Pineapple and banana fibre for car making

Scientists in Brazil have developed a more effective way to use fibres from pineapple, bananas and other plants in a new generation of automotive plastics that are stronger, lighter and more eco-friendly than plastics now in use.

Study leader Alcides Leão, PhD, said the fibres used to reinforce the new plastics may come from delicate fruits like bananas and pineapples, but they are super strong. Some of these so-called nanocellulose fibres are almost as stiff as Kevlar, the renowned super-strong material used in armour and bulletproof vests. Unlike Kevlar and other traditional plastics, which are made from petroleum or natural gas, nanocellulose fibres are completely renewable.

“The properties of these plastics are incredible,” Leão said, “They are light, but very strong - 30% lighter and 3 to 4 times stronger. We believe that a lot of car parts, including dashboards, bumpers, side panels, will be made of nanosized fruit fibres in the future. For one thing, they will help reduce the weight of cars and that will improve fuel economy.”

Besides weight reduction, nanocellulose reinforced plastics have mechanical advantages over conventional automotive plastics, Leão added. 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 used within two years.

Cellulose is the main material that makes up the wood in trees and other parts of plants. Its ordinary-size fibres 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 ultrasmall, or ‘nano’ cellulose fibres, so tiny that 50,000 could fit inside across the width of a single strand of human hair. Like fibres made from glass, carbon and other materials, nanocellulose fibres 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. He is with Sao Paulo State University in Sao Paulo, Brazil. Another is curaua, a plant related to pineapple that is cultivated in South America. Other good sources include bananas; coir fibres found in coconut shells; typha, or ‘cattails’; sisal fibres produced from the agave plant; and fique, another plant related to pineapples.

To prepare the nanofibres, 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 aluminium 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.

So your next new car hopefully won’t be a lemon. But it could be a pineapple or a banana.