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Comparison of colour change in wood clear-coating systems including inorganic and organic UV absorbers for exterior use
2010 - IRG/WP 10-40499
The aim of this work is to compare the performance of inorganic and organic UV absorbers used in a wood coating application against weathering. Our study has investigated the colour changes of selected UV absorbers; hombitec 402 RM from the Sachtleben Company as an inorganic UV absorber, tinuvin 477 DW from the Ciba Company as an organic UV absorber. The study was carried out on two wood species; Fagus sylvatica L., Pinus sylvestris L. The results obtained after 28 days (672h) of accelerated weathering showed that the colour stability was the same for hombitec 402 RM and tinuvin 477 DW and both systems showed a significant improvement of colour stabilization compared to the control samples. In addition, the wood surface from cracks was protected with the clear-coat containing both of UV absorber.
Ö Özgenç, B Forsthuber, A Teischinger, C Hansmann

Comparison of exterior performance of two coating systems based polyurethane applied Pinus sylvestris L. and Picea orientalis L. wood
2012 - IRG/WP 12-40588
Some surface changes in sapwood and heartwood of two species before applying clear-coating were characterized after accelerated weathering time. Wood specimens covered with two types polyurethane (PU) films were also observed in accelerated weathering exposure. In this study, changes on the wood surface were compared of between wood specimens covered with two types polyurethane (PU) films after irradiation. The study was carried out on sapwoods and heartwoods two wood species; Fagus sylvatica L., Pinus sylvestris L. The artificial weathering experiment was performed by cycles of 2 hours UV-light irradiation followed by water spray for 18 minutes according to ASTM G 53-96. The surface changes of the weathered sapwood and heartwood samples applied clear-coating were characterized by surface roughness and color measurements. Color measurements were made by a with a Konica Minolta CM-600d (Canada) at several intervals (0-24-72-168-240-336-408-504-600-672 hours) in artificial weathering of treated and untreated wood. Additionally surface roughness was measured on the surface of all wood samples, unweathered and after 672 hours of weathering by a Mitutoyo Surfest SJ-301 instrument. According to the results, the scots pine and spruce sapwood samples provided better protection color changes than the scots pine and spruce heartwood samples showed lower color changes. The highest increasing surface roughness values were on the wood samples applied 2.system clear-coating (Y) by reason of the wood surfaces contain several checks, splits and cracks caused by weathering. The wood surface applied 1.system clear-coating (X) showed that no high cracks and substantially surface properties changes were observed significantly due to weathering.
Ö Özgenç, Û Cafer Yıldız

Management of the wood and additives wastes in the wood processing industries: Problematics and technical answers review
1996 - IRG/WP 96-50073
Management pathways for pure wood subproducts are well known and used; but as soon as additives like preservatives, glues, varnishes or coatings are present within the wood wastes, their disposal or valorization becomes more tricky. The different kinds of mixed wood wastes of the wood processing industries, from the sawmill to the furniture manufacture, are identified herewith and their diversity is examined. These wastes can be classified according to their danger characteristics, taking into account the type of additives, their concentration, their availability for the environment, the physical state of the waste. Different disposal pathways are then considered. Combustion, with the possibility of energetic valorization seems the best answer for a major part of these wastes. But this is only possible if good combustion conditions are defined, so that no harmful products are emitted. Moreover, these conditions must be affordable on the technical and economical point of view. Then, some wastes cannot be burned in such a simple way, and need a larger approach, which is presented in this document.
S Mouras, G Labat, G Deroubaix

JWPA method for testing effectiveness of surface coatings with preservatives against decay fungi
1981 - IRG/WP 2164
In 1979 JWPA established a new method for testing effectiveness of surface coatings in accordance with practical use of preservative-treated lumber. Comparing the new testing method with JIS A 9302, a few new trials - size of wood specimen, weathering procedure, and decay-test procedure - are incorporated.
K Tsunoda

Summary of development of pile wrappings in Los Angeles Harbour
1987 - IRG/WP 4141
G Horeczko

Blue stain in service on wood surface coatings. Part 2: The ability of Aureobasidium pullulans to penetrate wood surface coatings
1992 - IRG/WP 92-1557
The ability of Aureobasidium pullulans to penetrate seven different wood surface coatings was examined. Eight isolates of Aureobasidium pullulans were used. Following penetration, light microscopy was used to examine the effect of the fungus upon the coating, and growth at the wood-film interface. The fungus showed different growth capabilities with different types of surface coatings. Some isolates were able to penetrate alkyd based coatings, but were unable to grow in the film. In contrast, after penetration through latex based coatings several isolates were able to produce growth in the films themselves.
P R Sharpe, D J Dickinson

Factors affecting leaching of preservatives in practice
1978 - IRG/WP 3113
At the 7th Meeting of the IRG in Poland in May 1975, the findings of collaborative laboratory leaching techniques were discussed, and the dangers inherent in using such results to predict the behaviour of preservative-treated components in service were emphasised. In order to improve our understanding of the factors governing leaching of preservatives in practice, and to identify areas where further research is required, it was agreed that a literature review should be prepared. This is presented below. Some points may be made regarding its format and content. First, the review shows that a large number of factors are of importance, including the properties of the wood, the leach water, the preservative and method of application and the nature of the environment to which the product is exposed. In many situations these factors interact and it is clearly impossible within the scope of this short paper to discuss all aspects of the problem in detail. However, the compilation of references will give ready access to the literature on particular topics. For ease of collation, the findings are discussed under a number of different headings. Secondly, less than one-third of the references cited deal with the results of service or field trials, while the others describe laboratory experiments designed to provide comparative data. The reservations expressed above concerning such small-scale experiments must be borne in mind when considering the validity of these findings. The information available on this topic up till 1964 was comprehensively reviewed by Wallace who identified and commented upon many of the factors discussed below. Her paper contained discussion on the performance of individual preservatives and on the mechanism of their fixation within the wood. These topics will not be considered here in any detail except insofar as they reflect general trends.
R Cockcroft, R A Laidlaw

Surface coatings for impregnated wood
1992 - IRG/WP 92-3684
The use of proper surface coatings enhances the aesthetic and protective properties of impregnated wood. Good results with especially water-borne coatings have been obtained for class-A impregnated L-joints and claddings in field tests started in 1982.
L Kotama

Surface Barriers for Protection of Culture and Heritage Wooden Objects from Insect Attack
2004 - IRG/WP 04-40286
Anoxic treatment is an environment friendly procedure for eradication of wood boring insects in wooden objects of cultural and historical heritage. However, after the anoxic treatment, wooden antiques remain susceptible to further insect attacks. Possible protection against insects could be provided by the so-called post-repression protective barriers. Potential coating materials for such barriers to be used on hidden unpainted surfaces of wooden antiques were investigated. We studied relevant properties of five different coating materials: thickness, hardness by resistance to scratching, adhesion, flexibility, resistance to temperature changes, conformability to the concept of reversibility and bioresistance against wood boring insects. The most promising results were exhibited by the coating that is commercially used for protection of fresh log ends in forests, immediately after a tree is cut.
M Petric, M Pavlic, B Kricej, M Humar, F Pohleven

Practical testing of wood preservatives to prevent weathering damage and infection by micro-organisms on spruce and pine
1989 - IRG/WP 3530
Brush application, is generally used to prevent wooden window frames from decay caused by influence of weathering and fungi. Accordingly 10 boards of pine (Pinus sylvestris) and spruce (Picea abies) were treated with 10 commercially used wood preservatives. The efficiency of fungicides by using chiptest and blue stain test (EN 152), the effectiveness against weathering as well as the course of colonization of microfungi were measured on boards, that had been hurted by sawing. Results after one year's exposure showed that neither the normally required amount of 250 ml/m² nor the effective depth of penetration of the fungizidal equipment had been realized by using brush application. The smaller the permeability of the coating system, the more likely ideal conditions for the growth of fungi (e.g. basidiomycetes) are provided, answering hurtings of the coating and moisture contents of more than 30%. The variety of fungi (on pine 32 and on spruce 17 species) can be a result of anatomical differences and distinguished compounds of the wood species. After 24, respectively 36 weeks of exposure the frequent occurrance of basidiomycetous yeasts (Cryptococcus albidus, Rhodotorula mucilaginosa), blue stain fungi (Aureobasidium pullulans, Hormonema dematioides), Epicoccum nigrum, Alternaria alternata and Phoma species was noted.
R Gründlinger, O Janotta, H Melzer, K Messner

The efficacy of polyurethane coatings on wood samples exposed in the marine environment. Final Report -10 Year Assessment
1996 - IRG/WP 96-10170
The results of an IRG collaborative marine trial to investigate the long-term permanence and efficacy of polyurethane coatings against marine borers are reported. PU-coated wood samples were exposed at a range of sites from tropical to cold temperate locations. The marine borer species present at the sites included teredinids, pholads, limnoriids and sphaeromatids so that each site offered its own peculiar degree of hazard. At most sites the integrity of the PU-coating was sound and wood samples were undamaged by marine borers after periods of exposure extending up to ca. 10 years. Where damage to the wood was recorded, mechanical abrasion of the coating had exposed the wood to attack by teredinids and pholads at one site and at a second site, sphaeromatids had perforated the coating. The significance of the results is discussed in terms of the protection afforded to submerged maritime timber structures coated with elastomeric polyurethane.
R A Eaton

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

Influence of a dipping preservative treatment on the performance of wood finished with waterborne coatings
1998 - IRG/WP 98-40121
Within a larger European research project on the performance of joinery finished with waterborne coatings, the influence of a water based dipping preservative treatment was studied in several ways. Six different waterborne coatings were tested with and without a preservative underneath the coating. The performance was tested on pine sapwood and spruce panels in a 2-year outdoor weathering trial on two different sites in Europe. The panels were evaluated visually with respect to cracking, flaking, surface mould growth and development of blue stain underneath the coating. In several cases the preservative treatment improved the performance of the coating, not only with respect to biological deterioration but also for cracking and flaking of the paint. A limited number of coatings were also tested on L-joints according to the EN-330 and of national dutch design. The EN-330 L-joints appeared to be a more challenging substrate compared to the national type, which had a glued connection between tenon and mortise. The influence of the preservative on the moisture content of the wood was evaluated by monthly weighing of the samples exposed outdoors and by laboratory measurements of the coating permeability. At least in laboratory trials the dipping treatment caused a slight reduction of the water permeability. This is most likely the result of the polymeric binder material present in the preservative. The presence of polymeric material underneath the coating was also confirmed in a microscopic evaluation of the distribution of the dipping preservative. The preservative was not equally distributed in the wood, but showed a clear preference for the ray-tissue.
M De Meijer, J Creemers, W Cobben, P Ahola

Observations on the uptake and penetration of various liquids in clear heartwood and sapwood of Pinus radiata D.Don
1983 - IRG/WP 3224
Volumetric uptake of water (aqueous copper-chrome-arsenic (CCA)) or methanol, applied by bulk hydrostatic pressure to air dried clear heartwood specimens of Pinus radiata D. Don, far exceeds that of a wide variety of polar and non-polar solvents. In air dried sapwood, the volumetric uptake of CCA tends to be less than that achieved for most solvents including methanol. No comprehensive explanation of the penetration mechanism in these two substrates can yet be offered. High temperature drying effects a significant increase of volumetric uptake of all liquids by heartwood, but not by sapwood, possibly because air dried material is nearly saturated after pressure treatment.
J E Barnacle

Durability of surface preserved wood particle boards submitted to atmospherical influence
1995 - IRG/WP 95-40039
The worldwide problem of the continuously growing deficit of high quality natural wood material has caused the attempts of many research workers to find effective composites such as wood particle boards (WPBs) for replacing the massive wood for constructive purposes, depending on where the boards are exploited - in the open or under a shed, they are submitted to various climatic factors such as heating, drying, moistening, frosting, irradiation, that's why for reaching high atmospheric resistance, it is very important, a durable protection of the WPBs with suitable coatings against the atmospheric influence to be ensured.
L Valcheva

Surface Barriers for Protection of Culture and Heritage Wooden Objects from Insect Attack
2004 - IRG/WP 04-20286
Anoxic treatment is an environment friendly procedure for eradication of wood boring insects in wooden objects of cultural and historical heritage. However, after the anoxic treatment, wooden antiques remain susceptible to further insect attacks. Possible protection against insects could be provided by the so-called post-repression protective barriers. Potential coating materials for such barriers to be used on hidden unpainted surfaces of wooden antiques were investigated. We studied relevant properties of five different coating materials: thickness, hardness by resistance to scratching, adhesion, flexibility, resistance to temperature changes, conformability to the concept of reversibility and bioresistance against wood boring insects. The most promising results were exhibited by the coating that is commercially used for protection of fresh log ends in forests, immediately after a tree is cut.
M Petric, M Pavlic, B Kricej, M Humar, F Pohleven

A collaborative test to determine the efficacy of polyurethane coatings on wood samples in the marine environment. 2nd Interim Report
1990 - IRG/WP 4161
The results of a collaborative international test to evaluate the performance of elastomeric polyurethane coatings of wooden test samples exposed in seawater at 13 sites around the world are reported. The samples have been exposed at sites with known infestations by molluscan and/or crustacean wood borers. Performance data for up to 4 years exposure at some sites is presented providing information on the soundness and adherence of the coatings to wood and the degree of surface fouling. To date, all samples coated with polyurethane remain unattacked by marine borers.
R A Eaton

Observations on the activities of Sphaeroma in Australia
1994 - IRG/WP 94-10059
Polyurethane coated timber specimens are being attacked at Townsville by Sphaeroma terebrans in the tidal zone. To understand this marine borer better, the results from several other marine tests at Townsville are briefly described, and information about Sphaeroma spp. from elsewhere in Australia is presented. At Townsville, Sphaeroma seems to prefer the shady side of timber fender piles. Also, it is rarely found below the tidal zone. After two years, CCA-treated slash pine mooring piles were lightly attacked, and after 5.7-8 years eight double-treated eucalypt fender piles were only lightly attacked, while three were moderately attacked in the tidal zone. Untreated turpentine piles last about 10-16 years in Townsville, due to the damage caused by Sphaeroma. At nearby Bowen, Sphaeroma terebrans in two experimental piles died after the piles were pulled from the sea, and took more than 3 years to recolonise the piles after they were reinstalled. During this time after reinstallation, the original Sphaeroma terebrans holes were inhabited by Sphaeroma walkeri, a non-wood borer. At a brackish water test site at Port Stephens, Sphaeroma is more often found below low tide. It also prefers to bore upwards rather than downwards, perhaps to lessen the amount of silt entering its burrow. In the southern state of Victoria, Sphaeroma is not an economic problem, causing only minor etches and few holes. There in the tidal zone, it can scallop out disused longicorn beetle emergence holes to give an unusual pattern of attack on the pile surface.
L J Cookson

The practice of using concrete on wood piling for marine use in Thailand
1982 - IRG/WP 492
The practice of using concrete on wooden poles has been carried on in Thailand for a long time in pile-houses and pier constructions which have been situated in, or partly in the sea. In such instances, the hewed round and/or square-sawn heartwood poles of naturally durable timber species have been coated with concrete of about 5 to 10 cm or more in thickness, and to about 100 cm above the highest tide level. Very durable species such as Xylia kerrii Craib & Hutch., Shorea obtusa Wall., Pentacme suavis A.DC., Hopea odorata Roxb., and Pterocarpus macrocarpus Kurz were used for such poles. They were well air-dried before the application and coated with a special mixture of concrete, which consisted of sand, crushed lime and stone, and cement powder which was used 1-2 times more than the concrete mixture used for general masonry. The performance of these poles treated in this way, as far as could be ascertained from the users, is about 15 to 20 years, or even more in some instances. Unfortunately it has not been possible to obtain exact data on the service life of these concrete-coated poles. Also palm trees have been used in sea-water without any treatment. The palm trees that have been used are Livistona saribus Herr., and Livistona speciesa Kurz. These have been used as piling for anchoring fishing boats to, because of their high elasticity and also as piles for supporting piers. They have given performances of more than 10 years of service. The outer parts of these trees are very strong and naturally durable to marine borer attack, but the inner parts of them are not resistant to decay fungi, although even though their inner parts have become rotted, they have remained strong enough for the above-mentioned purposes of utilization. If these palm trees are treated with suitable preservatives before being put into use, in order to protect them against the decay fungi, their service lives are much greater than those of untreated palms.
B Anuwongse

The degradation of wood by metal fastenings and fittings
1972 - IRG/WP 302
As well as the hazards of biological decay, timber used in boat building is subject to the effects of chemical decay associated with the corrosion of metallic fastenings. The title has been deliberately chosen to emphasize that in wooden construction the troubles are not just those of corrosion of the fastenings, but also the destructive secondary effects on the wood caused by the products of the corrosion processes (Plate I). For centuries the world has lived with these troubles commonly referred to as "nail sickness". In contrast to biological decay the chemical decay associated with corrosion is confined to the wood adjacent to corroded fastenings and it is regrettable that in repair work so much wood has to be replaced because of a small percentage degrade in vital spots. Before methods can be devised to overcome these troubles, it is necessary that a better understanding is reached of the mechanisms operating in the degradation process, and recent work at FPRL has thrown some light in this area. The general problem will now be considered in some detail followed by suggestions on possible preventative and remedial measures. Corrosion is the result of an electrochemical process in which the corrosive effect is proportional to the current which flows between areas of potential difference. There are a number of causes of this electrochemical effect such as dissimilar metals in contact, differences in concentration of some chemical factor such as the electrolyte or oxygen availability, stress etc. In all cases areas of different polarity are produced and corrosion only proceeds when the electrical circuit is completed by an electrolyte bridge eg sea water, and a conductor between the anodic and cathodic areas. Figure 1 shows a simple diagram of electrochemical corrosion.
L C Pinion

Durability of surface coating systems. Mycologg - an accelerated mycological test.
2004 - IRG/WP 04-20301
Field testing and natural aging/degradation of test sample, e.g. coated wooden surfaces is a slow process. Accelerated tests focus on mechanical properties, water uptake or sometimes stain fungi. Artificially weathered coated panels are not easily compared with naturally aged panels, and show the importance of involving the biological component among the degrading facors. It is a need for accelerated tests and especially tests that concider the interaction between the property of water uptake, weathering and biological factors. The Mycologg can combine artificial weathering, monitoring of moisture uptake and fungal growth.
L Ross Gobakken, J Mattsson, B Jacobsen, F G Evans

A laboratory study on effect of coating materials on leaching of copper from CCA treated wood
2001 - IRG/WP 01-50176
Components of CCA preservatives can leach into surrounding soil and water and have some effect on germination and growth of some plants. In this report, the effect of coating materials in reducing chemical concentration in the leachate were evaluated. Rubber wood blocks (Hevea brasiliensis) treated with CCA were fixed at room temperature at high humidity. After air dried, they were painted with coating materials, then followed by leaching procedure. The concentration of copper in the leachate was analysed by atomic absorption spectrophotometry. The results showed that coating materials could reduced the concentration of copper in leaching water. In addition, the resistance of treated wood against destroying fungi was studied. After painted with coating materials, wood specimens were exposed to fungi for the periods of time and results were discussed.
A Veenin, T Veenin

Blue stain in service on wood surface coatings. Part 1: The nutritional requirements of Aureobasidium pullulans
1992 - IRG/WP 92-1556
The nutritional requirements of Aureobasidium pullulans was examined with regard to nutrient sources that are potentially available in fresh and weathered wood. The study was designed to determine how far wood cell wall components need to be broken down during weathering before they provide a useful nutrient source for Aureobasidium pullulans. Various carbon sources were tested, with eight different isolates of Aureobasidium pullulans. It was found that the organism could utilise the simple sugars well, but not the oligosaccharides. The organism was also able to utilise well several lignin precursor compounds.
P R Sharpe, D J Dickinson

A collaborative test to determine the efficacy of polyurethane coatings on wood samples in the marine environment. 3rd Interim Report
1993 - IRG/WP 93-10046
The results of al long-term marine trial to assess the protective effect of polyurethane coatings on wood samples exposed at different sites around the world are reported. The condition of samples exposed in the sea for up to 88 months was generally sound, although instances of marine borer infestation were reported at two sites. At one site, mechanical damage of a non-biological nature is believed to have breached the polyurethane coating resulting in attack of the underlying wood by teredinids and pholads. At a second site, infestation by sphaeromatids had perforated the coating after 4 years exposure.
R A Eaton

Research on wood protection at the Princes Risborough Laboratory 1975 & 1976
1977 - IRG/WP 3109
This paper is the latest of a 2-yearly series presenting a summarised account of the Laboratory's work in wood preservatives and related fields. The topics dealt with include: environmental studies on the usage of copper-chrome-arsenic and organic solvent preservatives; development of National and International Standards; recent developments in the preservation of external doors and windows including remedial treatment of incipient decay in-situ; preservation of motorway fencing; distribution of house longhorn beetle; formulation of insecticides; permanence of preservatives and protection by finishes and coatings. A full list of publications for the period is appended.
J M Baker, R A Laidlaw, E R Miller, J G Savory

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