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1.
The wood–adhesive interface was analyzed using five methods with the objective of quantitatively assessing penetration of adhesive into the porous wood network. Methods included fluorescence microscopy, scanning electron microscopy, backscatter electron imaging, wavelength dispersive spectroscopy, and X-ray microtomography (XMT). Each method provided a visual inspection, and all of the analysis methods were applied to the same field of view. XMT was the primary technique of interest. Rubidium hydroxide was used in place of sodium hydroxide in the formulation of phenol–formaldehyde adhesive. Rubidium was found to increase the X-ray attenuation of the adhesive. However, rubidium migrated beyond the adhesive interphase during specimen preparation, thus reducing its effectiveness for image contrast enhancement. The wood species studied included red oak (Quercus rubra), Douglas-fir (Pseudotsuga menziesii), and hybrid poplar (Populus deltoides × Populus trichocarpa). All techniques used for this study were useful, but each presented some limitations for bondline analysis. Despite the problem with rubidium migration, XMT for this application was promising. 相似文献
2.
Sofia Leal Vicelina B. Sousa Sofia Knapic José Luís Louzada Helena Pereira 《European Journal of Forest Research》2011,130(6):1023-1029
Cork oak (Quercus suber L.) has a dense wood that allows high-quality uses. In the present work, we study the influence of vessel characteristics,
measured through image analysis and optical microscopy, on wood density, measured using X-ray microdensitometry, on 40-year-old
trees. Vessel area increases with cambial age (5403–33064 μm2), while wood density decreases (1.229–0.836 g/cm3). The number of vessels is relatively constant at 6 vessels/mm2, while vessel proportion in cross-section increases from 3.3% near the pith to 20.5% near the bark. In growth rings closest
to the pith, with high wood density and low vessel area, the relationship between the two variables is linear (R
2 = −32.1%, P < 0.01) but with increasing tree age and vessel size, the wood density remains rather constant, suggesting that decreases
in density might compromise mechanical support of the tree at a stage when the increase in cross-sectional area alone might
not provide mechanical stability. Other anatomical characteristics not considered in this study, like large xylem rays that
increase with cambial age, may be responsible for the constant density. 相似文献
3.
Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was employed to examine the chemical emissions from the glued wood
samples at elevated temperatures (150, 200, 250, 300, 350, 400, 450, and 500°C). Two wood species, Douglas-fir (Pseudotsuga menziesii) and southern pine (Pinus palustris), one structural adhesive, phenol–resorcinol–formaldehyde (PRF), PRF-bonded Douglas-fir, and PRF-bonded southern pine were
evaluated. The volatile compounds with a mass range of 35–300 m/z emitted from the pyrolysis samples were separated by gas
chromatography (GC) and identified by mass spectrometry (MS). The results indicated that compared to neat wood and resin film
samples, several additional pyrolysis products were observed for the PRF-bonded wood samples including (1) acetaldehyde and
butanedial for PRF-bonded Douglas-fir and (2) acetaldehyde, furfural, 2-furanmethanol, butanedial, 2,3-butanedione, cyclopropyl
carbinol, 1,2-benzenediol, and 1-(acetyloxy)-2-propanone for PRF-bonded southern pine. These additional compounds were possibly
associated with the interaction between wood and PRF resin. The results also indicated that bonded wood products would be
less thermally stable than those of neat wood and PRF resin samples. 相似文献
4.
Integration of shrubs into the smallholder crop-rangeland-livestock farming systems in non-tropical dry areas could reduce
feed gaps, rangeland degradation and desertification, but data on yield and fodder quality of most native and exotic shrubs
are scanty. The study aimed at identifying shrubs for dryland agroforestry based on agronomic and fodder quality attributes.
Fodder and wood yield, percent fodder (FBR) and fodder quality of 26 non-legume shrubs were determined from 6 to 8 months
regrowth in north-west Syria. Seed yield was estimated from plants that were not cut. Fodder (31–87 Mg DM ha−1), wood (16-2064 Mg DM ha−1) and seed (0-132 Mg DM ha−1) yield, FBR (24–87%), fodder concentrations of crude protein (69–195 g kg−1.), acid detergent lignin (ADL) (24–109 g kg−1), acid detergent fiber (ADF) (102–267 g kg−1), neutral detergent fiber (NDF) (214–526 g kg−1), in vitro organic matter digestibility (IVOMD) (391–526 g kg−1), and in vitro gas production after 24 h of incubation (25–39 ml 200 mg−1 DM) varied (P < 0.05) among the shrubs. Atriplex halimus-halimus and A. herba-alba from Spain, A. canescens, A. ploycarpa and A. lentiformis from USA, A. halimus and A. herba-alba from Syria and A. nummularia from Australia and South Africa had greater potential for development of dryland agroforestry technologies. The promising
shrubs could be integrated into the rangeland-crop-livestock systems in non-tropical dryland environs to provide fodder, fuel-wood,
shade, medicine, stabilize sand-dunes, and sequester carbon; thereby contributing to mitigation of rangeland degradation and
global warming; if major constraints to adoption of fodder trees such as agronomic problems, low multipurpose value, land
shortage and quality seed supply could be overcome. 相似文献
5.
Dong-heub Lee Myung Jae Lee Dong-Won Son Byung-Dae Park 《Wood Science and Technology》2006,40(3):228-236
The extended use of woods treated with traditional or alternative preservatives for exterior applications requires an assessment
of wood adhesive performance. This study attempts to evaluate the performance of wood adhesives for woods treated with various
waterborne preservatives. Two softwood species, i.e. Korean pine (Pinus koraiensis Sieb. et Zucc.) and Japanese Larch (Larix leptolepis [Sieb. et Zucc.] Gordon) were treated with copper–chrome–arsenic (CCA), CB-HDO, or copper azole (CY), and then bonded with
four different wood adhesives such as urea–melamine–formaldehyde (UMF) resin, melamine–formaldehyde (MF) resin, phenol–formaldehyde
(PF) resin, and resorcinol–formaldehyde (RF) resin. The performance of these adhesives was evaluated by measuring the dry
shear strength of adhesive-bonded wood block on compression. Both UMF and MF resins produced a relatively strong adhesive
strength for CY-treated pine and larch woods. The PF resin also produced good bond strength when bonded with either larch
wood treated with CY or pinewood treated with CB-HDO. The best result was obtained when the CB-HDO-treated woods were bonded
with RF resin. For a better bond strength development, a proper combination of adhesive, preservative, and wood species should
be selected by taking into consideration of the characteristics of these three parameters as well as their interactions. 相似文献
6.
Bakary Traoré Loïc Brancheriau Patrick Perré Tatjana Stevanovic Papa Diouf 《Annals of Forest Science》2010,67(8):815-815
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• Vène wood (Pterocarpus erinaceus Poir.) is currently the favorite wood for manufacture of xylophone in Mali. A dynamic analysis method with free boundary
conditions, known as BING, was used to determine the main acoustic properties: specific dynamic modulus (E
L
/ρ), damping coefficient or internal friction (tan δ), sound radiation coefficient (SRC) and peak response (PR). 相似文献
7.
Density profile relation to hardness of VTC wood composites was evaluated using X-ray densitometry and modified Brinell hardness
method using different applied forces. Moreover, surface elasticity was evaluated. Prior to lamination, the low-density hybrid
poplar (Populus deltoides × Populus trichocarpa L.) and Douglas-fir (Pseudotsuga menziesii L.) thin boards were compressed to 1.22 or 1.14 g/cm3, respectively. Two different kinds of laminations were made, either single layer of 1.5 mm thickness or two 1.5-mm layers
bonded to unmodified wood. The results show that thicker laminate has a great positive influence on Brinell hardness. This
study suggests that results from the existing method for Brinell hardness are not comparable, and if applied force is chosen
without restraint, the effect on the hardness value is significant for inhomogeneous wood composites. 相似文献
8.
Sabrina Palanti Giovanni Predieri Francesca Vignali Elisabetta Feci Antonella Casoli Elena Conti 《Wood Science and Technology》2011,45(4):707-718
Wood modification with siloxanes bearing amino groups with copper-linking function was carried out by a sol–gel process. Tetraethoxysilane
(TEOS) and 3-aminopropyltriethoxysilane (APTES) were the main components. Two different procedures were followed: a two-step
process (impregnation with the TEOS/APTES mixture followed by dipping into a copper sulphate solution) and a one-step process
(impregnation with a homogeneous sol mixture of TEOS, APTES and copper (II) chloride). The obtained materials were characterized
by infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis. The determination
of copper content before and after leaching was performed by atomic absorption spectroscopy. The efficacy against the brown
rot fungus Coniophora puteana was tested by an accelerated procedure. SEM analyses showed that silicon penetrated into wood, while copper is effectively
drawn into wood only in the one-step treatment. Copper fixation to the silica gel proved to be adequately strong. Both sol–gel
treatments gave good protection against Coniophora puteana. 相似文献
9.
Eucalyptus camaldulensis × globulus and E.
camaldulensis × grandis hybrids have been developed to combine the salt–waterlogging tolerance and high-quality wood fibre of their respective parents.
The aim is to develop trees that will grow in relatively dry and/or saline environments and provide commercial wood products.
Previous studies indicate that the hybrids exhibit faster growth than either of their pure species parents, and that there
are significant differences in growth rates between them. We undertook a comparative study of the partitioning of above-ground
biomass (AGB) to examine biomass and chloride (Cl) allocation of trees growing on two saline-irrigated sites in south-eastern
Australia. Eucalyptus camaldulensis × globulus had a higher proportion of AGB in leaves (20–29% cf. 15–16%), and lower proportion in live branches (3–10% cf. 6–14%) than
E.
camaldulensis × grandis. The concentration of Cl was highest in the stembark (4.2–9.6 g kg−1) and lowest in the stemwood (0.6–2.0 g kg−1), suggesting that trees can export Cl through bark shedding. Total Cl content was strongly related to volume under bark (R2 = 0.99), and differences in partitioning of Cl into tree components differed between the hybrids in the same way as AGB.
Preferential partitioning of Cl to live branches rather than foliage in E. camaldulensis × grandis suggests that this hybrid may be compartmentalising Cl to reduce the risk of Cl toxicity in the leaves. 相似文献
10.
David Mannes Federica Marone Eberhard Lehmann Marco Stampanoni Peter Niemz 《Wood Science and Technology》2010,44(1):67-84
Possible applications for synchrotron radiation tomographic microscopy in the field of wood research were tested and evaluated
at the TOMCAT beamline (TOmographic Microscopy and Coherent rAdiology experimenTs) at the Swiss Light Source (SLS) at the
Paul Scherrer Institute (Villigen, Switzerland). For this study, small cylindrical samples (∅ 1 and 3 mm) were examined with different experimental setups resulting in a nominal voxel size of approximately 1.48 × 1.48 × 1.48
and 3.7 × 3.7 × 3.7 μm3, respectively. Suitability of the TOMCAT microscope for 3D investigations of wood anatomy was tested on several softwood
and hardwood species revealing microscopic features (e.g. tyloses, wall thickenings or pits) down to the nominal pixel size.
The results suggest that even features in the sub-voxel range can be made visible. Tomographic microscopy was also tested
for wood technological applications, i.e. penetration behaviour of a wood preservative and also of three wood adhesives (poly-urethane
resins) with different viscosities. Although the experiments with the preservative yielded no clear results, the method seems
suitable for examining the penetration of the different adhesives. The adhesive penetrates the wood mainly by the vessels
where it can be easily discerned from the wood structure. 相似文献
11.
Heat-induced colour changes of pine (Pinus pinaster) and eucalypt (Eucalyptus globulus) wood 总被引:4,自引:0,他引:4
Bruno Esteves António Velez Marques Idalina Domingos Helena Pereira 《Wood Science and Technology》2008,42(5):369-384
Heat treatment of Pinus pinaster and Eucalyptus globulus wood was carried out by hot air in an oven for 2–24 h at 170–200°C and by steam in an autoclave for 2–12 h at 190–210°C.
The colour parameters L*, a* and b* were determined by the CIELAB method on radial, tangential and transverse sections of untreated and treated wood, and their
variation with regard to the treatment (ΔL*, Δa* and Δb*) were calculated in percent. For untreated eucalypt wood, lightness (L*) varied between 54.1 and 63.8% with a* between 7.4 and 8.5, and b* between 15.7 and 19.9. For untreated pine wood, L* varied between 67.3 and 76.1%, a* between 6.9 and 7.6 and b* between 16.3 and 24.1. Oven heat-treated wood became darker (ΔL* about 50% for 4% mass loss), and this was more for eucalypt wood under the same treatment conditions. In general, the contribution
of red (a*) and yellow (b*) colour decreased with heat treatment. The transverse section of the two species darkened less for both the treatments with
small differences between radial and tangential sections. Lightness decrease was related to chemical changes; with good correlations
with glucose (R
2 = 0.96), hemicelluloses (R
2 = 0.92) and lignin (R
2 = 0.86). As regards colour, the heat treatments showed an interesting potential to improve the wood quality for solid timber
products from pine and eucalypt. 相似文献
12.
Ingela Bjurhager Lars A. Berglund Stig L. Bardage Björn Sundberg 《Journal of Wood Science》2008,54(5):349-355
Functional analysis of genes and proteins involved in wood formation and fiber properties often involves phenotyping saplings
of transgenic trees. The objective of the present study was to develop a tensile test method for small green samples from
saplings, and to compare mechanical properties of juvenile European aspen (Populus tremula) and hybrid aspen (Populus tremula × tremuloides). Small microtomed sections were manufactured and successfully tested in tension parallel to fiber orientation. Strain was
determined by digital speckle photography. Results showed significantly lower values for juvenile hybrid aspen in both Young’s
modulus and tensile strength parallel to the grain. Average Young’s moduli spanned the ranges of 5.9–6.6 and 4.8–6.0 GPa for
European aspen and hybrid aspen, respectively. Tensile strength was in the range of 45–49 MPa for European aspen and 32–45
MPa for hybrid aspen. The average density (oven-dry) was 284 kg/m3 for European aspen and 221 kg/m3 for hybrid aspen. Differences in mechanical properties correlated with differences in density.
Part of this article was presented at the 3rd International Symposium on Wood Machining, May 21–23, 2007, Lausanne, Switzerland 相似文献
13.
研究了一种用含有少量硫酸的乙酸溶液分离杨木成分的方法。考察了反应时间、乙酸浓度、液比和催化剂浓度对木材成分分离的影响。对分离出的木材三种成分进行了表征。结果表明,分离杨木成分的较佳条件为:硫酸浓度0.3%,液比6,反应时间3h和乙酸浓度90%。残渣的主要成分是α-纤维素和半纤维素。水不溶沉淀物(乙酰化木质素)的重均分子量分布在341到253之间,分散性系数分布在1.1到1.2这一窄范围内。糖分析结果表明,可溶性成分主要来源于半纤维素,以单糖形式存在。 相似文献
14.
In order to improve wood properties of triploid clones of Populus tomentosa, urea-formaldehyde (UF) resin was compounded with nano-SiO2, coupling agents and flame retardants in different ways to prepare five kinds of modifiers. The poplar wood samples were
impregnated with the modifiers and heated to prepare UF-SiO2-wood composites. The antiswelling efficiency, resistance of water absorption, oxygen index and hardness of the composites
were measured. Results show that all of the modifiers reduced water absorption of poplar wood and enhanced flame resistance
and hardness. Nano-SiO2 showed a marked effect in improving the hardness of wood. In addition, all of the modifiers, except UF-C-SiO2-polymer, improved the dimensional stability of poplar wood. The UF resin and nano-SiO2 compound improved general properties of poplar wood.
__________
Translated from Journal of Beijing Forestry University, 2006, 28(2): 123–128 [译自: 北京林业大学学报] 相似文献
15.
Sung Phil Mun M. Sarwar Jahan A. Al-Maruf D. A. Nasima Chowdhury 《Wood Science and Technology》2011,45(2):281-288
Lack of data especially pertaining to the chemistry of mangrove wood species makes it difficult to prepare successful plans
for their conservation and to use mangroves as a source of wood fiber. In this paper, chemical characterizations of the six
main mangrove species of Bangladesh [namely Keora (Sonneratia apetala), Geoa (Excoecaria agallocha), Bine (Avicennia alba), Sundari (Heritiera fomes) Pashur (Xyloccarpous mekongests), and Kakra (Bruguiera gymnorhiza)] were investigated. The chemical results revealed that these species contain high percentages of dichloromethane followed
by methanol extractives. Methanol extracts in Pashur, Sundari, and Bine were higher than 10%, which indicates high percentage
of tannin material. The total lignin content in these species was higher than 25%, except for Gewa (23.6%) and Pashur (21.3%),
which is higher than that of the normal range of hardwood. The pentosan content in these six species was within the range
of 19.4–22.8%. The α-cellulose content in Keora and Gewa was acceptable for pulp production, but the others were lower than
the normal range of hardwood. Alkaline nitrobenzene oxidation showed that all these species had a very high syringaldehyde
to vanillin (2.6–5.0) ratio except Keora (1.6). Surprisingly, rhamnose is the main constituent with xylose of hemicelluloses
of these six mangrove species. The ash content in these six mangrove wood species was also higher than that in normal hardwood. 相似文献
16.
Improving the thermal stability of one-component polyurethane adhesives by adding filler material 总被引:1,自引:0,他引:1
Sebastian Clauβ Karin Allenspach Joseph Gabriel Peter Niemz 《Wood Science and Technology》2011,45(2):383-388
The aim of the current study is to improve the thermal stability of one-component moisture-curing polyurethane adhesives.
The approach here tends to add suitable filler materials to the adhesive and to study the resulting effects. The investigation
covers mechanical tests to determine the shear strength of the glued wood joints according to EN 302-1 (2004). Furthermore, the distribution of the filler material within the adhesive is shown by means of environmental scanning electron
microscopy combined with energy-dispersive X-ray spectroscopy analysis. The thermal stability of the glued wood joints could
be significantly improved by adding chalk with a volume fraction of 30% to the adhesive. 相似文献
17.
Lloyd Donaldson 《Wood Science and Technology》2007,41(5):443-460
The organization of wood cell wall components involves aggregates of cellulose microfibrils and matrix known as macrofibrils.
A combination of field emission electron microscopy and environmental scanning electron microscopy was used to visualise the
organization of macrofibrils in different cell wall types comparing normal and reaction wood of radiata pine and poplar as
examples of a typical softwood and hardwood. The size of macrofibrils is shown to vary among cell wall types with the smallest
structures occurring in the gelatinous layer of tension wood (14 nm) and the largest structures in the S2L layer of compression wood (23 nm). A positive correlation between macrofibril size and degree of lignification is observed,
with macrofibrils apparently increasing in size in more highly lignified cell wall types. The fibrillar structure of the secondary
wall varies from microfibril-sized structures of 3–4 nm up to large aggregates of 60 nm diameter. The size of macrofibrils
also varies slightly among adjacent cells of the same cell wall type. Macrofibrils occur predominantly in a random arrangement,
although radial and tangential lamellae may sometimes be seen in individual cells.
18.
Ameur M. Manceur Greg J. Boland Naresh V. Thevathasan Andrew M. Gordon 《Agroforestry Systems》2009,76(2):295-301
In 2004 and 2005, the yield, leaf area, dry weight and dry weight partitions of soybeans were determined at the Agroforestry
Research Site (ARS) (est. 1987, Ontario, Canada). Soybean was intercropped with poplar (Populus deltoides x nigra DN-177 L., 556 m3crown tree−1), silver maple (Acer saccharinum L., 308 m3), black walnut (Juglans nigra L., 148 m3) and pecan (Carya illinoensis Wangenh., 114 m3), or grown alone (monoculture). Yield of soybean was not different in either year between the monoculture and the black walnut
or pecan intercrops. In the poplar and silver maple treatments, yield was 66 and 85% (2004 and 2005) lower than in the monoculture.
Despite the fact that different tree species were used, there was a significant negative linear regression between yield and
tree crown volume (R
2 = 0.76, P = 0.0049 and R
2 = 0.93, P < 0.0001 in 2004 and 2005, respectively). With increasing tree crown volume, soybean tended to partition more dry matter
to the photosynthetic and reproductive parts and less to structural tissue and petiole. This demonstrates the phenotypic flexibility
of the crop component in agroforestry systems. Contrary to theoretical predictions, soybean leaves were thicker as shade increased
(increase by 6.2 × 10−4–1.2 × 10−3 mg cm−2, per unit of crown volume), pointing to competitive interactions specific to tree-based intercrops. 相似文献
19.
Marko Peura Klaas Kölln Ingo Grotkopp Pekka Saranpää Martin Müller Ritva Serimaa 《Wood Science and Technology》2007,41(7):565-583
The effect of strain on dry, clear Norway spruce (Picea abies [L.] Karst.) wood was studied by tensile testing along the cell axis and by in situ X-ray diffraction measurements. The mean
microfibril angle (MFA) was initially 3–12 degrees and did not decrease due to strain. Based on the positions of the reflections
200 and 004 of crystalline cellulose, cellulose chains elongated and the distance between the hydrogen bonded sheets of chains decreased
due to the strain. The elongation of the unit cell parallel to the cellulose chains was twice as high in juvenile wood as
in mature wood. The (X-ray) Poisson ratio ν
ca
for crystalline cellulose in Norway spruce was calculated from the deformation of the unit cell. The average ν
ca
of earlywood was 0.28 ± 0.10 in juvenile wood and 0.38 ± 0.23 in mature wood. In latewood, the average ν
ca
was 0.48 ± 0.10 in juvenile wood and 0.82 ± 0.11 in mature wood. The average ν
ca
values were not directly correlated to the crystallite dimensions or to the mean MFA in juvenile and mature earlywood and
latewood. The results show that the amorphous matrix has a definite effect on the deformation of cellulose crystallites. 相似文献
20.
Fibre morphology, anatomy and ultrastructure in cell wall of Salix gordejecii normal wood were examined by transmission electron microscopy (TEM). S. gordejecii tension wood can be recognized anatomically by the presence of gelatinous (G) fibres, which contain a conspicuously thickened inner cell wall layer. TEM images showed that cell wall of S. gordejecii normal wood was typically divided into three layers including the primary wall (P), the middle lamellar (ML) and the secondary wall (S1, S2 and S3). Lignin distribution was determined by using confocal laser scanning microscopy (CLSM) and transmission electron microscopy with energy dispersive X-ray analysis (TEM-EDXA). Confocal images (530 nm) of S. gordejecii normal wood showed strongly lignified CCML, and weakly lignified ML and S2 layer. Weakly lignified fibres (F) and strongly lignified vessels (V) were also detected by using CLSM. Results obtained from confocal microscopy were further confirmed by using TEM-EDXA, indicating that the ratio of lignin concentration in CCML, ML and S2 is 1.72 (1321):1.31 (1006):1 (768). Lignin distribution in tension wood is similar to that in normal wood, except for the non-lignified G layer. 相似文献
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