Natural Superplastics

Brazilian researchers are developing a new generation of plastics from natural fibers extracted from agroindustrial residues. The project is attracting the interest of the automobile industry

By Elton Alisson

Agência FAPESP – The agriculture industry produces fibers that could be the nexus of a new generation of superplastics. Lighter, more resistant, and more ecologically correct than conventional polymers used in industry, the alternatives are being researched by the group led by professor Alcides Lopes Leão at Universidade Estadual de São Paulo’s (Unesp) School of Agronomy Sciences in Botucatu.

Obtained from residues of crops such as curauá (Ananas erectifolius)—a plant from pineapple family found in the Amazon—as well as banana, coconut shell, sisal, pineapple, water and residue from cellulose production, the natural fibers began being studied on scales of centimeters and millimeters by professor Lopes Leão and his colleagues at the beginning of the 1990s.

When testing them on a nanometric scale (the billionth part of a meter) in the last two years, the researchers discovered that the fibers were as resistant as carbon and glass fibers, and therefore can be substituted as raw material for plastic manufacture. The results are stronger, more durable materials with the advantage of being completely renewable as opposed to conventional plastics from petroleum and natural gas. “The mechanical properties of these fibers increase enormously on a nanometric scale. Pieces made with this sort of material are 30 times lighter and 3 or 4 times more resistant,” said Lopes Leão to Agência FAPESP.

In trials run by the group through a research agreement with Braskem where 0.2% of the nanofiber was added to the company’s polypropylene, the materials proved to be 50% more resistant. In trials performed with injected plastics used in the manufacture of shock absorbers, internal and side panels and carter protection plates for cars where from 0.2% to 1.2% of nanofibers were added, the parts were lighter and more resistant than those found on the market today, according to the scientist. “We substituted fiberglass with the nanocellulose in all the injected polypropylene parts used by the automobile industry and obtained better results,” he affirmed.

Aside from increased safety, the nanofiber plastics make it possible to reduce the weight of the vehicle, making it more fuel-efficient. They are also less affected by heat and spillage of liquids like gasoline.

“For the time being, we are focusing on applications for nanofibers by substituting automotive plastics. But in the future, we will be able to substitute parts that today are made from steel or aluminum with these materials,” said Lopes Leão.

Through a project funded by FAPESP’s Technological Innovation Research Partnership Support Program (PITE), the curauá fiber started being used in the ceiling, the insides of the doors and the luggage compartment lid in Volkswagen’s Fox and Polo.

Other automobile industries have already shown interest in the technology according to Lopes Leão. Among them is an Indian company whose name was not revealed, which learned of the research after it was presented at the American Chemical Society’s 241st Meeting and Exposition in Anaheim, California at the end of March.

More promising fibers

According to the study’s coordinator, aside from the automobile industry, the nanofibers can be applied in other sectors like medical and dental materials. In a project performed in partnership with the Unesp Araraquara’s School of Dentistry, researchers intend to substitute the titanium used in the fabrication of metal pins for dental implants with the nanofibers.

In another project developed with Unesp Botucatu’s School of Veterinary Medicine and Zootechny, the group is using the nanofibers to develop vegetal bacteria cellulose membranes. In live trials of biocompatibility performed on rats, the animals survived for six months with the material. “No other study of this type had ever achieved these results until now,” affirmed Lopes Leão.

In other projects funded by FAPESP, the Unesp group is also studying the use of natural fibers for the development of reinforced composites and for treatment of water polluted by oil. According to the coordinator, among the plant fibers, pineapple fibers are those that present the most resistance and best lend themselves to the fabrication of bioplastics.

The most promising of the materials is paper cellulose slurry, a residue from the fabrication process that industries discard in enormous quantities and at great cost, both financial and environmental, as the waste is buried in landfills.

Lopes Leão intends to begin a research project with paper manufacturer Fibria to discover how to use this residue as a source of nanofibers. The company’s cellulose slurry would be transformed into a commercial product. “It’s much simpler to extract nanofibers from this material than from wood, for example, because it’s already clean and treated by the paper factories,” he said.

To prepare the nanofibers, the scientists developed a method in which they place the leaves and stems of pineapple or other plants in a piece of equipment similar to a pressure cooker. The “sauce” resulting from this mixture is formed by a set of chemical compounds and the cooking is done in a number of cycles until a fine material resembling talcum powder is produced. One kilogram of the material can produce 100 kilos of light and super-strong plastics.