waste.

Polypropylene plastic caps and shipping aids from GM’s Fort Wayne, Indiana, facility are mixed with other materials to make 25 percent of the radiator shrouds for the Chevrolet Silverado and GMC Sierra pickup trucks built at the plant. The company also uses recycled plastic parts along with other recycled materials in the manufacturing of air deflectors on the Chevy Volt.

Ford used Repreve®, a hybrid fiber made with recycled plastic water bottles, for seating fabric in several of its models. The seat fabric of a Ford Focus is made up of about 22 plastic, 16-ounce water bottles; 39 bottles are used in the seats for two Fusion models, and up to 110 in the seats for the popular F-150 pickup.

Chrysler uses recycled polyurethane plastic in the seat cushions for the Jeep’s top-of-the-line Grand Cherokee, and recycled plastics are used for the wheel liners on the Jeep Wrangler and Chrysler 200.

The Many Uses of Plastics in Auto Manufacturing

Because of their versatility, modern plastics can be made to fit many different uses in the manufacturing of automotive vehicles. Advanced performance materials such as plastics and plastic composites continue to push what’s possible in car design. Breakaway covers for automobile airbags? They’re made of plastic. Fuel tanks? Plastics make them corrosion-resistant, and because of their one-piece construction, plastic tanks can be safer in crashes because they have no seams that have been welded together.

Plastic fuel tanks also can help dissipate potential electrostatic charges that can ignite fuel, and designers like them because they’re light and can easily be molded to fit into just about any space in a vehicle.

Plastics also have a hand in making auto glass even more effective. A thin layer of plastic built between the two layers of auto glass makes the windshield shatter-resistant and also lighter and stronger than tempered glass.

Nearly 50 years ago in one of the great movie lines of all time, Dustin Hoffman in The Graduatewas given one word of advice for his future: “Plastics.” Auto designers and engineers must have been listening.