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Effectos de la intemperización artificial sobre la madera de mezquite (Prosopis laevigata)
2008 - IRG/WP 08-40430
The effects of artificial weathering on Prosopis laevigata wood were studied on eight replicates (150 x 72 x 15mm (l x t x r)) free of knots, cracks and resin. The samples were exposed tangentially to UV light and to water spray during three cycles (1 cycle corresponded 1 week of artificial weathering). The conditioning time between each cycle was thirty days. The effects were measured according to visual appearance, crack formation, and colour changes; the results were then compared to two other well known timber species, namely teak (Tectona grandis) and beech (Fagus sylvatica). The specimens displayed changes in colour after three cycles of exposure. P. laevigata changed from brown to white. Delta C (Delta colour) increased from 5.6 to 9.6. There was less crack formation than in F. sylvatica but more than in T. grandis. Lightness was reduced from 61 to 37 after the first cycle; the lightness value of 35 was maintained at the end of the second and third cycles. The P. laevigata specimens showed several changes in colour after artificial weathering. The Delta C was higher due to the photodegradation of lignin and phenolic compounds caused the UV light and the leaching caused by water.
A Carrillo-Parra, F Hapla, C Mai


Colour change monitoring of photodegradation in Scots pine (Pinus sylvestris) – a short term focus
2009 - IRG/WP 09-40442
Colour change monitoring of photodegradation is a quick and easy method for monitoring rates of photodegradation in timber. A study was undertaken to compare this technique to other monitoring methods, including microtensile strength changes and weight loss. Colour changes due to accelerated sunlight exposure were monitored using a Datacolor check spectrophotometer and compared with a set of controls. Measurements on both samples and controls were performed hourly for the 1st 24 hours and there after daily until 168 hours’ exposure with extra measurements at 200, 350 and 500 hours. A subset of samples, were extracted prior to exposure to check the effects of any colour change due to the presence of extractives. Data was analysed using the reflectance spectra (400-700nm) as well as the CIE-L*a*b* system and ΔE. The majority of colour changes were found to occur within the 1st 24 hours. This was unaffected by the removal of extractives from the wood and was independent of temperature. When compared to the other monitoring methods, colour monitoring has been shown to be the most sensitive method out of the methods compared for monitoring photodegradation in Scots pine.
V Sharratt, C A S Hill, D P R Kint


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


Study of UV resistance and natural weathering of coatings on chemically modified wood
2013 - IRG/WP 13-40629
In this study, UV resistance and weathering performance of rubberwood (Hevea brasiliensis) and radiata pine (Pinus radiata) modified with benzoyl chloride and acetic anhydride was studied. Performance of polyurethane based wood coatings on modified wood was also evaluated. Unmodified and chemically modified specimens were exposed to accelerated and natural weathering. Modified and unmodified wood specimens were coated with commercially available polyurethane based transparent and opaque finishes and exposed to natural weathering for a period of 2 years. Physical and chemical deteriorations on uncoated / coated wood panels due to weathering were periodically monitored. Analysis of colour changes and chemical deteriorations of weathered specimens showed rapid discolouration and lignin degradation on unmodified wood surface exposed to weathering. Modified wood showed resistance to weathering and was partially effective in inducing UV resistance as compared to unmodified wood. Results clearly indicate that performance of coating can be significantly improved by chemically modifying wood substrate with benzoyl chloride. Benzoylation of wood polymers improved coatings adhesion and enhanced life of paints by 3-4 times. The performance of opaque coating was better than transparent coating, presumably due to photodegradation of wood substrate in transparent coating.
K K Pandey, K Srinivas


Effect of nano-particle characteristics and concentration on UV protection of timber: A field exposure test
2022 - IRG/WP 22-40941
Wood has a well-known susceptibility to ultra-violet light degradation, leading to premature replacement. A variety of products have been developed to protect against this damage, but most provide less than 12 months of protection and must be regularly reapplied. Developing improved coatings would help reduce wood losses and reduce maintenance costs. Nano-particles have a variety of attractive properties that may make them suitable UV protectants. The effects of nano-particles on surface appearance, colour, and wettability of radiata pine (Pinus radiata) sapwood samples were investigated over 20 weeks of outdoor exposure. Nanometer to micron-sized water dispersions of ZnO, α and γ Fe2O3, rutile and anatase TiO2, Fe3O4, Fe(OH)3, spherical and porous SiO2, and α and γ Al2O3 were used to evaluate the effects of concentration and crystal shape on UV performance. Surface colour changes were characterized by measuring CIE L*a*b* parameters, while surface wettability changes were assessed using water droplet contact angle. Wood appearance changed markedly over the 20-week exposure and mould fungi appeared on the surface. Nano-particles protected wood from photo-discoloration to differing degrees with rutile TiO2 and alpha Fe2O3 providing the most effective protection especially at higher concentrations. Larger micron-sized alpha Fe2O3 provided more sustained UV protection. Mould growth reduced the yellowness on wood surfaces and thus influenced overall colour change. Nano-particles did not reduce wettability of wood after UV exposure. While none of the systems completely prevented UV damage, some showed promise and further trials are underway using combinations of nano-particles.
T Yi, J J Morrell


Effects of acetylation on the dimensional stability and decay resistance of kenaf (Hibiscus cannabinus L.) fiberboard
1996 - IRG/WP 96-40059
The objective of this study was to investigate the influence of the acetylation treated kenaf fiber, Phenol formaldehyde resin content level, and three fungi species on the dimensional stability and decay resistance of high density non wood composition boards. A standard ASTM method was used to evaluate weight loss and thickness change. The linear shrinkage and expansion of each species were also determined. All specimens were exposed to decay chambers for 16 weeks. Test results indicated that most of the main factors significantly influence the thickness, length changes, and decay resistance of the high density kenaf fiberboards.
P Chow, T Harp, R Meimban, J A Youngquist, R M Rowell


Combined effects of the treatment of wood with formaldehyde
1978 - IRG/WP 3117
Treatment of fibrous materials with reagents in a vapor phase is neither new nor unique. Numerous examples exist in literature of vapor phase experiments on cellulose fibers and fabrics, and on wood. For many years the textile research and industry have used vapor phase processes for the treatment of textiles. The chemical modification of cellulose is based on different types of reactions e.g. esterification, alkylation, resin formation or polymerization, monomer grafting and crosslinking. Vapor phase treatment of wood offers certain potential advantages over the conventional liquid phase wood impregnation. The higher mobility of low molecular weight compounds in the gaseous state ensures a rapid, uniform and homogeneous distribution throughout the wood structure. The vapor phase treatment of wood is also a better approach from the standpoint of cell wall penetration. Bulking, which takes place in the cell wall only, means that less chemicals are required and that the final weight of the composite is limited. Furthermore, due to the low viscosity of a gas, the application of a lower pressure differential remains possible. Within the framework of a wood improvement programme carried out at the Laboratory of Wood Biology and Wood Technology (University of Ghent, Belgium) the treatments were based on the impregnation of wood with liquid synthetic monomers and with gaseous formaldehyde. The results of the hygroscopic and dimensional behaviour of the wood-plastic-combinations have been published previously. Other papers deal with the physical and chemical interactions between the synthetic products and the natural polymers of the cell wall. This contribution will be restricted to the treatment of wood with formaldehyde in the gaseous state.
M Stevens, J Schalck


Safer alternative reagents for colour differentiation of heartwood and sapwood
1994 - IRG/WP 94-20028
Benzidine and dimethyl yellow reagents have been used for distinguishing heartwood from sapwood in the Pinaceae and Araucariacae families, and in Eucalypt species. Both have been classified as carcinogenic by European and United States authoritites, yet the need for effective heartwood/sapwood differentiation remains, not only in the laboratory but also out in the timber processing chain. Safer alternative reagents have been proposed over the past twenty years, but some of these have since been linked with health problems, and most of the rest lack the specificity and general usefulness of those traditionally used. Recent research has investigated various azo, diazo, and other nitrated reagents. Safe but useful alternative methods of sapwood/heartwood differentiation are being established, and recommendations are made for several timber species.
A Zosars, M J Kennedy


Biodegradation of acetylated southern pine and aspen composition boards
1994 - IRG/WP 94-40020
This objective of this study was to investigate the influence of the acetylation treated wood fiber, Phenol-formaldehyde resin content level, two wood fiber species, three fungi species on the dimensional stability and decay resistence of high density composition boards. A standard ASTM method was used to evaluate weight loss and thickness change. The linear shrinkage and expansion of each species were also determined. All specimens were exposed to decay chambers for 16 weeks. Test results indicated that most of the main factors significantly influence the thickness and length changes and the decay resistance of the high density composition boards.
P Chow, T Harp, R Meimban, J A Youngquist, R M Powell


Towards a colour assay of wood degradation
1982 - IRG/WP 2180
A colour assay for the enzyme catalase is described. Since the activity of this enzyme has previously been shown to be correlated with degree of wood degradation as determined by other methods, this assay may provide a rapid quantitative indicator of superficial and internal wood decay.
M A Line


Effects of boron treatments on partially decayed oak and pitch pine heartwood
1996 - IRG/WP 96-30106
This paper reports results of borate based preservative treatment and leaching experiments on partially decayed oak and pitch pine heartwood. Previous experiments have shown little damage is caused to sound timber of these types when treated with Polybor and Boracol 20 preservatives. This experiment was carried out to assess the suitability of selected borate based preservatives for use in historical ships' timbers and therefore the physical effects of these preservatives on such timber was investigated. The results indicate that weight losses incurred due to treatment with Polybor or Boracol 20 are no more damaging than those incurred by treatment with water. Weight changes were more apparent in decayed timber than in sound timber with greater uptakes in non-leached samples and greater weight losses in leached samples. However, comparable weight changes were recorded between water treated samples and preservative treated samples. Dimensional changes were minimal in most cases, the greatest found in non-leached Boracol 20 samples as expected. These results indicate that treatment with these preservatives is suitable for partially decayed oak and pitch pine heartwood.
S McCutcheon, G M Smith, J W Palfreyman, P Durrant


Correlation between changes in colour and chemical composition during photo-degradation of wood surfaces
2005 - IRG/WP 05-40301
Changes in colour of wood (yellowing) during photo degradation or weathering reflect chemical changes in wood. Therefore, the relationship between changes in chemical composition and CIELAB colour parameters is very important to characterize photodegradation of lignocellulosic surfaces. In this study, the changes in chemical composition and yellowing due to photo-degradation was studied by exposing wood surfaces of Pinus roxburghii (chir pine) to a xenon source. Changes in chemical composition were monitored by measuring IR and fluorescence spectra and were correlated with colour changes. A linear correlation between degradation of lignin and total colour change (E) was observed.
K K Pandey


Effect of cyclic change of temperature on fungal growth and mass loss
1994 - IRG/WP 94-10065
For estimating the effect of cycling change of temparature on fungal growth, four Japanese species, sugi (Cryptomeria japonica), hinoki (Chamaecyparis obtusa), akamatsu (Pinus densiflora) and buna (Fagus crenata), four fungal species, Tyromyces palustris, Gloeophyllum trabeum, Coriolus versicolor, Pycnoporus coccineus, and five temperature conditions, 10, 20, 27, 35°C and cyclic temperature (20°C 12 hours and 30 or 27°C 12 hours) under constant humidity (75% RH) were examined. The results were summarised that the cyclic condition was rather high fungal growth rate in the case of majority of fungi tested but was not surely increased the mass loss of wood. This tendency is rather clear in the case of brown rot like Tyromyces palustris. The cyclic temperature conditions were not favorable to the groth of Serpula lacrymans.
K Suzuki, K Okada


Steam/hold/APM boron treatment - Treatability trials with green gauged radiata pine
1987 - IRG/WP 3439
Freshly sawn 100 x 50 mm radiata pine was green gauged, steam conditioned and preservative treated with a mixture of borax and boric acid using a modified Alternating Pressure Method (APM) treatment schedule. A 12 hour holding period between steam conditioning and treatment resulted in the necessary moisture loss and moisture re-distribution to facilitate treatment to NZ Timber Preservation Authority preservative retention and distribution requirements.
P Vinden


The impact of global warming on the UK distribution of house longhorn beetle Hylotrupes bajulus (L)
2001 - IRG/WP 01-10414
This paper reviews the effects of global warming on insect populations and distribution. The affects of global warming on the spread of Hylotrupes is predicted through a review of research related to the influence of temperature on its life-cycle and flight. Records of Hylotrupes distribution were obtained from published surveys, entomologists and museum collections and were plotted for the UK. The UKCIP98 model for climate change was then used to present the average maximum daily temperatures over the emergence period at present, and in the future. The model predicts a 3°C rise in annual temperature by the 2080's. This increase may enable mated females to fly on a greater number of days and over a greater area. The discussion highlights gaps in knowledge concerning the UK population that makes rate of spread difficult to predict at present.
P Oevering, A J Pitman


Some practical implications from recent research on the fixation of CCA preservatives
1975 - IRG/WP 358
The mechanism of fixation of CCA preservatives is briefly described. If the temperature is increased during the primary fixation period, the formation of intermediate fixation compounds is less extensive. The length of the primary fixation period is of practical interest. It is determined by preservative composition and concentration, temperature and wood species. Diagrams are given for Pinus sylvestris. Light exposure and drying during the primary fixation period cause variability in colour intensity of CCA treated wood. Disproportionation of preservative elements with penetration depth is explained by the fixation mechanism. Conversion of intermediate fixation compounds into stable ones occurs even below the fibre saturation point, as long as the moisture ratio is sufficiently high to allow ion transport. Conversion reactions are very slow. A correlation was found between the final pH of treated timber and leachability in fresh water of copper and arsenic. The final pH depends on preservative composition and concentration, wood species and to some degree of drying and storage conditions. An electrolyte such as sodium sulfate does not affect the leachability. In saline waters leachability is increased by complex formation of Cu(II) and Cr(III) with chloride and hydroxide and the salt effect on activity coefficients. The leaching of arsenic is delayed.
S-E Dahlgren


Preference of swarming termites for various colored lights
1984 - IRG/WP 1238
The ability of the alates of the drywood termite Bifiditermes beesoni (Gardner) to discriminate ten different colored lights was studied. When an alternative choice of any of two colors was offered, the light-blue was preferred to all other tested colors by 97.7% of the alates. A lower degree of attractivity was found for some other colors and certain other colors were indistinguishable. Furthermore, the effects of light intensity and preconditioning to certain colors have been studied and finally the response of swarming alates from natural colonies is compared to that of the individuals from laboratory colonies.
M Afzal


Preliminary investigation on the natural durability of Guayule (Parthenium argentatum)-based wood products
2000 - IRG/WP 00-40154
Conventional preservatives used to protect wood from insect and microbial damages are presently of major concern to human health and the environment. Finding alternative and economical preservatives has not been successful. Previous studies have shown that the resinous material extracted from the guayule plant (Parthenium argentatum, Gray) has both insect- and microbial-resistant properties. Unfortunately, it has not been accepted commercially because of the lack of an adequate supply of the raw material. However, the potential domestication of the guayule plant to produce hypoallergenic rubber latex will result in the production of large amounts of waste wood material. This should provide opportunity to use this natural source of the biologically resistant resinous chemicals. The objective of this preliminary study was to determine the effects of the rubber latex-removed wood residues or bagasse and the resinous extracts on termite- and decay-resistant properties. Two types of test materials were used in the study. One was wood impregnated with organic-solvent extracted resinous material from the plant. The other was composite wood fabricated using the residue or whole plant and plastic binder, which was used to improve the physical properties of the composite. Accelerated laboratory tests were conducted to determine the resistance of the wood products against the Eastern subterranean termite and wood fungi (brown-rot). The wood and stem of the guayule plant, wood treated with the resinous extract, and particle and composite wood made from ground guayule exhibited termite and wood fungal resistance.
F S Nakayama, P Chow, D S Bajwa, J A Youngquist, J H Muehl, A M Krzysik


Heat treatment of less-valuable Nigerian-grown Ceiba pentandra wood for improved properties
2006 - IRG/WP 06-40332
The hardwood Ceiba pentandra locally known as “ araba “ in Nigeria is rarely used for structural and construction works due to its high dimensional instability, low strength and durability values. Samples (10 x 10 x 150mm) were removed from four green boards (25 x 200 x 3000mm) of this species originating from a natural forest stand in Nigeria and subjected to 2-hour heat treatment at 160°C and 220°C. Heat treatment reduced swelling, hygroscopicity and swelling intensity of Ceiba pentandra wood with the reductions being generally higher in the 220°C treatment than the 160°C treatment. The reductions constitute improvements in these properties. These improvement in properties have the potential to increase the market value of this species through wider acceptability for various purposes hitherto considered impossible. This however is subject to further investigations on the effects on durability and strength properties which are other key features in the choice of wood for various purposes.
L Awoyemi


The Effect of Flavonoids on Colour and Spectral Changes of the Wood Surface Caused by Heat Treatment or Ultra-violet Irradiation
2006 - IRG/WP 06-40341
Both heat treatment and UV irradiation can cause discolouration and change in the spectral properties of wood surface. Some of the characteristic flavonols have significant role on colour and spectral changes, despite of their relative small quantities in wood. Colour changes and spectral properties of natural and extracted black locust (Robinia pseudoacacia L.) and poplar (Populus nigra L.) were investigated by CIELAB colour measurement system, FTIR and UV/Vis spectrophotometry. Spectral properties of representative flavonols, impregnated on inert silica gel thin layer, were studied in addition to the two types of wood samples. Chemical structure of flavonols was established to have both influence on the colour and spectral changes of woods and close connection with their thermal and photo stability. A slow but continuous decrease of lightness was observed in the case of quercetin and its homologous compounds. Chemical reaction of robinetin was detected by thermal analysis and differential scanning calorimetry under 200 °C and both oxidative and inert conditions. The colour changes of quercetin homolog compounds, kaempferol and fisetin, which contain one and two hydroxyl group on their “B” ring, are similar to quercetin; while myricetin with three hydroxyl groups on its “B” ring shows “robinetin-type” changes. The colour changes of the hardwoods are depended on the time and temperature of heating, as well as on the time of light irradiation. The character of spectral changes of black locust can be classified on the type of robinetin, in contrast with the “quercetin-type” of poplar.
R Csonka-Rákosa, L Molnár-Hamvas, E Börcsök, J Molnár, K Németh


A New Decay Hazard Map for North America Using the Scheffer Index
2008 - IRG/WP 08-10672
Wood decay experts in the USA and Canada use the Scheffer Index for above-ground wood decay potential to decide among design and treatment options to ensure the durability of wood construction. This paper provides an updated North American decay hazard map and includes data on Central America. Index values calculated from recent climate data are higher than published values due to directional or cyclical climate change. Compared to previously published maps there is considerable expansion of the moderate decay hazard zone in the interior wet belt of British Columbia, across the northern edge of the Prairies and around the Gulf of St. Lawrence. This suggests a greater need for preservative treatment in these parts of Canada.
P I Morris, J Wang


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


Anatomical, physical and chemical changes of Bamboo (Phyllostachys puberscence ) during weathering processes
2008 - IRG/WP 08-10650
Bamboo (Phyllostachys puberscence) culms with 1, 2, 3 year old were exposed to natural weathering condition in Gwangju, Korea for 12 months. Changes in color, surface topography, strength and chemical properties were investigated using various microscopic and instrumental techniques. After one year’s weathering, the color of bamboo became lighter but strengths of bamboo did not change significantly. Depending upon the age of bamboo culms, the rate of the check development and the surface erosion were different. Numerous checks were developed in the 2 and 3 year old bamboo whereas little checks in the 1 year old bamboo were appeared. Regardless of bamboo age, most of parenchyma cells in the ground tissues were degraded and lignin was rapidly decreased at initial period of weathering, although structural polysaccharides were also degraded by weathering.
Jong Sik Kim, Kwang Ho Lee, Mi Young Cha, Yoon Soo Kim


Surface color and roughness characteristics of medium density fiberboard (MDF) panels treated with fire retardants
2008 - IRG/WP 08-40420
The objective of this study was to determine surface characteristics and color change properties of Medium Density Fiberboard (MDF) treated by fire retardants (FR) with 10% concentration. Experimental panels were made using by melamine ureaformaldehyde (MUF) adhesive having 10%, 15%, 20% of melamine. The surface properties of the samples were determined using a fine stylus technique. Three roughness parameters, namely average roughness (Ra), mean peak-to-valley height (Rz), and maximum roughness (Rmax) were determined from the surface of the samples. Color change properties of MDF samples were evaluated to CIE L*a*b* methods by a spectrophotometer (Minolta CM-2600d). It was found that the surface roughness values of the FR treated MDF panels were higher than those of control panels. The highest surface roughness values obtained from MDF panels treated with MAF+BA+NPB, MAF+BA+BX, the lowest values obtained from MDF panels treated with MAF+AL. Also surface roughness of the MDF panels improved with increasing melamine additive rate in the MUF adhesive. According to CIEL*a*b method, color change properties of the samples showed variation as function of chemicals type. Especially, while the highest color change(?E) were determined for MDF samples treated with MINPB and MAF+BA+NPB, the lowest color change (?E) were obtained from MDF samples treated with MAF+AL, MIN.
D Ustaömer, M Usta, S Hiziroglu


Wood protection, a tool for climate change mitigation?
2008 - IRG/WP 08-50257
In the context of global warming and the search for possible strategies to mitigate climate change, forest and forest products have important advantages. Sustainable management makes forest a carbon sink, wood products have the potential to be a carbon sink as well, and their low carbon intensity is a potential for reducing CO2 emissions by substitution to competing materials. After describing these assets of wood products, this paper analyses how wood protection can reinforce them. This reinforcement effect is probably important, but still needs to be quantified.
G Deroubaix


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