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1.
To obtain new information about the mechanical and physical properties of dry wood in unstable states, the influence of heating history on viscoelastic properties and dimensional changes of dry wood in the radial, tangential, and longitudinal directions was studied between 100° and 200°C. Unstable states of dry wood still existed after heating at 105°C for 30 min and were modified by activated molecular motion in the first heating process to temperatures above 105°C. This phenomenon is thought to be caused by the unstable states reappearing after wetting and drying again. Dry wood components did not completely approach the stable state in the temperature range tested, because they did not entirely surpass the glass transition temperatures in most of the temperature range. In constant temperature processes at 135° and 165°C, E′ increased and E″ decreased with time regardless of the direction. This indicated that the unstable states of dry wood components were gradually modified with time at constant temperatures. On the other hand, anisotropy of dimensional change existed and dimension increased in the longitudinal direction, was unchanged in the radial direction, and decreased in the tangential direction with time at constant temperatures. Part of this report was presented at the 13th Annual Meeting of the Chubu Branch of the Japan Wood Research Society, Shizuoka, August 2003  相似文献   

2.
To investigate micropores and mesopores in the cell walls of dry wood, CO2 gas and N2 gas adsorption onto dry wood were measured at ice-water temperature (273 K) and liquid nitrogen temperature (77 K). CO2 gas adsorption isotherms obtained were used for determining micropore volumes smaller than 0.6 nm by the HK method (Horvath-Kawazoe method), and N2 gas adsorption isotherms obtained were used for determining the mesopore volume between 2 nm and 50 nm by the Barrett-Joyner-Halenda (BJH) method. Micropores and mesopores existed in cell walls of dry wood, and the cumulative pore volume was much larger for micropores than for mesopores. Micropores in the cell wall of dry wood decreased with elevating heat treatment temperature, and the decreased micropore was reproducible by wetting and drying. Mesopores did not decrease so much with elevating heat treatment temperature. Micropore volumes for the softwood Hinoki and the hardwood Buna were compared. A larger amount of micropores existed in hardwood Buna than in softwood Hinoki, and this relationship was considered to correspond to the difference in thermal softening properties for lignin in water-swollen Hinoki and Buna. This result probably indicates that micropores in the cell walls of dry wood relate to the structure of lignin.  相似文献   

3.
In this study heartwood from a Chinese fir [Cunninghamia lanceolata (Lamb.) Hook] plantation was treated using a high-temperature drying (HTD) method at 115°C, a low-temperature drying (LTD) method at 65°C, and freeze vacuum drying (FVD), respectively. The dynamic viscoelastic properties of dried wood specimens were investigated. The measurements were carried out at a temperature range of −120 to 250°C at four different frequencies (1, 2, 5, and 10 Hz) using dynamic mechanical analysis (DMA). We have drawn the following conclusions: 1) the storage modulus E′ and loss modulus E″ are the highest for HTD wood and the lowest for FVD wood; 2) three relaxation processes were detected in HTD and LTD wood, attributed to the micro-Brownian motion of cell wall polymers in the non-crystalline region, the oscillations of the torso of cell wall polymers, and the motions of the methyl groups of cell wall polymers in the non-crystalline region in a decreasing order of temperatures at which they occurred; and 3) in FVD wood, four relaxation processes were observed. A newly added relaxation is attributed to the micro-Brownian motions of lignin molecules. This study suggests that both the HTD and the LTD methods restrict the micro-Brownian motion of lignin molecules somewhat by the cross-linking of chains due to their heating history. __________ Translated from Journal of Beijing Forestry University, 2008, 30(3): 96–100 [译自: 北京林业大学学报]  相似文献   

4.
A dead tree of Pinus armandii Franch. var. amamiana (Koidz.) Hatusima (abbreviated to PAAm) was obtained from a natural habitat on Tanega-shima Island and various properties of its wood were investigated. Grain angle was measured and soft X-ray analysis was undertaken to obtain the density in each annual ring. Unit shrinkage and dynamic properties were measured by shrinkage, bending, and compression tests. Variations of wood properties in the radial direction, relationships of wood properties to density, and annual ring width were examined. Roughly speaking, variations in the radial direction of the grain angle, twist angle by drying, Young’s modulus and strength in static bending, absorbed energy in impact bending, compressive Young’s modulus, compressive strength, and compressive proportional limit corresponded to the variation of annual ring width. As a result, it was determined that if PAAm is afforested artificially for the purposes of lumber production and conservation, the annual rings of logs should not be too widely spaced. Wood properties of PAAm were similar to those of Japanese black pine (Pinus thunbergii Parl.), which is another representative pine on Tanegashima Island. This study was presented in part at the 56th Annual Meeting of the Japan Wood Research Society, Hiroshima, August 2007  相似文献   

5.
The effects of 120 methanol extracts prepared from bark and heartwood of 69 types of Japanese wood on the melanin production of B16 melanoma cells were examined. The melanin content of B16 melanoma cells was determined spectrophotometrically at 405nm. The extracts were also examined for their effects on cell viability. We found that the methanol extracts of Fagus crenata (buna, wood, 100μg/ml), Sapium sebiferum (Nankinhaze, wood, bark, 10μg/ml), and Zelkova serrata (keyaki, wood, 10μg/ml) greatly inhibited the melanin production of B16 melanoma cells without significant cytotoxicity. However, these extracts did not inhibit tyrosinase activity at the concentration of 100μg/ml. These findings indicate that the depigmenting mechanism of these extracts involves the suppression of some pigmenting signals in stimulating melanogenesis rather than the inhibition of tyrosinase activity. Part of this study was presented at the 53rd Annual Meeting of the Japan Wood Research Society, Fukuoka, Japan, March 2003  相似文献   

6.
The adsorption properties of wood carbonized at various temperatures were investigated using a mixed gas containing toluene and α-pinene. Hinoki (Chamaecyparis obtusa) samples carbonized at 500°–1100°C were exposed to gas mixtures of toluene and α-pinene at 20°C. The samples carbonized at 500°–700°C only adsorbed toluene, whereas those carbonized at 800°–1100°C adsorbed both toluene and α-pinene. Analysis of the surface structure of the carbonized wood by nitrogen adsorption at liquid nitrogen temperature indicated that the sample carbonized at 700°C had micropores mainly 0.6 nm in diameter and few mesopores, whereas the samples carbonized at 900°C and 1100°C had mesopores and micropores larger than 0.8 nm in diameter. With the sample carbonized at 700°C, the flat-shaped toluene molecules could probably penetrate into the narrower pores, 0.8 nm in diameter, whereas the bulky globular-shaped α-pinene molecules could not. Carbonization at temperatures higher than 900°C probably enlarged the pore size and thereby reduced the selectivity of adsorption. The results revealed that wood carbonized below activation temperature has a unique flat-pore structure that seems to work as a kind of molecular sieving carbon, successfully removing only the harmful volatile organic compound (VOC), toluene, and leaving behind a pleasant aroma of α-pinene in the atmosphere.  相似文献   

7.
The catalytic effect of aluminum on graphitization of wood charcoal was examined. Wood charcoal impregnated with aluminum triisopropoxide to various levels was subjected to direct electric pulse heating. Electric conductivity and heat conductivity of the products showed strong, systematic dependence on the amount of aluminum added. X-ray diffractometry indicated that these effects result from a larger degree of graphitization. Because the amount of aluminum in the final product was negligible, aluminum, before being lost by vaporization, apparently catalyzed graphitization at a lower temperature than is used for conventional treatments.Part of this report was presented at the 17th Annual Meeting of the Association of Wood Processing and Technology, November 1999; the 11th MRS-J Annual Meeting, Kawasaki, December 1999; and the 50th Annual Meeting of the Japan Wood Research Association, April 2000  相似文献   

8.
To investigate the changes in microstructures of wood with elapsed time in the environment, CO2 adsorption onto dry wood was measured at ice-water temperature (273 K) for samples aged from 0.1 years to over 1000 years. The micropore size distribution was obtained using the Horvath-Kawazoe method. Micropores smaller than 0.6 nm in wood decreased in number with elapsed time in the environment, and a negative correlation was found between cumulative pore volume for pores smaller than 0.6 nm and elapsed time in the environment. Cumulative pore volume in the 1000-year sample was almost half of that in the 0.1- year sample. Micropores smaller than 0.6 nm in wood with a few decades or more of elapsed time increased in number after rewetting and drying. Consequently, microstructures of wood with longer time elapsed in the environment were considered to be more stable, because of longer-term thermal motion and possibly more repeated moisture adsorption and desorption and/or temperature variation in the environment.  相似文献   

9.
The effect of ultraviolet (UV) light irradiation on the color and chemical structure of water-cured polymeric diphenylmethane diisocyanate (PMDI) was investigated using a UV long-life fade meter. Control treatment was performed without UV light irradiation using a thermohygrostat for comparison. Two kinds of resin were used in this study: that to which only water had been added, and resin to which a small amount of polyol and water had been added. In addition, lauan (Shorea spp.) wood was used as a reference. The photodegradation of the resins over a period of up to 300 h was observed using a colorimeter and Fourier transform infrared (FT-IR) spectroscopy. When the resins were treated with UV light, the color difference (ΔE * ab) of the resins increased signifi cantly in a short time, and then reached a near-constant value. For lightness, L * decreased rapidly for a few hours and then decreased gradually. The color darkened compared with that of the wood used. When treatment was performed without UV light irradiation, ΔE * ab and ΔL * of the resins showed negligible change. Based on the results of FT-IR analysis, severe degradation such as cleavage of the main chemical bond was hardly observed under UV light irradiation irrespective of the type of resin. Part of this report was presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, Japan, and at the 6th International Wood Science Symposium, Bali, Indonesia  相似文献   

10.
In our preceding study, we clarified that liquids having similar molecular sizes to ethanol were mainly adsorbed onto lignin among the major constituents of wood. This suggests that most micropores or adsorption sites loosely hydrogen-bonded to each other, which are accessible to these liquids, exist in lignin. In the present study, to examine micropores in wood and lignin, micropore distribution was measured by CO2 gas adsorption at ice-water temperature (273 K). Dry samples prepared by gradual delignification from wood meal were used as adsorbents. The pore-size distributions were determined by analyzing adsorption isotherms using the Horvath-Kawazoe method. It was found that the number of micropores decreased with the decrease in residual lignin, and micropores were hardly found in cellulose and hemicellulose. It is considered that most micropores smaller than 0.6 nm in wood exist in lignin.  相似文献   

11.
 Supercritical carbon dioxide (SC-CO2) was tested for its potential as a carrier solvent for preservative treatment of solid wood and wood-based composites. A preliminary trial showed that the treatability of solid wood varied with its original permeability and that the SC-CO2 treatment was not promising for refractory timber species such a Larix leptolepis Gordon. In contrast, 3-iodo-2-propynyl butylcarbamate (IPBC)/SC-CO2 treatment resulted in enhanced decay resistance without any detrimental physical or cosmetic damage in all structural-use wood-based composites tested: medium density fiberboard, hardwood plywood, softwood plywood, particleboard, and oriented strand board (OSB). Further trials under various treatment conditions [25°C/7.85 MPa (80 kgf/cm2), 35°C/7.85 MPa, 45°C/7.85 MPa, 35°C/11.77 MPa (120 kgf/cm2), and 45°C/11.77 MPa] indicated that although small changes in the weight and thickness of the treated materials were noted the strength properties were not adversely affected, except for a few cases of softwood plywood and oriented strand board. The results of this study clearly indicated that the treatment condition allowed SC-CO2 to transport IPBC into wood-based composites, and the optimum treatment condition seemed to vary with the type of wood-based composite. Received: October 24, 2001 / Accepted: February 15, 2002 Part of this work was presented at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 2001; and the 32nd Annual Meeting of the International Research Group on Wood Preservation, Nara, May 2001 Correspondence to:M. Muin  相似文献   

12.
The influences of heating history, cooling method, and cooling set on microstructures and the mechanical properties of water-swollen wood were studied by measuring viscoelastic properties and dimensional changes while elevating temperatures between 20°C and 90°C. Both the viscoelastic properties and dimensional changes of waterswollen wood in the first heating process were quite different from those in the other heating processes. The results revealed that the molecular state of green wood around room temperature was stabilized and could not return to this state if drying or heating was carried out. Cooling methods greatly affected the viscoelastic properties, while they hardly affected dimensional changes when the temperature was elevated. Localized stress in the microstructures of water-swollen wood produced by quenching affected the mechanical properties in the heating process, while external stress less than the proportional limit caused by a cooling set had no effect. This revealed that much greater localized stress linked to the instability of waterswollen wood than the external stress in relation to the cooling set occurred. Part of this report was presented at the 53rd Annual Meeting of the Japan Wood Research Society, Fukuoka, March 2003  相似文献   

13.
Manufacture of plywood bonded with kenaf core powder   总被引：3，自引：0，他引：3  
Kenaf (Hibiscus cannabinus L.) core powder was used as a binder to manufacture three-ply plywoods of sugi (Cryptomeria japonica D. Don) by conventional hot pressing under various manufacturing conditions: hot-pressing conditions (pressure, temperature, and time) and powder conditions (grain size, spread volume, and moisture content). The adhesive shear strength and wood failure of plywoods were measured in accordance with the Japanese Agricultural Standard (JAS) for plywood. The result showed that fine kenaf core powder played a role as an effective binder when plywoods were pressed at high pressure, which caused extreme compression of veneer cells. In addition, the adhesive shear strength of plywoods in dry conditions was high regardless of pressing temperature and time, but it was sensitive to pressing temperature and time in wet conditions. The highest adhesive shear strength was obtained from plywoods manufactured with kenaf core powder (grain size 10 μm, spread volume 200 g/m2, moisture content 8.6%) under hot-pressing conditions (pressure 5.0 MPa using distance bars 4 mm thick, temperature 200°C, time 20–30 min). However, the plywood could not meet the requirement for the second grade of plywood by JAS because of its low water-resistance properties. Part of this article was presented at the 58th Annual Meeting of the Japan Wood Research Society, Tsukuba, March 2008, and the 10th World Conference on Timber Engineering, Miyazaki, June 2008  相似文献   

14.
Methanol extractives from the red heartwood of Bengal catechu (Acacia catechu) contained (+)-catechin as a major component making up 0.3% of the wood. A new polyphenolic compound with a (+)-homo-iso-catechin structure and having catechol and phloroglucinol moieties constituted 0.005% of the wood, and probably its epimeric compound in trace amounts, were also found.This report was presented at the 49th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1999 and the 44th Lignin Symposium, Gifu, October 1999  相似文献   

15.
A new method for monitoring moisture content during radio-frequency (RF)/vacuum drying was developed by measurement of temperature and pressure in wood. Temperature and pressure inside the wood were measured simultaneously during RF/vacuum drying at the same point. The relative humidity (RH) and moisture content (MC) below the fiber saturation point (FSP) were calculated based on temperature and pressure, and the relationship between the temperature, RH, and equilibrium moisture content (EMC) at the measurement point. When the moisture content was below the FSP, the calculated MC was slightly greater than the value given by oven drying. The absolute error was within 0.8% near the open cross side, and was within 1.8% at another measurement point. Thus, we concluded that it was practicable to monitor the moisture content below the FSP according to the temperature and pressure inside the wood. Part of this study was presented at the 15th Annual Meeting of the Chugoku Shikoku Branch of the Japan Wood Research Society, Higashi-Hiroshima, Japan, September 2003  相似文献   

16.
The transverse shrinkage variation within trees was examined for five sugi cultivars. The within-tree trends of tangential shrinkage (α T) were different by cultivar, whereas radial shrinkage (α R) increased from pith to bark in most cultivars. The tangential/radial shrinkage ratio (α T/α R) decreased from pith to bark in most cultivars, because the radial variation of α R was larger than that of α T. The cultivars showed significant differences among cultivars in α T, α R, and α T/α R, but the difference among cultivars for α T/α R was smaller. The relationships between transverse shrinkage and microfi bril angle (MFA), basic density (BD), tree ring parameters, and modulus of elasticity were examined. The α T and α R showed positive relationships with BD, latewood percentage, latewood density, and modulus of elasticity, and negative relationships with MFA and ring width. The relationships with earlywood density were weak. Sugi exhibited variation in transverse shrinkage within stem and among cultivars, with the variation affected by MFA, density, and tree ring parameters. Part of this article was presented at the 56th Annual Meeting of the Japan Wood Research Society, Akita, Japan, August 2006, and the 57th Annual Meeting of the Japan Wood Research Society, Hiroshima, Japan, August 2007  相似文献   

17.
The distributions of boron in Japanese cedar (Cryptomeria japonica D. Don) sapwood blocks treated with aqueous or methanolic boric acid [B(OH)3] solutions were explored through Raman spectroscopy and prompt gamma-ray analysis (PGA). B(OH)3 was the sole boron species observed in Raman spectra of the wood blocks treated with either solution. Plots of weight gain of the treated wood blocks versus boron concentration in treatment solutions were found to be linear. The results indicated that the methanolic solution makes it possible to impregnate wood with much larger amounts of boron than the aqueous solution. PGA confirmed that B(OH)3 was highly enriched near the end grains of the treated wood blocks. Raman measurements suggested that boron content in the bulk of the wood block is not as large as expected from the weight gain of the treated wood blocks when an ordinary air-drying method is used. It was concluded that the aqueous solution impregnates the cell walls of wood with boron more easily than the methanolic solution. Part of this report was presented at the 55th (Kyoto, March 2005) and 56th (Akita, August 2006) Annual Meetings of the Japan Wood Research Society. This article follows the previous rapid communication “Analysis of boron in wood treated with boric acid solutions using Doppler broadening method of prompt gamma-rays.” J Wood Sci (2006) 52:279–281  相似文献   

18.
Test samples of Japanese larch (Larix leptolepis) heartwood and Japanese beech (Fagus crenata) sapwood were heated for 22 h at constant temperatures (50°–180°C) under three water content conditions. Raman spectra of the samples were recorded before and after the heat treatments, and spectral changes in the range from 1000 cm−1 to 1800 cm−1 were evaluated using the difference spectrum method. For both wood species, the Raman band intensity at 1655–1660 cm−1 due mainly to the C=C and C=O groups in lignin clearly decreased with increasing heat-treatment temperature (HTT). The spectral change was thought to reflect the progress of condensation reactions of lignin molecules during the heat treatment. Moreover, the decrease in band intensity was considerably facilitated by the presence of water in the cell wall, suggesting that the condensation is closely related to the softening of lignin. From the spectral changes in the wavenumber region of 1200–1500 cm−1, it was considered that wood constituents are partially decomposed at the higher HTT. Part of this article was presented at the 53rd Annual Meeting of the Japan Wood Research Society, Fukuoka, March 2003  相似文献   

19.
Application of near-infrared spectroscopy to wood discrimination   总被引：4，自引：0，他引：4  
 This study deals with a new nondestructive discriminant analysis by which wood can be classified on the basis of a combination of near-infrared (NIR) spectroscopy and Mahalanobis' generalized distance. Its accuracy and reasonability were examined for wood samples with various moisture contents ranging from oven-dried to a fully saturated free water state. In a discriminant analysis employing second derivative spectra, each wood group was well distinguished. Mahalanobis' generalized distances between softwoods are relatively independent of analytical pattern, whereas the distances between hardwoods are large for easy classification. There may be two reasons for selecting a wavelength: (1) when the chemical component of wood substance relates to the discriminant analysis; and (2) when the difference in moisture content with wood species relates to them. When we correctly construct the database of NIR spectra, confirming the purpose of the analysis, suitable wood discrimination should be possible. Received: January 23, 2002 / Accepted: March 15, 2002 Acknowledgment The authors sincerely thank the Tanabe Southeast Asia Nations Friendship Foundation for financial support. Part of this report was presented at the 51nd Annual Meeting of the Japan Wood Research Society, 2001 Correspondence to:S. Tsuchikawa  相似文献   

20.
Reaction of Japanese beech (Fagus crenata) in an ionic liquid, 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), which can dissolve cellulose, was investigated. Although both lignin and polysaccharides such as cellulose and hemicelluloses can be liquefied at a treatment temperature of around 100°C, the liquefaction of polysaccharides mainly occurs at the beginning of the treatment with [C2mim][Cl]. Cellulose crystallinity in the wood was gradually broken down as the treatment continued. The solubilized polymers were depolymerized to low molecular weight compounds. The results indicate that [C2mim][Cl] is an effective solvent and reagent for the liquefaction of wood components and subsequent depolymerization of them. Part of this report was presented at the 58th Annual Meeting of the Japan Wood Research Society, Tsukuba, April 2008  相似文献   

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