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New Materials

Plastic from the buriti palm

Oil from the palm tree mixed with a polymer produces a material capable of absorbing and emitting light

From the fruit of the buriti palm tree, found in flooded areas of the Amazon and the Cerrado (wooded savanna), it is possible to extract an oil that, when mixed with a polymer, results in a plastic capable of absorbing part of solar radiation, including ultraviolet rays. The new material has shown in laboratory tests that it also has the optical properties necessary for it to be used in the manufacture of light emission diodes (LEDs), used, for example, in computers, cell phones and traffic lights. The studies were carried out at the Research Laboratory into the Chemistry-Physics of Polymers of the University of Brasilia (UnB) by Jussara Angélica Durães, supervised by professor Maria José Araújo Sales.

The idea to use the oil as a component of polymers mainly came about because of its optical properties, such as the absorbance of visible light and radiation in the ultraviolet range. “Beta-carotene and oleic acid are the two main components, among the various present in the oil, that are responsible for these properties”, explains Jussara. It so happens that the beta-carotene, a yellow-reddish pigment present in carrots and other vegetables is recommended for inclusion in food to combat vitamin A deficiency, has the property of absorbing light. “The buriti palm has the highest percentage of beta-carotene of all known plants”, says Jussara. On the other hand the oleic acid, present in 76% of the buriti oil is the main component of olive oil, and is responsible for the emission of light.

Continuous process
The researcher explained that the type of molecular bonding of beta-carotene allows the electrons to easily shift from one energy level to another. When light is incident upon the material, the electrons absorb energy, changing to a higher energy level and gain more movement. On returning to their original level, they give the energy back in the form of light. “The process of absorption and emission of light is continuous”, explains Jussara. As the process leaves the oil with a highly accentuated color, in the same tonality as beta-carotene, it’s possible to see it in the visible region of the spectrum. Nevertheless, when the polymer receives the addition of buriti oil, it emits light in the green region of the spectrum.

The discovery that buriti palm oil absorbs ultraviolet radiation was made by professor Sanclayton Moreira, from the Physics Department of the Federal University of Pará (UFPA), who has been studying the physical properties of oils from the region since the start of the decade of the 1990’s. He verified that the buriti oil, extracted both from the pulp and from the skin of the fruit, is a natural solar filter. As he was interested in making tests with plastics, he entered into contact with the Polymer Research Laboratory of the University of Brasilia at the start of 2002. The study, developed in partnership with the UFPA, was the theme of Jussara’s masters degree dissertation and had financial backing  from the National Council for Scientific and Technological Development (CNPq), resulting in the registration of a patent for the plastic compounds that absorb solar radiation and work as photo-protectors. “The natural oil makes the material absorb solar radiation in the ultraviolet region of the spectrum. This occurs because the plastic incorporates the oil’s properties easily, also allowing the material to become photo-luminescent, capable of emitting light in the visible region”, explains the advisor Maria José. The oil was added to polystyrene, the material used in the production of disposable plastic cups, and the polymer methyl methacrylate, the raw material for acrylic materials such as the lenses of sunglasses.

Now, in her doctorate thesis, Jussara is going to evaluate the degradation time of the plastic compound. And as well, she is going to research, to a greater depth, the buriti oil’s light emission property in order to construct a light emission device (LED). The new photo-luminescent plastic possibly represents a cheaper alternative for the LEDs existing on the market, made from inorganic substances such as silicate crystals, which makes the process expensive. Another property of the buriti oil is its capacity, verified in preliminary tests, to accelerate polymer degradation. “As yet it’s not possible to estimate precisely how long it would be necessary for it to decompose naturally, but there’re  already strong indications that it’s a material with a degradation property that’s much faster than the pure polymer”, says Jussara. When thrown away, common plastics take between 200 to 450 years to decompose naturally, contributing to the increase in the quantity of garbage and to a reduction in petroleum reserves, the raw material from which the product is made. Another research line that is also being developed in the same UnB laboratory is the addition of cassava starch to polystyrene and the buriti oil in order to manufacture environmentally friendly plastics. The biodegradation of this material is also being studied.

Tree of life
Also called the palmeira-do-brejo, the buriti palm is found in abundance in lowlands and marshlands. Many Amazonian communities live off the extraction of the palm tree with its fan shaped palm leaves, it also called the tree of life. They use the roots, the leaves and the trunk, as well as its fruit for eating and oil extraction. Annually a tree produces eight bunches, with around 500 individual fruit in each one. The fruit are similar to those of the coconut palm with a reddish brown color, elliptically shaped, covered with a shiny hard skin. Inside one finds a golden yellow colored pulp, with which sweets, ice creams, creams, jams and liquors can be prepared. It is also the pulp that has an edible seed, from which the intense reddish colored oil is extracted, traditionally used by the local populations against burns and as a healing lotion. From the palm’s leaves baskets, mats, sleeping nets and ropes are made. If as well as its traditional applications, the buriti were to be made into computer screens, cell phones and the lenses of sunglasses, not only would Brazilian technology gain new original products originating from such an unusual material, but as well the various families within the Amazonian community would be the main beneficiaries through the extraction of the palm product in a sustainable manner, as is also forecast in the UnB research.