Effect of the ethylene/vinyl acetate ratio of ethylene-vinyl acetate emulsion on the curing behavior of an emulsion polymer isocyanate adhesive for wood

We investigated the curing behavior of an emulsion polymer isocyanate adhesive for wood with different ethylene-vinyl acetate (EVA) emulsions, because it was found that the ethylene/vinyl acetate weight composition (E/VA ratio) of EVA could control the volume of gas emitted from the adhesive. EVA with higher VA content reduced the volume of gas emitted at the initial stage, which was caused by the extent of the reaction between the NCO groups and water. The reaction scheme of NCO could not be determined because the broad infrared (IR) absorptions due to CaCO3 and water masked the information of the NCO products in IR spectra. Examination of the degree of swelling suggested that the adhesive films stored for 3 weeks had the same degree of cross-linking structure in spite of the variation of EVA. This result was supported by IR spectroscopy, which showed the same amounts of NCO remained in these films. All the adhesives prepared in this study had satisfactory bond performance. The findings indicate that the E/VA ratio affects the curing behavior of the adhesive in the initial curing stage, whereas the cross-linking structure and the bond performance were independent of the E/VA ratio after storage for 3 weeks. Part of this report was presented at Wood Adhesives 2005, November 2–4 2005, San Diego, CA, USA     

A multi-species comparison of delta13C from whole wood, extractive-free wood and holocellulose

The stable carbon (C) isotope composition (delta13C) of tree rings is a powerful metric for reconstructing past physiological responses to climate variation. However, accurate measurement and interpretation are complicated by diagenesis and the translocation of compounds with distinct isotopic signatures. Isolation and analysis of cellulose minimizes these complications by eliminating variation due to biosynthetic pathways; however, isolation of cellulose is time-consuming and has no clear endpoint. A faster and better-defined analytical method is desirable. Our objectives were to determine if there is a direct relationship between the isotopic compositions of whole wood (WW), whole wood treated with solvents to remove mobile extractives (extractive-free wood; EF) and holocellulose (HC) isolated by extractive removal and subsequent bleaching. We also determined if total C concentration could explain the isotopic composition and variation among these three wood components of each sample. A set of wood samples of diverse phylogeny, anatomy and chemical composition, was examined. The mean offset or difference between HC and EF delta13C was 1.07 +/- 0.09 per thousand and the offset between HC and WW was 1.32 +/- 0.10 per thousand. Equivalence tests (with alpha = 0.05) indicated that the relationship between EF delta13C and HC delta13C had a slope significantly similar to 1 +/- 5.5%, whereas for the WW delta13C: HC delta13C relationship, the slope was significantly similar to 1 +/- 10.08%. A regression model using EF delta13C to predict HC delta13C had a slope of 0.97, which was not significantly different from unity (P = 0.264), whereas the regression for WW had a slope of 0.92 which was significantly different from unity (P = 0.0098). Carbon concentration was correlated with HC:WW offset and cellulose:EF offset (P = 0.0501 and 0.007, respectively), but neither relationship explained much of the variation (r2 = 0.12 and 0.14, respectively). We suggest that HC extraction is unnecessary for most analyses of tree-ring delta13C; a simple solvent extraction is a suitable alternative for many applications.     

Methods for the determination of wood properties,Kraft pulp yield and wood fibre dimensions on small wood samples.

A trial set-up with methods for sampling, treatment and analysis of small wood chips are presented in this paper, to determine important wood and fibre properties, like basic density, dry density, volume swelling of wood, Kraft pulp yield, fibre length, fibre coarseness, fibre width, lumen width and fibre wall thickness. The required time for one sample is about 1.5 man-hour, but this requires relatively larger series and trained personnel. Acceptable measurement accuracy is achieved when the volume of the wood sample is at least 1.5 ml, except that of wood volume swelling. To gain acceptable measurement accuracy for volume swelling, the wood volume should be increased to at least 3 ml, and preferably more than 5–6 ml per sample. The level of pulp yield and wood density do not show a significant effect on the measurement accuracy for fibre cross-section dimensions. Fibre coarseness, on the other hand, has a significant influence on these accuracies. A double measurement of fibre coarseness will improve the accuracy to an acceptable level. The method presented here may, together with information about trees and growth locations, form the basis for greater insight into the mechanisms involved in development of wood and fibre properties in trees, which in turn may provide better control and utilisation of wood for pulp and paper production.Abbreviations CWD cell wall density in dry wood=1500 kg/m³ - Ww dry weight of wood (kg) - Vmax green (wet) volume of wood (m³) - Vmin dry volume of wood (m³) - BD basic wood density (kg/m³) - DD dry wood density (kg/m³) - VS maximum volume swelling of wood (%) - Wp dry weight of pulp (kg) - PY pulp yield (%) - C fibre coarseness, the average weight of a unit length of fibre (g/m) - CL average chip length (mm) - CWT average cell wall thickness (m) - FW average fibre width (m) - l average native fibre length in solid wood - L chip length - lc average fibre length in wood chip (mm) - Lc length-weighted fibre length in wood chip (mm) - lw native average fibre length in wood (mm) - Lw native length-weighted fibre length in wood (mm) - LW average lumen width (m) - llw average native fibre length, length weighted, in wood - X average fibre length in chip - Xlw average fibre length, length weighted, in chip     

Effects of wood species and retention levels on removal of copper,chromium, and arsenic from CCA-treated wood using sodium hypochlorite

Chemical extraction, bioremediation, and electrodialytic processes have been extensively studied for removal of copper, chromium, and arsenic from wood treated with chromated copper arsenate(CCA). However,one problem has not been addressed: the effects of wood species and retention levels on remediation efficiency. The objectives of this study were to investigate the effects of wood species and retention levels on removal of copper,chromium, and arsenic from CCA-treated wood samples using sodium hypochlorite. Our results showed that sodium hypochlorite(Na OCl) was very effective for removal of copper, chromium, and arsenic from CCA-C treated milled wood samples for all three species used in this study. The Cu, Cr, and As extraction efficiencies for red pine were95 % Cu, 97 % Cr and 94 % As, for maple were 95 % Cu,97 % Cr, and 98 % As at 4.0 kg m-3retention levels, and for aspen were 95 % Cu, 92 % Cr, and 91 % As at9.6 kg m-3retention level, respectively. However, the results showed that wood species and initial retention levels of CCA-treated wood products played very important roles in terms of removal of Cu, Cr, and As.     

木材工业发展的机遇与挑战及其对策

综述我国木材工业的现状及严峻的形势，在加入世贸组织后木材工业将会面临着挑战与机遇并存局面。为此，木材工业应豚时调整产品结构，提出新的对外经济发展战略与布局。制定相应对策，面对即将来临的国际竞争与挑战。     

Colour responses from wood,thermally modified in superheated steam and pressurized steam atmospheres

Abstract

In this study, two different methods were used to produce thermally modified wood. One was carried out in a typical kiln drying chamber using superheated steam (SS) and the other used pressurized steam in an autoclave cylinder (PS). Overall, both processes followed the same principles and the wood was not treated with any chemicals. Two wood species were studied, Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). Treatments in the autoclave were carried out under pressure using temperatures of 160°C, 170°C and 180°C. Temperatures of 190°C and 212°C were used in treatments in the chamber at normal air pressure. The colour was measured using L*C*H colour space. Results for both species showed that similar L* (lightness) can be reached at lower (20–30°C) temperatures using PS compared with SS treatment. The hue angle of PS-treated wood was smaller than that of SS-treated wood. No significant difference in C* (chroma) was detected. The difference in E value between PS- and SS-treated wood was smaller for Norway spruce than for Scots pine. The residual moisture content was about 10% higher in wood treated by the PS process compared with the SS process.     

Utilization of wood biomass residues from fruit tree branches,evergreen hardwood shrubs,and Greek fir wood as raw materials for particleboard production. Part B. Hygroscopic properties and formaldehyde content

This paper investigates the basic hygroscopic properties and formaldehyde content (FC) of particleboards produced with wood biomass from fruit tree branches and evergreen hardwood shrubs as substitute raw materials for fir particles. One-layer laboratory particleboards with two distinct target densities (0.63 g/cm³ and 0.69 g/cm³) were produced using various mixtures of the above materials. Industrially produced wood particles were also used for comparison purposes. The results showed that the replacement of fir wood (FW) by evergreen hardwood material significantly upgraded board's quality in terms of thickness swelling (TS) and water absorption (WA) (except boards with density of 0.63 g/cm³) after immersion in water for 24 h and residual swelling (RS) after reconditioning. The contribution of branch-wood (BW) particles in the production of FW boards with density of 0.63 g/cm³ induced increase of TS, WA, and RS while for boards with density of 0.69 g/cm³ did not result to significant changes except for RS. In terms of FC, boards made of BW and evergreen hardwood showed significantly lower FC compared to those produced by FW and industrial particles.     

Effect of oxalic,acetic acid,and ammonia on leaching of Cr and Cu from preserved wood

Wood treated with CCB (chromated copper borate) has an expected service life of 20–50 years, depending on conditions of service and method of treatment. After this period, treated wood is discarded as special waste. Due to toxic elements (Cu, Cr, and B) in such treated wood, burning and landfill disposal are not considered as environmentally sound solutions. Chemical extraction seems more promising. The principle of the method is to convert fixed biocides in wood into soluble form and leach them out of the wood. In order to elucidate this process, copper(II) sulfate, potassium dichromate, and CCB-treated samples were leached using five different agents, namely, water, an aqueous solution of oxalic or acetic acid, and an aqueous solution of oxalic or acetic acid with ammonia. Afterwards, the amounts of leached copper and chromium were determined. In a parallel experiment, electron paramagnetic resonance measurements of wet- and dry-leached and unleached samples were performed in order to determine the paramagnetic complexes that were formed. The highest chromium leaching was achieved with the aqueous solution of oxalic acid, as chromium was converted into water-soluble chromium oxalate. While the mixture of oxalic acid and ammonia resulted in the highest copper leaching, EPR observation revealed that in this case water-soluble complexes of copper, oxalic acid, and ammonia were formed. We found out that oxalates formation is not the only mechanism responsible for copper or chromium leaching. High acidity may play an important role too.     

Utilisation of wood biomass residues from fruit tree branches,evergreen hardwood shrubs and Greek fir wood as raw materials for particleboard production. Part A. Mechanical properties

This paper investigates the potential of utilising wood biomass from fruit tree branches and evergreen hardwood shrubs as raw materials in the production of particleboards when mixed with Greek fir wood particles. The main mechanical properties of the boards made therefrom were determined and compared with those made of typical industrial wood (IW) particles. The highest modulus of rupture and elasticity (30.0 N/mm² and 4330 N/mm², respectively) in bending and screw withdrawal (SW) resistance (127.8 N/mm) were reported for boards made of Greek fir and were downgraded when the fruit tree branches or evergreen hardwood shrub particles also participated. The participation of fruit tree branch particles in proportions higher than 50% improved the internal bond (IB) of fir produced boards, while the highest IB strength (0.95 N/mm²) was reported for boards made of fruit tree branches. Particleboards made of evergreen hardwood shrubs showed inferior mechanical properties compared with those made of IW particles. The latter also showed superior bending strength but inferior SW resistance compared with boards made of fruit tree branches. Hygroscopic and other properties are under determination and will be presented and discussed in the second part of the work.     

Characterization of residues from thermal treatment of treated wood and extraction of Cu, Cr, As and Zn

Thermal treatment of chromated copper arsenate (CCA) impregnated waste wood is a way to utilize the energy resource of the wood and at the same time to reduce the volume of the waste. An issue of concern in relation to the thermal treatment is As emission to the air. Meanwhile, there is still a matter to cope with when methods to avoid As emission are implemented: the residues with increased concentrations of Cu, Cr and As. In the present paper two different residues after thermal treatment are characterized: a mixed bottom and fly ash from combustion of CCA impregnated wood, and a charcoal from pyrolysis of treated waste wood. By SEM/EDX it was seen that the charcoal still showed wood structure with both tracheids and rays and that Cu, Cr and As were found inside this wood structure. Cu was found alone while Cr and As were often found together. By chemical analysis it was found, too, that the charcoal contained a high concentration of Zn, probably from paint. Chemical extraction experiments in HNO₃ were conducted with the charcoal and it was found that the order of extraction (in percentage) was Zn > Cu > As > Cr. A SEM/EDX investigation of the mixed ash from combustion showed the presence of small particles with wood structure with elevated Cu and Cr concentrations, but most particles were irregular shaped matrix particles rich in Si, Al and K. Cr was abundant in many different particles including the lignin skeleton of the small, unburned wood pieces, but also inside silica-based matrix particles. Ca was often found associated with char-like (porous) particles, indicating that Ca-arsenates had been formed during combustion. Cu was often associated with Cr in the unburned wood pieces, whereas it was less abundant inside the silica-based matrix particles. Cu was also found in an almost pure form in a small layer on the surface of some matrix particles indicating condensation of volatile Cu species. Chemical extraction with inorganic acids showed the order of percentages mobilized as: As > Cu > Cr.     

Efficacy of radio frequency treatment and its potential for control of sapstain and wood decay fungi on red oak,poplar, and southern yellow pine wood species

The effectiveness of radio frequency (RF) treatment in the control of wood decay fungi (Gloeophyllum trabeum, Ganoderma lucidum, and Irpex lacteus) and sapstain fungus (Ceratocystis fimbriata) in red oak (Quercus spp.), poplar (Populus alba), and southern yellow pine (Pinus spp.) was evaluated in the laboratory as an alternative to methyl bromide (MB) treatment. Wood samples (15.5 x 10 x 10 cm) were inoculated with fungi from a 7-day culture by dipping them to a depth of one face deep (2 cm) into inoculum and incubating them at 25°C for 14 days. Identical wood samples were left uninoculated as controls. Subsequent to incubation, the wood blocks were exposed to RF radiation in an industrial 40-kW dielectric oven at temperatures between 60° and 70°C for 2 min. The test fungi were recovered and reisolated from all of the control wood blocks but not from RF-treated wood blocks. RF treatment resulted in complete inhibition of the fungus in 98%-100% of the wood samples. Moisture content loss (≥1%) was noted after wood had been exposed to RF treatment. Moisture content may be an important factor to consider with RF treatments. RF treatment can, therefore, potentially provide an effective and rapid quarantine treatment as an alternative to MB fumigation for certain pathogen-wood combinations. This article reports the results of research only. Mention of a product does not constitute an endorsement or recommendation by USDA for its use.     

Fibril angle of loblolly pine wood as related to specific gravity,growth rate,and distance from pith

Summary Fibril angles were greater for earlywood (avg. 33.4°) than for latewood tracheids (avg. 26.9°). For earlywood, fibril angle did not differ between growth rates when the specific gravity was low (avg. 33.3°). When the specific gravity was high, wood of fast growth had a higher fibril angle (avg. 35.1°) than wood of slow growth (avg. 32.0°). No differences were detected between core, middle, and outer wood. In latewood tracheids, fibril angles were greater in corewood (avg. 28.0°) than in middle or outer wood (avg. 26.3°). For whole wood (a weighted average of earlywood and latewood), fibril angle averaged 30.7° and was greater in corewood (avg. 32.2°) than in middle or outer wood (avg. 29.9°).     

Chemical composition of Loblolly pine wood as related to specific gravity,growth rate,and distance from pith

Summary The alpha-cellulose, hemicellulose, holocellulose, lignin, and extractive contents of wood removed from stems of loblolly pine (Pinus taeda L.) and factorially segregated by specific gravity, rings from the pith, and growth rate were determined from sample chips. The independent relationships of each factor with chemical composition are described.

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Zusammenfassung Aus Probespänen von Loblolly pine (Pinus taeda L.) wurden die alpha-Cellulose, Hemicellulose, Holocellulose, Lignin und Extraktstoffe bestimmt und faktorenanalytisch gegen die Dichte, den Jahrringabstand vom Mark und die Wuchsgeschwindigkeit abgegrenzt. Die gereinigten Beziehungen jedes Faktors zur chemischen Zusammensetzung des Holzes werden beschrieben.In the research reported here, the chemical composition of a sample of loblolly pine wood was analyzed in relation to three readily measured gross wood characteristics: specific gravity, growth rate, and distance from the pith. As in a previous study relating fiber morphology to these three properties [McMillin, 1968], wood was removed from many stems and stratified by two densities and two growth rates at each of three radial positions in the stem. Thus, the factorial design permitted isolation of the independent relationships of each factor with various chemical components. Characterizing wood types in this way is quite distinct from studying variations in the chemical composition of stems.

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The Roy O. Martin Lumber Company, Alexandria, Louisiana, and R. A. Leask and J. Adams, Bauer Bros. Company, Springfield, Ohio, assisted in collecting and preparing the experimental material. D. Bower, Mathematical Statistician, Southern Forest Experiment Station, New Orleans, Louisiana, aided in the statistical interpretation.     

基于叶、皮、材兼用的高密度杜仲栽培模式研究

杜仲是我国十分重要的国家战略资源。为了探索基于叶、皮、材兼用的杜仲高效栽植模式,以‘华仲1号’杜仲良种为研究对象,连续6年对6种高密度栽植模式的杜仲生物量进行了测定与分析。结果表明:不同林龄、密度和留侧枝数量对杜仲生物量的影响均显著。由于皮、叶、材兼用的高密度建园模式每年都要收割其地上部分,故初植密度对其整体生物量积累的影响较大。建园密度小、留侧枝数量少,单个侧枝生长量较大,但其单位面积的经济产量却相对较低;而建园密度大,单个侧枝生长量相对较小,但其单位面积的经济产量却相对较高。适于叶、皮、材兼用的杜仲高密度栽植模式为:宽窄双行栽植,宽行行距1.0 m,窄行行距0.5 m,株距0.5 m,每株留侧枝4个,建园第6年杜仲的平均产叶量达到15.77 t·hm~(-2),叶片和树皮的总产胶量达到0.56 t·hm~(-2),平均木材产量达到22.01 t·hm~(-2)。采用基于叶、皮、材兼用的高密度杜仲栽培模式,大幅度地提高了杜仲的生物量,还将有效促进杜仲叶、皮及木材的综合开发及利用,提高杜仲产品的附加值,降低杜仲橡胶的提取成本,获得较高的经济收益。     

Studies on pre-treatment by compression for wood impregnation I: effects of compression ratio,compression direction,compression speed and compression-unloading place on the liquid impregnation of wood

To improve the impregnation of wood, the pre-treatment by compression was systematically studied in terms of effects of compression ratio, compression direction, compression speed and compression-unloading place on the liquid impregnation in poplar and Chinese fir. The results showed: the impregnation increased 0.0065 or 0.0074 g/cm³ for every 1% increase of compression ratio when the compression ratio was lower or equal to 50 and 40% for poplar and Chinese fir, respectively; it continued to increase afterwards while the variation was quite big. There existed a significant difference of the impregnation of wood compressed at different directions in Chinese fir, but not in poplar. There existed a significant difference of the impregnation of wood compressed at different speed in both species. The impregnation of wood is likely to be in favor of radial compression in terms of the amount of impregnation. 5 and 10 mm/min were recommended as a compromise of impregnation and pre-treatment efficiency. The impregnation of wood that the compression unloaded in water was about 18.2 (poplar) and 9.2% (Chinese fir) higher in amount and was much quicker in speed than that the compression unloaded in air, and the difference between them was significant, suggesting that compression unloaded in water is significant to improve the impregnation.