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June 1, 2005
Abstract
The influence of acetone, as a solvent on crystalline structure of the cellulose, was investigated. Crystalline changes brought about by the solvent treatment on the residual cellulose have been foundto be noticable. The crystallinity index of solvent treated celluloses has shown a trend of a small gradual increase with the progressive increase of acetone concentration in the treatment. The crystallite size of the residual cellulose has also been found to decrease successively with the increase of acetone content in the solvent composition. While the decrease in crystallite size reached approximately 8 %, the equivalent weight loss was only about 0.9 %. The influence of kinetic parameters on crystalline structure of cellulose during solvent purification (e. g., temperature, reaction time, acidity and type of acid catalyst) was also examined. Acidity and acid catalyst type were found to contribute to crystalline structural changes of cellulose. The use of higher concentrations for acids (TFA, HCl) has led to a decrease in crystallite size and crystallinity index. However, lower concentrations of TFA have a positive impact on the crystallinity index of the treated cotton cellulose. The crystallinity index of the residual cellulose has shown a slight increase with the increase in temperature, while the crystallite size has indicated a successive decrease. The reaction time has offered, in general, better chances for enhancement of the crystallinity index of the cellulose.
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June 1, 2005
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A special furnace for smoke-heating logs, with increased far-infrared radiation (FIR), was produced to improve the wood quality. Green sugi ( Cryptomeria japonica D.Don) logs were smoke-heated with the direct use of this system. In a short time, this process increased the temperature inside the logs up to 80–100 °C uniformly, without any damage to the wood. The great increase in steam pressure inside the log resulted in the rupture of pit membranes (PMs) with a high frequency, leading to a decrease in the moisture contents of the logs. It was found that when a temperature of 80 °C is attained inside the log, the rupture of PMs occurs. The rupture proceeds from the outer sapwood towards the pith, accompanied by the radiation heat transfer within the log. By the rupture of PMs, smoke-heated sugi wood showed a large improvement in permeability.
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June 1, 2005
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A laboratory evaluation was conducted to study the effectiveness of a biotreatment for deresinating wood chips from aged aspen. This treatment involves inoculating chips with a fungal inoculum, Cartapip 97 ® that feeds on wood resin components. This study demonstrated that, at room temperature and at 5°C, Cartapip can colonize chips from aged aspen despite the lower extractives content of the wood. Fungal treatment resulted in an additional 8% removal of wood resin in treated chips than in untreated chips after 3 weeks of seasoning. Analysis of the extractives by gas chromatography showed a significant reduction of steryl esters (25%), which are troublesome non-saponifiable wood resin components often found in aspen pitch deposits. The fungal treated chips were brighter than the untreated chips because the fungus prevented colonization of the chips by staining fungi. These results imply that fungal treatment of aspen chip piles in the winter will reduce the amount of wood resin in the chips and maintain their brightness. Such treatment will help alleviate pitch deposition problems attributable to aspen wax and reduce bleaching costs.
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June 1, 2005
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The mechanism of wood degradation by white-rot fungi is not understood in detail other than it is involving phenol oxidases (which are lignin-degrading enzymes) and cellulases. The possible role of hydroxyl radicals in degradation by the white-rot fungus Phanerochaete chrysosporium was studied. The production of a low-molecular-weight substance that is secreted was measured periodically. The substance catalyzes a redox reaction between O 2 and an electron donor producing hydroxyl radicals in the culture fluid of this fungus with glucose or wood as the carbon source. We examined the possible role(s) of one-electron oxidation activity by phenol oxidases and hydroxyl radicals in wood degradation by this fungus. Assays of phenol oxidase activity showed that P. chrysosporium produced much manganese peroxidase in wood culture, and that the activity peaked early in incubation. The generation of hydroxyl radicals in the redox reaction was related to the rate of wood degradation, but the activity of phenol oxidases was not related. Therefore, hydroxyl radicals are important in wood degradation by this fungus.
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June 1, 2005
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June 1, 2005
Abstract
Chemical analysis of Cistanche deserticola showed the presence of 7.5% of Klason lignin. Different lignin-carbohydrate fractions have been isolated from the methanol pre-extracted and depectinated Cistanche drug by sequential extractions using dioxane-water, cold and hot water, and 4% NaOH solution. 13 CNMR spectroscopy in combination with sugar analysis were used to characterize the isolated fractions. The proportions of the guaiacyl-, syringyl- and p -hydroxyphenyl units in the lignin-rich fractions differ significantly from those of both hardwood and softwood lignins and resemble more those of gramineous lignins. The carbohydrate portion consists of xylan, starch, pectic polysaccharides, and cellulose in proportions which are not typical of wood tissues.
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June 1, 2005
Abstract
Refluxing of trans –2-(3,4-dimethoxyphenyl)-3-hydroxymethyl-7-methoxy-2,3-dihydrobenzo[ b ]furan with dioxane-water (9 : 1) in the presence of various acid catalysts led to the formation of 2-(3,4-dimethoxyphenyl)- 7-methoxy-3-methylbenzo[ b ]furan, the trans and cis forms of 2-hydroxy-3,3′4′-trimethoxystilbene and cis –2-(3,4-dimethoxyphenyl)-3-hydroxymethyl-7-methoxy-2,3-dihydrobenzo[ b ]furan. The proportions of the products were strongly dependent on the particular acid used as catalyst. HCl and to a greater extent HBr favored the formation of the 2-arylbenzofuran (phenylcoumarone) while the trans -stilbene derivative predominated in reaction products from the experiments with trifluoromethane sulfonic acid as the catalyst. Isomerization of the starting material occurred, regardless of the nature of the catalyst (small amounts of the cis -isomer formed). The number of phenylpropane units in spruce lignin attached to an adjacent unit by a β−5 linkage was estimated to be 6–9% on the basis of 1 H NMR spectrometric measurements of the formation of phenylcoumarone structures on refluxing of milled wood lignin from spruce with 0.1M HBr in dioxane-water (9 : 1).
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June 1, 2005
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The α-hydroxyl group in lignin model compounds 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol ( 1 ) and 1-(4-hydroxy-3-methoxyphenyl)ethanol ( 3 ), and the α-carbonyl group in 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)ethan-1-one ( 5 ) are removed by treatment of the model compounds with trifluoroacetic acid (CF 3 CO OH) and triethylsilane (Et3sih) in methylene chloride. The reaction is highly chemoselective and it tolerates the lignin γ-hydroxyl group, phenol and β-O-4-aryl ether linkage. The α-hydroxyl group in 1 has also been removed with triethylsilane in aqueous trifluoroacetic acid (CF 3 CO OH : H 2 o = 75 : 25). The combination of trifluoroacetic acid and sodium borohydride, or sodium triacetoxyborohydride, is also effective in removing the α-carbonyl group in 5 and the α-hydroxyl group in lignin model compound 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)ethanol ( 7 ) and in milled wood lignin. The selective removal of the lignin α-hydroxyl and α-carbonyl groups may potentially be used, in conjunction with the protection of the lignin phenol, to inhibit the light and/or heat-induced yellowing of mechanical pulps.
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June 1, 2005
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A detailed examination was made of the behavior and distribution of ash and silica during atmospheric acetic acid pulping and subsequent bleaching of rice straw. Ash-rich pulps (in unbleached pulp, about 18%; and in bleached pulp, 16%) with matchable strength properties for conventional alkaline pulps were obtained from rice straw by acetic acid pulping. More than 50% of the ash and about 75% of the silica in rice straw were retained in the pulp after pulping. Because only those acid-soluble mineral components were dissolved during acetic acid pulping, the ash remained in the pulp consisted mainly of silica (92.9% of the ash in unbleached pulp and 97.3% of the ash in bleached pulp). Although part of the ash dissolved during bleaching, the ash content of bleached pulp was still 15.5%, a value much higher than that in other conventional pulps. This type of ash might be good as a filler for paper. Fractionation analysis and the profile and mapping of silica by scanning electron microscope combined with an energy dispersive X-ray analysis (SEM-EDXA) indicated that the silica in the bleached pulp was located mainly in epidermal cells and not in other elements, such as fibers and parenchyma, and that the silica-rich epidermal cells were scattered throughout the pulp as single cells or in bundles.
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June 1, 2005
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The chemical composition of suberin was studied in cork planks from three different trees of Spanish Quercus suber at four different stages of the industrial processing of first transformation: stripping (a), first rest (b), boiling followed by open air rest (c1) and boiling followed by store-room rest (c2). The monomeric composition was determined by gas chromatography/mass spectrometry in the product of depolymerization of the free of extractives cork with sodium methoxide-methanol. The average concentrations of the main monomers were: 1-alkanols (C 20 –C 26 ) 4.17 %; alkanoic acids (C 20 –C 26 ) 5.99%; α, ω-alkanedioic acids (C 16 –C 24 ) 6.20%; ω-hydroxy-alkanoic acids (C 20 –C 26 ) 29.41%; erythro and threo -9,10-dihydroxyoctadecanedioic acids 6.76%, erythro- and threo -9,10,18-trihydroxyoctadecanoic acids 9.50%, 9,10-epoxy-18-hydroxyoctadecanoic acid 2.72% and 9,10-epoxy-octadecanedioic acid 2.93% and ferulic acid 5.05%. Significant differences were observed between samples taken at the stripping and after boiling with store room rest, and both groups of samples differed from those picked after the other two processing stages. Ten components were selected as providing the greatest discrimination among stages: 9-octadecenedioic, 18-hydroxy-9-octadecenoic, eicosanedioic and 9,10-epoxy-18-hydroxy-octadecanoic acids, tetracosanol, and five unidentified components.
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June 1, 2005
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The storage modulus (E′) and the loss tangent (tanδ) of reed ( Arundo donax L.) used for woodwinds were measured at 20°C and 60% relative humidity and the effects of water soluble extractives on these properties were discussed. The extractives increased both the E′ and tanδof reed. There was a linear relationship between the tanδ change and the weight loss due to extraction. By using an uniaxial rheological model considering the anatomical structure of reed, the E′ and tanδ of reed were described using the storage moduli, loss tangents, and volume fractions of bundle sheaths and parenchyma cells. It was suggested that the extractives in parenchyma cells increased the modulus of elasticity for parenchyma cells by 25% and reduced the relaxation time of parenchyma cells by a factor of three. The main constituents of extractives were glucose, fructose and sucrose.
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June 1, 2005
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An electrical impedance frequency spectrum (20Hz to 1MHz) was measured in wood specimens with uniform, absorption and desorption transverse moisture content (MC) gradient. Parallel plate single sided capacitive and conductive electrodes were used. Capacitance, conductance and impedance locus analyses were included in the study, the desorption and absorption moisture gradients (MG) were estimated using frequency based analysis. This study suggests that the transverse MG can be estimated using impedance spectroscopy analysis. Both used electrode types and all the studied methods gave similar results which shows that frequency based analysis can be used. It was not possible to achieve very good accuracy when estimating MG using pure conductive or capacitance measurement method. The electrical distributed network circuit modelling was found to be the most promising method in estimation of transverse MG.
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June 1, 2005
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In this study, permeability measurements and flow rate-pressure-relationship analysis were carried out to determine whether non-Darcian flow due to nonlinear flow is present during air flow through red oak and red alder heartwood, and ponderosa pine and Douglas-fir sapwood. The results indicated that there was no evidence of nonlinear flow in red alder, ponderosa pine, and Douglas-fir throughout the entire range of flow rates, and for red oak at flow rates below 19.57 cm 3 /s. At higher flow rates, the results for red oak showed that the superficial specific permeability at the mean pressure of 50kPa decreased with the increase of the flow rates, and the equation relating pressure drop and flow rate at a given mean pressure of 50 kPa involved both a linear and quadratic dependence, thus demonstrating the presence of nonlinear flow components in wood. The calculated Reynolds number that was in the range of 0.263 to 1.05, further suggested that the nonlinear flow found in red oak heartwood at higher flow rates was probably nonlinear laminar flow due to the kinetic-energy losses occurring in the curved openings.
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June 1, 2005
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In this study, the detection and evaluation of non-Darcian air flow due to slip flow through four species were carried out. The results indicated that non-Darcian air flow due to slip flow existed in all the specimen groups studied. The true permeability of red oak heartwood, red alder heartwood, ponderosa pine sapwood and Douglas-fir sapwood was 20.91, 7.05, 0.51 and 0.068μ 3 /μm, respectively. The average ratios of the superficial specific permeability at 50kPa mean pressure to the true permeability were found to be: 1.047 for red oak heartwood; 1.204 for red alder heartwood; 1.292 for ponderosa pine sapwood; and, 1.53 for Douglas-fir sapwood. The slip flow constant b was highest (26.5kPa) for Douglas-fir sapwood, followed by that for ponderosa pine sapwood (14.6 kPa) and red alder heartwood (10.2 kPa), and lowest (2.3kPa) for red oak heartwood. The radius (r) and the number of average effective openings (n) were found to be: 17.432μm and 0.066×10 6 per cm 2 for red oak heartwood; 3.955 μm and 7.5 ×10 6 percm 2 for red alder heartwood; 2.972μm and 3.3 ×10 6 percm 2 for ponderosa pine sapwood; and, 1.552μm and 3.6 ×10 6 per cm 2 for Douglas-fir sapwood respectively.
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June 1, 2005
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This report describes two attempts to test the effect of removing the layer of damaged cells—the mechanical weak boundary layer. In both trials, the wood has been laser ablated using different types of lasers with different wavelengths. The goal has been to determine whether the glue joint strength is influenced by the mechanical weak boundary layer and to show how the laser wavelength affects the glue joint strength. The statistical evaluation of the results shows however no great differences between glue joints made of ablated and glue joints made of unablated surfaces. Nor are there any real differences between the different lasers and different wavelengths. This may be because there are indeed no differences between ablated and unablated surfaces, in terms of a mechanical weak boundary layer, but it may also be due to cracks which occurred in the wood specimens, and it is also possible that the glue itself was too weak. An ESEM (Environmental Scanning Electron Microscope)—analysis showed that fracture occurred primarily in the glueline and not in the boundary layer. In addition to the ESEM analysis and the statistical evaluation, a theoretical FEM (Finite Element Method)—analysis has been used to explain the crack initiation in the second trial.
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June 1, 2005
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As an essential preliminary to understand the hydration of wood-cement composites, the effects of some additives on the delayed setting due to wood of an Ordinary Portland Cement have been investigated by isothermal calorimetry. With the addition of calcium chloride and activated charcoal, an increase of 50% of the total enthalpy is observed in wood-cement composites hydration, because calcium chloride mostly influences aluminate phases and activated charcoal silicate phases.
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