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Leaching of the new boron based biocide from coated wood
2001 - IRG/WP 01-30267
We investigated leachability of the new boron based biocide - a complex of an amine and boric acid - from vacuum impregnated spruce wood samples. It was determined by the standard ENV 1250-2 procedure that the new biocide is susceptible to leaching so from the water borne as well as from the ethanol borne boron containing preservative treated wood. Leaching may be retarded by application of surface coatings. The ability of a surface finish to prevent leaching is correlated to its water vapour permeability.
M Petric, M Pavlic, F Cadez

The resistance of wood coated with different solvent-borne paints against colonisation by decay fungi
2009 - IRG/WP 09-40468
This paper examines different solvent-borne paints characteristics and their decay resistance when applied on pine wood surface. It was determined by the standard ENV 839 procedure. The part of samples were subjected to accelerated ageing according to the EN 84 standard. The discussed commercial paint systems were typical stains or penetrating oil-based products, with or without biocides.
B Mazela, P Hochmańska

How to keep coated wood structures sufficiently dry to avoid damage caused by rot
1991 - IRG/WP 2376
During the last ten years, a new type of problems with wood rot has emerged in Scandinavia. Thousands of houses have been damaged by wood rot attaching to the exterior wood panel. This paper provides an overview of finished and ongoing work in order to identify the cause of these problems. In field tests, the moisture conditions were measured in panels coated with different paint systems. The influence of the panel structure and end-grain sealing on the moisture balance was also studied. The results from these tests show a large difference in the moisture balance between panels with different exterior wood coatings. In laboratory tests, the transmission of water vapour through paint films was measured using a modified cup method, which provides more realistic conditions for coated wood than the common cup method. One interesting observation made in the studies reported here is that latex paints seem to be much more permeable at high levels of relative humidity than earlier research has shown.
S Hjort

Corrosion of fasteners in treated wood
1971 - IRG/WP 303
Surveying tests for determining the corrosion rates of some metals and alloys in wood untreated as well as treated have been made. It is shown that ordinary steel corrodes faster than other common fastener metals such as copper, brass, aluminium and stainless steel do. Zinc coatings, however, will prevent the steel corrosion effectively provided that the coatings are thick sufficiently. Catalytic decomposition of cellulose by rusting iron is briefly discussed since the expectation of life for a fastener joint is not only depending on after the corrosion remaining cross-section of the fastener but also from the wood deterioration.
T Wallin

The resistance of wood coated with different water-borne paints against colonisation by decay fungi
1996 - IRG/WP 96-10165
The susceptibility of wood painted with model paints of known composition to decay fungi was tested without previous weathering. Included in the study were five alkyd emulsion paints and five acrylic paints; one linseed oil paint and two solvent-borne alkyd paints. It was found that several components influenced the susceptibility of these paints. The results of the present study indicate that the particle size of latex paints, the pigment volume concentration and the amount and type of surfactant in the water-borne paints are critical for colonisation by decay fungi of painted wood. An anion surfactant was somewhat fungicidal. The results are briefly discussed in relation to major paint components and to available knowledge of the properties of water-borne coatings on wooden substrates. The present study is part of a larger project aiming at improvement of the durability of painted wood.
J Bjurman

Blue Staining of Coated Modified and Unmodified Wood
2006 - IRG/WP 06-10589
We investigated resistance of unmodified, DMDHEU modified and oil heat treated uncoated and coated Scots pine wood against blue stain fungi. Both EN 152-1 and the reverse exposure tests showed excellent resistance of DMDHEU and especially of oil heat treated wood against blue staining. It is not needed to add any additional protective coating layers to prevent modified wood from staining. However, alkyd solventborne finishes can play an important protective role against blue stain infestations of unmodified wood. Acrylic waterborne stains, due to their high permeability, exhibit lower efficacy.
M Petric, M Pavlic, M Humar, M Tomažic

Identification of fungi colonising coated and modified wood exposed outdoors using sequencing and T-RFLP profiling
2006 - IRG/WP 06-20326
Wood decay and staining fungi are known to colonize coated and modified wood. Rapid and reliable ways of identifying fungi on coated and modified wood may improve diagnostics and product development. In this work nine fungi growing in painted wood panels exposed outdoors at a test field in Uppsala, Sweden, were identified using sequencing and T-RFLP (Terminal Restriction Fragment Length Polymorphism) profiling. Using T-RFLP profiles, four fungi from modified wood were identified. T-RFLP profiling allows for the direct identification of several fungi in a single sample. Results indicate that these two methods may be successfully used to study the fungal deterioration of coated and modified wood.
U Råberg, J Bijelovic, C J Land, S Bardage, N Terziev

Photo-degradation of modified and non-modified wood, coated with water borne acrylic coatings during artificial light exposure
2007 - IRG/WP 07-30416
A series of experiments were carried out to investigate photo-degradation of thermally modified (at 210oC and – 0.9 bars for two hours) and non-modified spruce wood (Picea abies L (Karst)), coated with transparent and semitransparent (with 3% pigment content) acrylic coatings during artificial UV light irradiation for 200 hours. Photo-degradation was evaluated in terms of colour changes throughout the irradiation period at an interval of 50 hours, along with IR and EPR spectroscopic study. One set of modified and non-modified woods was painted with coatings, while the other set was covered with free films made of coatings, just to simulate coated wood. The average thickness of paint-coats and dried free films at 25oC and 50% RH was 144.8?m and 143.4?m for transparent and semitransparent coating, respectively. The colour changes for both modified and non-modified wood samples without paint-coat and free film cover were comparable to that of wood samples with paint-coat and free film cover for transparent coat type, which indicated its ineffectiveness to prevent photo-degradation of wood underneath. However, the colour changes for both modified and non-modified wood samples with paint-coat and free film cover were much more lower than that of samples without paint-coat and free film cover for semitransparent coat type, which might be due to hindrance of transmission of light energy through pigment to reach the underlying wood surface. On the other hand, whole substrate-coating systems showed better photo-stability, when thermally modified wood was used as substrate. It might be due to increase in lignin stability by condensation during thermal modification process of wood substrate. However, the colour changes of coat-painted and free-film covered samples for both modified and non modified woods might be due to due colour changes of wood specimen underneath, because free films of both the coat types showed negligible colour change during UV irradiation.
M Deka, M Tomažic, M Petric

Natural Weathering of Coated Oil Heat Treated Wood
2007 - IRG/WP 07-30440
Oil heat-treated (thermally modified) pine wood was coated with 9 different types of solvent- or water-borne exterior finishes. The systems with modified wood substrate as well as unpainted and painted non-modified controls were exposed to weathering (EN 927-3) on two locations with sub-alpine and alpine climate. The influence of natural ageing on surface systems was evaluated after one year of exposure. It was stated that in terms of surface damages (cracking, flaking, mould growth) the coated oil heat-treated wood performed better then the painted non-modified wood. In terms of colour stability, partially pigmented semi-transparent stains gave encouraging results on oil heat-treated wood while the “modified wood – unpigmented transparent coatings” systems performed less satisfactorily.
M Petric, B Kricej, M Pavlic, A Rapp

Assessment of mould growth on coated wood - methods and application
2009 - IRG/WP 09-20423
Discolouring fungi reduce the service life of coated wooden claddings in façades and increase the total cost of ownership due to shorter maintenance intervals. The project “Enhanced service life on coated wooden facades” has as its main objective to develop new methods for early prediction of durability and longer aesthetic service life of coated wooden cladding related to consumer needs and new building and environmental regulations. Different methods for mould growth assessment on the surface of coated wood exposed outdoors will be looked in to and Quantitative Real-Time Polymerase Chain Reaction (QRT-PCR) and Fourier Transform Infrared Spectroscopy (FTIR) will be developed as tools for objective quantification. In this paper four methods for assessment of mould growth on the surface of coated wood are presented; visual assessment, digital image analysis, QRT-PCR and FTIR, and the application of the different methods are discussed. Further, a comparative study was done using visual assessment and digital image analysis when measuring mould growth coverage on coated wood. 7 coatings with different typology and fungicide were tested according to EN927-3 outdoors for 2 years at Sogn test station, Oslo, Norway. Results obtained from visual assessment by using the rating scale in EN927-3 and a chosen algorithm for digital image processing was compared and the methods showed conformity. Alkyd modified acrylic coatings were found to perform significantly better than pure acrylic and modified alkyd coatings.
L Ross Gobakken, C M Whist, O Høibø, P J Hovde, E Larnøy

Early detection of colonisation by blue stain and mould on modified wood using PCR technique
2010 - IRG/WP 10-10730
The aim of this research was the early detection of fungal attack on the surfaces of modified and unmodified wood after natural weathering. The investigation was carried out by molecular techniques and the development and establishment of genus/species specific PCR for important moulds and sapstain fungi was part of this work. After adaption of the method, a monitoring of the succession of Ascomycetes on surfaces of modified wood with and without coatings after natural weathering started. After 3 months of natural weathering all panels were infestated by Ascomycetes. All modifications and coating systems were more affected by Aureobasidium pullulans than by Cladosporium sp. Over the investigation period of twelve months no Trichoderma sp. and no Aspergillus sp. were detected.
A Steitz, B Schmöllerl, N Pfabigan, S Bollmus, G Grüll

Performance of selected types of coated and uncoated modified wood in artificial and natural weathering
2010 - IRG/WP 10-40510
The objective of the present work was to investigate the influence of commercial wood modification methods on weathering behaviour and coating performance. It was aimed to compare modification methods and to set up maps of weathering behaviour for these methods with and without a semi-transparent wood stain. Artificial and natural weathering trials were carried out with a selection of different types of modified wood. Unmodified pine sapwood was used as reference. Acetylated radiata pine wood revealed outstanding performance in colour stability and as coating substrate in all weathering trials. The performance of thermally modified pine sapwood was comparable to the unmodified reference. Its colour change was characterised by bleaching of the original dark colour. Uncoated furfurylated pine sapwood samples showed strong colour change with extensive bleaching, whereas coated furfurylated wood showed good colour stability. Coated Cr-free impregnated pine sapwood showed sensitivity to mechanical defects of the semi-transparent coating film, leading to strong discolouration. These results indicate the possible influence of preservative impregnation on coating performance of semi-transparent stains.
G Grüll, L Podgorski, M Truskaller, I Spitaler, V Georges, S Bollmus, A Steitz

Aesthetic service life of coated and uncoated wooden cladding - influencing factors and modelling
2011 - IRG/WP 11-20470
Mould growth on exterior coated cladding façades is an undesirable element and will often shorten the aesthetical service life. Mould growth on painted surfaces is influenced by type and concentration of film fungicides, the paint formulation and the wood substrate itself, and wooden cladding may experience exponential fungal deterioration caused by variation in the climatic factors, often within a small limited area. The objective of this study was to gain knowledge about which factors influence surface mould growth on coated and uncoated wooden cladding in an outdoor environment, with a special attention to modified wood substrates. The data are based on evaluation of mould growth coverage on outdoors exposed wood panels consisting of different combinations of wood substrates and surface finishes. Panels were exposed on three locations; Bogesund (Sweden), Birkenes and Sørkedalen (Norway). The panels were monitored up to 4.5 years. The analysis showed that coating typology and exposure time both had highly significant influences on mould growth. Furthermore, wood substrate, temperature and relative humidity had a significant influence on mould growth, but comparatively less than coating typology and exposure time. Siberian larch heartwood, copper-organic preserved Scots pine and Scots pine heartwood performed best among the wood substrates. Heartwood as wood type was less susceptible to mould growth than a mix of sapwood and heartwood wood and pure sapwood. Acetylated Scots pine as wood substrate and Aspen as wood species had lower resistance to mould growth than the other wood substrates and wood species, respectively. The physical surface structure of a paint film also influences the mould growth. A hard model paint was significantly more susceptible than the other model paints. A soft model paint performed best, with the least mould growth coverage. Aureobasidium pullulans (deBary) Arnaud was the dominating fungal species on all the wood substrates.
L Ross Gobakken, O A Høibø

Detection of Aureobasidium as the dominant fungus on coated wood
2013 - IRG/WP 13-10796
Wood is often covered with a coating in order to protect the surface. Unwanted dark mold growth on paint covered surfaces in external conditions is a familiar phenomenon. Simple microbial techniques have commonly been used to determine the dominant fungal species present in the discoloured area, for example morphological analysis of microscopic preparations of fungal pieces sticking to an adhesive tape. When using this method Aureobasidium is frequently recognized to be the dominant fungus. This is a curious outcome since this fungus can not be identified by its commonly occurring dark chlamydospores but only by the synchronous conidia production from young expanding hyphae. To understand the uncertainties in the diagnostics of the dominant molds on coated wood a case study is done on wood impregnated with raw linseed oil. The reason for selecting this oil treated wood is that raw linseed oil or its fatty acids are a common ingredient of coatings and a quick dense mold growth is assured. Three microbial techniques were used to detect Aureobasidium as the dominant species. The CFU technique based on colony forming unit counts of swap samples indicated a dominancy of more than 50% of Aureobasidium on wood impregnated with linseed oil. Adhesive tape preparation and examination of the culturable fungal microbiota, did not counter this degree of dominancy. The ability of Aureobasidium to grow on pure linseed oil provided supporting evidence of the dominancy of Aureobasidium.
E J Van Nieuwenhuijzen, M F Sailer, R A Samson, O C G Adan

Using hyperspectral imaging to detect and quantify mould and blue stain on coated and uncoated wood
2014 - IRG/WP 14-10822
Hyperspectral imaging has been applied on the surface of samples of coated and uncoated Norway spruce (Picea abies) as a new technique to detect and quantify growth of mould and blue stain fungi. Principal Component Analysis of the hyperspectral images resulted in a clear visualization of the fungi and the amount of mould coverage could be estimated. This indicates that NIR hyperspectral imaging can be used as a tool for assessing coverage of surface fungi and event spectral classification for each of the two test species: Aureobasidium pullulans and Cladosporium cladosporioides. Additional studies in an outdoor environment are in progress and are briefly presented in the paper.
L Ross Gobakken, I Burud, A Flø, K Kvaal, T K Thiis

Acceptance levels of surface disfigurement - tolerance to defects of coated wood
2015 - IRG/WP 15-20564
Service life planning (PSL) has become an important issue in performance based building and substantial progress has been made in recent years. The role of predicting the aesthetical service life of wooden building components has been underestimated for quite long time but is recently attracting more and more notice. It is influenced by numerous factors such as discoloration, fading, flaking, cracking, and in extreme deformation due to interior rot. However, still the acceptance of such superficial disfigurement is subjected to the subjective sensation of consumers and end-users. This study aimed on evaluating different ‘technically defined’ limit states of weathered coated wood surfaces with respect to the acceptance of users. Therefore different groups of users were addressed in the frame of a survey as well as two different commodity groups were looked at separately, i.e. wooden window joinery and claddings. A remarkably high percentage of respondents ranked color and gloss related deficiencies as high as technical defects of the coating and recommended maintenance measures even when the coating was still fully intact. Technical characteristics such as the formation of cracks and flaking need to be considered separately from optical and aesthetical parameters for the definition of acceptance levels of coating disfigurements and defects. Limit states need to get defined specifically for different building components since acceptance varied significantly as shown exemplarily in this study between windows and cladding boards. For service life planning the overruling role of the subjective sensation of the user necessitates careful consideration.
C Brischke, P Kaudewitz

Accelerated Weathering Performance of Impregnated Wood Samples Coated with Zinc by Means of Plasma-Assisted Particle Deposition
2016 - IRG/WP 16-30682
Many different methods are currently applied for wood protection against outdoor conditions. The most important of these is the process of impregnation with liquid substances. However, this kind of wood preservatives cannot provide a long-term protection of wooden surfaces. Weathering-resistant surfaces can be obtained by applying UV absorbing agents. In this study, the influence of zinc particles applied by a plasma process at atmospheric pressure against UV light was investigated. First, wood samples were impregnated with boric acid, tall oil or copper azole. After impregnation, the samples were coated with zinc (Zn) particles, and coated and uncoated samples were exposed to accelerated weathering tests. The changes of the surface properties of the treated and untreated wood samples were studied by color changes, glossiness. Physical properties such as color changes, glossiness and surface roughness decreased for the samples coated with Zn particles. Brightness values also increased with the increasing weathering period.
A Can, H Sivrikaya

Fungal growth on coated wood exposed outdoors: influence of coating pigmentation, cardinal direction and inclination of wood surfaces
2017 - IRG/WP 17-10896
The objective of the SERVOWOOD project was to develop and establish European Standards that will facilitate the prediction of service life for exterior wood coatings. One of the objective of this project was to study fungal growth of the field exposed panels. Two coatings applied in 2 and 3 coats were exposed for one year outdoors at 45° south: one solventborne (alkyd based) and one waterborne (acrylic based) both in clear and pigmented versions. Fungal growth visually assessed was compared to fungal enumeration and the influence of exposure time on the main fungal species was studied. Results clearly showed that a lower fungal growth was observed on pigmented coatings. Despite the clear solventborne coating included a higher amount of biocide it was more susceptible to blue stain than the pigmented recipe. A new multifaceted exposure rig (MFER) designed for the project also contributed to the study of fungal growth. It allowed samples to be exposed with 9 different exposure directions and angles. The exposure using this MFER has shown that the worst cases (high area and high intensity of blue stain) were for samples with the clear coating exposed to north 45° and at the top of the MFER (horizontal surfaces). For any cardinal direction all surfaces inclined at 45° displayed more blue stain than vertical surfaces due to higher moisture content.
L Podgorski, C Reynaud, M Montibus

Aesthetic changes of coated thermally modified wood after artificial weathering
2017 - IRG/WP 17-40819
The thermal modification process affects the chemical configuration of the wood matrix improving some physical properties and durability. In addition, the distinctive dark tones of thermally modified timber increase the economic value of several light-coloured species. However, heat-treatment alters the substrates and it could influence in the application of coating products, necessaries to maintain the surface features in certain end-use sectors. Ash wood (Fraxinus excelsior L.) samples industrially treated at 212 ºC were coated with decorative and industrial coatings. Afterwards, the samples were subjected to accelerated weathering test and estimated the aesthetical response compared to untreated wood. The surface topography was monitored with a 3D scanner and a profilometer, showing slight visual changes although finding dissimilar roughness where irregularities in modified -samples increased with waterborne product but not with UV-curable; remarkable the changes in roughness below 5% in modified samples. The colour changes were calculated by hyperspectral information of the visible range, generating the profile map of L*, a*, b* parameters. The results point out an acceptable photostability of coated thermally modified wood. Heat-treated wood could be an appropriate substrate with similar conditions as unmodified wood; nevertheless the interaction with water-base products could vary depending on the treatment temperature and the layer thickness.
R Herrera, J Sandak, E Robles, J Labidi

Wood protection with cement – Part 1: Coating matters and durability of cement coated wood
2020 - IRG/WP 20-40911
The use of wood in geotechnical applications has seen renewed interest. However, concerns related to the durability and service life of wood in ground contact applications remain. Wood has the potential to substitute commonly used steel and concrete in the geotechnical engineering sector, but solutions to extending the service life and maintenance intervals require long-lasting wood protection systems capable of inhibiting fungal and bacterial decay. Cement, one of the constituents of concrete was identified as a potential coating material for wood used in soil stabilisation works. Spruce and beech wood rest rolls from commercial veneer peeling has been identified as a potential source for cement-coated geotechnical wood products. Norway spruce and European beech wood was subsequently used in this study. In this study, a series of tests related to dimensional stability and fungal durability were undertaken to investigate the adhesion of a cement coating to wood and to assess the effect of a cement coating on the resistance to fungal decay. Swelling and shrinkage tests of uncoated specimens were undertaken to investigate dimensional stability. Laboratory fungal durability tests assessed changes in wood durability of specimens coated with a novel, flexural cement coating. Wood impregnated with Polyethyleneglycol-dimethacrylate (PEGDMA) prior to cement coating was investigated to improve wood dimensional stability and reduce cracking of the cement coating under changing wood moisture conditions. Cement coating thickness and delamination tests then assessed the durability of the novel cement coating itself. Results from fungal durability tests showed that a continuous, flexural, and crack-free cement coating was imperative to a wood durability improvement. Double cement-coated spruce wood showed improved resistance to decay by basidiomycetes (Coniphora puteana and Trametes versicolor). Results from swelling and shrinkage tests showed that an improvement in dimensional stability would assist in achieving a durable cement coating and impregnation with Polyethyleneglycol-dimethacrylate (PEGDMA) is one manner to improve dimensional stability and therefore cement adhesion to the wood substrate.
S Hirschmüller, B Marais, C Brischke, A Krey, J Bösing

Surface morphology and short-term water uptake of charred and coated wood
2021 - IRG/WP 21-40916
Charring of the wood surface represents a traditional alternative surface treatment technique with the purpose of aesthetics and protection. By the treatment with flame the surface of wood becomes carbonized and a few millimetres thick charred layer is formed on the top of the wooden element. Further, the charred layer can be removed by brushing, which accentuates the structure of the surface. Additionally, for appearance and protective purposes, a different kind of oils and coatings may be applied to the charred wood surfaces. Although this type of wood surface protection has been known for centuries, there is still a lack of knowledge about the water uptake properties of charred and surface finished wood. The aim of the present study was to find out how the treatment with charring, charring and brushing, and surface finishing affect the surface morphology of Norway spruce (S) and European larch (L) wood. By immersing the samples with treated radial surfaces in deionized water, the water uptake in the samples was monitored via the mass increase measurements on the tensiometer. Confocal laser scanning microscope examination showed that charring of wood greatly increased the surface roughness (S by 10-times and L by 6.5-times). Brushing of the charred wood surface further increased surface roughness (S by 21-times and L by for 23-times), completely removing the earlywood structure, while the latewood regions remained present. Surface finishing with water-borne stain noticeably increased only the roughness of the sanded wood surfaces, while the roughness of the other surfaces was not affected. In general, the S wood absorbed more water than the L wood. The highest amount of water was absorbed by the samples with the charred surface (S 0.048 g·cm–2, L 0.031 g·cm–2) and even the surface finishing of these could not prevent water absorption. The water uptake of the other surface types was quite comparable (S about 0.026 g·cm–2, L 0.021 g·cm–2). The higher water uptake seemed to be related to the higher surface roughness or to the specific surface to which the water molecules can attach and possibly penetrate into the wood.
J Zigon

Danish wood preservatives approval system with special focus on assessment of the environmental risks associated with industrial wood preservatives
2001 - IRG/WP 01-50166-01
The following is a description of the procedure used by the Danish Environmental Protection Agency to assess the environmental risks associated with preservatives used in the pressure impregnation of wood. The risk assessment covers issues considered to be of significance for the environment and which are adequately documented so as to allow an assessment. Such issues are persistence and mobility in soils, bioaccumulation and the impact on aquatic and terrestrial organisms. Unless required in special circumstances, the assessment does not apply to birds and mammals as the normal use of preservative treated wood is not expected to involve any noteworthy exposure of these groups. Approval of wood preservatives will be based on a general assessment of the environmental risk associated with the normal use of wood treated with the preservative in a realistic worst case situation. The assessment may address other aspects such as disposal and total life cycle.
J Larsen

Data sheet on wood-boring insects. Apate monachus Fabricius. 2. Position systématique, nomenclature, identification et distribution - Espèces végétales attaquée
1981 - IRG/WP 1105
R L A Damoiseau

Confocal laser scanning microscopy of a novel decay in preservative treated radiata pine in wet acidic soils
1997 - IRG/WP 97-10215
Light microscopy of radiata pine (Pinus radiata D. Don) field test stakes (20x20x500mm3) exposed in wet acidic (pH 3-4) soil for 12 - 24 months showed predominance of an unusual type of decay characte-rised by tunnelling attack of wood cell walls. After two years decay was moderate to severe in wood treated to ground contact CCA specifications and also equivalent retentions of creosote, and a number of new generation preservatives. Relative to other New Zealand temperate test sites and also an Australian tropical site, the New Zealand acidic soil test site was very aggressive. Correlative scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were used to elucidate the micromorphology of this attack. Tunnels of diameter 0.2-5 µm were present throughout all layers of the cell wall, and their orientation was not related to cellulose microfibril orientation. They also showed no preference for particular cell wall layers, indicating a lignin degrading capability. CLSM images showed that living, connecting fungal hyphae were present in the cell lumina and tunnels. This type of attack was predominant in wood that was highly saturated with water whereas wood that was less moist was predominantly attacked by classical white rot. Ongoing isolation and incubation studies in conjunction with further microscopy should enable identification of the fungal species involved.
R N Wakeling, Ying Xiao, A P Singh

Effect of acetylation on decay resistance of wood against brown-rot, white-rot and soft-rot fungi
1989 - IRG/WP 3540
Effect of acetylation on decay resistance of wood was investigated using wood blocks of Cryptomeria japonica, Pinus densiflora, Albizia falcata and Fagus crenata. Blocks were treated with uncatalyzed acetic anhydride for different lengths of time and exposed to Tyromyces palustris, Serpula lacrymans, Coriolus versicolor and unsterilized soil. The action of OH-radical on acetylated wood was also examined using Fenton's reagent. The enhancement of decay resistance by acetylation was revealed clearly for all cases of exposures but varying with fungal and wood species used. For a brown-rot fungus Tyromyces palustris, the weight loss reached almost nil in all woods at 20 WPG (weight percent gain) of acetylation, after the striking decrease from 10 to 15 WPG. For a white-rot fungus Coriolus versicolor, it was counted until 12-15 WPG in the perishable hardwoods used, but not in a softwood Cryptomeria japonica, even at 6 WPG. In cases of another brown-rotter Serpula lacrymans and soil burial, effect of acetylation was intermediate between Tyromyces palustris and Coriolus versicolor. Anti-degradation mechanism by acetylation was discussed, from these weight loss - weight gain relationships, and the IR-and 13C-NMR spectral analyses of fungus-exposed wood.
M Takahashi, Y Imamura, M Tanahashi

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