Roberto Carlos Costa Lelis

Influência da composição da resina tanino-uréia-formaldeído nas propriedades físicas e macânicas de chapas aglomeradas

In the production of the wood base particleboards, synthetic adhesives are used as melamina-formaldehyde (MF), phenol-formaldehyde (FF), urea-formaldehyde (UF), among others. Due to the high cost of these adhesives, researches that a seek the introduction of alterations in their formulations are important for the reduction of costs in the productive system. This work had as objective verify the influence of the several levels of Acacia mearnsii tannin in a commercial resin of urea-formaldehyde an the physical and mechanical properties of the particleboard. The particleboard was produced with Eucalyptus urophylla wood. They were four treatments: T1 - 100% of resin UF (control); (T2) 90% of the resin UF + 10% of the tannin 50%; (T3) 85% of the resin UF + 15% of the tannin 50% and (T4) 70% of the resin UF + 30% of the tannin 50%. The results showed that it is possible to add tannin to the resin urea-formaldehyde without to alter the physical and mechanical properties of the boards.

DEVELOPMENT OF ACTIVATED CARBON FROM BAMBOO (Bambusa vulgaris) FOR PESTICIDE REMOVAL FROM AQUEOUS SOLUTIONS

Considering the water scarcity problems facing many countries, the need for water reuse can make activated carbon (AC) an essential product for modern society. In this context, to contribute with better activated carbons that could be used to serve in water treatment, this article discusses these materials production, using bamboo as raw material, and analyses their application effectiveness. The bamboo was collected, transformed into activated carbon, by simultaneous chemical and physical activations, and named H3PO4/H2OAC. The obtained material was characterized by its yield, apparent density, ash content, thermogravimetric analysis, surface area, methylene blue and iodine indexes, pH and point of zero charge analysis, scanning electron microscopy and Boehm titration method. The AC was used as adsorbent for removing the metribuzin, 2,4-dichlorophenoxyacetic acid and furadan pesticides. The H3PO4/H2OAC had a surface area of 1196.30 m².g-1 and the obtained adsorption capacity was elevated for furadan (868.98 mg.g-1), metribuzin (756.47 mg.g-1) and 2,4-dichlorophenoxyacetic acid (274.70 mg.g-1).

CHAPAS AGLOMERADAS CONFECCIONADAS COM UREIA-FORMALDEÍDO SOB ADIÇÃO DE TANINO EM PÓ

This work aimed to evaluate the technological properties of particleboards manufactured with particles of Acacia mangium and urea-formaldehyde adhesive by addition of powder form commercial tannin of Acacia mearnsii to their particles. The boards manufactured under different compaction ratio and the effect of these in the properties of the boards evaluated. It used a completely randomized design in the factorial outline 4 x 4 as follows: four percentages of substitution of powder form tannin to the adhesive urea-formaldehyde - 0, 10, 20 and 30%; and four nominal compaction ratios: 1.39, 1.55, 1.73, and 2.00. The pressing cycle used was 3.92 specific pressure with temperature of 140oC by 8 minutes. The addition of powder tannin to particles with urea-formaldehyde provided some improvements in the physical and mechanical properties. The results indicate that the addition of tannin powder is a viable alternative of use in particleboards, with no need for dilution.

Propriedades químicas de extratos tânicos da casca de Pinus oocarpa e avaliação de seu emprego como adesivo

This work evaluated the properties of aqueous extracts obtained from the bark of Pinus oocarpa under addition of sodium sulfite and sodium bisulfite and the possibility of employment of tannins from the bark as an adhesive for bonding wood. After evaluation of the chemical properties of tannic extracts it was decided to employ the extraction with distilled water under addition of / 5% sodium sulfite to prepare for the tannin-formaldehyde adhesive. Adhesive phenol formaldehyde and urea-formaldehyde were modified with 10% tannin Pinus oocarpa and the effect of this addition on the quality of the adhesive was evaluated. The addition from the bark of Pinus oocarpa showed that it is possible to use pure tannin as an adhesive because of its good gluing characteristics. The addition of tannic extract to synthetic adhesives contributed to increase viscosity values. Thus the substitution of synthetic adhesives by tannins is possible only up to 10%.

DENSITOMETRIA DE RAIOS X NA AVALIAÇÃO DA DENSIDADE EM PAINÉIS DE PARTÍCULAS

This study aimed to determine the apparent density, by gravimetric technique and X-ray microdensitometry of particleboard produced with Acacia mangium wood and search existence of correlation between both methods. It was used urea formaldehyde adhesive and commercial tannin Acacia mearnsii applied in powder form directly to the previously glued particles. The panels manufactured using four compression ratios (1.39, 1.55, 1.73, and 2.00) combined four levels of powdered tannin (0, 10, 20 and 30%), making up 16 treatments (4 panels by treatment). The particleboard apparent density parameters (mean, maximum and minimum) and gravimetric density were determined, analyzed and compared. The density profile presented graphically and interpreted by analysis of variance and multiple linear regression. The apparent density, medium, maximum and minimum for particleboard obtained by microdensitometry X-ray ranged 357-697 kg/m 3 , 386-824 kg/m 3 , and 334-634 kg/m 3 , respectively, and gravimetric method 369-742 kg/m 3 . The technique was effective in determining variations in the density profile in the thickness of the particleboards in all treatments, as well as direct obtain the apparent density. These variations could be reduced if the tannin used was previously hydrated in water. Was found strong correlation (R 2 = 0.99) between the mean apparent density obtained by X-ray microdensitometer and gravimetric method.

ACTIVATED CARBON FROM BAMBOO ( Bambusa vulgaris ) FOR METHYLENE BLUE REMOVAL: PREDICTION TO THE ENVIRONMENT APPLICATIONS

The bamboo was used as a raw material for producing activated carbon (AC) through simultaneous direct physical-chemical activation by using phosphoric acid (H 3 PO 4 ) and water steam (H 2 O) as activating agents at 500oC for 1 hour. Adsorption kinetic and equilibrium studies at batch system were realized at room temperature to evaluate the adsorption influence of the methylene blue dye (MB) over the AC and the Langmuir and Freundlich isotherms systems were selected for understanding the adsorption process. The produced AC showed a relatively high value of surface area equal to 1193.65 m² g -1 . The required contact time for the MB to reach equilibrium was 12 hours. The adsorption performance was better delineated by the Langmuir isotherm, which maximum adsorption capacity was of 374.75 mg g -1. In addition, the R L dimensionless factor reveled the favorable nature of the adsorption process in the used conditions. Thereby, the high quality and low cost AC production was validated in this work and the results herein obtained suggests the use of the H 3 PO 4 /H 2 O AC for MB dye removal in water. Finally, complementary researches must be conducted to improve, even more, the quality of the produced AC.

AVALIAÇÃO DE ADESIVOS À BASE DE TANINOS DE Pinus caribaea var. bahamensis E DE Acacia mearnsii NA FABRICAÇÃO DE PAINÉIS AGLOMERADOS

This work aimed to evaluate the methods for extraction of tannin from the bark of Pinus caribaea var. bahamensis, as well as to evaluate the technical feasibility of using tannins from the barks of Pinus caribaea var. bahamensis, of Acacia mearnsii, the mixtures of black wattle and pine tannins and the mixture of adhesive urea formaldehyde (UF) with black wattle and pine tannins in the production of adhesives for particleboard. The barks of Pinus caribaea var. bahamensis were fragmented in hammer mill, sieved and extracted under reflux for 2 hours, using a bark: liquor relation of 1:15, in nine treatments. The best extraction was used to obtain large quantities of extracts, which were used in the manufacture of adhesives and mixtures with UF adhesive and tannins of black wattle and the manufacture of particleboard. The addition of sodium sulfite gave higher extraction of tannin, which was extracted with the addition of 5% sodium sulfite. The results showed that both the black wattle tannin, as the bark of Pinus caribaea var. bahamensis have good bonding properties. It is possible to add pine tannin solution to the solution of black wattle and to replace part of the UF adhesive for the wattle tannins up to 25%, without compromising the glue quality. Replacing 10% of UF for tannic extract, both pine and black wattle, did not alter the values of thickness swelling (TS) of the panels. It is possible to obtain good mechanical properties with UF adhesives modified with tannic extracts at a ratio of 10%. The high values found for the internal bond (IB) panels containing tannin extracts showed the potential of these tannic extracts for bonding wood materials.

O uso da farinha de Orbignya speciosa na formulação de adesivo para compensados

O objetivo deste estudo foi avaliar o efeito da adicao da farinha de babacu nas propriedades do adesivo a base de ureia-formaldeido e compara-lo ao adesivo produzido com farinha de trigo, extensor usualmente utilizado na producao de paineis compensados. A resina ureia-formaldeido foram adicionados, em partes por massa de adesivo, 0, 10, 20 e 30% de farinha de babacu, e, como catalisador, sulfato de amonio, na proporcao de 1,5% sobre a massa seca de solidos da resina. Determinaram-se as seguintes propriedades dos adesivos: viscosidade, teor de solidos, tempo de gelatinizacao, tempo de trabalho e pH. A farinha de babacu apresentou propriedades semelhantes as da farinha de trigo. Ambas, de modo geral, embora tenham contribuido para o aumento da viscosidade dos adesivos, reduziram sua reatividade, pois elevaram o valor pH, o tempo de gelatinizacao e o tempo de trabalho.

PRODUÇÃO DE PAINÉIS DE CIMENTO-MADEIRA COM ADIÇÃO DE DIFERENTES PROPORÇÕES DE CASCA E MICROSSÍLICA

This work’s objective was to evaluate the effect of three percentages of addition of microsilica (0, 20 and 30%) on the physical and mechanical properties of wood-cement bonded particleboards of Eucalyptus urophylla composed by three wood:bark ratios (100:0, 95:5 and 90:10). Results showed that the most significant effect of the additive on the produced panels was in those containing bark, and that of 20% of additive was more efficient on the physical and mechanical properties.