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1.
Abstract

Development in surface mould growth on painted/unpainted wooden claddings and acting climatic factors were investigated over a period of 3 years. Eight wood substrates, including modified, preservative-treated and untreated wood, were tested in combination with three types of paint: (1) water-borne alkyd modified acrylic paint without fungicide; (2) solvent-borne alkyd paint without fungicide; and (3) ICP (internal comparison product). One set of samples was exposed unpainted. The samples were tested according to a modified version of EN 927-3. A logistic regression model was fitted to the data. The degree of mould growth varied with exposure time, coating typology, wood substrate, temperature and relative humidity. Exposure time and coating typology contributed most to the model. After 3 years of outdoor exposure unpainted panels and panels coated with solvent-borne paint without fungicide had more mould growth than panels coated with ICP and water-borne paint without fungicide. Unpainted oil/copper–organic preservative-treated claddings had higher resistance to mould growth than other unpainted wood substrates. Coated untreated pine and coated acetylated pine were more susceptible to mould growth than other coated wooden substrates.  相似文献   

2.
Outdoor performances of a polyurethane varnish and an alkyd-based synthetic varnish coated over chromium-copper-boron (CCB)-impregnated Scots pine (Pinus sylvestris L.) and chestnut (Castanea sativa Mill.) [10 (R) × 100 (T) × 150 (L) mm] were investigated. These varnishes were also applied to the wood surface as sole coatings or impregnated into wood as water-repellent (WR) solutions. Outdoor exposure was performed in the Black Sea region of northern Turkey (41°N, 39.43°E) where humid weather predominates throughout the year and accelerates decomposition of coated wood surfaces. The wood panels were exposed at 45° south on their tangential surfaces. After 9 months of exposure to summer, autumn, and the following winter season, the color and glossiness changes of the exposed surface, adhesion of the coating layer to the wood surface, water absorption through the coating layers, mass loss, and the hardness of the board surface were studied. CCB impregnation greatly stabilized the surface color of varnish-coated panels of both wood species. Gradual decreases of adhesion between varnished layers and preimpregnated surfaces were attributed to probable weakening of interactions at the interface of the treated wood and the film layer. A superficial cleaning process of treated wood is suggested to improve glossiness and adhesion. The coated wood surface became harder with time on outdoor exposure until a maximum hardness occurred followed by softening, whereas the uncoated surface softened steadily. Polyurethane varnish yielded a harder surface than synthetic varnish. Mass losses of wood panels after 9 months of exposure were negligible for all treatments compared with the untreated controls, which were totally discolored and eroded on the surface. It is concluded that long-term exterior wood protection has been achieved by a successful combination of an appropriate preservative treatment followed by a compatible surface-coating process.  相似文献   

3.
Mould growth on coated wood is today a genuine challenge for house owners. Environmentally sound wooden facades with long service lives and acceptable appearance are desired. The objective in this study was to investigate the accumulated mould growth on 13 different wood substrates with 3 surface coating systems by identifying the factors that contribute to the variation and to predict future performance. A generalized linear mixed model was fit to the data with the analysis showing that coating and exposure time both had highly significant influences on mould growth. Further, wood substrate was significant, but comparatively less than coating and exposure time. A smaller coefficient for mould coverage in the beginning of the exposure period gave the panels with one of the coating systems, BAP, a delay in mould growth, and the extrapolated values for years 6–12 indicate a longer aesthetic service life than panels with the two other coating systems. Coated heartwood as wood type was less susceptible to mould growth than coated mixed wood and coated sapwood. Acetylated pine as wood substrate and aspen as wood species had lower resistance to mould growth than the other wood substrates and wood species, respectively.  相似文献   

4.
ABSTRACT

The quality of finished wood products depends on the quality of its coating layer. An important indicator for evaluating the quality is Adherence of the paint on the wood surface. The purpose of this research was to analyze the effect of wood surface roughness and the viscosity of acrylic paints (pure acrylic and acrylic copolymer) to the wettability and Adherence for long and short rotation teaks. Wood surface with various degrees of roughness was prepared by sanding with abrasive papers of P120, P240, and P360 grits. Different viscosity of the acrylic paints was prepared composition between paint and water (w/w) of 100:0, 90:10, 80:20, and 70:30. The wettability of the acrylic paints on teak wood surfaces was measured using a sessile drop contact angle method with the S/G model. Adherence of the coating layer was measured using a crosscut test. The results showed that the increase in the roughness (Ra) and the decrease in the viscosity of the paints resulted in the increase in the wettability which leads to better Adherence of acrylic paints on the surface of teak woods. The pure acrylic paint generated better wettability and Adherence compared to the acrylic copolymer.  相似文献   

5.
ABSTRACT

The effects of a fire-retardant treatment (FRT) and wood grain on three-dimensional changes of aircraft sandwich panels were evaluated. Unvarnished and varnished panels having the outer decorative layer made with bubinga (Guibourtia spp.) were studied. Half of the samples from each type of panel received an FRT (phosphate-based) on all three layers of the decorative plywood. The other half had the two inner layers treated and the outer layer untreated. Three different figures formed by the rotary cutting and grain orientation were identified and separately studied on veneer surfaces. Samples pre-conditioned to 20°C and 40% relative humidity (RH) underwent an adsorption (25°C, 90% RH) and then a desorption (25°C, 40% RH) treatments. Changes in moisture content (MC), swelling, shrinkage, roughness, and waviness were measured after each moisture exposure condition. The results showed that the FRT increased significantly MC, swelling, and shrinkage of unvarnished and varnished panels. This treatment as well as the type of wood figure affected roughness and waviness variations of unvarnished panels. However, the effects of these two factors were not noticeable once panels were varnished.  相似文献   

6.
Abstract

The indoor relative humidity in dwellings and offices is an important factor in building physics. The ability of hygroscopic materials and especially wood materials to store and release moisture helps to regulate the indoor climate naturally and to avoid extremes of humidity. In the present study, cyclic sorption experiments with coated Scots pine were performed. Materials with different coating compositions were exposed to day-to-day relative humidity changes. The moisture buffering capacity was estimated by a gravimetric method and the moisture buffer value was computed. The results show that the coating has a significant impact on the moisture buffering capacity of the underlying Scots pine. The moisture distribution in the wood sample was appraised for each coating system using a proton magnetic resonance imaging technique. This study confirmed that the dynamics of moisture exchange between the indoor environment and the wooden material during typical daily moisture fluctuations is confined to a few millimetres behind the air–wood interface.  相似文献   

7.
Summary Western red cedar panels, one coated with a soft latex-based acrylic polymer clear coating and the other uncoated, were exposed outdoors under a series of cut-off filters for 50 weeks. FTIR-ATR spectra of the panels showed that the extent of delignification increased with decreasing wavelengths of the solar radiation incident at the wood surface. The results support the proposal that it is the UV component of sunlight that is primarily responsible for the degradation of lignin. The extent of loss of lignin from the surface of the exposed coated panel was significantly less than that for the exposed uncoated panel suggesting that the coating confers some protection from weathering to the underlying timber. Colorimetric measurements also showed that the degree of discoloration of the panels is related to the wavelength of the radiation penetrating the wood surface.This work was supported financially by ICI Dulux Australia and the Australian Research Council. The authors also express their appreciation for helpful discussions with G. J. Wilson of the Commonwealth of Australia Scientific and Industrial Research Organization (C.S.I.R.O.) and I. Leaver of Dulux Australia  相似文献   

8.
Abstract

Organic–inorganic hybrid sol-gel coatings derived from sols synthesized using two organically modified precursors were generated on wood specimens using dip and spray coating techniques. One of the sols was synthesized using methacryloxypropyltrimethoxysilane (MPTMS) and nanoscaled boehmite particles and the other was synthesized using dimethyldiethoxysilane (DMDEOS) and tetraethoxysilane (TEOS). The coatings were generated on the wood specimens by dipping into the sols for specific time periods and by using spray coating method. The coatings were cured at different temperatures for varying soaking times. The dipping times, curing temperature, and soaking times were varied between 24–96 h, 130–200°C and 1–5 h, respectively. The coated samples were characterized for their water contact angles, microstructure, and resistance to water uptake. The coatings derived from MPTMS+boehmite sol were seen to exhibit better performance than DMDEOS+TEOS sol by forming a good barrier on the wood surface, thereby providing superior resistance to water and weather. Dipping of wood into the sol was seen to provide better protection when compared to spray coating. Dipping into the MPTMS+boehmite sol for 24 h and curing at 130°C for 2 h were found to be the optimal processing parameters yielding the best properties.  相似文献   

9.
Abstract

Scots pine log specimens were given three different surface treatments and two different orientations of large cracks, and subjected to cyclic wetting and drying. Individual fitting of a mechanistic growth model was used to study the shape of absorption and accumulation curves and the final drying curve. Two parameters from this model (increase/decrease rate and maximum/minimum weight gain) were used for statistical analysis. The results indicate that wood tar results in less accumulated moisture over time than solvent-borne or water-borne coating or no treatment at all. An incipient attack by a white-rot fungus on parts of the material during storage affected water uptake greatly, often overriding surface treatment.  相似文献   

10.
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   

11.
In this research, acoustic emission technology was used to estimate the moisture excluding effectiveness of coatings on wood. Moisture interaction with wood causes damage, and coatings such as paints and varnishes can effectively limit this interaction. Over time, the moisture excluding effectiveness of wood is reduced by the actions of weathering and the resulting wood-water interaction leads to problems due to the dimensional instability of the wood. Five coating types, at two spreading levels, were applied to samples of southern yellow pine. The samples were exposed to three weathering conditions to simulate the effects of exposure then immersed in water while the moisture interaction was monitored using acoustic emission monitoring equipment. Cumulative counts as well as changes in size and moisture content were measured or calculated. The results show that acoustic emission technology is an effective and sensitive estimator of the moisture excluding effectiveness of coatings on wood. The acoustic emission method is sensitive to local changes and coating fractures whereas the more traditional methods are sensitive to gross changes in sample characteristics. Of five coatings tested, the most effective one was found to be an oil-based paint, and the worst performance was by a water-based, clear poly-urethane. Received: 10 September 1998  相似文献   

12.
Abstract

This study evaluated the capability of nuclear magnetic resonance (NMR) technology based on small portable magnets for in situ studies of the local moisture content in wood. Low-field and low-resolution [1H]NMR with a unilateral permanent magnet was used to monitor and map the moisture content of wood cladding materials of various types in a spatially resolved manner. The results show that portable NMR equipment based on small open-access permanent magnets can be successfully used for non-invasive monitoring of the moisture content in various extended wood specimens. The moisture content was measured with a depth resolution of 0.2 mm and a maximum penetration depth of 3 mm. This makes the technique suitable for in situ local moisture content measurements beneath a coating layer in the cladding, for example, and it is also possible to relate the moisture level to specific properties of the wood material.  相似文献   

13.
漆酚铁聚合物-醇酸树脂互穿聚合物网络涂料的研究   总被引：1，自引：0，他引：1  
研究由漆酚甲醛缩聚物(PUF)、多羟基醇酸树酯(AIR)和三氯化铁制备互穿聚合物网络(IPN)涂料的方法,并采用动态机械热分析(DMTA),红外光谱(IR)和其它手段对IPN涂料的结构特征与性能进行表征。结果表明,Fe^3 与PUF中的酚羟基形成Fe-O键,PUF分子之间的交联程度增加,对AIR的包裹和缠结能力增强,从而提高了漆膜的综合性能,尤其是耐腐蚀性能和抗溶剂性能得到很大的提高。  相似文献   

14.
木材导热系数的研究   总被引：8，自引：2，他引：8  
侯祝强 《林业科学》1992,28(2):153-160
本文运用非平衡态热力学线性理论分析了含水率在纤维饱和点以下木材的传热,结果表明木材中的水蒸汽和束缚水参与了传热,木材导热系数由传导导热系数与因水蒸汽和束缚水扩散产生的两个等效导热系数组成。推广Siau关于木材细胞的导热理论,依据水分吸附和扩散的原理,导出了木材弦向和径向导热系数计算公式,与已发表的36种气干材弦向实验值和23种气干材径向实验值符合较好。分析木材径向传热的方法也适用于木材纵向传热。  相似文献   

15.
Abstract

The aim of the present work was to examine an advanced image-processing algorithm for moisture content (mc) calculation and also to use this algorithm to analyse moisture loss data for low temperature drying. Since wood starts to shrink below the fibre saturation point during drying, the geometrical shape of the wood piece will change. The dry wood image was thoroughly transformed to the shape of the wet wood image prior to calculating the dry weight mc. The results show that the algorithm for the dry weight mc on density data from the CT-scanning during low-temperature drying in the climate chamber is a powerful tool for analysing the moisture loss inside the wood piece. This method can make it possible to get a higher quality on the product.  相似文献   

16.
Woodpermeabilityhascloserrelationshipwiththemanyfiledsofwoodworkingandusing,woodfluidpermeabi1-ityisrelatedtoinprocessingsuchaswooddrying;fireretartenttreatmen;pup1ingandpaper;woodpreservation.Theflowoffluidinwoodincludestwokindsoftransportprocess.Oneispenetrationfromwoodoutsidetoinside,suchas'woodpreservationandfireretartenttreatment,anotherisdiffusionfromwoodinsidetooutside'suchaswooddrying,Infact,woodpermeabilityinfulenceddirectlythequalityofwoodwaterheattreatment,Forthisreasontheresearchin…  相似文献   

17.
Abstract

Black alder wood has a great potential for more wide-spread use in the woodworking industry. This study describes the colour changes that appeared the first few hours after cutting thin veneer sheets from fresh, unseasoned black alder wood. CIELab coordinates were recorded for 50 spots at time intervals from 0 to 140 minutes exposure of the fresh-cut surfaces. The most pronounced change was increased lightness developing from 20 to 60 minutes after cutting. A model for total colour change as function of exposure time was developed. Redness of veneer sheets increased only slightly, i.e. the expected transfer to orange discoloration of the surface did not occur. The reason for this was probably that part of the free water in the wood was squeezed out during veneer production. The findings of this study give useful information about the colour change that appeared directly after veneer cutting, advising to avoid excess water on wood surface and ensuring quick surface drying.  相似文献   

18.
Abstract

Two wood plastic composite (WPC) boards, one experimental and one commercial, were exposed to exterior conditions and evaluated non-destructively using a clinical magnetic resonance imaging (MRI) unit for moisture content (MC) and distribution. The experimental board was exposed in Vancouver, British Columbia, for more than 8 years, and the commercial board was exposed near Hilo, Hawaii, for 2 years. Both boards were characterized in terms of wood content, density, water uptake properties and voids content. The experimental board was additionally destructively analysed for water absorption of the WPC and MC calculated based on the wood content for verification of MRI results. MRI detected the presence of free water and its distribution in both of the WPC boards. Fibre saturation in the experimental board was found to be about 22–24%, in comparison to 25–30% present in most wood species. There was good correlation between the detection of free water by MRI and by destructive testing. Magnetic resonance images showed various major points of water entry in the WPC boards such as the support area, the cut ends, the dripping edge and the sides of the boards. For the experimental board, significant water entry also occurred at the upper exposed surface.  相似文献   

19.
吸湿范围内毛白杨木材径向透气性的研究   总被引：2，自引：0，他引：2  
文章利用自行研制的木材透气性实验装置,探讨了木材含水率、厚度和压力对毛白杨透气性的影响。实验证明：实验装置结构合理,气密性较高,操作方便,满足测量要求;在吸湿范围内：木材透气性与含水率呈负二次曲线关系,含水率为10％左右透气性最大;透气性随着压力差的增加而增加,并呈直线上升趋势;透气性随着厚度的增加而减少,并呈指数下降趋势;在本实验探讨的影响因素中,含水率和厚度对透气性的影响显著。  相似文献   

20.
Currently computed tomography (CT) scanning provides a non-destructive method to determine moisture content in wood in three dimensions. With the current methodology two measurements are needed, one with the scanned piece of wood’s moist state and one after drying. Then the difference of the images can be calculated. The drawback and challenge is that dimensional changes due to shrinkage of wood in the drying process have to be compensated for by image processing. In this study a dual-energy CT scanning method is tested based on the consecutive scanning of wood samples at different energy levels to differentiate water from wood, without the necessity to dry the sample and thus without the need for complex image correction. Not quantified but visible differentiations due to moisture content were obtained on small cubical pine samples of different densities by quick consecutives scans at 60 and 200?kV. The results suggest that given that the pixels in the CT images are representing absorption coefficients it should be possible to directly measure moisture content in wood non-destructively in small volume elements inside solid wood in three dimensions. Further applications of this technique in industrial CT scanning of wood are discussed.  相似文献   

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