Nanotechnology

[FreeGrass]

Cellulosic nanocrystals from biomass waste for thermoplastics for automotive applications

By Green Car Congress on 03/28/2011

Scientists in Brazil are studying the production and incorporation of cellulosic nanocrystals (also known as cellulose whiskers) derived from several sources such as pineapple, curaua, banana and coir into thermoplastics matrix composites for automotive applications. They described the work, which could lead to stronger, lighter, and more sustainable materials for cars and other products, at the 241st National Meeting & Exposition of the American Chemical Society (ACS) in Anaheim.

Cellulose nanocrystals are the crystalline domains of cellulosic sources. They have the potential to improve, among others, the mechanical, optical, and dielectric properties of these polymeric matrices, and have been of significant research interest for a number of years.

Some of these nano-cellulose fibers are almost as stiff as Kevlar, but unlike Kevlar and other traditional plastics, which are made from petroleum or natural gas, nano-cellulose fibers are completely renewable.

The properties of these plastics are incredible. 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 nano-sized fruit fibers in the future. For one thing, they will help reduce the weight of cars and that will improve fuel economy.

So far, we’re focusing on replacing automotive plastics. But in the future, we may be able to replace steel and aluminum automotive parts using these plant-based nanocellulose materials.
—Alcides Leão, Ph.D., study leader, São Paulo State University

Besides weight reduction, nano-cellulose 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 nano-cellulose-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 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, nano-cellulose 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 nano-cellulose. 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. It takes just one pound of nano-cellulose to produce 100 pounds of super-strong, lightweight plastic, the scientists said.

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 scientists acknowledge funding from the government of Brazil, Pematec, Toro Industria and Comercio Ltd., and other private companies.