IRG Documents Database and Compendium


Search and Download IRG Documents:



Between and , sort by


Displaying your search results

Your search resulted in 36 documents. Displaying 25 entries per page.


Finishes for outdoor timbers
1975 - IRG/WP 378
Anonymous


Proposed method for out-of-ground contact trials of exterior joinery protection systems
1981 - IRG/WP 2157
Methods for testing the efficacy of preservative treatments for exterior joinery are described using the format of a European Standard. Commercially used treatments applied to jointed test units (L-joints) which are then protected by conventional finishes are exposed to normal outdoor hazards out of ground contact. Assessment is made a) by determining eventual failure through decay and b) by destructive examination of replicate treated and untreated units, after increasing time intervals, rating comparative performance in terms of wood permeability increase and the progress of microbial colonisation.
J K Carey, D F Purslow, J G Savory


Effect of protective additives on leachability and efficacy of borate treated wood
2002 - IRG/WP 02-30290
Borate preservatives have been used extensively in many countries as an effective means for protecting wood against fungal and insect attack especially in interior environments. Under exterior conditions, borate compounds have a main disadvantage as they can be leached from treated wood as a result of their water solubility. In this study, we compared the potential of different additives for reducing the leachability of boron preservatives from treated wood. Scots pine sapwood (Pinus sylvestris) and poplar (Populus trichocarpa x deltoides) test samples were vacuum treated with 1 % BAE (Boric Acid Equivalent) disodium octaborate tetrahydrate (DOT) solutions containing various additives e.g. glycerol/glyoxal, polyvinylpyrrolidone (PVPY), a commercial resin compound and a commercial water repellent. The European Standard EN 84 was used as a leaching test for both coated and uncoated specimens. The results of chemical analysis of leachates taken at different periods showed that the use of protective additives reduces the boron leachability. The glycerol/glyoxal additive applied to treated pine sapwood showed the best performance. The percent of boron retained in uncoated pine sapwood was 26% while coated samples still retained 45% after 14 days of intense leaching. Similar tests on poplar revealed 19% and 34% for uncoated and coated samples, respectively.This represents a gain of 20 to 25% compared to pure DOT treated specimens of both wood species. Preliminary biological tests were carried out on malt agar using a miniblock technique for uncoated pine sapwood and beech, with Poria placenta and Coriolus versicolor, respectively. After six weeks of exposure to fungal attack all boron protective systems tested proved their effectiveness, as none of the test samples exhibited a mass loss exceeding 4%. The reference 1% BAE without protective additives showed an average mass loss of 15%. Finally, test data are reported of standard EN 113 testing in view of a further evaluation of the biological efficacy of combined DOT-additive treatments.
A Mohareb, J Van Acker, M Stevens


Exterior weathering trials on radiata pine roofing shingles
1985 - IRG/WP 3240
A series of test roofs clad with radiata pine (Pinus radiata D. Don) shingles that had been pressure-treated with various water-borne preservative formulations were installed at a Forest Research Institute test site in Rotorua in 1977. A further series of test roofs installed in 1978 included radiata pine shingles pressure-treated with a commercial light organic solvent preservative (LOSP). Evaluation of selected radiata pine shingle test roofs in early 1984 showed that, although preservative leaching had occurred from shingles treated with an alkyl ammonium compound (AAC), a copper-chrome-arsenic (CCA) preservative, and an LOSP, the shingles appeared sound when examined microscopically. Slight lichen growth was evident on some shingles. In contrast, untreated radiata pine shingles displayed marked fungal infection, early stages of decay, and plentiful mould and lichen growth. Western red cedar (Thuja plicata D. Don) shingles, which were used as a reference point from which to judge radiata pine shingles, showed lichen and mould growth after seven years' exposure. Checking and cupping of western red cedar shingles were attributable in part to the inclusion of some flat-sawn material.
D V Plackett, C M Chittenden, A F Preston


Protecting wooden structures
1980 - IRG/WP 392
Chromium-containing chemicals that effectively retard weathering of wood improve performance of subsequently applied finishes. Current work is focusing on the performance of wood-derived products (plywood, hardboard, fiberboard, particle board) after surface treatment with inorganic chemicals. The overall objective of the continuing research is to investigate new environmentally safe procedures to stabilize wood surfaces and to improve performance of applied finishes.
W C Feist


The use of zirconium as an inert fixative for borates in preservation
2001 - IRG/WP 01-30256
Stand-alone borates have been used in internal protected situations as wood preservatives for about 60 years. They have not been deemed acceptable for external situations because of their leaching characteristics. Work carried out to reduce the leachability of borates has been reviewed briefly here, and a specific fixation agent based on zirconium has been tested in standard leaching and decay tests. It was found that the performance of zirconium could be optimized for fixation at specific drying temperatures and at higher formulation pH. Using sufficient quantities of ammoniacal zirconium carbonate and potassium zirconium carbonate such formulations are then able to pass both Standard European and American Wood-Preservers' Association methods designed for testing exterior wood preservatives. Formulations based on borate with a zirconium additive are probably suitable for use in exterior above ground and possibly ground contact situations. As only initial indicative tests have been carried out so far, further testing with a range of wood destroying organisms and field tests should be carried out to evaluate this system further.
J D Lloyd, J L Fogel, A Vizel


Exterior wood stains
1980 - IRG/WP 3135
Experience has shown that conventional paints cannot now be relied upon to provide a complete seal against water entry, that in practice water can often circumvent the film and that the paint, far from serving to keep water out will seal it in. Moreover present-day paints are often subject to localised and premature failure out of doors and consequently entail high maintenance costs. Problems of wood decay and premature paint failure reached a high level during the 1960s, and led to the acceptance of the need for the preservative treatment of softwood joinery and cladding. The question remains however, whether, in the light of changes in the quality of timber and how it is used, the traditional approach of attempting to seal the outer surface of the wood is still valid, or should be abandoned in favour of using different types of finish which are more permeable to moisture and prevent it accumulating in the timber. One of the reasons for the remarkable success of semi-transparent exterior wood stains is that they met the demand for finishes of increased water vapour permeability for timber which was susceptible to decay. They also possessed two other important attractions: they provided natural finishes for exterior timber which were without the technical problems of clear varnish; and their mode of breakdown by erosion reduced the preparation work in maintenance and hence the overall maintenance costs. These are valid commendations for stains and remain important factors encouraging their use. Stains offer the architect additional design freedom and, used effectively, can make a pleasing contribution to the appearance of modern buildings. They do reduce average moisture levels in the timber and are simple to maintain, though these advantages may be offset to some extent if more frequent maintenance is necessary and if the higher permeability creates problems from dimensional movement.
E R Miller


Preservative requirements for exterior particleboard as predicted from accelerated laboratory evaluations
1976 - IRG/WP 265
Arguments for and against preservative treatment of exterior particleboard were considered; it was concluded that preservative treatment is desirable. Laboratory decay tests were conducted to determine levels of sodium pentachlorophenoxide required to protect exterior particleboard from decay fungi. The decay resistance of treated board was compared with that of timber (both naturally durable and preservative-treated) currently used in situations for which exterior particleboard is designed. A retention of 0.35% sodium pentachlorophenoxide per oven-dry board weight was considered to offer adequate protection to the board.
M E Hedley


Blue stain resistance of exterior wood coatings as a function of their typology
1998 - IRG/WP 98-20145
Paints and wood stains were evaluated on their blue stain resistance using both EN 152 method and the reverse method. The typology of these exterior coatings was varied including standard and high solid solvent-borne coatings as well as different types of waterborne coatings. For the water-borne acrylic, alkyd based and hybrid coatings both applied as opaque primer paints and as decorative wood stains a range of synthetic resins were used. Though some components like dryers or bactericides are present in a number of formulations examined, a clear tendency of dependence of blue stain resistance on the typology of the coating seems obvious when evaluating blue stain development in an early stage. Longer exposures to test fungi fade away the effect of resin and indicate the role of a chemical protection of the coating.
J Van Acker, M Stevens, C Brauwers, V Rijckaert, E Mol


Natural durability of European wood species for exterior use above ground
2003 - IRG/WP 03-10499
The main interest in using more timber for exterior constructions is to protect the environment, where wood is considered an environmentally friendly material. However, chemicals for wood protection are getting more and more restricted, consequently, the focus on the natural durability of wood is increased. Good, well-documented data on the durability of wood species in ground contact exist, which form the basis of the standard EN 350-2:1995. Yet, we have, however, no useful documentation for the natural durability of wood, when used outdoors above ground. The study is large-scale field trials, including more than 30 species, where the objective is to define and document the natural durability of European wood species when used outdoors above ground. The idea of the test set-up is to simulate different application situations of wood to recommend individual wood species for specific purposes – fit to purpose. Two basically different test set-ups are used: 1. Panels in close-to-practice applications: Horizontally oriented with and without covering. Vertically north turning and vertically south turning oriented with and without covering as well as 45 degrees south turning oriented without covering. 2. Lap-joints in standardised field exposures: The set-up is according to the CEN-standard ENV 12037: Wood Preservative – Field Test Method for determining the relative protective effectiveness of a wood preservative exposed out of ground contact – Horizontal lap-joint method. The paper presents the results of the appearance, the moisture fluctuation, mould growth and wood decay after 3 years field trial.
B Lindegaard, N Morsing


Blue Stain Testing of Alkyd and Acrylic Stains
2003 - IRG/WP 03-20273
Resistance against blue stain of semi-transparent alkyd and acrylic stains was tested by both EN 152 and the so-called reverse exposure test methods. Comparison of the results, obtained by both methods was the most important aim of this study. As expected, performance of the water-borne acrylic paint was lower compared to protective effectiveness of the alkyd stain. This difference was even more pronounced when artificially accelerated aged samples were exposed. It seems that the reverse exposure method may give more distinctive results. In general, our results confirm previous literature reports on adequacy of the reverse test method for evaluation of blue stain resistance of surface finishes.
M Petric, M Pavlic, B Kricej, M Humar, F Pohleven


Evaluation of chlorpyrifos and fungicides alone and in combination for control of insects and fungi in wood and wood composites
1998 - IRG/WP 98-30187
Wood composites are rapidly being adapted for use in exterior applications. The incorporation of a preservative system to prevent fungus and insect attack is necessary with most exterior composites. Research studies were reviewed pertaining to organic preservative systems based on Lentrek* insecticide wood treatment which contains the active ingredient chlorpyrifos alone and in combination with tebuconazole and propiconazole (fungicides) for use as a combination treatment preservative system for solid wood and wood composites. Effective retentions for chlorpyrifos for protection of wood from termite and beetle attack was determined to be 0.2 kg/m3 set by the high retentions needed for field control of Coptotermes formosanus. In addition, this retention also provides effective control of the termites; Coptotermes lacteus, Reticulitermes flavipes, and Nasutitermes exitiosus, and the Lyctiid powderpost beetle, Lyctus brunneus. Retentions needed for control of Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot) were determined to be 0.11 kg/m3 and 0.06 kg/m3 for tebuconazole and propiconazole, respectively. Discussions with the manufacturers of tebuconazole and propiconazole indicated that the two fungicides work best together when in a 1:1 ratio. Given the need for the 1:1 ratio then, retentions needed for the tebuconazole and the propiconazole for treatment of wood composites are therefore 0.1 and 0.1 kg/m3, respectively, using tebuconazole as the benchmark. Tebuconazole and propiconazole retentions of 0.08 and 0.08 kg/m3, respectively, afforded moderate stain and mold protection of treated wood with a 64% reduction in stain and mold coverage by 3 weeks; thereafter, protection diminishes with time to a 40% reduction in coverage by 8 weeks. Overall, the retentions needed for a mixture of tebuconazole/propiconazole/chlorpyrifos (T/P/C) for use in wood composites are 0.1/0.1/0.2 kg/m3, respectively, to protect the wood from attack by insects and decay fungi while at the same time providing some moderate reduction of stain/mold coverage. Also, in order to compensate for the anticipated long term degradation of the two fungicides under field conditions, the fungicide retentions were increased by 50% thereby resulting in final recommended retentions for use of T/P/C in wood composites as 0.15/0.15/0.2 kg/m3, respectively.
M P Tolley, P E Laks, R Fears


Durability of exterior natural wood finishes in Brazil
1985 - IRG/WP 3343
Wood finishes systems were evaluated in natural weathering conditions during 5 (five) years, over "Parana-pine" (Araucaria angustifolia). Test samples results show that: - Semitransparent wood preservative stains, based on polimerized linseed oil, provided very good protection to the wood, compared with the one based on alkyd varnish; - Solid color wood preservative stains provided good durability. However, film degrading process was identical to the one of conventional finishes; - Conventional paint and varnish showed decomposition caused by cracking, checking and flaking (scaling).
D R Macedo


Weathering trials on natural wood finishes in New Zealand
1986 - IRG/WP 3383
The weathering properties of various transparent and semi-transparent exterior finishes for New Zealand-grown radiata pine are currently being examined. After 12 to 16 months' weathering, unpigmented water repellents have failed to provide satisfactory protection from weathering under field test conditions. With the exception of two formulations, penetrating oil-based stains are already showing signs of deterioration by surface erosion. Non-penetrating solid colour stains have generally remained in good-to-excellent condition. Acrylic emulsion formulations are the most durable of the transparent finishes under test.
D V Plackett, C M Chittenden


Preservatives stains as exterior wood finishes
1977 - IRG/WP 389
For many years wood preservatives and paints have been used as the only treatment for exposed wood surfaces. Because of the inherent color of the preservatives, such as creosote, the wood surface was stained as well as protected from attack by micro-organisms. Paints protect surfaces from weathering, but recently, with an increased interest in maintaining the more natural appearance of exterior wood surfaces, painting is being replaced by staining. Stains have the advantages, in addition to preserving the natural wood appearance, that they do not peel, blister or crack, can be applied easily and renewed with little difficulty. The cost is less than that of paint, initially and over the life of the building. One of the major attractions for homes is that stains blend in with the environment. If the home owner desires a white exterior or bright colors, paint rather than a preservative stain must be used. Paints are more effective in protecting the wood from damage by sunlight and will avoid discoloration of the exterior surface resulting from the natural extractives present in wood. Special aluminium or stainless steel nails are not needed with paints, but are needed with stains. Preservative stains can be classified in various ways. Wood preservatives, such as creosote and pentachlorophenol, have been used for many years primarily for preventing deterioration caused by fungi, including fungus species which discolor and those that decay the wood. These compounds provided some degree of water repellency, but this was not a major objective in their use. Later, water repellents were added to the preservatives to reduce the rapid uptake of moisture and thus provide some dimensional stability to the product. More recently water solutions of inorganic salts have demonstrated that they provide protection to the wood, add color and are beneficial primary treatments if the wood surface is to be painted. Some of the water soluble formulations may provide some fire retardant properties as well. A common system of classification today includes three general types of natural finishes as follows: 1. water-repellent preservatives; 2. pigmented penetrating stains; 3. inorganic water soluble salts. It is possible to obtain a satisfactory exterior surface if no treatment is applied. Such an approach, however, is satisfactory only where the weather is not favorable for micro-organisms. If the fungi and other micro-organisms are allowed to develop, the coloring will be very nonuniform, the wood surface will deteriorate, and warping and the like will occur to excessive degrees. Thus in most environments one of the above systems must be used.
D W French


Exterior wood stains
1979 - IRG/WP 3136
The use of semi-transparent exterior wood stains has grown remarkably since their development during the 1960s. This can be partly attributed to their offering a break with tradition at a time when it was being recognised that changes in the quality of timber and how it was used demanded different methods of exterior wood finishing. Information is already available on the characteristics and uses of exterior wood stains. This paper presents the current opinion on their performance and limitations, based on continuing research and considerable site experience. Until now there has been greater use of the so-called lowbuild stains which deposit little film onto the timber and so come closest to the ideal natural finish. They have a high moisture permeability, which has the benefit of reducing the level of any decay hazard but can lead to wide fluctuations in moisture content in service and to consequent problems of surface splitting and dimensional movement. In order to limit movement it is necessary to maintain the water repellency of the stain by periodic retreatment which, on exposed aspects, is likely to be necessary at intervals of about three years. High-build stains form a surface film about half the thickness of a conventional paint film and they possess a moisture permeability between that of paint and typical lowbuild stains. They exert more control on wood moisture content, reducing the problems of dimensional movement and surface splitting, and should not require such frequent maintenance as the low-build types. However, high-build stains are more prone to localised failure by flaking and this tendency will increase after a number of maintenance coats, which will also tend to obscure the natural features of the wood. Thus it is possible that the improved protection provided by high-build stains may be offset by losses in appearance and ease of maintenance, but there is at present insufficient experience of them in Britain to establish the extent to which this is so. Some high-build stains are based on water-borne acrylic agglutinants and have very good durability although when used as the sole treatment they lack the freshness of the solvent-borne materials and the thermoplastic nature of the film creates problems on contacting surfaces. Interest continues to grow in the opaque stains, or moisture-regulating paints. These materials share with stains the characteristics of being applied coat on coat instead of by the normal primer/undercoat/finish procedure, and of weathering by erosion. They have the appearance of satin finish paint but should possess improved flexibility and higher moisture permeability, and be easier to maintain. There has also been a revival in interest in the Swedish Royal Process which effectively combines wood preservation and decoration. The timber is vacuum-pressure impregnated with a water-borne preservative and is then subjected to a pressure treatment with a heated mixture of oil and pigments to confer colour and weather resistance to an outer zone of the wood. Experience suggests that the maintenance requirements of Royal-treated wood are much reduced.
E R Miller


Minimisation of the Environmental Impacts of Coatings on Exterior Wood by Optimisation of their Life Spans
2003 - IRG/WP 03-50197
The study has shown that the environmental impacts from coatings on exterior wood are dependent criteria on their life spans. A minimisation of the environmental impacts can be performed with the help of the integrated design model, which is tested in this study. The optimal life spans, found as reference service lives from the exposure tests, statistical evaluation and the assessment of experts were used for forecasting in Life Cycle Assessment of the coatings on exterior wood. The integrated life cycle design, performed in this study, showed that the water-borne acrylic coating and the water-borne acrylic stain are the best choice as regards the integrated assessment of the environmental impacts and service lives of the coatings. The discussed coating systems are a solvent-borne alkyd coating, a water-borne acrylic coating, a water-borne acrylic stain, a solvent-borne alkyd stain and an alkyd oil.
L Strömberg


L-joint based testing for service life prediction of exterior plywood in out of ground contact conditions
2006 - IRG/WP 06-20342
Good biological performance of several plywood types in exterior conditions is most probably related to altered wood moisture behaviour compared to solid wood. Therefore a test set up was developed, using EN 330 L-joint testing methodology, to facilitate differentiation of plywood for exterior applications. The proposed test set up is an adaptation of an accelerated L-joint method introduced by Van Acker and Stevens (2003). Regular L-joints are used to expose plywood specimens as an infill window system. The L-joints simulate bottom corners of a low quality joinery unit. Accelerated testing is based on a moistening device using a drip irrigation system feeding a horticultural rock wool sponge as wetting agent. This keeps the lower corner of the plywood sample wet and creates a moisture gradient in the panel. The specimens are inclined for 10 degrees, the face veneer of the plywood is facing south and inclined 45°. The newly developed exposure method is intended to be severe and acts as a simulation of a worst case situation. The accelerated weathering makes differentiation among several plywood products possible after only one year of outdoor exposure. Visual appreciation of the tested plywood, mass loss measurements, alterations in moisture absorption and desorption patterns and isolations of fungi present on the samples help to rank plywood in view of fit for purpose for use class 3 exposure conditions.
J De Smet, I De Windt, J Van Acker


Decay Hazard Classifications in China for Exterior Above-Ground Wood
2007 - IRG/WP 07-20357
A decay hazard map for exterior above-ground wood structures is presented based on Scheffer’s Climate Index, with the major purpose of promoting awareness for proper protection of wood structures in different locations in China. A very large area in the South, including southern Yunnan, most of Sichuan Province and Chongqing, and part of Hunan, Hubei, Anhui, Jiangxi, and Zhejiang, as well as all the more southern areas, has decay hazard ratings above 70, considered a severe decay hazard zone according to the accepted classifications. The moderate decay hazard zone, Index values between 35 and 70, consists mainly of the central areas of China, from the west to the east, including parts of Xizang, Yunnan, Qinghai, Gansu, Shaanxi, Shanxi, Henan, Hubei, Anhui and Jiangsu, as well as Shanghai. It also includes most areas in Northeast China, together with a small pocket around Beijing. By comparison, large areas in the north, from the west to the east, including most areas in Xinjiang, Inner Mongolia, part of Qinghai, Gansu, Ninxia, Shaanxi, Shanxi, and Hebei, and a small part of Henan, are in a low hazard zone with index ratings below 35. The research demonstrates that the areas across China in the Southwest, South, Central China, Southeast, and Northeast, with the highest population densities and also containing areas on the east coast with the strongest economic development, have severe to moderate decay hazard for above-ground wood structures, making proper wood protection more critical and economically important.
J Wang, X Wu, M Jiang, P I Morris


Service life prediction for exterior timber cladding
2010 - IRG/WP 10-20460
This discussion paper considers service life prediction for timber and the work within the pan-European WoodExter project. The project aims to develop a model for service life prediction of exterior timber cladding, to enable better end use selection of material suitable for delivering the required service life of cladding and to provide information for professionals wanting to understand and use timber cladding. Service life prediction of buildings is discussed in the context of ISO 15686 the international suite of standards for service life prediction. The challenges that are ahead to enable a successful predictive approach to be developed are considered.
E Suttie, F Englund


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


Impact of wood species on the performance of exterior wood coatings
2010 - IRG/WP 10-40519
To prolong the service life of a wooden construction the protective function of a coating is of utmost importance. The chemical composition as well as the wood-coating interface affects the performance of this protective layer and obviously wood species have an impact too. This paper discusses the influence of wood species on the overall coating performance. Therefore, a range of opaque waterborne acrylic coatings applied on industrially finished window frames made of frequently used commercial hardwood and softwood species were tested. Both, artificial and natural weathering, were considered for the durability assessment. Complementary studies on moisture dynamics and fungal growth were included as well. Coatings applied on dense tropical hardwood with large vessels perform fairly well in regard to water related failure, but erosion or weathering phenomena occur early. The opposite is true when examining small or medium porous hardwoods. Coatings applied on softwood substrates performed the worst. Yet, in contrast to hardwood, the performance of softwood based systems under laboratory test conditions is less correlated with outdoor performance.
I De Windt, J Van den Bulcke, J Van Acker


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


Modern Instrumental Methods to Investigate the Mechanism of Biological Decay in Wood Plastic Composites
2014 - IRG/WP 14-40674
Various instrumental techniques were used to study the fungal decay process in wood plastic composite (WPC) boards. Commercial boards exposed near Hilo, Hawaii (HI) for eight years in both sun and shadow locations were inspected and tested periodically. After eight years of exposure, both boards were evaluated using magnetic resonance imaging (MRI), while a selected area of the board exposed in shadow was additionally tested using microscopy and micro x-ray computed tomography (CT). Experimental boards exposed to either exterior conditions in Vancouver, British Columbia (BC) or a laboratory decay process were used for verification of MRI and CT results obtained from the commercial board. MRI detected the presence of free water and its distribution in the exposed commercial board samples tested. Fibre saturation in the experimental board was found to be about 22%, in comparison to 27 – 30% present in most wood species. There was good correlation between the detection of free water by MRI and by destructive testing. Reconstructed volumes from CT scans of the tested boards allowed for the WPC microstructure to be observed in various planes of view and for void analysis of the material to be conducted. A significantly higher average percentage volume of voids was detected in the exposed sample compared to its reference unexposed counterpart. CT scans and subsequent void analysis of the experimental soil block culture test samples of known weight loss in wood demonstrated this technique to be reasonably accurate in the detection of voids created due to biological decay. No obvious relationship was established between the presence of free water detected by MRI and the average volume of voids detected by CT. Scanning electron microscopy (SEM) confirmed the presence of fungal mycelia in the exposed commercial board cross-section imaged by both MRI and CT. It was confirmed that both MRI and micro CT could be used for non-destructive evaluations of WPC materials, including their decay process. This work also found that many different decay fungi species could colonize and internally damage WPC, and that fungal decay in WPC seems to be a self-propagating process requiring an initiation time period where no obvious decay damage is observed.
G Sun, R Ibach, M Gnatowski, J Glaeser, M Leung, J Haight


Indentation and pendulum hardness tests: two convenient assessment methods of the performance of exterior wood coatings
2015 - IRG/WP 15-40689
Developing formulations of exterior wood coatings with long service life is a big challenge. For many years in Europe the performances have been mainly evaluated through weathering tests (within the EN 927 series) followed by visual assessment (blistering, flaking, mould growth, chalking and cracking), colour and gloss measurements, and adhesion tests. Very recently the importance of the mechanical properties of coatings has been taken into consideration within the CEN/TC 139/WG2 and a test method (CEN/TS 16360) has been suggested to assess the film extensibility by indentation of a coating on a wooden substrate. In 2014 this technical specification was added in the EN 927-2 standard. The aim of this work was to investigate this destructive indentation test for several commercial acrylic coatings applied on spruce and Scots pine. In addition, pendulum hardness tests were carried out as a non-destructive test to gain further information about mechanical properties of the tested coatings. The influence of thickness was examined. This work discusses the advantages and the limits of both methods. They allowed a discrimination of the coatings studied and gave a similar ranking for most of the coatings. The paper also shows the relationship between pendulum hardness variation and long-term performances. Indentation and pendulum hardness tests are shown as useful investigations in addition of the conventional assessment framework of exterior wood coatings.
L Malassenet, L Podgorski, M Truskaller, G Grüll


Next Page