No description available.

No description available.

No description available.

M.S.

M.S.

The results of this investigation check the earlier work done by Czapek (1) in which he isolated an aldehyde which he termed “Hadromal”, and indicated as possibly being coniferyl aldehyde. The work was extended considerably, however, to positively identify “Hadromal” as being coniferyl aldehyde and to show that it was the substance responsible for the color reactions of wood. A new method as found to isolate “Hadromal”, namely, forming a bisulfite addition product and decomposing this product in the presence of iso-propyl ether. The crystals of “Hadromal” could then be recovered from the iso-propyl ether and purified. By this method, it was possible to identify “Hadromal” as coniferyl aldehyde, and show it to be responsible for the color reactions of wood. If ligroin was used as the solvent in place of isopropyl ether, a yellow oil separated, which evidently had a prohibiting effect upon the formation of crystals of coniferyl aldehyde and which was difficult to separate from the crystals. This oil was present when iso-propyl ether was used, but in a much lesser quantity. This oil was found to contain guaiacol. Pinene and a small amount of resin. As some of the investigation, Risi and Labri (1), who disagreed with Czapek (2) and Hoffmeister (3) used ligroin as the solvent, it is possible that their conclusions that “Hadromal” was composed of guaiacol, furfural, and catechol might have been influenced by the presence of oil. Results of this investigation also show what most earlier investigators had predicted, with the exception of Hoffmeister (3), that “Hadromal” is present in woody tissue in extremely small amounts. / M.S.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2017-04-27T11:59:34Z No. of bitstreams: 1 2012 - Cintia Silva Nunes.pdf: 1126230 bytes, checksum: 45346dd33d53277fd3bc88d1d3d22157 (MD5) / Made available in DSpace on 2017-04-27T11:59:34Z (GMT). No. of bitstreams: 1 2012 - Cintia Silva Nunes.pdf: 1126230 bytes, checksum: 45346dd33d53277fd3bc88d1d3d22157 (MD5) Previous issue date: 2012-06-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Heat treatment provides desirable characteristics to the wood such as higher dimensional stability, higher natural durability and, in some cases, changes on original color. However, the treatment can also drastically alter the physical and chemical characteristics of wood surfaces, which affect the adhesion quality and coating application. In this context, the objectives of this study were: (1) to evaluate the effect of heat treatmens on physical properties (density, equilibrium moisture content and mass loss) of Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson and Eucalyptus pellita F. Muell. woods; (2) to determine the effect of heat treatment on color change of both woods; (3) to evaluate the effect of heat treatments on adhesion quality of glued joints by shear strength testing; and (4) to evaluate the effect of physical and chemical modifications following heat treatment on adhesion characteristics. Heat treatments were performed in a laboratorial electric oven at 180 and 200?C. Color measurements were carried out on the CIE-L*a*b* space by using the CM-2600d portable spectrophotometer. Shear strength tests of the glued joints and solid woods were performed according to ASTM D 905 and ASTM D 143 standards, respectively. Three adhesive types were used: resorcinol, resorcinol-tannin 80:20 and resorcinol-tannin 60:40. Density and equilibrium moisture content of both wood species were reduzed by heat treatment. Both woods had mass loss, which increased with the increase of temperature and was more pronounced for Eucalyptus pellita. The original color of the woods changed following heat treatment, mainly to Eucalyptus pellita. The shear strength of solid wood and glued joints of both species was severely affected by heat treatments. The resorcinol-tannin 80:20 adhesive showed the best performance for untreated woods, however, after heat treatment, the adhesive type did not affect the shear strength. Glued joints of heat-treated woods had high percentage of wood failure due to higher porosity and adhesive penetration. The acidity of heat-treated woods affected the shear strength and presented a strong correlation with equilibrium moisture content due to degradation of hemicelluloses. Heat treatments at 180 and 200oC are extremely severe to Corymbia citriodora and Eucalyptus pellita woods / O tratamento de termorretifica??o proporciona ? madeira caracter?sticas desej?veis tais como maior estabilidade dimensional, maior durabilidade natural e, em alguns casos, altera??o da cor original. Entretanto, o tratamento tamb?m pode alterar drasticamente as caracter?sticas f?sicas e qu?micas das superf?cies da madeira, as quais afetam a qualidade de ades?o e a aplica??o de revestimentos. Neste contexto, os objetivos deste estudo foram: (1) avaliar o efeito dos tratamentos nas propriedades f?sicas (densidade, teor de umidade de equil?brio e perda de massa) da madeira de Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson e Eucalyptus pellita F. Muell.; (2) determinar o efeito dos tratamentos termorretificadores na altera??o da cor da madeira de ambas as esp?cies; (3) avaliar o efeito dos tratamentos na qualidade de ades?o de juntas coladas atrav?s de testes de resist?ncia ao cisalhamento; e (4) avaliar o efeito das altera??es f?sicas e qu?micas causadas pela termorretifica??o nas caracter?sticas de ades?o. A termorretifica??o foi realizada em um forno mufla el?trico laboratorial a 180 e 200?C. As medi??es de cor foram realizadas no espa?o CIE-L*a*b* com o aux?lio do espectrofot?metro port?til CM-2600d. Os ensaios de cisalhamento das juntas de madeira colada e das madeiras s?lidas foram realizados segundo as normas ASTM D 905 e ASTM D 143, respectivamente. Foram utilizados tr?s tipos de adesivos: resorcinol, resorcinol-tanino 80:20 e resorcinol-tanino 60:40. A densidade aparente e o teor de umidade de equil?brio das madeiras de ambas as esp?cies foram reduzidos pela termorretifica??o. Ambas as madeiras apresentaram perda de massa, sendo esta crescente com o aumento da temperatura e mais acentuada para a madeira de Eucalyptus pellita. A cor original das madeiras foi alterada pelo tratamento, principalmente para o Eucalyptus pellita. A resist?ncia ao cisalhamento da madeira s?lida e das juntas coladas de ambas as esp?cies foi severamente afetada pelos tratamentos termorretificadores. O adesivo resorcinol-tanino 80:20 apresentou o melhor desempenho para as madeiras n?o termorretificadas de ambas as esp?cies; entretanto, ap?s a termorretifica??o, o tipo de adesivo n?o afetou a resist?ncia ao cisalhamento. As juntas coladas das amostras de madeiras termorretificadas apresentaram uma alta porcentagem de falhas na madeira devido ? maior porosidade e maior penetra??o do adesivo. A acidez das amostras da madeira termorretificada afetou a resist?ncia ao cisalhamento e apresentou uma forte correla??o com o teor de umidade de equil?brio devido ? degrada??o das hemiceluloses. Os tratamentos termorretificadores a 180 e 200?C s?o extremamente severos para as madeiras de Corymbia citriodora e Eucalyptus pellita

This paper investigates chemical bleaching of wood and its ageing to make specie specific recommendations on which bleaching solutions to use when color adjusting veneer for furniture restoration.  In more detail, chemical bleaching of European walnut (Juglans regia), Rio rosewood (Dalbergia nigra), purpleheart (Peltogyne spp.), Honduras mahogany (Swietenia macrophylla) and padauk (Pterocarpus spp.) has been investigated using eleven different bleaching solutions. Both oxidative (e.g. hydrogen peroxide and potassium permanganate) and reductive (e.g. oxalic acid and sodium bisulfite) solutions have been used. Furthermore, to investigate aging of the bleached surfaces they were subjected to sunlight behind a glass window until a change in Blue Wool Scale 3 was obtained. Visual examination has been used to rank the color change after the chemical bleaching and the sun light exposure experiment. A small color change after the sun light exposure experiment indicates a high degree of lightfastness and is preferred for long term stability when restoring furniture. The results show that the wood species react in different ways to the investigated bleach solutions and to sun light exposure. It can also be noted that all investigated solutions were not suitable for all wood species. Moreover, the sun light exposure experiment identified effective bleach solutions that gave an unacceptable low lightfastness for mahogany and padauk after chemical bleaching. Based on the chemical bleaching and sun light exposure results, preferred bleaching solutions are recommended for the investigated wood species. / En vanlig restaureringsuppgift är att ställvis ersätta borttappat träfaner på en möbel. Originalfaneret har blekts med tiden, varför det nya faneret ofta är för färgstarkt och färgen behöver reduceras. När vi upplever en bit padouk som intensivt röd eller amarant som lila, beror det på att det i trät finns ämnen som tar upp energi motsvarande energin i våglängder av synligt ljus. När ämnena absorberar en del av det synliga ljuset registrerar våra näthinnor att de saknas, vilket tolkas som en färg av vår hjärna. De ämnen som absorberar synligt ljus kan brytas ner av solljus över längre tid eller på några minuter genom tillförseln av ett oxidations- eller reduktionsmedel. I mitt examensarbete undersöker jag hur olika oxidations- och reduktionsmedel bleker olika träslag. Jag har valt att undersöka hondurasmahogny, europeisk valnöt, brasiliansk jakaranda, padouk och amarant, då det är träslag som ofta behöver blekas när de används i kompletteringar. Vidare undersöker jag hur den genom blekning erhållna färgen i trät i sin tur påverkas av solljus. Detta är viktigt för att förstå hur de restaurerade delarna på möbeln kommer att åldras. De viktigaste resultaten sammanfattas nedan: Valnöt, jakaranda och amarant reagerade på liknande sätt vid kemisk blekning med de i studien använda lösningarna. De blekas mest av natriumhydroxid och salter med väteperoxid. Mahogny och padouk reagerade på liknande sätt vid kemisk blekning. De blektes mest, med ett jämnt resultat, av väteperoxid med natriumhydroxid eller ammoniak. Oxidationsmedel blekte effektivare än reduktionsmedel. Enbart väteperoxid gjorde jakaranda mörkare. En hög ammoniakkoncentration gav blekare resultat än en låg på alla träslag utom amarant. Valnöt var mest ljusäkta av de undersökta träslagen. Majoriteten av mahognyproverna mörknade av solljusexponeringen. Jakaranda och padouk blektes av solljusexponeringen. Flertalet amarantprover mörknade och ett mindre antal blektes av solljusexponeringen. Solljusexperimentet identifierade blekningslösningar som gav oacceptabelt låg ljusäkthet på mahogny och padouk.   För effektiv blekning och godtagbar ljusäkthet rekommenderas följande lösningar för respektive träslag. Välj lösning beroende på önskad blekningsgrad (se Tabell 2 sid 10). Mahogny: väteperoxid, oxalsyra eller kaliumpermanganat och natriumbisulfit. Valnöt: väteperoxid med eller utan ammoniak, väteperoxid och natriumhydroxid med eller utan salter eller natriumbisulfit och oxalsyra. Jakaranda: väteperoxid med ammoniak, oxalsyra, väteperoxid och natriumhydroxid med eller utan salter, natriumbisulfit och oxalsyra eller kaliumpermanganat och natriumbisulfit. Padouk: natriumhydroxid, natriumsilikat och kalciumhydroxid följt av väteperoxid. Amarant: väteperoxid med eller utan ammoniak, väteperoxid och natriumhydroxid med eller utan salter eller kaliumpermanganat och natriumbisulfit.