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1.
A series of experiments were carried out to investigate the colour stability of chemically treated and thermally modified wood compared to non-modified wood during long term artificial UV light irradiation. One set of wood samples was vacuum-pressure impregnated with alkaline (pH 9.8) copper (II) ethanolamine aqueous solution, while another set of samples from the same wood block was thermally modified at 210°C and −0.90 bar for 2 h. The treated and modified wood samples along with the non-modified ones were exposed to artificial UV light with the wave length in the region of UVA (315–400 nm) and UVB (280–315 nm) intermittently for 500 h. Colour measurements were carried out throughout the irradiation period at an interval of 100 h according to CIEL*a*b* system, where the results are presented in terms of ΔE, ΔL*, Δa* and Δb* values. Better photo-stability in terms of colour changes was recorded for both treated and modified woods compared to the non-modified one. By means of EPR and DRIFT spectroscopic study it was shown that some degree of colour stability of treated and modified woods, achieved during artificial UV light irradiation, resulted from lignin modifications and monomers of phenolic compounds.  相似文献   

2.
ABSTRACT

Acetylated wood is now commercially available and designed to be used in certain outdoor applications as an alternative to preservative-treated wood. Fastener corrosion can be a concern in preservative treated wood when the wood remains wet for long periods. However, little data on the corrosiveness of acetylated wood exists beyond the product literature. Here we examine the corrosiveness of commercially obtained acetylated wood and compare it against unmodified (untreated) southern pine (Pinus spp.). Corrosion rates of plain carbon steel, hot dip galvanized steel, and stainless steel were calculated gravimetrically after a one year exposed in the wood. Four different moisture conditions were examined: 90% relative humidity (RH), 95% RH, 100% RH, and a fully water saturated condition. When compared to literature data on the corrosion of fasteners in preservative treated wood at 100% RH, the acetylated wood had much lower steel corrosion rates than all preservatives examined; the measured corrosion rates for galvanized steel were lower than all preservatives except chromated copper arsenate. These measured corrosion rates across a range of moisture conditions can be used to inform the selection of appropriate corrosion resistant fasteners when building with acetylated wood.  相似文献   

3.
Abstract

This work summarizes the output of durability, reaction to fire properties, and environmental impact of wooden claddings subjected to treatments modified with TiO2 and clay nanoparticles. The objective was to investigate the effects of 1 wt% of TiO2 and clay nanoparticles in existing water-based and stain coatings and preservatives regarding the properties mentioned above. Water vapor resistance properties were used to assess the moisture transfer properties of the specimens by using the cup test. The reactions to fire properties of the specimens were analyzed using small-scale cone calorimeter test. Accelerated aging was used to study the weathering properties of specimens, where the performance of the specimens with aging was characterized using Fourier transform infrared (FTIR) analysis. The effect of increasing the percentage of nanoparticles from 1 wt% to 3 wt% on the weathering properties of the specimens was further analyzed. Moreover, comparison between the overall environmental impact between unmodified water-based paint and water-based paint modified with 1 wt% of TiO2 nanoparticles was performed using available environmental data and weathering test results as analyzed by FTIR.  相似文献   

4.
Element content and pH value in wood tissues of veneer grade logs of P. serotina Ehrh. were investigated with regard to wood colour variations, measured in the CIEL*a*b* system. The average pH value of heartwood tissue was about pH 4.0 and medium colour parameters of veneer sheets were determined at L* = 73, a* = 9.8, and b* = 23.5. Optical emission spectroscopy (ICP-OES) analyses showed differences in the element contents between two regional forest sites coming from Pennsylvania and West Virginia, USA, respectively. The latter is mainly characterised by higher variations of micro-element content in the transition zone (influencing heartwood formation) and also pH value of wood tissue, which contributes to higher variations in colour response of industrially produced veneer sheets. Investigations under industrial conditions underline the correlation between length and intensity of heat treatment in veneer production and colour development: with increasing duration and temperature of hot water treatment, veneer surfaces become darker and wood colour is intensified (ΔL = 3.6, Δa = 2.1, comparing 12 and 72 h of hot water treatment at 60°C). However, no equalisation of wood colour was achieved by modifying the treatment conditions. Artificial radiation by UV–visible light, quickly and extensively darkens and intensifies wood colour (ΔL = 16, Δa = 3.5, and Δb = 4.0 after 15 h of artificial radiation), but variations in wood colour deriving from different treatment conditions during veneer production, were not reduced.  相似文献   

5.
Effects of different thermal treatments (maximum treatment temperatures of 200, 210 and 220°C for 2.5 hours) on solid spruce (Picea abies L. Karst.) and ash (Fraxinus excelsior L.) were investigated in this study. The fracture behaviour in radial/longitudinal as well as in tangential/longitudinal and the change of the wood colour (CIEL*a*b* colour space) on all principal anatomical surfaces (cross sectional, radial and tangential) were analysed. The specific fracture energy and the maximum breaking load decreased almost significantly after all thermally treated samples in comparison to the untreated (standard dried) sample. The wood colour changed also significantly, in particular the lightness decreased with increasing intensity of thermal treatment on all investigated surfaces. A comparison of the percentage loss of the different fracture and colour values has shown a strong correlation between the maximum breaking load and the lightness after several thermal treatments, in both investigated crack propagation systems, on all measured surfaces and for both analysed species.  相似文献   

6.
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.  相似文献   

7.
We evaluated fungal decay and mold resistance, leaching, and water absorption of nano-compounds and Paraloid B72® (PB72) in treated wood specimens to develop new methods of consolidation by combining nano-particles and consolidants. Scots pine wood specimens were treated with dispersions of nano-CuO, nano-ZnO, nano-B2O3, nano-TiO2, and nano-CeO2. PB72 treatments of nano-particle-treated wood specimens were then carried out by either vacuum or immersion for 24 h. Previously, decayed wood specimens were also consolidated with the nano-compounds and PB72. PB72 treatments reduced element release from treated wood specimens. Nearly all nano-compounds + PB72 treatments increased the biological performance of treated wood specimens against decay fungi tested. PB72-only treated wood specimens had the highest weight losses in decay tests. No improvements were obtained in mold resistance tests when the nano-compounds and PB72 were combined. In nano-compound-only treatments, unleached specimens showed slightly lower water absorption values compared to untreated control specimens. Incorporation of PB72 into nano-compound-treated wood specimens resulted in considerably lower water absorption and volumetric swell. In previously decayed specimens treated with the nano-compounds and PB72 solution, water absorption after 2-h immersion declined compared to control specimens.  相似文献   

8.
ABSTRACT

This research was aimed to investigate mechanical properties, color and cell-wall components changes, and durability of pre-dried rubberwood (Hevea brasiliensis) after superheated steam (SS) treatment. Wood samples were treated at different SS temperatures (140–180°C) for 1–3?h. The highest compression strength parallel-to-grain, hardness and impact strength were found for samples treated at 160°C for 3?h (30.7% higher than untreated), at 150°C for 1?h (26.6% higher than untreated) and at 150°C for 2?h (52.6% higher than untreated), respectively. The surface color became darker after each treatment in comparison with the untreated wood. The number of accessible hydroxyl groups decreased and the relative cellulose crystallinity increased with SS temperature, indicating decreased hygroscopicity of the treated wood. Also, SEM micrographs of wood surface showed consistent decrease in starch particles with treatment temperature. Both decay and termite resistances of treated rubberwood improved with treatment temperature. All the analyzes showed that dried rubberwood treated with SS had some improvements in the mechanical properties, decreased hygroscopicity, and increase resistance to decay.  相似文献   

9.
A new wood preservative containing low molecular weight and low-toxicity silicic acid (LWSA) was investigated. To prevent environmental pollution with the wood preservative, a silicic acid monomer aqueous solution (SAMS) or colloidal silicic acid solution (CSAS) was combined with various metal compounds or boric acid. Agents where SAMS or CSAS was combined with boric acid gave good protection against decay caused by the brown-rot fungus Fomitopsis palustris, the treated wood (Cryptomera japonica D. Don) specimens after the leaching test maintained a high resistance to decay. The leaching and decay tests revealed high quantities of chemicals leaching from wood treated with SAMS-metal agents. However, when wood was treated with SAMS-boric acid, there was little leaching of agent in either test. The mechanism of resistance of wood, which was treated with boric acid mixed with CSAS or SAMS, to the brown-rot fungus F. palustris were investigated. When the concentration of boric acid was high, mycelial growth was inhibited completely and no protein production was detected. When the amount of boric acid was low, the xylanase, mannase and cellulase activities were lower than with control wood powder. When powdery boric acid was combined with CSAS, it was considered that the treated woods have higher anti-weather properties than when boric acid-methanol solution was mixed with CSAS. The agent-preparation method adopted should be considered carefully after taking the treatment process and the intended use of the preservative-treated wood into account. Received 26 September 2000 This study was supported by a Grant-in-Aid (09460079) for Scientific Research from the Ministry of Education, Science, and Culture of Japan.  相似文献   

10.
The effect of heat treatment on the surface colour and hygroscopic properties of pine wood were investigated in this study. Boards of Scots pine wood (Pinus sylvestris L.) were subjected to thermal treatment at 200°C, for 4, 6, and 8 h. The change of equilibrium moisture content and density values of the specimens in order to facilitate the understanding of the treated material behavior. The colour parameters L*, a* and b*, used to depict the total colour change (Δ E) of wood surface, were shown to change proportionally to the treatment intensity. Moreover, swelling in the tangential and radial directions and absorption of the specimens appeared to be enhanced in great extent by the thermal treatment process. The mean value of swelling percentage in the tangential direction decreased 10.26%, 17.22%, and 19.60% for specimens treated for 4, 6, and 8 h, respectively, referring to the final measurement after 72 h of immersion. In radial direction, mean value of swelling percentage decreased 19.56%, 32.75%, and 34.65% for treated for 4, 6 and 8 h, respectively, after 72 h immersion, which attests the decrease in swelling and improvement in the hygroscopic behavior of Scots pine wood.  相似文献   

11.

The effects of felling season, log storage and kiln drying on stemwood discoloration of sixty mature silver birches ( Betula pendula ) were studied and provided with CIEL*a*b* colour coordinates. The colour differences were expressed as j E* including split up of j L*, j a* and j b*. The results showed that fresh wood colour depends on the felling season: light and pale colours were recorded for samples taken from autumn- and winter-felled trees, whereas the colour of fresh wood was considerably darker if the felling took place in the spring or summer. After storage, notable changes in colour were observed. After drying, all samples showed low lightness, moderate redness and relatively high yellowness under the drying conditions used in the study regardless of the felling season or duration of storage. The main colour component responsible for the discoloration was lightness, while chroma values redness and yellowness played a minor role.  相似文献   

12.
Abstract

Thermal modification has been developed for an industrial method to increase the biological durability and dimensional stability of wood. In this study the effects of thermal modification on resistance against soft- and brown-rot fungi of sapwood and heartwood of Scots pine and Norway spruce were investigated using laboratory test methods. Natural durability against soft-rot microfungi was determined according to CEN/TS 15083-2 (2005) by measuring the mass loss and modulus of elasticity (MOE) loss after an incubation period of 32 weeks. An agar block test was used to determine the resistance to two brown-rot fungi using two exposure periods. In particular, the effect of the temperature of the thermal modification was studied, and the results were compared with results from untreated pine and spruce samples. The decay resistance of reference untreated wood species (Siberian larch, bangkirai, merbau and western red cedar) was also studied in the soft-rot test. On average, the soft-rot and brown-rot tests gave quite similar results. In general, the untreated heartwood of pine was more resistant to decay than the sapwood of pine and the sapwood and heartwood of spruce. Thermal modification increased the biological durability of all samples. The effect of thermal modification seemed to be most effective within pine heartwood. However, very high thermal modification temperature over 230°C was needed to reach resistance against decay comparable with the durability classes of “durable” or “very durable” in the soft-rot test. The brown-rot test gave slightly better durability classes than the soft-rot test. The most durable untreated wood species was merbau, the durability of which could be evaluated as equal to the durability class “moderately durable”.  相似文献   

13.
In this study, twenty-five heat treatments were conducted at the various treating conditions of five temperatures and five durations. At each treatment, 15 poplar specimens were used. Twelve variables that represented wood color, physical and mechanical properties and durability were measured for both treated and untreated specimens. To evaluate the effect of heat treatment on the wood performance, a comprehensive cluster analysis was applied to the measured variables of treated and untreated specimens. Cluster analysis showed that treating and control specimens can be distinctly classified into 2, 3 or 4 clusters according to the intended purposes. Two clusters can represent the control group and twenty-five testing groups. Four clusters represented the control group and three groups of testing specimens having mild, moderate and severe treating conditions, respectively. At the mild treatment, modulus of rupture (MOR) was reduced <11 %. Wood durability increased to moderate resistant. At the moderate treatment, EMC decreased by 28 %, and MOR was decreased by more than 12 %. In the severe treatment, wood durability increased to resistant or highly resistant; however, its MOR was reduced half.  相似文献   

14.
Optimisation of a two-stage heat treatment process: durability aspects   总被引：1，自引：1，他引：1  
Heat treatment of wood at relatively high temperatures (in the range of 150–280°C) is an effective method to improve biological durability of wood. This study was performed to investigate the effect of heat treatment process optimisation on the resistance against fungal attack, including basidiomycetes, molds and blue stain fungi. An industrially used two-stage heat treatment method under relatively mild conditions (<200°C) was used to treat the boards. Heat treatment of radiata pine sapwood revealed a clear improvement of the resistance against the brown rot fungi Coniophora puteana and Poria placenta. Increasing process temperature and/or effective process time during the first process stage, the hydro thermolysis, appeared to affect the resistance against C. puteana attack, but the effect on the resistance against P. placenta was rather limited. Heat treated radiata pine showed a limited resistance against the white rot fungus Coriolus versicolor and process variations during the hydro thermolysis stage appeared not to affect this resistance. A clear difference between the resistance of heat treated Scots pine sapwood and heartwood against fungal attack is observed. Scots pine heartwood showed a higher resistance against C. puteana and P. placenta but also against the white rot fungus C. versicolor. Similar results were obtained when heat treated birch was exposed to brown and white rot fungi. Heat treatment showed an improved resistance against C. puteana attack, especially at higher temperatures during the hydro thermolysis stage. A clear improvement of the durability was also observed after exposure to the white rot fungus C. versicolor and especially Stereum hirsutum. Increasing the process temperature or process time during the hydro thermolysis stage appeared to have a limited effect on the resistance against C. versicolor attack. Heat treated radiata pine and Norway spruce were still susceptible to mold growth on the wood surface, probably due to the formation of hemicelluloses degradation products (e.g. sugars) during heat treatment. Remarkable is the absence of blue stain fungi on heat treated wood specimen, also because the abandant blue stain fungi were observed on untreated specimen. Molecular reasons for the resistance of heat treated wood against fungal attack are discussed in detail contributing to a better understanding of heat treatment methods.  相似文献   

15.
以水蒸气作为保护气体,在170,185,200和215℃的条件下分别热处理橡胶木3h,对热改性橡胶木的生物耐久性进行研究.结果显示:高温热改性可提高橡胶木的耐腐性,其改善效果随着处理温度的升高而提高,当处理温度为185℃或更低温度时,改善效果不明显.215℃处理3h后,褐腐(密黏褶菌)质量损失率由51.6％降至21.6％,白腐(采绒革盖菌)质量损失率由27.6％降至6.8％.选用烟曲霉、哈茨木霉、产紫青霉和可可球二孢进行防霉试验,结果显示热改性橡胶木的防霉性能与对照相比没有明显的改善;经涂饰后,热改性试材的防霉性能优于未处理材.野外耐久性试验结果显示,高温热改性不能提高橡胶木的防白蚁性能.  相似文献   

16.
Studying the impregnation and distribution of oil-based preservative in dried wood is complicated as wood is a nonhomogeneous, hygroscopic and porous material, and especially of anisotropic nature. However, this study is important since it has influence on the durability of wood. To enhance the durability of thermally modified wood, a new method for preservative impregnation is introduced, avoiding the need for external pressure or vacuum. This article presents a study on preservative distribution in thermally treated Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) sapwood using computed tomography scanning, light microscopy, and scanning electron microscopy. Secondary treatment of thermally modified wood was performed on a laboratory scale by impregnation with two types of preservatives, viz. Elit Träskydd (Beckers) and pine tar (tar), to evaluate their distribution in the wood cells. Preservative solutions were impregnated in the wood using a simple and effective method. Samples were preheated to 170 °C in a drying oven and immediately submerged in preservative solutions for simultaneous impregnation and cooling. Tar penetration was found higher than Beckers, and their distribution decreased with increasing sample length. Owing to some anatomical properties, uptake of preservatives was low in spruce. Besides, dry-induced interstitial spaces, which are proven important flow paths for seasoned wood, were not observed in this species.  相似文献   

17.
Abstract

Differences in durability between heartwood and sapwood of Norway spruce [Picea abies (L.) Karst.] were investigated to determine wood qualities most favourable for use in outdoor constructions above ground. Trees grown on sites with either good or poor access to water were used. Seventy-eight specimens measuring 20 × 50 × 300?mm3 separated into heartwood and sapwood, half untreated, half painted, were exposed horizontally outdoors above ground for 5.5?years with the pith side up and the bark side down. Crack length and crack number were measured. Fungus growth and surface changes were visually estimated. Fungus type was determined by microscopic analysis. The main finding was that spruce heartwood had fewer and shorter cracks and less surface-discolouring fungus growth than sapwood. This was valid for both painted and untreated wood. After 2?years’ exposure, the cracks in sapwood (upper surface) were more than three times longer and about five times more numerous than in heartwood for both painted and untreated boards. Microscopic study showed that surface discoloration was due mainly to Aureobasidium pullulans, together with a few other discolouring fungi. After 5.5?years, initial decay was established on the surface and in the end grain of four untreated test objects.  相似文献   

18.
Evaluation of wood preservatives in soil-contact tests is becoming an important issue since detoxification of wood-protecting compounds by fungi and bacteria found in soil may decrease the resistance of treated wood. In this study, the decay resistance of wood treated with didecyl dimethyl ammonium tetrafluoroborate (DBF), a recently developed quaternary ammonia compound, was evaluated in both soil bed and laboratory decay resistance tests. Small specimens (5×10×100 mm3) of DBF-treated and untreated sugi sapwood were subjected to decay in laboratory soil bed tests (DIN ENV 807 (2001)) followed by Basidiomycetes tests (DIN EN 113 (1996)). Exposure in field soil and compost soil substrates was used to observe the effects of wood degrading and other soil-inhabiting micro-organisms on the decay resistance of the specimens. Soil bed tests showed that DBF-treated wood specimens at 7.7 kg/m3 retention level (1% DBF solution concentration) showed better performance compared to 0.01 and 0.1% DBF treatments. The 7.7 kg/m3 retention level was also effective to protect the wood specimens against Coniophora puteana and Coriolus versicolor in Basidiomycetes tests. It is concluded that detoxification of wood preservatives in soil contact is an important factor to determine protective properties of treated wood in ground contact applications. Further experiments with larger specimens are needed to observe the performance of DBF-treated wood at higher retention levels in field above ground and ground contact tests. Dedicated to Prof. Dr. H.C. Mult. Walter Liese on the occasion of his 80th birthday.  相似文献   

19.
Abstract

The potential of near infrared spectroscopy (NIRS) to estimate wood moisture content (MC), surface energy characteristics and adhesive bond strength were evaluated on aspen (Populus tremuloides Michx.) veneer subjected to different drying times. For samples dried progressively at 103°C, the best MC prediction model was for the total MC range (0–100%) with an R2 value of 0.68. However, exposure at 180°C produced surface colour changes, and the CIE L*a*b* colour parameters measuring colour changes were better estimated using the 400–900 nm spectral data than the 1100–2400 nm spectral data. Increased exposure time at 180°C resulted in lower wettability and, hence, larger contact angles, especially when ethylene glycol was used as probe solvent. Lap shear strength tests on veneers showed that adhesion by phenol formaldehyde resins was impaired by the high temperature exposure; however, the lap shear strength test had high variability so there was not always a clear relationship between contact angle and lap shear strength test.  相似文献   

20.
A laboratory no-choice termite bioassay was conducted to evaluate the ability of copper HDO (CX-A or copper xyligen) to protect radiata pine (Pinus radiata D. Don) wood samples from attack by two subterranean termite species, Reticulitermes speratus and Coptotermes formosanus. A series of sapwood samples were pressure treated with either 0.25%, 0.50%, 0.75%, or 1.00% copper HDO solution. Samples treated with equivalent concentrations of a benchmark preservative, CCA-C, were used as treated controls. All samples (including controls) were subjected to an artificial weathering schedule before the bioassay. The samples were exposed to 30-day R. speratus tests and 3-week C. formosanus tests. Copper HDO was shown to deter termites from significant feeding on the treated wood. At a retention of 5.8 kg/m3 (treated with 0.75% solution) or higher, the mass loss from termite feeding did not exceed 3% for both the 30-day R. speratus tests and the 3-week C. formosanus tests. At each of the retentions tested, copper HDO performed comparably with equivalent retentions of CCA-C; however, field data are needed to validate these laboratory results. The preliminary findings are that copper HDO pressure treatment has potential as a viable method of protecting wood from attack by both termite species tested.  相似文献   

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