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Technology

Travel light: New polymers could help electric cars take flight

Prospects for improved mileage and safety has Japanese automakers excited

An artist's rendering of a prototype car made using high-performance polymer materials. (Courtesy of University of Tokyo professor Kozo Ito)

TOKYO -- Generations hence, people may scratch their heads at the phrase, "put the pedal to the metal." The reason? New materials are poised to radically change what cars are made of.

Researchers in Japan from industry, academia and the government are developing stronger, lighter materials for auto components, including body panels, wheels and windows. At the heart of their efforts are polymers, the building blocks of plastics. The aim is to cut the weight of cars in half using these materials, thereby speeding the rollout of electric vehicles, perhaps even allowing them to fly one day.

Kozo Ito, a professor at the University of Tokyo, is leading a project under the auspices of the Cabinet Office's ImPACT program, which was launched in 2014. His research team aims to unveil in September a "car made from high-performance polymer materials that previously did not exist," Ito said at a news conference in June, highlighting a number of achievements in the development of "tough polymers."

Polymers, both natural and synthetic, are composed of chains of tiny molecules. They are found in everyday products, including the resins that make up plastics and films, and the rubber in tires and the earthquake dampers used in buildings.

Cars on the road today are built from parts made of heavy materials such as steel and glass. These are durable and enhance safety, but they limit fuel efficiency. Plastics are lighter, but break more easily. If new types of plastics can be devised that offer the same strength as, say, steel, but are lighter, the range of cars could be greatly extended.

One area showing promise is materials for car windows. Researchers at Sumitomo Chemical, led by Tatsuya Kasahara, are developing plastics that can replace the metal and glass used in car windows, greatly reducing their weight. The team's goal is to create a transparent plastic for windshields that is tougher than glass.

They have developed a highly durable transparent plastic by analyzing the molecular structures of PMMA, a clear thermoplastic that is hard but brittle, and polycarbonate, which is durable but soft. The new plastic, which combines the useful properties of both, has passed impact tests used to measure the strength of windshield glass. Japanese automakers are already asking Sumitomo Chemical about the material, Kasahara said.

One legal hurdle prevents the use of the new plastic for car windshields in Japan: Regulations require that they be made of glass. But Ito said he believes the rules will change "if [regulators] come to understand that this transparent plastic offers sufficient performance."

Tire manufacturer Bridgestone is also making progress in creating a more durable type of rubber that lets tires be made lighter. Bridgestone researchers have identified how rubber becomes susceptible to blowouts when stretched tightly. They discovered that if the initial crack in the rubber has a pointed shape, it is more likely to widen, leading to a blowout.

Using the findings, Bridgestone has developed a polymer with a crack resistance five times higher than the one commonly used today. Its meshed molecular structure keeps stress from becoming focused on a single point, This allows the tire to be made with 30% to 40% less rubber.

Industrial textile maker Toray Industries, meanwhile, has developed a technology that strengthens plastics by mixing resins with a material called polyrotaxane. This increases a plastic's tensile strength by eight times and its resistance to bending by 50 times. Fiberglass components treated in this way could be used to better absorb the shock of a collision. In combination with carbon fiber, these materials could form a car's body frame, again reducing weight and increasing durability.

"People involved in developing cars have high expectations for polymers," said the University of Tokyo's Ito. Some countries are moving toward banning gasoline-powered cars, heating up the race to develop electric vehicles. Although batteries and motors get most of the attention, they are not the only things that need improving. Making cars lighter with polymers, by improving their range and performance, would be a huge step forward. Lighter materials are even more critical if the dream of a flying car is to become a reality.

The prototype car scheduled to be rolled out in September is expected to weigh 38% less than comparable existing models, thanks to the use of tough polymers, including carbon fiber-reinforced plastics in the body panels. The experimental car is thought to weigh just 832 kg, versus 1,333 kg for a vehicle using steel and glass. The prototype will weigh 45% less than a comparable sedan, which usually tips the scales at 1,500 kg.

One obstacle that must be overcome before the new polymers find their way into the average car is their high cost, which is several times higher than that of conventional materials. "We aim to improve performance tenfold for a cost increase of several dozen percentage points," Ito said. "We're not going to allow our achievements to remain in the lab."

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