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1.
Makoto Ohkoshi Atsushi Kato Kentaro Suzuki Noriko Hayashi Mitsuro Ishihara 《Journal of Wood Science》1999,45(1):69-75
The objective of this study was to characterize the decay of acetylated wood due to brown-rot and white-rot fungi by analysis of chemical composition, X-ray measurements, and13C-NMR spectroscopy. The decay by brown-rot fungus became inhibited at a weight percent gain (WPG) due to acetylation of more than 10%, and the mass loss (LOSS) due to decay became zero at a WPG of about 20%. The LOSS due to white-rot fungus decreased slowly with the increase in WPG, reaching zero at a WPG of about 12%. The losses of lignin by brown-rot decay increased initially with the decrease in LOSS owing to the progressing acetylation and then decreased at a LOSS of less than 60%. Polysaccharides were more easily decomposed than lignin during the decay of acetylated wood due to brown-rot fungus. The losses of both components due to white-rot decay decreased as the LOSS decreased with progressing acetylation. The white-rot fungus tended to preferentially decompose the lignin during the decay of acetylated wood. The brown-rot fungus decomposed the cellulose in the crystalline region to a large degree when the LOSS was more than 40%, whereas the white-rot fungus decomposed the crystalline region and the noncrystalline region in acetylated wood to the same degree. The brown-rot fungus preferentially decomposed unsubstituted xylose units in acetylated wood and partly decomposed the mono-substituted xylose units. It was suggested that the mono- and disubstituted cellulose were partly decomposed by brown-rot fungus.This paper was presented at the 46th and 47th annual meetings of the Japan Wood Research Society at Kumamoto and Kochi in April 1996 and April 1997, respectively 相似文献
2.
Makoto Ohkoshi 《Journal of Wood Science》2002,48(5):394-401
The objective of this study was to characterize the surface changes in acetylated and polyethylene glycol (PEG)-impregnated wood caused during light irradiation by Fourier transformed infrared photoacoustic spectroscopy analysis to determine their effects on the reduction of light deterioration. Light irradiation made the color of the chemically modified wood lighter or more vivid, whereas it deepened the color of the untreated wood. The color difference during light irradiation was less in the chemically modified wood than the untreated wood. The color difference of PEG-impregnated wood increased with increasing irradiation time. The light irradiation generated much carbonyl and significantly degraded lignin in the untreated wood. The generation of carbonyl and lignin degradation diminished in the acetylated wood in comparison with the untreated wood, indicating that acetylation restrained the photochemical degradation of wood. Deacetylation did not occur during light irradiation of the acetylated wood. The PEG impregnation decreased the generation of carbonyl and degradation of lignin during light irradiation. However, the irradiation occurred a little photochemical degradation of PEG, generating the carbonyl. Therefore, longer light irradiation should increase the degradation of PEG, thus reducing the effect of treatment. The correlation between the color difference and lignin degradation was high, indicating that the color changes during light irradiation significantly depended on lignin degradation. The chemical modification reduced the degradation of lignin and consequently decreased the color difference. Some of the compounds containing the carbonyl generated during light irradiation were water-soluble.This paper was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000 相似文献
3.
To investigate the affinity of acetylated wood for organic liquids, acetylated yezo spruce wood specimens were soaked in various liquids, and their swellings were compared to those of untreated specimens. The acetylated wood was rapidly and remarkably swollen in liquids having low hydrogen bonding power such as benzene and toluene in which the untreated wood was swollen only slightly or very slowly. On the other hand, the swollen volume of wood in water, ethylene glycol, and alcohols remained unchanged or slightly decreased after the acetylation. The effect of acetylation was greater in liquids having smaller solubility parameters. The easier penetration of aprotic organic liquids into the acetylated wood was considered to be due to the reduction of polarity and the scission of hydrogen bonds in the amorphous wood constituents where the hydrophilic hydroxyl groups were substituted by hydrophobic acetyl groups. 相似文献
4.
Eiichi Obataya 《Wood Science and Technology》2005,39(6):472-483
Dimensional changes of acetylated wood were measured during wet–dry cycling and heating to clarify the reversible and irreversible
effects of those after-treatments. During wet–dry cycling, the acetylated wood showed slight swelling in its completely dry
condition, while its weight decreased slightly. Similar swelling was recognized when the acetylated wood was heated dry above
140°C. On the other hand, the anomalous effects of wet–dry cycling and heating disappeared after soaking in acetone. It was
considered that the rearrangement of hydrophobic wood polymers during wet–dry cycling and heating induced the expansion of
voids, whereas the wood polymers recovered their initial conformation after soaking in organic liquids. The wet volume of
acetylated wood also exhibited reversible changes during wet–dry cycling. Just after the acetylation, the wood was highly
swollen in acetic anhydride. The swollen volume of acetylated wood was reduced by leaching in water, and additional decrease
in the wet volume resulted from the following drying or boiling. However, the reduced wet volume was recovered almost completely
after acetone-soaking. These results suggested that the water molecules remaining in the hydrophobic region expanded the wet
volume of acetylated wood, while such weakly bound water was easily removable by drying or boiling. 相似文献
5.
Unmodified and acetylated cedar wood specimens were swollen in various liquids and dried under radial compression. Two stress
relaxation processes were observed during drying, and the second process observed below the fiber saturation point was responsible
for the drying-set and the temporary fixation of compressive deformation. The fixed shape of acetylated wood was partly recovered
by soaking it in water and toluene and completely recovered in acetone. The effective shape fixation and recovery of toluene-swollen
samples implied that the intermolecular hydrogen bonding was not necessary for the drying-set of acetylated wood. The degree
of shape recovery was not explained by initial softening, while the acetylated wood always exhibited greater recoverability
than unmodified wood. Although 85% stiffness was lost after large compression set and recovery of unmodified wood, such a
stiffness loss was limited to 39% when the acetylated wood was processed with organic liquids. This indicated that the swelling
of the hydrophobic region in the acetylated wood was effective in preventing mechanical damage due to large compressive deformation. 相似文献
6.
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
7.
In order to examine the contribution of wood components to the acetylation of wood, we acetylated wood meal that had been
partially delignified. The results were analyzed in terms of the reaction kinetics. The first-order rate equation was successfully
adjusted to the weight gain data. The rate constant for acetylation initially increased with progress of lignin elimination
and then turned to decrease; the apparent activation energy showed the reverse tendency and ranged from about 90 to 130 kJ/mol.
These results suggest that lignin elimination brings not only separation of lignin but also drastic change of the chemical
and/or physical structure in the residual lignin, and this affects the reactivity of wood meal as a whole. The ultimate weight
gain estimated by the regression of the rate equation showed a minimum when lignin was moderately eliminated, which was explained
in terms of enhanced reactivity of lignin and lower accessibility for holocellulose than predicted. The equilibrium moisture
content had a maximum when lignin was moderately eliminated. This tendency is the opposite of that observed for the ultimate
weight gain, and suggests that the sites for acetylation do not always correspond to those for moisture adsorption.
Part of this report was presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, August 2004 相似文献
8.
Yuka Miyoshi Ai Sakae Nao Arimura Keisuke Kojiro Yuzo Furuta 《Journal of Wood Science》2018,64(2):157-163
In this study, to summarize the changes of thermal-softening behaviors of wood and acetylated wood due to differences in the kinds of swelling liquids, the following measurements were conducted. Untreated and acetylated wood samples were swollen by various liquids and the temperature dependences of the dynamic viscoelastic properties were measured after the heating and cooling histories were unified among the samples. The results obtained are as follows. Untreated samples swollen by high-polarity liquid had lower peak temperature of tanδ, however acetylated samples had higher peak temperature of tanδ than those of untreated wood. On the other hand, untreated wood samples swollen by low-polarity liquid had higher peak temperature of tanδ, however acetylated samples had lower peak temperature of tanδ than those of untreated wood. The amount of swelling is determined by interaction between wood and liquid due to proton-accepting power and molar volumes of liquid and so on, therefore the peak temperature of tanδ and degree of reduction in dynamic elastic modulus (E´) with increasing temperature were corresponded to the amount of swelling. 相似文献
9.
Wood meals of Sugi (Cryptomeria japonica D.Don) passing 2.0 mm and retained on 1.0 mm mesh screens were milled along with acetic anhydride (AA) and pyridine as a catalyst in a high-speed vibration rod mill at ambient temperature. The weight percent gain (WPG) of the chemically modified wood was calculated based on the yield after washing with deionized water. The effects of amounts of AA and catalyst added, pulverization time, and saponification of the acetylated wood on WPG were examined. In addition, FT-IR analysis, and water vapor adsorption and desorption tests were performed as functions of the WPG. Increases in WPG, the acetyl contents of the acetylated wood after saponification, changes in the FT-IR spectra after pulverization, and the water vapor sorption isotherms showed that the one-step acetylation systematically modified the hydroxyl groups of the wood into acetyl groups. Up to 38 % WPG was obtained at 100 phr AA and 15 phr catalyst, and 120 min pulverization. Pulverization time and the amounts of AA and catalyst added to the wood meals could be adjusted to obtain acetylated wood meal with the desired WPG. These demonstrated that the mechanochemical acetylation is a method to prepare acetylated wood meals with high WPG at less reaction time and required AA addition. 相似文献
10.
Jorge Rencoret José C. del Río Ana Gutiérrez ángel T. Martínez Shiming Li Jim Park?s Knut Lundquist 《Wood Science and Technology》2012,46(1-3):459-471
The occurrence and nature of acetate groups in the milled wood lignin (MWL) isolated from birch (Betula pendula Roth) has been addressed by spectroscopic (2D-NMR) and chemical degradative (derivatization followed by reductive cleavage, DFRC) methods. Considerable amounts of acetate groups were present in the MWL preparation. However, 2D-NMR analysis indicated that the lignin polymer is not extensively acetylated and that the major part of the acetate groups is attached to the xylan moieties present in the MWL preparation. Nevertheless, evidence of the presence of minor acetylation of the γ-carbon of the lignin side chain (<3% of both syringyl and guaiacyl lignin units) was provided by DFRC analysis. 相似文献
11.
Sander C. Beckers E. P. J. Militz H. van Veenendaal W. 《Wood Science and Technology》2003,37(1):39-46
The properties of acetylated solid wood were investigated earlier, in particular the anti-shrink efficiency and the resistance against decay. This study focuses on the possible changes and damage to the wood structure due to an acetylation process leading to weight per cent gains of up to 20%. Electron microscopy (SEM and TEM) was used to investigate the fine structure of acetylated beech, pine and spruce. Cell wall swelling was observed, but no evidence of damage could be seen as a result of the acetylation procedure. The fine structure of the wood tissue such as the pits and the thin parenchyma walls appeared untouched. 相似文献
12.
Preparation of acetylated wood meal and polypropylene composites II: mechanical properties and dimensional stability of the composites 总被引：2，自引：0，他引：2
Acetylated wood meals of Sugi (Cryptomeria japonica D.Don) wood were prepared by mechanochemical processing using a high-speed vibration rod mill. Weight percent gain (WPG) of the acetylated wood meals ranged from 7.0 to 35.5 %. Wood–plastic composites (WPCs) containing 50 % acetylated woods were produced by an injection molding technique. The polymer matrix used was polypropylene homopolymer. Maleic anhydride-grafted polypropylene (MAPP) was also used as a compatibilizing agent. The mechanical properties of WPCs in bending and tensile tests were independent of WPG of acetylated wood meals, and the test values for WPCs containing acetylated wood meals were lower than that of unmodified wood meal. The use of MAPP increased bending and tensile strength, but no effect on bending modulus was found. An increase in WPG significantly decreased water absorbability and thickness swelling of WPCs as measured by dimensional stability tests. These results demonstrated that mechanochemical processing is a promising technique for preparing WPC material with improved dimensional stability. The future challenge is to inhibit the decreases in mechanical properties of WPCs containing acetylated wood meals. 相似文献
13.
《Wood material science & engineering》2013,8(3-4):106-117
Abstract One of the major issues in a long-term perspective for the use of wood–plastic composites (WPCs) in outdoor applications is the moisture sensitivity of the wood component and the consequent dimensional instability and susceptibility to biological degradation of the composite. In this work, the effects of using an acetylated wood component and a cellulose ester as matrix on the micromorphology, mechanical performance and moisture uptake of injection-moulded WPCs have been studied. Composites based on unmodified and acetylated wood particles, specially designed with a length-to-width ratio of about 5–7, combined with both cellulose acetate propionate (CAP) and polypropylene (PP) matrices were studied. The size and shape of the wood particles were studied before and after the processing using light microscopy, and the micromorphology of the composites was studied using a newly developed surface preparation technique based on ultraviolet laser irradiation combined with low-vacuum scanning electron microscopy (LV-SEM). The water vapour sorption in the composites and the effect of accelerated weathering were measured using thin samples which were allowed to reach equilibrium moisture content (EMC). The length-to-diameter ratio was only slightly decreased for the acetylated particles after compounding and injection moulding, although both the unmodified and the acetylated particles were smaller in size after the processing steps. The tensile strength was about 40% higher for the composite based on acetylated wood than for the composite with unmodified wood using either CAP or PP as matrix, whereas the notched impact strength of the composite based on acetylated wood was about 20% lower than those of the corresponding unmodified composites. The sorption experiments showed that the EMC was 50% lower in the composites with an acetylated wood component than in the composites with an unmodified wood component. The choice of matrix material strongly affected the moisture absorptivity of the WPC. The composites with CAP as matrix gained moisture more rapidly than the composites with PP as matrix. It was also found that accelerated ageing in a Weather-Ometer® significantly increased the moisture sensitivity of the PP-based composites. 相似文献
14.
The radial compression behaviors of acetylated cedar wood were measured in various liquids. The compressive Young’s modulus
(E) of acetylated wood was reduced by soaking in water, toluene, and acetone, but it was always greater than that of water-swollen
unmodified wood at the same swelling level. The behaviors of acetone-swollen unmodified wood were similar to those of acetylated
wood rather than those of water-swollen unmodified wood. These results indicated that the swelling of hydrophobic wood components
had a lesser influence on the E of wood than the water-swelling of unmodified hydrophilic components. After large compression (ε > 45%), a part of the strain
remained unrecovered because of irreversible mechanical deformation. Since the remaining strain was smaller in the wood specimens
indicating greater stress relaxation, it was assumed that the viscoelastic deformation of amorphous matrix components is important
for lesser irreversible deformation and effective shape recovery of wood. In contrast with water-swollen unmodified wood,
the acetylated wood and acetone-swollen unmodified wood exhibited greater shape recovery despite their relatively higher E. This suggested that the swelling of hydrophobic wood components reduced the viscosity of the matrix rather than its elasticity,
resulting in more effective shape recovery with lesser softening. 相似文献
15.
Five wood species were acetylated with acetic anhydride (AA) solution of glucose pentaacetate (GPA) at 120°C for 8h, and the effect of GPA on the dimensional stability of the acetylated wood was investigated. Some GPA was introduced into the wood cell wall during acetylation. The GPA remaining in the cell lumen penetrated the cell wall effectively after heating to more than 140°C for 10min. The bulking effects of GPA resulted in a 10%–30% increase in the anti-swelling efficiency of the acetylated wood with 20% GPA/AA solution in place of AA. Hydrophobic GPA did not deliquesce under highly humid conditions and it remained in the cell wall after boiling in water.Part of this paper was presented at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 1988 相似文献
16.
After enzymic hydrolysis of polysaccharides in milled wood or pulp the unhydrolysed lignin residue becomes soluble in certain polar solvents. Extensive disintegration of the wood is necessary to obtain a sufficient accessibility toward the enzyme. For milling a porcelain rotary ball mill is recommended. A relationship has been found between the milling energy, which is proportional to the size of the mill, the milling time, and the yield of ball-milled wood lignin (BMWL). Enzymatically isolated lignin (EIL) requires a critical milling time which is shorter than that for obtaining maximum yields of BMWL. A procedure for isolation of the total lignin content from wood and pulps in the form of three fractions has been developed, giving a water soluble, low molecular carbohydrate-lignin complex by water extraction of ball-milled wood, a BMWL-carbohydrate complex by subsequent extraction with dioxane, and a EIL-carbohydrate complex by dioxane extraction of the residue after enzymic hydrolysis. 相似文献
17.
Dynamic viscoelastic properties of wood acetylated with acetic anhydride solution of glucose pentaacetate 总被引：1，自引：0，他引：1
Spruce wood specimens were acetylated with acetic anhydride (AA) solutions of glucose pentaacetate (GPA), and their viscoelastic
properties along the radial direction were compared to those of the untreated and the normally acetylated specimens at various
relative humidities and temperatures. Higher concentrations of the GPA/AA solution resulted in more swelling of wood when
GPA was introducted into the wood cell wall. At room temperature the dynamic Young's modulus (E′) of the acetylated wood was enhanced by 10% with the introduction of GPA, whereas its mechanical loss tangent (tan δ) remained almost unchanged. These changes were interpreted to be an antiplasticizing effect of the bulky GPA molecules in
the wood cell wall. On heating in the absence of moisture, the GPA-acetylated wood exhibited a marked drop in E′ and a clear tan δ peak above 150°C, whereas the E′ and tan δ of the untreated wood were relatively stable up to 200°C. The tan δ peak of the GPA-acetylated wood shifted to lower temperatures with increasing GPA content, and there was no tan δ peak due to the melting of GPA itself. Thus the marked thermal softening of the GPA-acetylated wood was attributed to the
softening of wood components plasticized with GPA.
Received: March 29, 2002 / Accepted: May 21, 2002
Correspondence to:E. Obataya 相似文献
18.
ABSTRACT Acetylated wood is now commercially available and designed to be used in certain outdoor applications as an alternative to preservative-treated wood. Fastener corrosion can be a concern in preservative treated wood when the wood remains wet for long periods. However, little data on the corrosiveness of acetylated wood exists beyond the product literature. Here we examine the corrosiveness of commercially obtained acetylated wood and compare it against unmodified (untreated) southern pine (Pinus spp.). Corrosion rates of plain carbon steel, hot dip galvanized steel, and stainless steel were calculated gravimetrically after a one year exposed in the wood. Four different moisture conditions were examined: 90% relative humidity (RH), 95% RH, 100% RH, and a fully water saturated condition. When compared to literature data on the corrosion of fasteners in preservative treated wood at 100% RH, the acetylated wood had much lower steel corrosion rates than all preservatives examined; the measured corrosion rates for galvanized steel were lower than all preservatives except chromated copper arsenate. These measured corrosion rates across a range of moisture conditions can be used to inform the selection of appropriate corrosion resistant fasteners when building with acetylated wood. 相似文献
19.
Keisuke Kojiro Tsunehisa Miki Hiroyuki Sugimoto Masamitsu Nakajima Kozo Kanayama 《Journal of Wood Science》2010,56(2):107-111
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
20.
Preparation of sulfuric acid-catalyzed phenolated wood resin 总被引：22，自引：0，他引：22
Summary Birch wood meal was phenolated in the presence of sulfuric acid used as a catalyst by changing several reaction conditions, such as, phenol-to-wood ratio, temperature, time, and catalyst concentration to make novolak-type resin. A phenol-to-wood ratio of 2–5, reaction temperature of 60–150 °C, time of 60–120 min, and acid concentration of 1–3% were found to be usable values for obtaining good enough amounts of combined phenol and less amounts of unreacted wood residue. The flow properties (flow temperature and apparent melt-viscosity) of the phenolated wood obtained increased with the increase in the amount of combined phenol, however, decreased with the increase in the moisture content and free phenol in the phenolated wood. Furthermore, it was found that the solubility of the phenolated wood in the organic solvents depended, greatly, on the hydrogen bonding strength of the solvents. 相似文献