Coming soon: 'Green cars from pineapple, lemon'

A team at Sao Paulo State University in Brazil claims to have developed a more effective way to use fibre from these and other plants in a new generation of automotive plastics stronger, lighter, and more eco-friendly than plastics in use.

Team leader Alcides Leao said the fibre 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 nano-cellulose 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, nano-cellulose fibres are completely renewable.

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

Besides weight reduction, nano-cellulose reinforced plastics have mechanical advantages over conventional auto- motive plastics, he added. These include more resistance to damage from heat, spilled gasoline, water, and oxygen

With automobile manufacturers already testingnano- cellulose-reinforced plastics, with promising results, the team 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.

Leao said that pineapple leaves and stems, rather than wood, may be the most promising source for nano-cellulose.

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 nano-fibres, 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 nano-cellulose to produce 100 pounds of super-strong, lightweight plastic, the scientists said.

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