New Materials

Light and resistant

Curauá substitutes fiber glass in car parts and is one of the components of earthquake-proof beams

Eduardo CesarDry curauá fiber used as a compound with plasticEduardo Cesar

Fiber from the curauá, a native plant of the bromeliad species found in the Amazon Region, has high-resistance mechanical properties, low density – making it a lightweight material – and potential for recycling. It is being assessed as a possible substitute for the fiber glass used to reinforce plastic in small car parts with detailed characteristics, produced by injection molding, such as dashboard buttons, door handles and hinges. Big parts, such as the inside part of doors and the hoods of baggage compartments in some car models are already being made by a process that uses the plant fiber as one of its components. Demand for this material has grown significantly, and current production is unable to keep up with this growth, reflecting the interest aroused by the possibility of using the raw material extracted from the curauá (Ananas erectifolius) leaves in different ways, with proven results. This plant belongs to the same species as the pineapple. Thanks to their high mechanic resistance and lightweight properties, cuaruá leaves can be used for water tanks, swimming pools, in anti-allergic textiles and even as a substitute material for the iron beams used in earthquake-prone countries such as Japan.

The product which is left over from the crushing of the sugar cane leaves is called mucilage. It can be used for animal feed, because it has 7% protein; it can also be used for the manufacturing of paper by the pulp and paper industry and for the manufacturing of organic fertilizer. “Today, the automobile and textile industries have a demand for about one thousand tons of fiber a month,” says researcher Osmar Alves Lameira, from Embrapa Amazônia Oriental, a unit of the Empresa Brasileira de Pesquisa Agropecuária agricultural research center located in the city of Belém, State of Pará, who has been doing research on the curauá. Current production in Brazil, concentrated in the city of Santarém, Pará, totals 20 tons. Cultivation of this plant, however, is beginning to expand because of the interest aroused by the research studies involving this material. “Farmers from regions located along the Belém-Brasília highway and in municipal regions such as Santo Antônio do Tauá and Vigia, close to the Bay of Marajó, are organizing themselves to plant curauá,” says Lameira. “The idea is to set up groups to plant on a larger scale.”

The studies that resulted in the compound made of plastic and curauá fiber, to substitute fiber glass in parts manufactured according to the injection molding process by the automobile industry and by the electrical goods industry as external covering of tape recorders, mobile telephones and electric tools, were coordinated by professor Marco-Aurélio De Paoli, director of the Laboratório de Polímeros Condutores e Reciclagem laboratory at the Chemistry Institute of the State University of Campinas/Unicamp. GE Plastics South America, nowadays known as Sabic Innovative Plastics, installed in the Industrial Complex of Campinas, State of São Paulo was another partner. “Fiberglass is a raw material that requires a high amount of electric power to be produced; in addition, the products made from this material cannot be recycled by using any currently existing process,” says De Paoli. At the end of its useful life, the fiberglass-reinforced plastic is discarded into a garbage landfill.

Thermal recycling
The curauá fiber needs very little energy to be produced – only for the plant’s extraction and crushing process. Another advantage is the fact that it has less density than glass, which means lighter products. In the case of the automobile market, this is an interesting characteristic, because it saves fuel. Recycling also counts points in favor of this plant fiber. The products made from this material can be recycled by using the thermal process. “When the fiber is being burnt, less carbon monoxide is produced than the amount consumed by the plant when it was growing,” says De Paoli.

Embrapa Amazônia OrientalCurauá field with species used in reforestingEmbrapa Amazônia Oriental

The compound, the national and international patents for which have already been filed, is the result of a research study initiated in 2000 by a research group led by De Paoli; the objective was to see whether the plant fiber would be a good alternative to substitute fiber glass in thermo plastic reinforcement – hot-rolled plastics, such as polyethylene, polypropylene, polycarbonate and nylon, among others. The interest in the fiber began during a conference in 2000, when De Paoli learned of the results of the research studies on curauá, conducted by professor Alcides Lopes Leão, of the Universidade Estadual Paulista/Unesp state university, Botucatu campus (see Pesquisa Fapesp Nr. 104). The difference between the two lines of research is that the professor from Unesp develops fiber compounds with materials based on polypropylene by using a process called thermoforming, which uses heat to prepare the mixture and press it, whereas the Unicamp researchers use extrusion and injection molding system for the parts, which results in a final product with specific applications.

“The first project developed by our group involved – using extrusion – plant fiber with recycled polypropylene, a plastic used for packaging, pens and wastebaskets,” says De Paoli. The study resulted in a patent filed by Unicamp in March 2002. A few months later, the researcher was contacted by Paulo Santos, manager of applied technology for South America from the GE Plastics company, which was acquired this year by the Saudi Arabian company Sabic. Paulo Santos was very interested in the results of the research study. The company does not work with polypropylene, but with engineering plastics, used in car parts, electrical goods and structural pieces. The material has specific characteristics such as excellent resistance to impact and does not become damaged when exposed to high temperatures.

“We were interested in the research because the European and Japanese car industries are looking for car parts that can be recycled,” says Santos. Nylon 6, which has been manufactured with fiber glass reinforcement for many years, was the chosen material. The reinforcing agent is an additive used to modify the mechanical properties – resistance to impact or friction – of thermoplastic.

Choosing nylon 6 was crucial for the success of the research study. “As it has a low melting point, lower than the degradation point of plant fiber, we didn’t think we would have any problems in the melting temperature compatibility of the materials,” says Santos. A constraint when plastic is mixed with plant fiber is that plant fiber starts decomposing thermally at approximately 220ºC and many thermoplastics are processed at higher temperatures.

Smooth interaction
The agreement with Unicamp, signed at the beginning of 2003, provided for the supply of the product by the company and for the contracting of a chemistry student to work as a trainee – the trainee is Karen Fermoselli, – and for the financing of the consumption material and equipment maintenance. The university in turn would provide the lab facilities and the scientific expertise. The curauá fiber was supplied by the Pematec company, which grows the plant in the state of Pará. The compound, comprised of nylon 6 and the plant fiber with the same properties as that of fiber glass, was only possible after the material had been processed in a double-screw thread extruder owned by the company, which works on a pilot scale. “To obtain the compound, we need to promote good interaction between the thermoplastic and the fiber,” says De Paoli. Several strategies can be resorted to for this purpose. For example, the fiber glass can undergo a prior chemical treatment. Some precautions have to be taken in the case of nylon, because nylon undergoes a hydrolysis reaction if there is any humidity, and this can alter the material’s chemical composition. The researchers tested a number of treatments in the case of the plant fiber; reports on many of these treatments are found in scientific literature.

“We finally concluded that we would get better adhesion between the fiber and the nylon if we did not treat or dry the two materials,” says De Paoli. By doing so, the researchers achieved significant energy savings. The use of the double-screw thread extruder allowed the researchers to unweave the fiber, which was originally a sheaf of micro-fibrils, that is, the fibers are small and slim, and can only be seen through an electronic microscope. “This means that we’re reinforcing the plastic with the micro fibrils, which results in higher resistance,” De Paoli reports. All of this is done in a single step inside the extruding machine.

The company hasn’t scheduled the product’s launching date yet, because it has not finished adapting its extruding machines and the equipment that will mix the fiber and the plastic. The biggest difficulty being faced by the process is related to the feeding of the fiber into the extruding machine. The low density of the material, which provides the lightweight characteristic in the end product, generates a bulky volume which makes handling difficult and complicates the feeding of the screw thread. “We’re working on a number of alternatives to deal with this,” says Santos. One possibility being explored is to prepare the fiber first, by transforming it into a compact mass before it is fed into the feeder. Another alternative is to work with a specific dosage device for lighter loads. To this end, Sabic entered into a partnership with a small company from the State of São Paulo to design a dosage device, in view of the fact that the existing equipment of this kind is used for heavier materials, such as fiber glass, talc, calcium carbonate or carbon fiber.

Embrapa Amazônia OrientalFruit of curauáEmbrapa Amazônia Oriental

Once this obstacle is overcome, the next issue to be dealt with is the supply of the fiber at a competitive price. “Initially, we had expected the curauá fiber to be less expensive than the fiber glass,” says Santos. This is not reality yet, however, because of the scarce supply of the raw material to meet the existing demand. Studies conducted in the State of Pará show that planting curauá with other species used in reforesting, such as the paricá, mogno and freijó hardwoods, might be a good solution to expand the plantations. Two doctorate theses being advised by Lameira, from Embrapa Amazônia Oriental, have attested to the economic feasibility of this kind of planting and the quality of the fiber obtained from this kind of agricultural procedure. “When curauá is cultivated with other plant species, the yield of the fiber increases because of the shade from the trees,” the researcher explains. The symbiosis between the plants is evident, as one plant benefits from the production of the other plant. “The main advantage of this kind of planting technique is that the farmer obtains gains by cultivating curauá, at zero cost to the forest species,” says Lameira. The research also showed that the plant that grows in the shade of trees yields more fibers per kilo than the plant that grows in the sunlight.

The experimental work was conducted in an area that belongs to Tramontina, a manufacturer of tools, home appliances, electrical products and others. The company owns one thousand hectares on which it plants the paricá, a forest species that provides the light-colored wood used for cutlery, kitchenware, hammer handles and hoes manufactured by the company. The results of the study have motivated the farmers around the area to increase the area of cultivated land. “These actions have already been identified by the Banco da Amazônia, the financial agent; the bank is analyzing projects for large-scale plantations,” says Lameira.

Waiting line
The scarcity of urauá seedlings is a reflection of the expansion of the plantations. “A businessman contacted us last October; he was looking for seedlings to plant on 400 hectares, but he had to wait in line,” Lameira reports. 25 thousand seedlings can be planted on one hectare. The production technology is entirely familiar. Proof of this is the fact that in 2003, Embrapa Amazônia Oriental was awarded the Prêmio Finep prize in the regional category and a special award in the national category; these awards are granted by the Research and Projects Funding Department of the Ministry of Science and Technology (Finep/MST), for the development of a production process by means of the micro-propagating of curauá seedlings.

This technique quickly yields a large quantity of high-quality cloned seedlings. As a result, several bioplants have set up facilities in the region to cultivate curauá and other species. “All the plants being grown around the manufacturing facilities of Tramontina were born in labs,” says Lameira. The material is selected to grow up to a height of 1.60 meters. The planting technique, with the help of the shade from the trees, allows the plant to grow up to a height of 1.70 meters or more. Curauá does not need very fertile soil and can be planted at any time of the year. It grows very well in the deforested areas of the Amazon Region, provided that the soil is fertilized with organic fertilizer at the beginning.

One of the agronomic advantages of curauá is that the same plant can remain in the field from five to eight years, depending on how it was cultivated in conjunction with the forest species. Cuaruá matures one year after it is planted; the leaves can be picked at this time, up to four times a year. “Nowadays we have approximately 800 hectares of curauá plantations in the entire State of Pará,” says Lameira. At least 5 thousand hectares of curauá are necessary to meet the current demand.