Artificial weathering of tropical woods. Part 1: Changes in wettability

Holzforschung ◽  
2004 ◽  
Vol 58 (5) ◽  
pp. 552-557 ◽  
Author(s):  
Masanori Kishino ◽  
Takato Nakano
Keyword(s):  
Specific Gravity ◽  
Wood Species ◽  
Structural Changes ◽  
Adsorbed Water ◽  
Acacia Auriculiformis ◽  
Hydroxyl Groups ◽  
Eucalyptus Marginata ◽  
Artificial Weathering ◽  
The Difference ◽  
Tropical Woods

Abstract Changes in the wettability of eight species of tropical woods during artificial weathering up to 600 h are discussed from the aspect of chemical and structural changes in their surfaces: Amnurana acreana, Acacia auriculiformis, Dipterocarpus spp., Eucalyptus marginata, Eucalyptus robusta, Shorea spp., and Tabebuia spp. with relatively high and low specific gravity. On the whole, the wettability of specimens decreased upon irradiation up to 20 h; above that they increased. Changes in wettability during artificial weathering differed according to wood species. The IR spectra suggest that the specimen surfaces after irradiation for 600 h result in a cellulose-rich layer, and therefore the increase in wettability during artificial weathering can be explained in terms of the increase in hydroxyl groups originating from both the exposed cellulose and adsorbed water. However, the difference in wettability exists between species even after the surface develops a cellulose-rich layer. The stereoscopic micrographs showed the development of cracks for all of the specimens after irradiation for 600 h, and differences in their magnitudes according to species. From these results, the differences in wettability between species were estimated to be due to the structural changes on the surface during artificial weathering, whereas the increase in wettability was due to the chemical changes.

Artificial weathering of tropical woods. Part 2: Color change

Holzforschung ◽  
2004 ◽  
Vol 58 (5) ◽  
pp. 558-565 ◽  
Author(s):  
Masanori Kishino ◽  
Takato Nakano
Keyword(s):  
Diffuse Reflectance ◽  
Color Change ◽  
Reflectance Spectra ◽  
Acacia Auriculiformis ◽  
Eucalyptus Marginata ◽  
Artificial Weathering ◽  
Diffuse Reflectance Spectra ◽  
Before And After ◽  
The Difference ◽  
Tropical Woods

Abstract This paper describes the change in diffuse reflectance Fourier transform infrared (DRIFT) and ultraviolet-visible (UV-Vis) diffuse reflectance spectra of the following eight tropical woods during artificial weathering up to 600 h in relation to their color changes, especially to yellowing: Amnurana acreana, Acacia auriculiformis, Dipterocarpus spp., Eucalyptus marginata, Eucalyptus robusta, Shorea spp. and Tabebuia spp. with relatively high and low specific gravity. For A. acreana, A. auriculiformis, Dipterocarpus spp. and both Tabebuia spp., Δb* (yellowing) increased with exposure up to 50 h, and decreased above 50 h. For E. marginata, E. robusta and Shorea spp., on the other hand, both Δa* (shift to red) and Δb* decreased with increased exposure time. For woods in which Δb* increased, the Δb* showed a positive dependence on the difference in relative intensity ratio of a band at 1740 cm–1 to that at 2900 cm–1 (ΔD1740/D2900) in DRIFT spectra of specimens before and after exposure. This result indicated that the increased band at 1740 cm–1 played a significant role in the increased Δb*. Then again, also for woods in which Δb* decreased, the ΔD1740/D2900 increased, but was not related to the Db*. The ΔD1740/D2900 for woods in which Δb* decreased had a positive relationship to the difference in remission function at 410 nm (ΔF(R∞)410) in UV-Vis diffuse reflectance spectra for specimens before and after exposure, while woods in which Δb* increased were independent of the ΔF(R∞)410. Therefore, it is suggested that woods in which Δb* increased and decreased differ from one another in the contribution to the increase in the band at 1740 cm–1, resulting in either an increase or decrease of Δb*.

The impact of natural and artificial weathering on the visual, colour and structural changes of seven tropical woods

2017 ◽  
Vol 76 (1) ◽  
pp. 175-190 ◽  
Author(s):  
Ladislav Reinprecht ◽  
Miroslava Mamoňová ◽  
Miloš Pánek ◽  
František Kačík
Keyword(s):  
Structural Changes ◽  
Artificial Weathering ◽  
Tropical Woods ◽  
The Impact ◽  
Visual Colour

scholarly journals Insight of Weathering Processes Based on Monitoring Surface Characteristic of Tropical Wood Species

Coatings ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 877
Author(s):  
Agnieszka Jankowska ◽  
Katarzyna Rybak ◽  
Malgorzata Nowacka ◽  
Piotr Boruszewski
Keyword(s):  
Wood Species ◽  
Structural Changes ◽  
Middle Lamella ◽  
Surface Characteristic ◽  
Artificial Weathering ◽  
Tropical Wood ◽  
Weathering Processes ◽  
Short Period ◽  
Wood Section ◽  
Weathering Process

The main aim of the presented research was to compare the influence of selected ageing factors, such as UV radiation and complex artificial weathering methods, on the colour, wettability and roughness changes in garapa, tatajuba, courbaril and massaranduba from South America—tropical wood species that are popular for external usage in European countries. Both processes caused wood surfaces to become darker and turn to shades of brown. The highest total colour changes were shown in courbaril wood (wood with the highest extractives content). The wood surface roughness demonstrated variation, depending on the wood section and measurement direction, and increased after ageing treatments. Changes in surface contact angle were significant after the inclusion of water and drying in the weathering process (wettability decreased). Anatomical analyses of the tested tropical woods revealed structural changes after used artificial weathering treatments (distortion between cell elements, degradation of the middle lamella, micro-cracks in cell walls, thinning and degradation of parenchyma cells, cracks along pits within vessels). As a result of desorption tension, the changes caused by UV irradiation were much smaller than those caused by full artificial weathering. Fourier-transform infrared spectroscopy (FTIR) analysis indicated the occurrence of lignin and hemicelluloses oxidative changes after the weathering process which resulted in the formation of carbonyl and carboxyl compounds. The depolymerisation of cellulose was also identified. The results show that the observed changes may affect the long-term durability of finishes applied over wood subjected to weathering factors for a short period before finishing.

Influence of anatomy on the adhesion performance of four wood species

2020 ◽  
Vol 9 (4) ◽  
pp. e31942727
Author(s):  
João Gabriel Missia da Silva ◽  
Pedro Nicó de Medeiros ◽  
Denise Ransolin Soranso ◽  
Vinicius Peixoto Tinti ◽  
José Tarcísio da Silva Oliveira ◽  
...  
Keyword(s):  
Shear Strength ◽  
Specific Gravity ◽  
Wood Species ◽  
Tectona Grandis ◽  
Glue Line ◽  
Anatomical Characteristics ◽  
Ray Cells ◽  
Adhesion Performance ◽  
Adhesion Process

The aim of this study was to evaluate the influence of anatomical characteristics on the adhesion performance of Vatairea sp., Paulownia sp., Aspidosperma populifolium and Tectona grandis wood. Specimens for anatomical, physical and mechanical analyzes were produced from tangentially oriented boards. The treatments were joint glued from pieces of the same anatomical orientation (radial and tangential), evaluated for shear strength and glue line failure. The Vatairea sp wood had the highest specific gravity (0.74 g cm-3) and the Paulownia sp (0.34 g cm-3) wood was smaller. Aspidosperma populifolium species showed the highest shear strength in the glue line in the tangential and radial faces. The anatomical variables with higher influence on the wood adhesion process were pith ray cells and especially fibers that exhibit the greatest correlation with the shear strength of the glue line.

III. On the figure, dimensions, and mean specific gravity of the Earth, as derived from the ordnance trigonometrical survey of Great Britain and Ireland

1857 ◽  
Vol 8 ◽  
pp. 111-116 ◽  
Keyword(s):  
United Kingdom ◽  
Great Britain ◽  
Specific Gravity ◽  
Royal Society ◽  
The United Kingdom ◽  
The Earth ◽  
The Difference ◽  
The Government

The Trigonometrical Survey of the United Kingdom commenced in the year 1784, under the immediate auspices of the Royal Society; the first base was traced by General Roy on the 16th of April of that year, on Hounslow Heath, in presence of Sir Joseph Banks, then President of the Society, and some of its most distinguished Fellows. The principal object which the Government had then in view, was the connexion of the Observatories of Paris and Greenwich by means of a triangulation, for the purpose of determining the difference of longitude between the two observatories.

scholarly journals Summertime canopy albedo is sensitive to forest thinning

2013 ◽  
Vol 10 (9) ◽  
pp. 15373-15414 ◽  
Author(s):  
J. Otto ◽  
D. Berveiller ◽  
F.-M. Bréon ◽  
N. Delpierre ◽  
G. Geppert ◽  
...  
Keyword(s):  
Forest Management ◽  
Tree Species ◽  
Structural Changes ◽  
Near Infrared ◽  
Canopy Structure ◽  
Model Parameters ◽  
Transfer Model ◽  
Forest Thinning ◽  
Crown Volume ◽  
The Difference

Abstract. Despite an emerging body of literature linking canopy albedo to forest management, understanding of the process is still fragmented. We combined a stand-level forest gap model with a canopy radiation transfer model and satellite-derived model parameters to quantify the effects of forest thinning, that is removing trees at a certain time during the forest rotation, on summertime canopy albedo. The effects of different forest species (pine, beech, oak) and four thinning strategies (light to intense thinning regimes) were examined. During stand establishment, summertime canopy albedo is driven by tree species. In the later stages of stand development, the effect of tree species on summertime canopy albedo decreases in favour of an increasing influence of forest thinning on summertime canopy albedo. These trends continue until the end of the rotation where thinning explains up to 50% of the variance in near-infrared canopy albedo and up to 70% of the variance in visible canopy albedo. More intense thinning lowers the summertime shortwave albedo in the canopy by as much as 0.02 compared to unthinned forest. The structural changes associated with forest thinning can be described by the change in LAI in combination with crown volume. However, forests with identical canopy structure can have different summertime albedo values due to their location: the further north a forest is situated, the more the solar zenith angle increases and thus the higher is the summertime canopy albedo, independent of the wavelength. Despite the increase of absolute summertime canopy albedo values with latitude, the difference in canopy albedo between managed and unmanaged forest decreases with increasing latitude. Forest management thus strongly altered summertime forest albedo.

Root Occupation and Root Channels of Jarrah Forest Subsoils

1983 ◽  
Vol 31 (6) ◽  
pp. 615 ◽  
Author(s):  
B Dell ◽  
JR Bartle ◽  
WH Tacey
Keyword(s):  
Fine Roots ◽  
Dominant Role ◽  
Root Hairs ◽  
Forest Tree ◽  
Deep Soil ◽  
Eucalyptus Marginata ◽  
Shallow Subsurface ◽  
Clay Matrix ◽  
The Difference ◽  
Successive Generations

The role of root channels in the occupation of deep soil profiles by jarrah (Eucalyptus marginata Sm.) forest in south-western Australia was explored by coring and excavation. In profiles derived from granite, major descending roots are confined to channels that extend vertically from fissures and conduits in the shallow subsurface caprock layer deep in the clay subsoil. The channels are permanent features of the profile and are occupied by successive generations of trees. The channels have a diameter of 1-300 mm, abundance of 3 5 m-2 (all channels) or 1 m-2 (large channels), and occupy 1% of a horizontal surface at 6 m. Each forest tree has potential access to 100-200 channels. Large roots, fine roots with root hairs, and decaying root remains occur in the channels. Only fine roots (less than Imm diam.) penetrate the clay matrix and occupy the entire profile down to basement at depths of up to 40 m. In profiles derived from dolerite, occupation of the deep clay by large and fine roots is diffuse and root channels are absent. The dissimilar mode of root occupation of the two profile types may be explained by the difference in bulk density. In providing avenues for access by large roots as well as preferential wetting, the root channels may play a dominant role in the water and salt balance of jarrah forests on the granitic profile.

Softening Characteristics of Wet Wood under Quasi Static Loading

Holzforschung ◽  
2000 ◽  
Vol 54 (5) ◽  
pp. 557-560 ◽  
Author(s):  
S. Hamdan ◽  
W. Dwianto ◽  
T. Morooka ◽  
M. Norimoto
Keyword(s):  
Glass Transition ◽  
Relaxation Process ◽  
Wood Species ◽  
Static Loading ◽  
Chemical Structure ◽  
Steam Treatment ◽  
Radial Compression ◽  
Softening Behavior ◽  
Broad Leaf ◽  
The Difference

Summary In order to examine the possible influences of temperature on the wood constituents, two groups of wood species namely softwood (needle leaf wood) and hardwood (broad leaf wood) were subjected to heat or steam treatment during large radial compression between 0°C and 200°C. Two well-defined softening regions are observed. Both species showed the glass transition Tg of lignin at ~ 90°C and ~ 60°C for softwood and hardwood respectively and a second transition region at ~ 160°C. The softening behavior between the first and second transition in softwood is in contrast with the softening behavior of hardwood. This difference reflects the difference in the distribution of the relaxation process due to lignin, which suggests the difference in chemical structure of lignin between softwood and hardwood.

STUDIES ON LIGNIN AND RELATED COMPOUNDS: XVI. PHENOL LIGNIN FROM SPRUCE WOOD, FROM FREUDENBERG SPRUCE LIGNIN AND WILLSTÄTTER SPRUCE LIGNIN

1935 ◽  
Vol 13b (2) ◽  
pp. 61-77 ◽  
Author(s):  
Irene Koerber Buckland ◽  
Fritz Brauns ◽  
Harold Hibbert
Keyword(s):  
Condensation Product ◽  
Analytical Data ◽  
Insoluble Fraction ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Condensation Products ◽  
Building Unit ◽  
Spruce Wood ◽  
Analytical Results ◽  
The Difference

The condensation of lignin with phenol by treatment of spruce wood meal with this solvent, using hydrogen chloride as catalyst, yields two chemically different phenol lignins, namely, an ether-insoluble and an ether-dioxane–soluble phenol lignin, in a ratio of approximately 3 to 1. Duplicate preparations gave the same yields of these two fractions, analyses of which gave concordant results, indicating homogeneity and constancy of composition.The analytical results of the ether-insoluble phenol lignin, and of its methylated and acetylated derivatives, can be interpreted on the basis of the Brauns–Hibbert formula for the "native" lignin unit. It is found, in this way, that the ether-insoluble phenol lignin contains three new free phenolic hydroxyl groups capable of methylation with diazomethane, while one phenol group has reacted with one hydroxyl group in the lignin unit with formation of a phenyl-oxygen ether linkage.The analytical results of the ether-dioxane–soluble phenol lignin indicate that a much larger quantity of phenol has condensed with the "native" lignin building unit than in the case of the ether-insoluble fraction. The exact number of phenol molecules reacting to form this condensation product has not been determined experimentally although calculations based on analytical data point to a number as large as 15 or 21.The phenol condensation products were obtained from Freudenberg and Willstätter lignins in nearly quantitative yield and found to differ from the directly extracted phenol lignin in that neither of them could be resolved into two fractions, thus indicating that some change had taken place in the native lignin during the isolation process. The Brauns-Hibbert formula can also be applied to interpret the experimental data in both cases. These lignins appear to contain the same fundamental building unit as the ether-insoluble phenol lignin fraction isolated directly from spruce wood, with the difference that the former probably have one additional hydroxyl group capable of acetylation and diazomethane-methylation.The correlation found to exist in the present investigation between the phenol condensation products from native spruce lignin, isolated Freudenberg lignin and Willstätter lignin is regarded as providing definite experimental evidence indicating the presence of a chemical unit common to various lignins. The phenol condensation products, it is considered, may serve as valuable reference compounds for proving the identity of lignins obtained from different sources and by use of different chemical reagents.

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