Tainise V. Lourençon

Colour changes of Brazilian eucalypts wood by natural weathering

Abstract This study aimed to characterise wood discolouration of three Brazilian eucalypt species exposed to the action of natural weathering in two distinct places. To achieve this, tests were performed at an exposed outdoor site and under a forest canopy; both located in the state of Rio Grande do Sul, Brazil. Colorimetric measurements were performed every 45 days during the period of 1 year in order to obtain the parameters L*, a*, b*, C* and h*. The main results showed significant darkening in the first 4 months and subsequently increased the greyish colour. Colour variations were observed between species, field and exposure time in service.

Chemical modification of fast-growing eucalyptus wood

In this study, a new simple method for chemical modification of wood from fast-growing Eucalyptus saligna (blue gum) was tested by a two-step treatment with methacryloyl chloride. The wood samples were submerged in a solution of 10xa0% methacryloyl chloride in dichloromethane for 15xa0h and then exposed to three temperatures: air dried, 50 and 100xa0°C for 2xa0h. The chemical modifications of the wood were examined by ATR-IR and 13C CP/MAS solid-state NMR; quantitative chemical composition of wood samples by means of wet chemical quantification, HPLC, TGA; colorimetric evaluation by CIELAB method and UV–Vis spectroscopy. Water uptake tests were also performed. A partial substitution of the hydroxyl by methacrylate groups on the cell wall of blue gum wood was observed, and also loss of a hemicelluloses fraction after the treatments. The colour change increased with increasing temperature in the second step of the treatment. Dimensional stability and water repellence were improved by 40–50 and 60–75xa0%, respectively.

Chemical characterization of wood and extractives of fast-growing Schizolobium parahyba and Pinus taeda

Abstract This study aims to evaluate the chemical composition of wood and extractives of Pinus taeda and Schizolobium parahyba (guapuruvu) as potential feedstock for new applications in the biorefinery industry. For this purpose, their content of α-cellulose, hemicellulose, insoluble lignin, hot water solubility, NaOH1% solubility, inorganic materials (ash), and monomeric sugars by high-performance liquid chromatography was quantified. Attenuated total reflectance infrared spectroscopy and thermogravimetric analysis were also used to complete the physicochemical characterization of the studied woods. The extractives were obtained by soxhlet extraction with ethanol:toluene and dichloromethane and identified with pyrolysis-gas chromatography/mass spectroscopy technique. The results showed that guapuruvu wood has the higher amount of hemicellulose (16%) when compared to pine wood (10%), which resulted in higher solubility in alkali solution. Furthermore, in relation to other biomasses, the two woods presented more percentage of lignin and minor content of hemicelluloses. The P. taeda wood presented the highest percentage of extractives mainly composed of fatty acids and aromatic hydrocarbons, while guapuruvu wood had a higher percentage of phenolic compounds and also fatty acids. Both the materials have low content of extractives with dichloromethane and were mainly composed of lipophilic compounds.

Wood under fresh water: Effect on the chemical properties and on decay resistance

This study aimed to evaluate the effect of waterlogging on the chemical properties and on decay resistance of two fast-growing eucalypt species. Samples of spotted gum and rose gum wood were placed underwater and taken out at different times: after 4, 8 and 12 months. Chemical properties were performed via wet chemical quantification (Tappi standards), monomeric sugars by HPLC, and qualitative evaluation of extractives by Py-GC/MS and ATR-IR spectroscopy; biological performance was investigated using Trametes versicolor and Gloeophyllum trabeum rot fungi. The results showed slight changes to the chemical properties of both wood species, with an increase in lignin represented by the reduction of sugars due to waterlogging. Both species showed higher susceptibility to Gloeophyllum trabeum mainly in the sapwood, with no influence on decay resistance due the waterlogging.