Estudos do efeito da radiação ultravioleta em madeiras por espectroscopias raman (ft-raman), de refletância difusa no infravermelho (drift) e no visível (cie-l*a*b*)

Tese (doutorado)—Universidade de Brasília, Instituto de Química, 2004.Duas técnicas espectroscópicas de refletância foram usadas para monitorar as modificações causadas por 200 h de irradiação ultravioleta (UV) sobre a superfície das madeiras tropicais: angelim vermelho (Dinizia excelsa Ducke), jatobá (Hymenaea courbaril L. var. courbaril), garapeira (Apuleia molaris Spruce ex Benth) e marupá (Simarouba amara Aubl.). As variações de cor foram mensuradas por espectrocolorimetria (segundo o sistema CIE-L*a*b*) e as modificações estruturais dos componentes principais da madeira – celulose, holocelulose e lignina – foram detectadas por espectrometria de reflectância difusa no infravermelho com transformada de Fourier (DRIFT). Na região do visível, por meio do resultado da diferença entre os espectros Kubelka Munk (KM) da madeira (não-irradiadairradiada), pode-se observar em todas as espécies investigadas o aparecimento de banda forte próxima a 410 nm. Além desta banda, as madeiras de cor escura apresentaram absorções adicionais em outros comprimentos de onda. Pelos parâmetros CIE-L*a*b*, verificou-se que o jatobá deslocou a cor para o vermelho e as outras três espécies para o amarelo. O marupá foi a espécie que sofreu a maior variação de cor e o angelim vermelho foi o menos afetado. Os espectros de diferença KM (DRIFT) mostraram que as bandas associadas à lignina (1600 cm-1 e 1508 cm-1) diminuíram em intensidade, enquanto que a banda associada ao grupo carbonílico (1736 cm-1) aumentou de intensidade com o tratamento UV. Os resultados sugerem que os extrativos interferem no processo de fotodegradação, aumentando a tendência ao amarelecimento e contribuindo com o aumento de intensidade da banda do grupo carbonila. Na região do IR, verificou-se que a celulose também foi degradada pela radiação UV. A holocelulose apresentou tendência muito grande a formar compostos carbonílicos nãoconjugados e a celulose mostrou variação na intensidade da absorção. As quatro madeiras tropicais estudadas não puderam ser classificadas taxonomicamente via DRIFT, adotando-se os critérios de espécies de clima temperado. As duas técnicas de refletância correlacionaramsesignificativamente, indicando que a radiação UV formou produtos cromóforos resultantes da fotodecomposição da lignina, que continham o grupo carbonílico não-conjugado. A presença dos extrativos da madeira pode ser detectada pela espectroscopia FT-Raman, porém esta técnica não se mostrou adequada para monitorar a fotodecomposição. _________________________________________________________________________________________ ABSTRACTTwo reflectance spectroscopic techniques were used to monitor modifications caused by 200 h of ultraviolet (UV) irradiation on the surface of tropical hardwoods species: angelim vermelho (Dinizia excelsa Ducke), jatobá (Hymenaea courbaril L. var. courbaril), garapeira (Apuleia molaris Spruce ex Benth), and marupá (Simarouba amara Aubl.). Colour variations have been evaluated by spectrocolorimetry (according to the CIE-L*a*b* system). Chemical changes of the wood main components – cellulose, lignin and holocellulose – have been detected by Diffuse Reflectance Fourier Transform (DRIFT) spectroscopy in the infrared. The Kubelka Munk (KM) difference spectra (non-irradiated-irradiated) in the visible region, from the woods have shown that all investigated species developped a strong absorption band near 410 nm. Besides this band, darker woods showed addicional absorptions at other wavelengths. The CIE-L*a*b* parameters (∆L, ∆a, and ∆b) have shown that jatobá shifted its color to reddish while the other three species have a tendency to become yellowish. Marupá was the species that suffered major color changes and angelim vermelho was the least affected. In the IR region, the KM difference spectra have shown that bands associated to lignin (1600 and 1508 cm-1) decreased in intensity, while those associated to carbonyl group (1736 cm-1) have increased under UV exposure. The results suggest that the extractives interfere in the photodegradation process, increasing the tendency to yellowing and contributing to the increase of carbonyl band intensity. In the IR region, it was observed that cellulose was also degradeted by UV radiation. Holocellulose presented a very high tendency to produce nonconjugated carbonyl groups, while cellulose showed variation only in the absorption intensity. The four tropical wood species studied did not match the taxonomic classification by DRIFT, adopting the rules developted for temperated wood species. The two reflectance techniques were significantly correlated, indicating that the UV radiation has formed cromophores products resulting of lignin hotodecomposition and that these products contain nonconjugated carbonyl group. The presence of wood extractives was detected by FT-Raman spectroscopy, although this technique has not shown to be appropriated to monitor the photodegradation process

RESISTANCE TO ARTIFICIAL WEATHERING OF FIVE TROPICAL WOODS AND OF TWO FINISH PRODUCTS

Os objetivos do trabalho foram avaliar o processo de fotodecomposi\ue7\ue3o da madeira de cinco esp\ue9cies tropicais e analisar o efeito de prote\ue7\ue3o de dois produtos de acabamento de madeiras quando submetidos ao intemperismo artificial. Foram empregadas as madeiras de ip\uea-roxo ( Tabebuia impeginosa ), ita\ufaba ( Mezilaurus itauba ), ma\ue7aranduba ( Manilkara huberi ), tatajuba ( Bagassa guianensis ) e tauari ( Couratari sp. ). Amostras destas madeiras foram submetidas a ciclos de radia\ue7\ue3o ultravioleta (UV) e \ue1gua at\ue9 perfazer um total de 2.000 horas de irradia\ue7\ue3o e 400 horas de lixivia\ue7\ue3o em \ue1gua. A mudan\ue7a da cor natural das madeiras, indicativo do processo de fotodegrada\ue7\ue3o, e o grau de prote\ue7\ue3o de um verniz poliuret\ue2nico transparente e de um "stain" semitransparente foram monitorados por espectrocolorimetria. As esp\ue9cies mais resistentes foram o ip\uea-roxo e tauari, seguidas pela ma\ue7aranduba, ita\ufaba e tatajuba respectivamente. O verniz forneceu prote\ue7\ue3o por tempo maior ao ip\uea-roxo e \ue0 ma\ue7aranduba, enquanto o "stain" foi mais eficiente para a ita\ufaba e tatajuba. Ambos os produtos tiveram desempenho similar para a madeira de tauari.This work aimed at evaluating the photodecomposition process of five tropical wood species and the protection effect of two wood finishing products under artificial weathering. Woods of Tabebuia impeginosa , Manilkara huberi , Mezilaurus itauba , Bagassa guianensis and Couratari sp. were employed. Samples were submitted to cycles of 2,000 hours of ultraviolet radiation (UV) and 400 hours of water leaching.Changes in the natural color of wood, indicative of the photodegradation process, and the protection degree of a transparent poliuretanic varnish and a semitransparent stain were monitored by spectrocolorimetry. The most resistant wood species were Tabebuia impetiginosa and Couratari sp. followed by Mezilaurus huberi, Mezilaurus itauba and Bagassa guianensis, respectively. The varnish protected Tabebuia impetiginosa and Mezilaurus huberi for a long period, while the stain seemed to be more efficient for Mezilaurus itauba and Bagassa guianensis. Both products presented similar performance for Couratari sp

Resistance to artificial weathering of four tropical woods: the effect of the extractives

As madeiras tropicais: garapeira (Apuleia leiocarpa), tauari (Couratari stellata), itaúba (Mezilaurus itauba) e marupá (Simarouba amara) foram selecionadas para examinar o efeito da presença dos extrativos na variação de cor e no processo de fotodecomposição das suas superfícies. Amostras com e sem extrativos foram submetidas a ciclos de radiação ultravioleta (350 nm) e água até totalizar 2.000 horas de irradiação e 400 horas de lixiviação. A mudança da cor natural das madeiras foi monitorada por espectrocolorimetria de reflexão difusa. Amostras de marupá e tauari com teores de extrativos menores que 2% exibiram variação de cor com o aumento do tempo de tratamento quase iguais às amostras sem extrativos. A resistência anormal do tauari à alteração de cor não pode ser atribuída aos seus extrativos. Para a garapeira e para a itaúba, a presença de 11,7 e 7,42% de extrativos respectivamente acelerou a velocidade de variação de cor. A análise dessas variações de cor indica que os extrativos, nesse caso, agiram acentuando a cor natural da madeira. Adicionalmente, verificou-se que o tauari foi a madeira mais resistente à variação de cor do grupo estudado, seguido pela garapeira, marupá e itaúba todas com extrativos.The tropical woods Apuleia leiocarpa, Couratari stellata, Mezilaurus itauba and Simarouba amara were selected to examine the effect of the presence of the extractives in the color variation and in the photodecomposition process of their surfaces. Samples with and without extractives were submitted to cycles of ultraviolet radiation (350 nm) and immersion in water until totalizing 2,000 hours of irradiation and 400 hours of water leaching. Changings in the natural wood colors were monitored by diffuse reflectance spectroscopy. Samples of Simarouba amara and Couratari stellata with extractives content of 2% or less showed color variation with time of treatment almost similar to the samples without extractives. The abnormal resistance of Couratari stellata to color changing can not be attributed to extractives. For the Apuleia leiocarpa and Mezilaurus itauba woods, the presence of 11,7% and 7,42% of extractives compounds, respectively, accelerated the color variation rate. Analysis of the color variation indicated that the extractives, in this case, acted by intensifying the natural wood color. Additionally, it was verified that Couratari stellata was the more resistant wood to color variation in this studied group of woods, followed by Apuleia leiocarpa, Simarouba amara and Mezilaurus itauba, all with extractives

Resistance to artificial weathering of four tropical woods: the effect of the extractives

As madeiras tropicais: garapeira ( Apuleia leiocarpa ), tauari ( Couratari stellata ), ita\ufaba ( Mezilaurus itauba ) e marup\ue1 ( Simarouba amara ) foram selecionadas para examinar o efeito da presen\ue7a dos extrativos na varia\ue7\ue3o de cor e no processo de fotodecomposi\ue7\ue3o das suas superf\uedcies. Amostras com e sem extrativos foram submetidas a ciclos de radia\ue7\ue3o ultravioleta (350 nm) e \ue1gua at\ue9 totalizar 2.000 horas de irradia\ue7\ue3o e 400 horas de lixivia\ue7\ue3o. A mudan\ue7a da cor natural das madeiras foi monitorada por espectrocolorimetria de reflex\ue3o difusa. Amostras de marup\ue1 e tauari com teores de extrativos menores que 2% exibiram varia\ue7\ue3o de cor com o aumento do tempo de tratamento quase iguais \ue0s amostras sem extrativos. A resist\ueancia anormal do tauari \ue0 altera\ue7\ue3o de cor n\ue3o pode ser atribu\uedda aos seus extrativos. Para a garapeira e para a ita\ufaba, a presen\ue7a de 11,7 e 7,42% de extrativos respectivamente acelerou a velocidade de varia\ue7\ue3o de cor. A an\ue1lise dessas varia\ue7\uf5es de cor indica que os extrativos, nesse caso, agiram acentuando a cor natural da madeira. Adicionalmente, verificou-se que o tauari foi a madeira mais resistente \ue0 varia\ue7\ue3o de cor do grupo estudado, seguido pela garapeira, marup\ue1 e ita\ufaba todas com extrativos.The tropical woods Apuleia leiocarpa , Couratari stellata , Mezilaurus itauba and Simarouba amara were selected to examine the effect of the presence of the extractives in the color variation and in the photodecomposition process of their surfaces. Samples with and without extractives were submitted to cycles of ultraviolet radiation (350 nm) and immersion in water until totalizing 2,000 hours of irradiation and 400 hours of water leaching. Changings in the natural wood colors were monitored by diffuse reflectance spectroscopy. Samples of Simarouba amara and Couratari stellata with extractives content of 2% or less showed color variation with time of treatment almost similar to the samples without extractives. The abnormal resistance of Couratari stellata to color changing can not be attributed to extractives. For the Apuleia leiocarpa and Mezilaurus itauba woods, the presence of 11,7% and 7,42% of extractives compounds, respectively, accelerated the color variation rate. Analysis of the color variation indicated that the extractives, in this case, acted by intensifying the natural wood color. Additionally, it was verified that Couratari stellata was the more resistant wood to color variation in this studied group of woods, followed by Apuleia leiocarpa, Simarouba amara and Mezilaurus itauba, all with extractives

Resistance to artificial weathering of five tropical woods and of two finish products

Os objetivos do trabalho foram avaliar o processo de fotodecomposição da madeira de cinco espécies tropicais e analisar o efeito de proteção de dois produtos de acabamento de madeiras quando submetidos ao intemperismo artificial. Foram empregadas as madeiras de ipê-roxo (Tabebuia impeginosa), itaúba (Mezilaurus itauba), maçaranduba (Manilkara huberi), tatajuba (Bagassa guianensis) e tauari (Couratari sp.). Amostras destas madeiras foram submetidas a ciclos de radiação ultravioleta (UV) e água até perfazer um total de 2.000 horas de irradiação e 400 horas de lixiviação em água. A mudança da cor natural das madeiras, indicativo do processo de fotodegradação, e o grau de proteção de um verniz poliuretânico transparente e de um “stain” semitransparente foram monitorados por espectrocolorimetria. As espécies mais resistentes foram o ipê-roxo e tauari, seguidas pela maçaranduba, itaúba e tatajuba respectivamente. O verniz forneceu proteção por tempo maior ao ipê-roxo e à maçaranduba, enquanto o “stain” foi mais eficiente para a itaúba e tatajuba. Ambos os produtos tiveram desempenho similar para a madeira de tauari.This work aimed at evaluating the photodecomposition process of five tropical wood species and the protection effect of two wood finishing products under artificial weathering. Woods of Tabebuia impeginosa, Mezilaurus itauba, Manilkara huberi, Bagassa guianensis and Couratari sp. were employed. Samples were submitted to cycles of 2,000 hours of ultraviolet radiation (UV) and 400 hours of water leaching. Changes in the natural color of wood, indicative of the photodegradation process, and the protection degree of a transparent poliuretanic varnish and a semitransparent stain were monitored by spectrocolorimetry. The most resistant wood species were Tabebuia impetiginosa and Couratari sp. followed by Manilkara huberi, Mezilaurus itauba and Bagassa guianensis, respectively. The varnish protected Tabebuia impetiginosa and Manilkara huberi for a long period, while the stain seemed to be more efficient for Mezilaurus itauba and Bagassa guianensis. Both products presented similar performance for Couratari sp

Characterization of wood decay by rot fungi using colorimetry and infrared spectroscopy

Amostras de madeiras de marupá (Simarouba amara) e andiroba (Carapa guianenis) foram submetidas ao ataque dos fungos Trametes versicolor (podridão branca) e Gloeophylum trabeum (podridão parda). A colorimetria foi empregada para determinar as cores das madeiras antes e após o ataque dos fungos. Para acompanhar a variação do teor dos compostos químicos foi utilizada a técnica de espectroscopia de refletância difusa no infravermelho médio. Ambas as espécies foram consideradas não resistentes ao fungo de podridão branca. Para o fungo de podridão parda, a andiroba foi considerada resistente e o marupá não resistente. Ambas as espécies de madeira se apresentaram mais escuras após o ataque do fungo Gloeophyllum trabeum. Já o ataque do fungo Trametes versicolor causou clareamento na madeira da andiroba e escureceu ligeiramente o marupá. Os resultados da análise dos espectros de infravermelho mostraram que em ambas as espécies de madeira houve redução na intensidade das bandas de celulose, hemiceluloses e lignina após o ataque do Trametes versicolor, e redução somente na intensidade da banda de celulose após o ataque do Gloeophyllum trabeum.Wood samples of marupá (Simarouba amara) and andiroba (Carapa guianenis) were submitted to Trametes versicolor (white rot) and Gloeophylum trabeum (brown rot) fungi attack. Colorimetry was used to determine the color of the wood before and after wood decaying fungi. To evaluate the changes in chemical compounds levels in the wood samples, the diffuse reflectance medium infrared spectroscopy was used. Both wood were non resistant against white rot fungus, while with brown rot attack andiroba was resistant and marupá was not. After Gloeophyllum trabeum attack both woods changed to a darken color, and after Trametes versicolor attack andiroba changed to a lighter color and marupá darkened slightly, The analysis showed a reduction in the peak intensity of cellulose, hemicellulose and lignin, for both species, after Trametes versicolor attack and a reduction in the peak intensity of cellulose after Gloeophyllum trabeum attack

Efeito do intemperismo artificial em quatro madeiras tropicais monitorado por espectroscopia de infravermelho (DRIFT)

Four tropical woods, were investigated to compare their performance and natural resistances to artificial weathering using the diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). The species were garapeira (Apuleia leiocarpa), itaúba (Mezilaurus itauba) and tauari (Couratari sp.), woods traditionally indicated for exterior uses, and marupá (Simarouba amara), that served as reference. The samples were submitted to cycles of UV radiation (350 nm) and water until 2,000 h. The photodegradation processes of woods surfaces were accomplished monitoring the changes in the intensities associated to lignin (1508 cm-1) and carbonyl group (1736 cm-1) absorptions. The results have shown that lignin was the first component to be photodegradated, resulting in surfaces mainly composed by cellulose, after 2,000 h of UV irradiation. The processes of formation and lixiviation of carbonyl compounds were different for each species. The experimental conditions used in this work were too severe to evaluate the wood density and extractives content influences during the treatment

Monitoring of biodeterioration of three Amazonian wood species by the colorimetry technique

Objetivou-se avaliar o emprego da colorimetria na caracterização da biodeterioração das madeiras de marupá, jequitibá e cumaru submetidas ao ataque de fungos de podridão branca e parda. Para tanto, corpos de prova de cada espécie amazônica foram submetidos a ensaios de apodrecimento acelerado, de acordo com a American Society for Testing and Materials - ASTM D2017, durante 20 semanas. Os parâmetros colorimétricos L* (luminosidade), a* (coordenada verde-vermelho), b* (coordenada amarelo-azul) e a variação total da cor (∆E) foram determinados semanalmente até a quarta semana, e posteriormente a cada duas semanas até a vigésima semana, com auxílio de um espectrofotocolorímetro. Adicionalmente, foram determinadas as perdas de massa dos corpos de prova. Os resultados permitiram destacar que a colorimetria foi eficaz no monitoramento da biodeterioração da madeira, bem como para diferenciação da podridão branca e parda. As melhores predições da resistência natural aos fungos de podridão branca e parda foram obtidas com os parâmetros b* e L*, respectivamente. Enfatiza-se também, o emprego da ∆E como parâmetro auxiliar na estimativa da biodeterioração da madeira, em razão de suas correlações significativas com a perda de massa.This work aimed to evaluate the use of colorimetry in the characterization of biodeterioration marupá, jequitibá and cumaru wood, submitted to white and brown rot. For this purpose, specimens of each Amazonian species were submitted to accelerated decay tests, according to American Society for Testing and Materials - ASTM D2017, during 20 weeks. With a colorimeter, the colorimetric parameters L* (lightness), a* (green-red coordinate), b* (blue-yellow coordinate) and total color change (ΔE) were determined weekly until the fourth week, and then every two weeks until the twentieth week. Additionally, it was determined the mass loss. The results indicated that the colorimetry was effective in monitoring of biodeterioration of wood, as well as to differentiate white and brown rot. The best predictions of natural resistance to white and brown rot were obtained with the parameters b* and L*, respectively. We also emphasizes the use of ΔE to estimate the biodeterioration of wood, because of their significant correlations with weight loss

Effect of artificial weathering on tropical woods monitored by infrared spectroscopy (DRIFT)

Four tropical woods, were investigated to compare their performance and natural resistances to artificial weathering using the diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). The species were garapeira (Apuleia leiocarpa), itaúba (Mezilaurus itauba) and tauari (Couratari sp.), woods traditionally indicated for exterior uses, and marupá (Simarouba amara), that served as reference. The samples were submitted to cycles of UV radiation (350 nm) and water until 2,000 h. The photodegradation processes of woods surfaces were accomplished monitoring the changes in the intensities associated to lignin (1508 cm-1) and carbonyl group (1736 cm-1) absorptions. The results have shown that lignin was the first component to be photodegradated, resulting in surfaces mainly composed by cellulose, after 2,000 h of UV irradiation. The processes of formation and lixiviation of carbonyl compounds were different for each species. The experimental conditions used in this work were too severe to evaluate the wood density and extractives content influences during the treatment

Characterization of wood decay by rot fungi using colorimetry and infrared spectroscopy

Amostras de madeiras de marup\ue1 ( Simarouba amara ) e andiroba ( Carapa guianenis ) foram submetidas ao ataque dos fungos Trametes versicolor (podrid\ue3o branca) e Gloeophylum trabeum (podrid\ue3o parda). A colorimetria foi empregada para determinar as cores das madeiras antes e ap\uf3s o ataque dos fungos. Para acompanhar a varia\ue7\ue3o do teor dos compostos qu\uedmicos foi utilizada a t\ue9cnica de espectroscopia de reflet\ue2ncia difusa no infravermelho m\ue9dio. Ambas as esp\ue9cies foram consideradas n\ue3o resistentes ao fungo de podrid\ue3o branca. Para o fungo de podrid\ue3o parda, a andiroba foi considerada resistente e o marup\ue1 n\ue3o resistente. Ambas as esp\ue9cies de madeira se apresentaram mais escuras ap\uf3s o ataque do fungo Gloeophyllum trabeum. J\ue1 o ataque do fungo Trametes versicolor causou clareamento na madeira da andiroba e escureceu ligeiramente o marup\ue1. Os resultados da an\ue1lise dos espectros de infravermelho mostraram que em ambas as esp\ue9cies de madeira houve redu\ue7\ue3o na intensidade das bandas de celulose, hemiceluloses e lignina ap\uf3s o ataque do Trametes versicolor, e redu\ue7\ue3o somente na intensidade da banda de celulose ap\uf3s o ataque do Gloeophyllum trabeum.Wood samples of marup\ue1 ( Simarouba amara ) and andiroba ( Carapa guianenis ) were submitted to Trametes versicolor (white rot) and Gloeophylum trabeum (brown rot) fungi attack. Colorimetry was used to determine the color of the wood before and after wood decaying fungi. To evaluate the changes in chemical compounds levels in the wood samples, the diffuse reflectance medium infrared spectroscopy was used. Both wood were non resistant against white rot fungus, while with brown rot attack andiroba was resistant and marup\ue1 was not. After Gloeophyllum trabeum attack both woods changed to a darken color, and after Trametes versicolor attack andiroba changed to a lighter color and marup\ue1 darkened slightly, The analysis showed a reduction in the peak intensity of cellulose, hemicellulose and lignin, for both species, after Trametes versicolor attack and a reduction in the peak intensity of cellulose after Gloeophyllum trabeum attack