A Real ‘Green’ Car: Pineapple or Banana May Toughen its Plastics

Fibers from fruit and other plants could toughen and lower the weight of automotive plastics. CREDIT: Dreamstime View full size image

Your next new car hopefully won't be a lemon, but it could be a pineapple or a banana. That's because scientists in Brazil have developed a more effective way to use fibers from these and other plants in a new generation of automotive plastics that are stronger, lighter and more eco-friendly than plastics in use now.

Researchers said the fibers used to reinforce the new plastics may come from seemingly delicate fruits such as bananas and pineapples that are actually super-strong. Some of these so-called nanocellulose fibers are almost as stiff as Kevlar, the renowned material used in armor and bulletproof vests. Unlike Kevlar and other traditional plastics, which are made from petroleum or natural gas, nanocellulose fibers are renewable.

"The properties of these plastics are incredible," Alcides Leão of São Paulo State University in São Paulo, Brazil, said in a statement. "They are light, but very strong — 30 percent lighter and three to four times stronger. We believe that a lot of car parts, including dashboards, bumpers, side panels, will be made of nano-sized fruit fibers in the future."

Besides fuel economy-boosting weight reduction, nanocellulose reinforced plastics have mechanical advantages over conventional automotive plastics, Leão said. These include greater resistance to damage from heat, spilled gasoline, water and oxygen. With automobile manufacturers already testing nanocellulose-reinforced plastics with promising results, he predicted they would be in use within two years.

Cellulose is the main material that makes up the wood in trees and other parts of plants. Its ordinary-size fibers have been used for centuries to make paper, extracted from wood that is ground up and processed.

In more recent years, scientists have discovered that intensive processing of wood releases ultra-small, or "nano," cellulose fibers, so tiny that 50,000 could fit inside across the width of a single strand of human hair. Like fibers made from glass, carbon, and other materials, nanocellulose fibers can be added to raw material used to make plastics, producing reinforced plastics that are stronger and more durable.

Leão said that pineapple leaves and stems rather than wood may be the most promising source for nanocellulose. Another is curaua, a plant related to pineapple that is cultivated in South America. Other good sources include bananas; coir fibers, found in coconut shells; typha, or "cattails"; sisal fibers produced from the agave plant; and fique, another plant related to pineapples.

To prepare the nano-fibers, the scientists insert the leaves and stems of pineapples or other plants into a device similar to a pressure cooker. They then add certain chemicals to the plants and heat the mixture over several cycles, producing a fine material that resembles talcum powder. The process is costly, but it takes just one pound of nanocellulose to produce 100 pounds of super-strong, lightweight plastic, the scientists said.

"So far, we’re focusing on replacing automotive plastics," said Leão. "But in the future, we may be able to replace steel and aluminum automotive parts using these plant-based nanocellulose materials."

Similar plastics also show promise for future use in medical applications, such as replacement materials for artificial heart valves, artificial ligaments and hip joints, Leão and colleagues said.

The work was described at the 241^st National Meeting & Exposition of the American Chemical Society.

This story was provided by TechNewsDaily, a sister site to LiveScience.