Plastic is the most common lightweight material used in automobiles today. However, automakers continue to find new uses for the material, especially in under-the-hood applications.

When ASSEMBLY magazine debuted in 1958, the Hula Hoop was a new sensation that was sweeping the nation. It was made out of a new-fangled material called polyethylene.

In the late 1950s, most products contained metal parts and components. If you looked under the hood of a car or peeked inside the window, you’d have a difficult time finding anything made out of plastic. Metal ruled the road and chrome was king of the parking lot.

Fifty years ago, polyethylene, polypropylene and other thermoplastic materials were just being developed, in addition to new injection-molding techniques. But, because it was easy to process, plastic quickly became popular for numerous automotive applications.

The new material appealed to many manufacturers because of its superb design properties. Unlike metal, it was lightweight and colors could be molded in. The design flexibility of plastic allowed engineers to create single-piece, lightweight components that simplified assembly.

Many plastic developments over the years have been driven by the auto industry, which has long sought new ways to cut production costs and reduce vehicle weight. Automakers started using plastic for radiator grills in the late 1960s and then quickly developed plastic bumpers, wheels, headlamps, turn signals and body panels. Safety mandates also spurred many companies to produce plastic instrument panels.

“There has been a massive transformation from metals to plastics,” says Jordan Rotheiser, president of Rotheiser Design Inc. (Highland Park, IL). “As a result, products are lighter and less expensive to manufacture. Furthermore, there has been a significant change in appearance and features resulting from the design freedom provided by plastics.”

An unlimited amount of shapes and sizes of parts can be created with the tens of thousands of different grades of plastics that are available. As a result, plastic is the most common lightweight material used in automobiles today. In addition to bumpers and body panels, it’s used in various forms to create instrument panels, interior door assemblies, heating ducts, and protective covers under the hood, in addition to many other applications.

The plastic content in vehicles has increased dramatically in recent years. According to Richard Schultz, a consultant at Ducker Worldwide (Troy, MI), the average car now contains 340 pounds of plastic vs. 180 pounds in 1975. Within the next seven years, he predicts there will be more than 360 pounds of plastic per vehicle.

“Today, automakers are starting to run out of places to use plastic,” says Tim Bartlett, director of product development for Avdel products at Acument Global Technologies Inc. (Troy, MI). “There are very few things left in a car that could be made out of plastic.”

However, automakers continue to find new uses for the material, especially in under-the-hood applications. For instance, Mann + Hummel GmbH (Ludwigsburg, Germany) will soon start to mass-produce a plastic oil pan, which is one of the only large-volume parts of a passenger car engine that has not yet been manufactured out of the lightweight material. The all-plastic oilpan cuts weight by 60 percent compared to all-aluminum parts, or 30 percent compared to hybrid aluminum and plastic subassemblies.

“Further benefits with regard to cost, weight, installation space and assembly can be achieved by integrating additional components,” says Dieter Seipler, the company’s CEO. “For instance, with plastic, additional function can be integrated to the same extent as in air-intake systems.

“Integration of such components as oil tubes, pick-up pipes, strainers, separate oil reservoirs and baffles may be considered,” adds Seipler. “Installation of a complete oil module consisting of oil filter and oil cooler also offer considerable potential, both from a technical and economic point of view.”

Like all automakers, Nissan Motor Co. (Tokyo) is on a quest to reduce vehicle weight. It plans to make its cars 15 percent lighter by 2015. To accomplish that goal, Nissan is turning to plastic.

For instance, the company recently started to make plastic rocker covers and front covers for the diesel engines on its Navara and Pathfinder vehicles. By molding the parts from nylon, instead of aluminum, Nissan engineers were able to reduce weight by 40 percent. They achieved similar savings by converting the electric water valve assembly used on the Armada, Quest and Titan from steel to plastic.

In the future, electronic components may be embedded in plastic car parts during the injection molding process. The Warwick Manufacturing Group (Coventry, England) recently developed a process called In-spire that can mold electronic circuits directly within car bumpers and roofs. It uses a semiconducting film, an insulating paint and a conductive paint to build up layers of conductive pathways on an injection-molded part.