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Search Results: 1 - 10 of 10441 matches for " Benedito Rocha;Pimenta "
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Alcatr?o ou creosoto de eucalipto na produ??o de adesivos fenólicos para colagem de madeira
Pimenta, Alexandre Santos;Vital, Benedito Rocha;Fujiwara, Fred Yukio;
Química Nova , 1997, DOI: 10.1590/S0100-40421997000400005
Abstract: this study has shown that eucalyptus tar and creosote can be used in phenolic adhesive formulations (resols) for wood products bonding. some adhesives were prepared substituting 0; 17.7; 35.0 and 67.0% of the phenol by anhydrous tar and 0; 15.0 e 28.5% by creosote. in gluing brazilian pine veneers, eucalypt tar and creosote based adhesives required longer pressing times for curing than conventional phenol-formaldehyde adhesives. by using 13c nmr, the number of carbons in side chains and hydroxyl, carbonyl, carboxyl and methoxyl groups related to 100 aromatic rings could be estimated in tar and creosote. in creosote, after reaction with excess formaldehyde in alkaline medium, only 0,28 hydroxymethyl groups was detected per phenolic ring. this low amount of hydroxymethylation explains the lack of reactivity in curing observed when creosote was introduced in a standard adhesive formulation.
Efeito da varia??o do ph e da temperatura de síntese no desempenho de adesivos à base de creosoto vegetal desmetilado-formaldeído
Santos, Crístian Bacelar;Pimenta, Alexandre Santos;Vital, Benedito Rocha;Barbosa, Luiz Cláudio de A.;
Revista árvore , 2003, DOI: 10.1590/S0100-67622003000400016
Abstract: the objective of this work was the production of adhesives based on demethylated creosote for bonding of wood. different formulations of demethylated wood bcreosote/formaldehyde were evaluated aiming at improving their bonding properties. the initial ph value and the synthesis temperature were varied in order to obtain the best values for producing the adhesives. thus, seven ph values (12.00, 12.25, 12.50, 12.75, 13.00, 13.25, and 13.50) and two different temperatures (60 °c and 70 °c) were applied. it was observed by gel time evaluation that the best synthesis temperature was 70 °c. the kinetic parameters were obtained through dsc analysis (differential scanning calorimetry) to characterize the demethylated creosote adhesive formulations synthesized at 70 °c. the adhesives were used for hot bonding (160 °c) and under pressure (12 kgf/cm2) on araucaria angustifolia sheets. after bonding, mechanical resistance tests were carried out under both dry and wet conditions. it was verified that shear strength and wood failure under dry and wet conditions for demethilated wood creosote-based adhesives synthesized at 70 °c were lower than for laboratory-synthesized phenol-formaldehyde adhesive, used as standard.
Painéis de partículas aglomeradas de madeira de Pinus elliottii Engelm., poliestireno (PS) e polietileno tereftalato (PET)
Maciel, Ant?nio da Silva;Vital, Benedito Rocha;Della Lúcia, Ricardo Marius;Pimenta, Alexandre Santos;
Revista árvore , 2004, DOI: 10.1590/S0100-67622004000200012
Abstract: this work aimed determine the properties of wood particleboards containing particles of polystyrene (ps) and polyethylene therephthalate (pet). three amounts of polystyrene (0, 25 and 50%), two amounts of pet/ps (5/20 and 10/40%), three amounts (0, 4 and 6%) of urea-formaldehyde or phenol-formaldehyde adhesive and three amounts of polystyrene in toluene solution (0, 4 and 6%), combined with 50, 75 or 100% of particles of pinuselliottii wood were used. layer boards measuring approximately 400 x 400 x 10 mm with density approximately equal to 0.60 g/cm3 were produced. internal bond, rupture and elasticity modulus, screw withdrawal, water absorption and thickness swelling after 24 hours of immersion were determined. the mechanical properties of all the boards were superior to the established by ansi/a 208.1-1993 standard. all wood/plastic particleboards absorbed more water than those observed in commercial boards. however, the observed thickness swelling was quite similar to the values of commercial wood particleboards. boards in which the solution of polystyrene was applied presented, in general, the best values for all the properties.
Propriedades de chapas de aglomerado confeccionadas com misturas de partículas de Eucalyptus spp e Pinus elliottii
Cabral, Carla Priscilla;Vital, Benedito Rocha;Lucia, Ricardo Marius Della;Pimenta, Alexandre Santos;
Revista árvore , 2007, DOI: 10.1590/S0100-67622007000500014
Abstract: this work aimed to evaluate properties of particleboards manufactured with particles derived from planner shavings and flakes of eucalyptus grandis, e. urophylla and e. cloeziana. pinus elliottii particles were mixed with eucalyptus particles when necessary and in an amount enough to keep boards densities at 0.70 gr/cm3. eucalyptus wood was obtained from the municipalities of ponte alta (vale do rio doce) and três marias (cerrado region), both in minas gerais state, brazil. eucalyptus grandis, e. urophylla and e. cloeziana densities collected in ponte alta were 0.55; 0.61 and 0.70 g/cm3 whereas those collected from três marias were 0.58; 0.58 and 0.69 g/cm3, respectively. the density of pinus elliottii cultivated in the region of vi?osa was 0.45 g/cm3. particles were produced by processing flakes (0.48 x 20 x 90 mm) and planner shavings in hammer mill. mean slenderness ratios were 19.87 and 4.66 for particles produced from flakes and shavings, respectively. urea-formaldehyde adhesive was applied in the proportion of 8% of particle dry mass. boards manufactured with higher amount of eucalyptus particles absorbed more water and had higher swelling and linear expansion. highest hardness and parallel compression were observed on boards manufactured with particles from shavings, whereas highest internal bond, modulus of rupture and elasticity values were found for boards fabricated with particles from flakes. boards made with particles from wood derived from três marias had higher means for parallel compression, internal bond and modulus of rupture.
Avalia??o de algumas propriedades da madeira de Eucalyptus grandis, Eucalyptus saligna e Pinus elliottii
Serpa, Pedro Nicolau;Vital, Benedito Rocha;Della Lucia, Ricardo Marius;Pimenta, Alexandre Santos;
Revista árvore , 2003, DOI: 10.1590/S0100-67622003000500015
Abstract: this work aimed to determine sawn wood yield, as well as density, volumetric shrinkage, static bending and compression parallel to grain strength, glue line quality and machining for eucalyptus grandis, eucalyptus saligna and pinus elliottii wood. three trees of each species, with approximate ages of 50, 40 and 40 years, respectively, were cut into logs on the base, middle and top. property variations were analyzed in the pith-bark and longitudinal directions. the results showed that all the physical and mechanical properties varied inside the tree in the radial and longitudinal directions. basic density, bending and compression strength increased in the pith-bark direction, while volumetric shrinkage decreased. therefore, for obtaining denser, more stable wood with larger bending and compression strength it is necessary to harvest older trees. considering the variations in the longitudinal direction, it was observed that logs from the medium portion of the tree presented smaller values than those from the base and from the top, in all the analyzed properties. glue line strength and wood failure presented little differences in relation to adherence among juvenile wood and mature wood in all the positions. in the and mortise-and-tenon test, all the species showed satisfactory results, without occurrence of defects.
Compósitos de partículas de madeira de Eucalyptus grandis, polipropileno e polietileno de alta e baixa densidades
Milagres, Emerson Gomes;Vital, Benedito Rocha;Lúcia, Ricardo Marius Della;Pimenta, Alexandre Santos;
Revista árvore , 2006, DOI: 10.1590/S0100-67622006000300017
Abstract: the objective of this work was to establish the properties of particleboards fabricated with blends of eucalyptus grandis, low-density polyethylene, high-density polyethylene and polypropylene particles. two adhesives formulations were used (urea-formaldehyde and urea-formaldehyde plus 0,5% of epoxy adhesive). panel properties were affected by particle composition. panels with best properties were fabricated with 75% of wood particles and 25% of high density polypropylene. the addition of epoxy to the urea-formaldehyde adhesive improved of the values of modulus of rupture, hardness and reduced the amount of thickness swelling. except for the modulus of elasticity, board properties meet grade m-2 ansi/a1-208/93 requirements.
Análise cinética da cura de adesivos de taninos das cascas de três espécies de Eucalyptus por calorimetria diferencial exploratória (DSC)
Mori Fábio Akira,Vital Benedito Rocha,Pimenta Alexandre Santos,Trugilho Paulo Fernando
Revista árvore , 2002,
Abstract: O objetivo deste trabalho foi analisar a cinética de cura de adesivos à base de taninos de Eucalyptus grandis, Eucalyptus saligna e Eucalyptus urophylla por calorimetria diferencial exploratória (DSC), comparando-a com a cinética de cura de adesivos comerciais: fenol-formaldeído e de taninos de acácia-negra (Acacia mollissima D.Wild). Verificou-se que o adesivo de taninos de Eucalyptus urophylla apresentou os parametros cinéticos (energia de ativa o, entalpia, temperatura de pico e ordem de rea o) mais próximos aos do adesivo comercial de taninos de acácia-negra, que foram totalmente diferentes do adesivo à base de fenol-formaldeído. Com base nestes parametros constatou-se que, em rela o aos outros dois, o adesivo de taninos de Eucalyptus urophylla é o mais adequado para colagem, uma vez que em condi es industriais ele necessitará de uso mínimo de energia e de tempo de prensagem durante o processo de colagem.
Avalia o de algumas propriedades da madeira de Eucalyptus grandis, Eucalyptus saligna e Pinus elliottii
Serpa Pedro Nicolau,Vital Benedito Rocha,Della Lucia Ricardo Marius,Pimenta Alexandre Santos
Revista árvore , 2003,
Abstract: O objetivo deste trabalho foi determinar o rendimento em madeira serrada, bem como a massa específica, contra o volumétrica, resistência à flex o estática, resistência à compress o paralela, qualidade da linha de cola e trabalhabilidade das madeiras de Eucalyptus grandis, Eucalyptus saligna e Pinus elliottii. Foram colhidas três árvores de cada uma destas espécies, com idades aproximadas de 50, 40 e 40 anos, respectivamente. De cada árvore foram retiradas três toras, sendo uma na base, uma no meio e uma no topo do fuste. Foram analisadas as varia es em algumas propriedades, no sentido medula-casca e no sentido longitudinal. Os resultados mostraram que todas as propriedades físicas e mecanicas variaram dentro da árvore nos sentidos radial e longitudinal. A densidade básica e as resistências à flex o e à compress o aumentaram na dire o medula-casca, enquanto a contra o volumétrica diminuiu. Portanto, para obten o de madeiras mais densas, mais estáveis e com maior resistência à flex o e à compress o, é necessária a colheita de árvores mais velhas. Observou-se ainda que as toras da por o média do fuste, de modo geral, apresentaram menores valores para todas as propriedades determinadas do que as da base e do topo. A resistência da linha de cola e a porcentagem de falha na madeira para madeira juvenil e adulta apresentaram pouca diferen a em todas as posi es no fuste. No ensaio de confec o de espiga e fura o para espiga, todas as espécies apresentaram resultados satisfatórios, sem ocorrência de defeitos.
Efeito da varia o do ph e da temperatura de síntese no desempenho de adesivos à base de creosoto vegetal desmetilado-formaldeído
Santos Crístian Bacelar,Pimenta Alexandre Santos,Vital Benedito Rocha,Barbosa Luiz Cláudio de A.
Revista árvore , 2003,
Abstract: O objetivo deste trabalho foi a produ o de adesivos para madeira a partir de creosoto desmetilado. Para isto, foram sintetizadas diferentes formula es de adesivos para madeira a partir de creosoto desmetilado e paraformaldeído, variando-se o pH inicial da formula o (12,00, 12,25, 12,50, 12,75, 13,00, 13,25 e 13,50) e a temperatura de síntese (60 e 70 °C), para possibilitar a verifica o dos melhores pHs e da melhor temperatura para elabora o do adesivo. Foi verificado, por meio da avalia o do gel time, que a melhor temperatura de síntese foi 70 °C. Foram realizadas, ent o, análises por DSC (calorimetria diferencial exploratória), para obten o dos parametros cinéticos e caracteriza o das formula es adesivas de creosoto desmetilado sintetizadas a 70 °C. Os adesivos foram utilizados para colagem, a quente (160 °C) e sob press o (12 kgf/cm2), de laminas de Araucaria angustifolia. Após a colagem, foram realizados os ensaios de resistência mecanica ao cisalhamento por tra o, para condi o seca e úmida. Verificou-se que a resistência da linha de cola e a porcentagem de falha na madeira para os adesivos de creosoto desmetilado sintetizados a 70 °C foram inferiores às do adesivo de fenol-formaldeído sintetizado em laboratório, que foi utilizado como padr o.
PARTICLEBOARDS PRODUCED WITH Eucalyptus grandis W. Hill ex Maiden POLYSTYRENE AND POLYETHYLENE THEREPHTHALATE PARTICLES
Ant?nio da Silva Maciel,Benedito Rocha Vital,Ricardo Marius Della Lúcia,Alexandre Santos Pimenta
CERNE , 2004,
Abstract: This research investigated the properties of wood particleboards, containing particles of polystyrene (PS) and polyethylene therephthalate (PET). Particleboards were produced with 0%, 25% or 50% of polystyrene and 100%, 75% or 50% of Eucalyptus grandis particles. Additional boards were produced with two amounts of PET/PS (5/20% or 10/40%) and 75% or 50% wood particles. As binding agents three amounts (0%, 4% or 6%) of urea-formaldehyde or phenol-formaldehyde adhesive and three amounts of polystyrene in toluene solution (0%, 4% or 6%) were used. One-layer boards, measuring approximately 400,0 x 400,0 x 10,0 mm with density approximately equal to 0,60 g/cm3, were produced. Internal bond, modulus of rupture and elasticity, screw withdrawal, as well water absorption and thickness swelling, after 24 hours of immersion were determined. All mechanical boards’ properties were superior to the established by ANSI/A 208.1-1993 standards. All wood/plastic particleboards absorbed more water then those observed in commercial boards. However the observed thickness swelling was quite similar to the values of commercial wood particleboards. Boards in which the solution of polystyrene was applied were, in general, presented the best values for all properties.
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