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1.
Jürgen Follrich Alfred Teischinger Wolfgang Gindl Ulrich Müller 《Wood Science and Technology》2007,41(6):501-509
To evaluate the effect of grain orientation on the adhesive bond strength, three-layered Norway spruce wood specimens were
tested in shear. The two axial-oriented outer layers were jointed with the middle layer using three typical glues for load
bearing constructions, i.e. one-component polyurethane (PUR), melamine–urea–formaldehyde (MUF) and phenol–resorcinol–formaldehyde
(PRF). The grain orientation of the middle layers was varied from 0° (parallel to grain of the surface layer) to 90° (perpendicular
to grain of the surface layer) in incremental steps of 10°. Samples with middle layers oriented parallel to the outer layers
showed shear values in the range of solid spruce wood. Decreased shear strength values were expected for increased grain angles
of the middle layer. However, no explicit tendency was observed for the shear strength in dependence of the grain direction.
In general, MUF-bonded samples showed slightly higher shear strength values compared with PUR- and PRF-bonded specimens. 相似文献
2.
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
3.
Shin-ichiro Tohmura Atsuko Ishikawa Kohta Miyamoto Akio Inoue 《Journal of Wood Science》2012,58(1):57-63
A mechanism of acetaldehyde emission from wood induced by the addition of ethanol was proposed. It is known that acetaldehyde
generation is due to the oxidation of ethanol via a metabolic process involving alcohol dehydrogenase (ADH) in living bodies.
However, it remains unclear whether the enzymatic alcohol oxidation is applicable to wood. We investigated possible factors
of wood parts, conditioning, storage sites, and heating and sterilization treatments on acetaldehyde emission using the syringe
method and HPLC analysis. We reconfirmed that acetaldehyde emission was observed only when ethanol was added to wood. Greater
acetaldehyde emissions were obtained in heartwood compared to sapwood in both Japanese cedar (Cryptomeria japonica D. Don) and Japanese cypress (Chamaecyparis obtusa Endl.) specimens. In addition, an acetaldehyde conversion rate of 1–2 mol% was determined in green cedar heartwood samples,
while, conversely, air-dried cedar heartwood samples showed 4–5 mol%. Ethylene oxide gas sterilization had the effect of decreasing
acetaldehyde emission on air-dried wood, but not on green wood. Autoclave sterilization could completely prevent acetaldehyde
emissions from both green and air-dried wood. These results suggested that an original ADH in wood and an attached ADH from
the outside via microorganisms onto wood were assumed to be the primary causes of acetaldehyde emissions from wood induced
by the addition of ethanol. 相似文献
4.
Bruno Esteves António Velez Marques Idalina Domingos Helena Pereira 《Wood Science and Technology》2007,41(3):193-207
Heat treatment of Pinus pinaster and Eucalyptus globulus woods, two important species in Portugal, was performed in the absence of air by steaming, inside an autoclave, for 2–12 h
at 190–210°C. Mass losses increased with treatment time and temperature reaching 7.3% for pine and 14.5% for eucalypt wood.
The wood behaviour with moisture was improved. The equilibrium moisture content decreased by 46% for pine and 61% for eucalypt,
the dimensional stability increased (maximum anti-shrinking efficiency in the radial direction of 57 and 90% for pine and
eucalypt, respectively) and the surface wettability was lowered. In relation to mechanical properties, the modulus of elasticity
was little affected (maximum decrease of 5% for pine and 15% for eucalypt) but the bending strength was reduced (by 40% at
8% mass loss for pine and 50% at 9% mass loss for eucalypt wood). The variation of properties was related to treatment intensity
and mass loss but significant improvements could already be obtained for a 3–4% mass loss without impairing the mechanical
resistance. The response of eucalypt was higher than that of pinewood. Heat treatment of eucalypt wood shows an interesting
potential to improve the wood quality for solid timber products. 相似文献
5.
Proanthocyanidins (PAs) in the hot water extract prepared from Pinus radiata bark were isolated by a Sephadex LH-20 chromatography. The PAs were characterized using UV/Visible, FT-IR and 13C nuclear magnetic resonance (NMR) spectroscopic techniques, matrix-assisted laser desorption/ionization time of flight (MALDI-TOF)
mass spectrometry (MS), and gel permeation chromatography (GPC) analysis. Bate-Smith acidic alcoholysis and FT-IR spectrum
of the PAs indicated the predominant presence of the procyanidin (PC) structure. The 13C NMR spectrum revealed that the PAs comprise PC (94%) together with a small amount of prodelphinidin (PD, 6%), and also that
they contain the higher trans configuration rather than the cis configuration of C2–C3. The MALDI-TOF MS results obviously proved the presence of PD units, but the maximum degree of polymerization
(DP) was limited to octamer. The average molar mass (Mw, Mn), polydispersity (Mw/Mn), and DP of the pine bark PAs were 3,800
(Mw), 1,200 (Mn), 3.2, and 13, respectively. 相似文献
6.
The structures of the solid state products formed by the partial combustion of Korean pine wood treated with fire-retardant
FRW were analyzed by microscopic FTIR. The volatile pyrolytic products of basswood (Tilia amurensis) specimens treated with FRW and its components guanylurea phosphate and boric acid were analyzed by GC-FTIR. The pyrolytic
and charring process, the effects of fire-retardant, and the structural characteristics of the pyrolytic products were discussed.
It was concluded that upon heating and by the catalysis of FRW and its decomposition products reactions of wood took place
successively, namely the dehydration of polysaccharide, the elimination of acetic acid from hemicellulose, the degradation
of polysaccharide, the degradation of lignin, the polymerization of the pyrolytic products of wood, reactions of oxygen-element-elimination
of aliphatic polymers and the structural change of the latter to form aromatic structures, and charring. The pyrolysis process
of wood was altered and the yield of volatile pyrolytic products was decreased by FRW treatment.
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Translated from Scientia Silvae Sinicae, 2005, 41(4): 149–154 [译自: 林业科学, 2005, 41(4): 149–154] 相似文献
7.
The aim of this study was to determine changes in crystallinity and crystalline unit cell type of heat-treated Scots pine
(Pinus sylvestris L.) and Uludağ fir (Abies nordmanniana stev. subsp. bornmuelleriana Mattf.) wood samples by means of FT-IR spectroscopic method. Heat treatment was applied on the test samples in an oven at
three different temperatures (120, 150, and 180°C) and for two different periods of time (6 and 10 h) under atmospheric pressure.
It was designated that crystallinity of both Scots pine and Uludağ fir wood samples increased during heat treatment depending
on the duration. However, monoclinic structure in crystalline unit cells of Scots pine and Uludağ fir wood samples converted
to triclinic structure when heat treated. It was estimated that monoclinic structure was dominant in the crystalline unit
cell. It was established that the crystalline structure of Scots pine wood samples was more affected by heat treatment than
that of Uludağ fir wood samples. 相似文献
8.
introductionWaterbornepreservativesareamajorcomponentofthewood-treatingindustrybecauseoftheireaseofapplication,lowcost,andthecleanappearanceofthewoodattertreatment.Theuseofchromatedcopperarsenate(CCA)preservativesintheUSAhasgrownfroma14%shareofthewoodpreservativesmarketin1977to73%in1987(Micklewright1993).ThisismainlyduetotheincreasinguseofCCAtreatedwoodasdecksandoutdoorstructures.ThewaterbornepreservativeCCAhasbecomeoneofthemosteffectivetreatmentsforNorthAmericanwoodproduCts,usedinapplic… 相似文献
9.
The interactions between pine wood nematode and three bacterium strains isolated from the nematode, Bursaphelenchus xylophilus, which are two strong pathogenic bacterium strains, Pseudomonas fluorescens GcM5-1A and Pseudomonas putida ZpB1-2A and a weak-pathogenic bacterium strain, Pantoea sp. ZM2C, were studied. The result showed that the strong-pathogenic GcM5-1A strain and ZpB1-2A strain significantly increased
fecundity, reproduction rate, and the body volume of the adult nematode. Meanwhile, pine wood nematodes significantly promoted
reproduction of the two strong-pathogenic bacterium strains. However, the weak-pathogenic bacterium strain, ZM2C, completely
inhibited reproduction of pine wood nematodes. Aseptic pine wood nematodes significantly inhibited reproduction of the strain
ZM2C. The results indicated that mutualistic symbiosis exists between pine wood nematodes and the two pathogenic bacteria
it carries. The phenomenon showed that the pathogenic bacteria carried by the nematode were not accidentally contaminated,
but rather had existed as symbionts of the nematode with which it had coevoluted over a long period. The role of mutualistic
symbiosis in the process of pine wilt disease was also discussed.
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Translated from Journal of Nanjing Forestry University, 2005, 29(3): 1–4 [译自: 南京林业大学学报, 2005, 29(3): 1–4] 相似文献
10.
《Wood material science & engineering》2007,2(2):83-89
To study the effect of grain angle on the adhesive bond strength in wood, three-part Norway spruce wood specimens were bonded and tested in tension. The two axially orientated outer parts of the specimens were joined with the middle part by means of three adhesives typically used for load-bearing constructions, i.e. one-component polyurethane (PUR), melamine-urea-formaldehyde (MUF) and phenol-resorcinol-formaldehyde (PRF). The grain angle of the middle part was varied from 0° (end grain to end grain) to 90° (flat grain to end grain) in incremental steps of 10°. In general, PRF- and MUF-bonded samples exhibited highest tensile strength at end grain to end grain orientation of the three parts, while specimens bonded with PUR showed only 25% of the strength measured for PRF and MUF, respectively. At high grain angles (90°) all specimens showed similar strength values in the range of 30% of maximum strength of MUF- and PRF-bonded specimens. To explain the changing strength levels at different grain angle a composite failure criterion was applied. 相似文献
11.
Structure and characterization of Chinese fir (Cunninghamia lanceolata) wood/MMT intercalation nanocomposite (WMNC) 总被引:2,自引:0,他引:2
Wenhua Lü 《Frontiers of Forestry in China》2008,3(1):121-126
With water-soluble phenol-formaldehyde resin as an intermediate, Chinese fir (Cunninghamia lanceolata) wood/montmorillonite nanocomposite (WMNC) was prepared through vacuum impregnation and characterized with XRD, SEM, FTIR
and TG-DTA analyses. The XRD analysis indicated that the wood crystallinity of WMNC decreased, the MMT exfoliated and some
nano silicate layers entered into the non-crystallized microfibrillar region of the wood cell wall. Wood structure is anisotropic
and its impregnation is anisotropic. Due to the nonuniformity of the MMT organic modification, PF intercalation and wood impregnation,
the MMT configuration and distribution in wood were diverse. The SEM graphs of WMNC showed that some silicate grains were
blocked in the wood cell lumen, some silicate layers adhered to the inner surface of the wood cell wall, and some exfoliated
MMT layers even penetrated the wood cell wall. The obtained hydroxyl of WMNC increased and its ether linking decreased. It
was considered that MMT and wood interacted not only with hydroxyl bonds, but also involved some chemical linking. Compared
with untreated wood and the PF-impreg, the pyrolysis process of WMNC changed; its starting decomposing temperature decreased
and its pyrolysis weight loss at high temperatures greatly decreased. The WMNC indicated certain nanoeffects of the composition
of the inorganic MMT nanolamellae.
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Translated from Journal of Beijing Forestry University, 2007, 29(1): 131–135 [译自: 北京林业大学学报] 相似文献
12.
Evolved gas analysis (EGA) in combination with analytical pyrolysis is presented as a new technique for rapid investigations into wooden materials. In a first analytical step, the thermal behaviour of three wood samples was determined by EGA. Based on these results, analytical pyrolysis–gas chromatography/mass spectrometry was carried out to investigate the influence of wood-specific thermal behaviour and the chemical composition on the results. Furthermore, the influence of sample mass and particle size was examined. 相似文献
13.
《Wood material science & engineering》2013,8(2):83-89
Abstract To study the effect of grain angle on the adhesive bond strength in wood, three-part Norway spruce wood specimens were bonded and tested in tension. The two axially orientated outer parts of the specimens were joined with the middle part by means of three adhesives typically used for load-bearing constructions, i.e. one-component polyurethane (PUR), melamine–urea–formaldehyde (MUF) and phenol–resorcinol–formaldehyde (PRF). The grain angle of the middle part was varied from 0° (end grain to end grain) to 90° (flat grain to end grain) in incremental steps of 10°. In general, PRF- and MUF-bonded samples exhibited highest tensile strength at end grain to end grain orientation of the three parts, while specimens bonded with PUR showed only 25% of the strength measured for PRF and MUF, respectively. At high grain angles (90°) all specimens showed similar strength values in the range of 30% of maximum strength of MUF- and PRF-bonded specimens. To explain the changing strength levels at different grain angle a composite failure criterion was applied. 相似文献
14.
M. Grell 《Wood Science and Technology》2001,35(6):529-539
The reaction kinetics of wood (Corsican pine) with acetic, propionic, succinic, and hexenyl succinic anhydride dissolved
in pyridine were investigated. To determine reaction kinetics, anhydride depletion of the reactive liquid was monitored. This
approach allows to collect a complete sequence of kinetic data from a single experiment. The results carry information on
reaction kinetics without allowing for a precise determination of reaction turnover vs time. For all anhydrides investigated,
the reaction kinetics of wood samples of different size (300 μm–4 mm) do not depend on sample size, hence the reaction is
activation- not diffusion-controlled. All results are consistent with a remarkably simple model of purely activation-controlled
reaction kinetics with a single activation energy. Activation energies were determined. The result for propionic anhydride
agrees with an earlier investigation based on weight gain of reacted wood.
Received 16 March 1999 相似文献
15.
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
16.
Jaume Gort Ane Zubizarreta-Gerendiain Heli Peltola Antti Kilpeläinen Pertti Pulkkinen Raimo Jaatinen Seppo Kellomäki 《Annals of Forest Science》2010,67(7):705-705
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• We studied the differences in branch characteristics along the stems of six different genetic entries of 20 year old Scots
pines (Pinus sylvestris L.) grown at different spacing (current stand density range 2000–4000 trees ha−1) in central Finland. Furthermore, we studied the phenotypic correlations between yield, wood density traits and branch characteristics.
All the genetic entries had Kanerva pine (plus tree S1101) as a father tree, whereas the mother tree represented Finnish plus
trees from southern, central and northern Finland. 相似文献
17.
Jiying Song Youqing Luo Juan Shi Xiaosu Yan Weiping Chen Ping Jiang 《Frontiers of Forestry in China》2006,1(4):460-463
In November 2003 and June 2004, the insect borers and their spatial distribution within Pinus massoniana were investigated in Zhoushan City, in East China’s Zhejiang Province, where pine wood nematode (Bursaphelenchus xylophilus) are typically found. The niche width, proportional similarity of niche and the niche overlap of dominant species of dying
trees were computed. Results show that five insect species infect and damage Pinus massoniana, which had been infected by pine wood nematodes, among which four are wood boring beetles and one termite. Species within
host trees vary from winter to summer and all the species have their own niche width, proportional similarity of niche and
the niche overlap. They can achieve competitive equilibrium and coexistence according to their biological characteristics
and life habits.
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Translated from Journal of Beijing Forestry University, 2005, 27(6): 108–111 [译自: 北京林业大学学报, 2005, 27(6): 108–111] 相似文献
18.
Sanni Raiskila Kurt Fagerstedt Tapio Laakso Pekka Saranpää Mia Löija Leena Paajanen Riitta Mahlberg Anne-Christine Ritschkoff 《Wood Science and Technology》2006,40(8):697-707
It is known that active peroxidase isozymes exist in mature wood of Norway spruce (Picea abies L. Karst.) and that they remain active for years and are found even in the heartwood (in Scots pine), where all cellular activity has ceased. This peroxidase activity was utilised in the impregnation of wood blocks with a natural monolignol, coniferyl alcohol and hydrogen peroxide. The hypothesis was that the internal wood peroxidases would oxidise the added monolignol and bind it stably into the cell wall matrix, which could hinder fungal decay. Since coniferyl alcohol is not very soluble in water, the impregnation was done under vacuum with an acetone–water solution containing 10% coniferyl alcohol and 0.4 mM H2O2 at room temperature (ca. 0.02 g of coniferyl alcohol was added to 1 g of wood). After impregnation, dimers of coniferyl alcohol and free coniferyl alcohol were found in acetone extracts with GC–MS analysis. Penetration of coniferyl alcohol and non-extractable reaction products were studied from the wood blocks with FTIR PAS technique. The wood samples treated were also subjected to a fungal decay test with Coriolus versicolor. This treatment hindered fungal decay in a 60-day experiment and led to a dry weight loss of 8.8% in comparison with 19.9% in the control. The reactions of coniferyl alcohol and H2O2 in the presence of peroxidases are discussed as well as the use of monolignols to increase wood decay resistance. 相似文献
19.
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.
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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
20.
In this work, we present a fast and promising method to evaluate the natural durability of wood based on X-ray microdensitometry.
Tested on beech and Scots pine wood samples, our findings show that this methodology and the traditional EN standards methodology
based on mass loss are strongly correlated. X-ray methodology is less time consuming (we can detect the effectiveness of the
attack within 5–6 weeks) and less expensive (very cheap plastic Petri dishes instead of the expensive glass Kolle flasks);
moreover, the proposed method allows to thoroughly examine the phases and the kinetics of the fungal attack, and to investigate
the spatial repartition of the attack within the samples due to the low thickness of the sample. 相似文献
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