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1.
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
2.
Effects of low bondability of acetylated fibers on mechanical properties and dimensional stability of fiberboard 总被引:1,自引:0,他引:1
Hideaki Korai 《Journal of Wood Science》2001,47(6):430-436
Fiberboards were prepared from acetylated fibers with various weight gains: 0, 4.7, 9.4, 18.5, and 24.8 weight percent gain (WPG). The effects of low bondability of acetylated fibers on mechanical properties and dimensional changes were determined. The decreased mechanical properties of acetylated fiberboard are mainly due to low bondability. To improve bending strength, high face density is also needed. The thickness swelling according to JIS and the linear expansion under relative humidity changes decreased with increasing WPG. As for accelerated weathering and the outdoor exposure test, the thickness changes in 4.7–18.5 WPG boards were much higher than those in OWPG board and 24.8 WPG board. The high thickness change in 4.7–18.5 WPG boards is due to low bondability. Although 24.8 WPG board also has low bondability, the thickness change of 24.8 WPG board decreased. The high dimensional stability of acetylated fibers, caused by high WPG, probably outweighs the dimensional change caused by low bondability. On the other hand, during the boiling test the thickness changes in 24.8 WPG board and the 4.7–18.5 WPG boards were higher than those in 0 WPG board. The effect of the boiling test on the boards is more severe than that seen with the accelerated weathering and outdoor exposure test; therefore, the effects of the low bondability probably cancel the effects of the high WPG. It is necessary to increase the bondability of acetylated fibers to improve the dimensional stability and the mechanical properties. 相似文献
3.
Reaction between maleic anhydride (MA) and wood specimens was carried out in a vapor phase reaction system. Reaction conditions
such as the ratio of supplied MA to wood, initial moisture content, and reaction temperature were optimized. The MA supplied
to the reaction system was effectively absorbed by the wood, and a satisfactorily high dimensional stability was achieved
even at a low MA/wood ratio. The dimensional stability increased with rising initial moisture content. When the reaction was
conducted at an elevated temperature (180°C), high dimensional stability was attained without remarkable weight increase and
bulking. The mechanism of dimensional stabilization was discussed on the basis of the dimensional changes at high humidity
and during repeated water soaking and drying. It was shown that the dimensional stabilization arises mainly from a decrease
of hygroscopicity. When the reaction was conducted at 180°C, the formation of cross-links in the cell wall was apparent. Following
the MA treatment, the antifungal property was remarkably enhanced and met the Japanese Industrial Standard K1571. Therefore,
MA treatment in the vapor phase is an effective method to attain antifungal properties as well as high dimensional stability
with a small amount of nontoxic reagent. 相似文献
4.
To clarify the role of lignin in the affinities of acetylated wood for organic solvents, the effects of delignification on
the solvent adsorption of acetylated wood were investigated. Acetylated wood meals rapidly adsorbed organic solvents that
were hardly adsorbed by unmodified wood. For nonpolar and low-polarity organic solvents, a clear positive correlation was
observed between the amount of adsorption and the lignin content. This indicated that acetylated lignin was responsible for
the excellent affinities of acetylated wood for hydrophobic organic solvents. On the other hand, for lower alcohols and water,
the amount of adsorption reduced with an increase in the lignin content. It was suggested that the adsorption of such polar
solvents was dominated by insufficiently acetylated hydrophilic polysaccharides. 相似文献
5.
Ezomatsu wood blocks were acetylated in a mixture of acetic anhydride and acetic acid containing excess potassium acetate
(KAc). The mixture method enabled rapid acetylation at 120°C: a 20% weight gain (weight percent gain; WPG) was achieved within
30 min while the WPG did not exceed 18% after 120 min of conventional uncatalyzed acetylation. At 40°C, however, a satisfactory
WPG was not achieved with the mixture method because both the wood swelling and KAc concentration in the reagent solution
were limited at that temperature. In addition, the antiswelling efficiency attained by the mixture method was irregularly
low, probably because of nonuniform reaction involving shrinkage of the cell lumina. These results suggest that the mixture
method is not advantageous for low-temperature acetylation, whereas it enables simple and rapid acetylation at high temperature. 相似文献
6.
Ezomatsu wood blocks were impregnated with potassium acetate (KAc) and then exposed to acetic anhydride vapor at 25°C and
120°C. The KAc-impregnated wood was rapidly acetylated at 120°C, and only 6 min was needed to achieve 20% weight percent gain
(WPG). The WPG increased with increasing catalyst loading (CL), but it turned to decrease above 20% CL probably because the
diffusion of acetic anhydride vapor was hindered by excess KAc depositing in the cell lumina. Thus, careful control of CL
is necessary in the vapor-phase acetylation. KAc was also effective in catalyzing the vapor-phase acetylation at 25°C: the
KAc-impregnated wood attained 20% WPG within 7 days, whereas the WPG did not exceed 10% even after 1 month in the uncatalyzed
system. Irrespective of treatment methods, the hygroscopicity of wood was reduced and its dimensional stability was improved
with an increase of WPG. These results confirm that the use of KAc simplifies the acetylation process at room temperature
with minimal loss of acetic anhydride. 相似文献
7.
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
8.
The vapor phase reaction of wood with maleic anhydride (MA) was investigated from the aspect of the mechanism of dimensional
stabilization. Notably the existence of cross-links was examined by detailed analyses of dimensional stability and related
properties, diffuse reflectance infrared Fourier transform (DRIFT) spectra, and changes in mechanical properties such as creep
property and vibrational property. Higher reaction temperature resulted in less leaching of reagent. Also a peak in DRIFT
spectra at 1730 cm−1 showed the esterification of wood components with MA, while that at around 1780 cm−1, which became remarkable with increasing reaction temperature, suggested the formation of cross-linking. The loss tangent
decreased and the creep deformation was restrained for the specimens treated at high temperature. From these results it is
plausible that MA mainly forms monoester with wood components at lower temperature; however, at elevated temperature cross-linking
appears in addition to formation of the monoester. 相似文献
9.
木材液相乙酰化处理及处理材尺寸稳定性和耐腐性的研究 总被引:2,自引:0,他引:2
本文论述了马尾松、白桦和青杨三种木材的液相乙酰化条件及各种乙酰化木材的尺才稳定性和耐菌腐能力。以乙酸酐和二甲苯为处理液,反应的最佳条件是:温度120℃,时间7到11小时,乙酸酑与二甲苯配比1:1。当处理试样的增重到15%时,抗收缩率可达60%以上。增重为11.75—17.98%的不同处理试块,其耐菌腐能力可提高3—34倍。 相似文献
10.
乙酸酐对大豆基木材胶粘剂的改性研究 总被引:2,自引:0,他引:2
用乙酸酐改性大豆基木材胶粘剂,研究了乙酸酐为不同浓度时,双因素(pH值和温度)对耐水胶合强度的影响。试验结果得到4个不同浓度下pH值和温度的最佳组合值为:乙酸酐体积分数为1.2%、1.8%、2.4%、3.0%时对应的pH值/温度是8/55℃、8/55℃、7/70℃、7/70℃,最佳耐水胶合强度可提高到0.72 MPa。以乙酸酐体积分数为1.8%为例,采用茚三酮法测得大豆蛋白质的酰化程度,分析不同温度下pH值对酰化程度的影响,结果显示:耐水胶合强度与酰化程度不成正相关。由红外光谱分析可知,乙酸酐与大豆蛋白的游离氨基发生了交联反应,从而提高了大豆基木材胶粘剂的耐水胶合强度。 相似文献
11.
Jian-Zhang Li Takeshi Furuno Sadanobu Katoh Tohru Uehara 《Journal of Wood Science》2000,46(3):215-221
Acetylated, propionylated, butyrylated, isobutyrylated, and hexanoylated woods were prepared at several temperatures. The reaction rate, dimensional stability, and changes in the ratios of specific gravity and dimensions in the tangential and radial directions were estimated. The reaction rate of propionylation was slow at temperatures under 90°C but increased with the temperature. The butyrylated, isobutyrylated, and hexanoylated woods showed little or no weight percent gain (WPG) and little or no antiswelling efficiency (ASE) below 110°C even for 24h, but they achieved significant WPG and ASE values at 140°C with a longer reaction time. The acetylated, propionylated, and butyrylated woods showed almost the same values for dimensional stabilization efficiency based on WPG (DSE). The specific gravity and dimensions ratios for acetylated, propionylated, and butyrylated woods compared to those of untreated wood increased with an increase in WPG. 相似文献
12.
Improvements in dimensional stability and lightfastness of wood by butyrylation using microwave heating 总被引:1,自引:0,他引:1
Microwave heating was used as the heat source for butyrylation of wood with the aim of reducing the reaction time. The photostability and dimensional stability of butyrylated wood were also investigated in this study. Chemical changes of wood were confirmed by cross polarization/magic angle spin 13C-nuclear magnetic resonance and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) after butyrylation by microwave heating. Results from DRIFT with the Si-Carb sampling technique revealed that, using microwave heating, a higher degree of butyrylation of maple wood occurred in the middle of the specimen than on the outer surface. The increase in yellowness index of butyrylated wood treated with microwave heating was much less than that of untreated wood after the lightfastness test, indicating that photoyellowing of wood is effectively inhibited by butyrylation using microwave heating. The dimensional stability of wood was also improved after modification. 相似文献
13.
采用1%NaHCO_3水溶液对兴安落叶松(Larixgmelini)木材进行了处理,并用红外光谱、扫描电子显微镜和化学分析等方法对处理前后木材的尺寸稳定性、吸湿性、官能团和超微构造的变化进行了比较和分析。从而确定影响兴安落叶松木材尺寸稳定性的主要因素。本究研为兴安落叶松木材的改性和利用提供了理论依据。 相似文献
14.
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
15.
16.
后期热处理对酚类胶室外用刨花板尺寸稳定性的影响 总被引:1,自引:0,他引:1
研究了后期热处理对酚类胶室外用刨花板尺寸稳定性的影响,结果表明,后期热处理可以有效降低酚类胶刨 花板的吸水厚度膨胀率(TS),提高刨花板的尺寸稳定性,对强度性能指标影响不显著。在190℃温度下处理15min, 酚醛胶杨木刨花板的TS下降了18.53%,酚醛胶落叶松刨花板的TS下降了24.63%,单宁胶杨木刨花板的TS下 降了30.64%,单宁胶落叶松刨花板的TS下降了24.49%。 相似文献
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19.
Acetylation of wood was carried out in acetic anhydride only, acetic anhydride/xylene 1:1 (v/v), and acetic anhydride/pyridine 4:1 (v/v) solutions. The antishrink efficiency (ASE), hygroscopic properties, vibrational properties, and bending strength were compared among the three reaction solutions. The ASE was a simple function of weight gain (WG); the equilibrium moisture content at a given WG differed among the reaction solutions. Based on this fact and the results of repeated water soaking and oven-drying tests, it was found that the bulking effect was a major factor, and that decreased hygroscopicity contributes only slightly to the dimensional stabilization by acetylation. The difference in equilibrium moisture content among reaction solutions appears more significant in block samples than wood meal, probably due to the fiber-to-fiber bonds in the former. The tendencies for change in the specific Youngs modulus and the loss tangent differed among reaction solutions, whereas in the static bending test the difference was not marked.Part of this report was represented at the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, April 2002 相似文献
20.
阻燃剂WFRJ1改性木材的体积稳定性和涂饰性能 总被引:3,自引:0,他引:3
用阻燃剂WFRJ1处理大青杨木材并对处理材的阻燃性能、涂饰性能和体积稳定性进行测定。结果表明:WFRJ1可用于木制品的阻燃处理。当WFRJ1浓度为10%时,氧指数可达到50%以上,与水溶性RF树脂复配,可大幅度提高处理材的抗胀缩率和阻湿率,增加体积稳定性。经WFRJ1处理后杨木单板的涂饰性能未受影响。 相似文献