Fruit fibers used to create 'green' plastic for cars
By Paul Ridden
March 30, 2011
A research team from Brazil has developed a new form of plant fiber-based plastic that is claimed to be stronger, lighter, and more eco-friendly than plastics currently in use. Team leader Alcides Leão says that some of the so-called nano-cellulose fibers can be almost as stiff as Kevlar, but that the plastic differs from many in widespread use because the source material – such as pineapple and banana – is completely renewable. The researchers say that current production efforts are centered around the manufacture of automotive plastics, but future development could see steel and aluminum being replaced.
Ordinary-sized cellulose particles extracted from wood and then ground up have been used for centuries in the manufacture of paper. Recently, researchers have discovered that intensive processing of such material results in tiny fiber particles being produced. Mixing in these tiny cellulose fiber particles – so small that about 50,000 could fit across the width of a human hair – during the manufacture of plastic is said to result in a strong and durable end product.
Leão believes that pineapple leaves and stems, or the closely related curauá, could be a promising source of readily-available nano-cellulose. The leaves and stems are placed in a kind of pressure cooker, where certain chemicals are added to the mix. After several heat cycles, a fine powder is produced. The scientists from Sao Paulo State University admit that the process is currently a costly one, but state that one pound of nano-cellulose can be used to generate 100 pounds of reinforced plastic. Other possible sources include the ever useful banana, coir fibers from coconut shells and sisal fibers produced from the agave plant.
"The properties of these plastics are incredible," Leão said, "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 fibers in the future. For one thing, they will help reduce the weight of cars and that will improve fuel economy."
Mechanical advantages over plastics currently used in automobile manufacture are said to include a greater resistance to damage from heat, spilled gasoline, water, and oxygen.
Leão says that manufacturers have already had promising results from tests of nano-cellulose-reinforced plastics. Similar developments have also shown promise for medical applications like replacement hip joints, artificial heart valves and ligaments.
The results of the study were recently presented at the 241st National Meeting and Exhibition of the American Chemical Society.