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1.
INTRODUCTION Wood is far from a stable material. One of the biggest challenges for woodworking is learning to work within the constraints of wood properties. Discoloration of wood directly influences the decorative performance of wood products. Therefore, the degree of color change is a critical factor that determines the utilization area of dyed wood (Sakuragawa Satoshi, 1996). Discoloration has occurred because the wood components and dye molecules are degraded by UV-ray (Kaneko Shin… 相似文献
2.
Transverse swelling and its anisotropy in hinoki (Chamaecyparis obtusa) in several kinds of organic liquids and in water were investigated by means the replica method. There was more cross-sectional swelling of cell walls and cell wall thickness in earlywood than in latewood. Marked swelling toward cell lumens was observed in wood swollen in liquids that had higher swelling potentials than water. This suggests that the swelling of cell walls in these liquids is much greater than the external swelling. Feret's diameters of the cell lumens were reduced by swelling in all the observed cases except in the tangential direction of earlywood, suggesting that cell walls swell to a much less extent in width than in thickness. Deformation of cell shapes caused by the tensile force from the latewood were observed in the earlywood and in the transitional region from earlywood to latewood. When swollen in water, transverse swelling anisotropy caused only by the swelling in cell wall thickness were calculated to be 1.2 for the whole region over an annual ring and 1.4 for the earlywood. These values could not account for the external swelling anisotropy of 2.1. Considering obvious deformations of cell shapes in the earlywood and in the transitional region, we conclude that the interaction between earlywood and latewood is one of the prime factors contributing to the transverse swelling anisotropy of coniferous wood.Part of this report was presented at the 48th Annual Meeting of the Japan Wood Research Society, Nagoya, April 1998 相似文献
3.
In order to investigate the effects of chemical components and matrix structure on the destabilization of quenched wood, we
examined the physical and mechanical properties of steam-treated wood, hemicellulose-extracted wood, and delignified wood,
which were treated at different levels. For steam-treated and hemicellulose-extracted wood,the relative relaxation modulus
of the quenched sample was lower than that of the respective control sample. For delignified wood, the relative relaxation
modulus fell with weight loss and reached a minimum value at a certain weight loss, and subsequently increased significantly.
The hygroscopicity of all treated samples changed slightly by steaming, whereas increased with removing the component. More-over,
the average volumetric swelling per 1% MC at 100% relative humidity (RH) was less than at 75% RH and 93% RH for component-removed
wood. It was clear that a void structure existed. As a result, the destabilization evaluated by the fluidity (1 - E
t/E
0) of steam-treated wood was influenced by the amount of adsorbed water. For component-removed wood, destabilization increased
temporarily at lower weight loss because of nonuniform cohesive structure. At high weight loss, destabilization will decreased
because capillary-condensed water gathered in the voids and obstructed the motion of adsorbed water. However, the destabilization
of all treated wood changed less than that of chemically modified wood. 相似文献
4.
饱水和气干状态杉木的压缩成型及其热处理永久固定 总被引：18，自引：9，他引：9
该研究采用烘箱热处理和真空热处理方法 ,在热处理温度都为 180℃ ,热处理时间分别为 6,10 ,15 ,2 5h的条件下 ,研究比较了饱水状态和气干状态杉木试材的径向压缩成型特性及其在不同方式热处理条件下热处理永久固定的效果 .研究结果表明 :①在相同条件下 ,与气干状态杉木试材相比 ,饱水并经蒸煮的试材在压缩成型后 ,或经热处理后 ,其回复率Rs 较小 ,各项物理力学性质较好 ;②在热处理过程中 ,对照试材的重量损失率WL随着热处理时间的延长而增大 ,而且 ,WL与Rs 之间呈近似线性负相关 ;③在相同条件下 ,与空气介质中热处理相比 ,真空中热处理后试材的材色变化较小 ,但回复率较大 相似文献
5.
Liquid penetration of precompressed wood VI: Anatomical characterization of pit fractures 总被引：3，自引：0，他引：3
Pit fractures of refractory coniferous heartwoods caused by precompression in the radial direction were investigated and are discussed in terms of improved liquid penetration. Small cracks appeared at the boundary between the torus and margo, along the outer margin of the margo, and on the torus when specimens were compressed and deformation was fixed by drying. The remarkable cracks were generally observed for Cryptomeria japonica D. Don. Pseudotsuga menziesii Franco showed peculiar detachment of the torus from the pit border, and Larix leptolepis Gordon exhibited only small cracks on the torus. These fractures patterns were clearer when the precompressed specimens were recovered by water impregnation and then redried.This report was presented at the 46th Annual Meeting of the Japan Wood Research Society, Kumamoto, April 1996 相似文献
6.
Sudijono Dwianto Wahyu Yusuf Sulaeman Iida Ikuho Furuta Yuzo Minato Kazuya 《Journal of Wood Science》2004,50(4):371-374
Mechanical property changes due to the moisture content (MC) and/or temperature changes were examined for 15 Indonesian wood species. A static bending test was carried out at 20°C, 65% relative humidity (air-dry), and water-saturated at 20°C (wet-20) and 80°C (wet-80). For individual test conditions, modulus of elasticity (MOE) and modulus of rupture (MOR) increased linearly with specific gravity regardless of wood species; however, maximum deflection did not correlate with specific gravity for any MC or temperature conditions. The relative values of MOE and MOR measured in wet-20 to air-dry conditions were variously affected from slightly to strongly depending on the wood species. However, the relative values always decreased markedly when saturated in water at 80°C, regardless of wood species. The relative MOE, MOR, and maximum deflection values due to the change in MC or MC and temperature combined were independent of specific gravity but may be dependent on wood type: softwood or hardwood. 相似文献
7.
In order to understand the mechanism of destabilization occurring when wood is quenched, we applied chemical modifications,
and controlled the number of moisture adsorption sites in wood. The degree of destabilization was evaluated according to the
fluidity (1-E
t/E
0), increase in fluidity, and relative fluidity in relation to the nonmodified wood, and was discussed by comparing these quantities
with the hygroscopicity or swelling of wood. We found that destabilization of chemically modified wood was lower than that
in nonmodified wood, and the amount of adsorbed water controlled the magnitude of flow of wood. Moreover, according to the
analysis of water state by the Hailwood-Horrobin equation, it was shown that the function of dissolved water to the fluidity
is almost identical for both chemical modifications, whereas hydrated water has more effect on acetylated wood than on formaldehydetreated
wood. We speculate that the motion of water molecules due to quenching accompanied with the redistribution of energy resulting
from the exchange of their potential energy and movement to attain a new balance, and the introduced acetyl groups and cross-linking
restrict the water molecule movement.
An erratum to this article is available at . 相似文献
8.
Yutaka Ishimaru Kazutoshi Arai Masato Mizutani Katsuhito Oshima Ikuho Iida 《Journal of Wood Science》2001,47(3):185-191
Some properties of wood (hinoki:Chamaecyparis obtusa) moisture-conditioned by an adsorption process from a dry state and by two desorption processes (from a water-saturated state and from a state with a moisture content slightly below the fiber saturation point) were investigated. The moisture contents of wood conditioned by the adsorption process and by the desorption process continued to approach to one another for the moisture-conditioning period of over 50 weeks. Accordingly, sorption hysteresis should be regarded as a transitional phenomenon that occurs during the process of approaching the true equilibrium, which requires a long time. The wood conditioned by the desorption process beginning from a water-saturated state showed slightly smaller dimensions than those conditioned by the adsorption process with the same moisture content; however, the wood conditioned by the desorption process from a moisture content below the fiber saturation point showed slightly larger dimensions than those conditioned by the adsorption process. The wood conditioned by the adsorption process from a dry state showed a higher modulus of elasticity and modulus of rupture than did the wood conditioned from a water-saturated state with the same moisture content. The mechanical properties of the wood also varied based on the states at which the desorption process was started. This is a notable characteristic of the relation between the drying condition and the mechanical properties of wood. 相似文献
9.
Ikuho IIDA 《中国林学(英文版)》2012,14(2):107-111
Elastic and strength properties(proportional-limit stress(σ prop ),Young's modulus(E),breaking stress(σ max )in static bending parallel to grain in a longitudinal direction),as well as stress relaxation in air-dried condition and water-saturated conditions at seven different constant temperatures and increasing and decreasing temperatures were investigated for wood from Chinese-fir and poplar plantations.The results show that hygrothermal conditions considerably affect these mechanical properties.The higher the moisture content(MC)or temperature,the lower the strength of wood.Further investigation of the effects of constant temperature on stress relaxation indicates that high temperature specimens have low relaxation moduli and high fluidity.In the case of increasing temperature the range of the modulus of relaxation is larger than in the case of a reduction in temperature,while the residual moduli do not show large differences.This is because the modulus at high temperatures decreases more than that at low temperatures.The fluidity of specimens in a state of water desorption increases slowly at the beginning,increases quickly until the MC reaches an equilibrium moisture content(EMC)and then becomes stable,which is quite different from that in a water-saturated state.Fluidity in a desorption state is much higher than in a water-saturated state.This is probably due to the fact that the former is in an unstable state which can be interpreted as a state with internal strain and has therefore a greater potential to release strain. 相似文献
10.
Yoshinori Kobayashi Ikuho Iida Yuji Imamura Ugai Watanabe 《Journal of Wood Science》1998,44(6):432-437
Seven species of bacteria were isolated and identified from ponded sugi (Cryptomeria japonica D. Don) logs, and six species showed potent wood-degrading activities. To evaluate the effects of these isolated bacteria on the drying and anatomical characteristics of wood, small fresh blocks of sugi were immersed in water suspensions containing bacteria for 1–7 months. The permeability and drying properties were evidently improved. Most of the encrusting substances adhering to the cell lumens and the pit chambers were removed, and the pit membranes were destroyed. These anatomical changes due to bacterial activity were assumed to improve the permeability of sugi wood.Part of this report was presented at the 40th annual meeting of the Japan Wood Research Society, Tsukuba, April 1990; the 41st annual meeting of the Japan Wood Research Society, Matsue, April 1991; and the IUFRO XX World Congress, Tampere, August 1995 相似文献