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Maintaining the adoption of the equilibrium moisture content in timber by bifluorides under outdoor circumstance
1989 - IRG/WP 3541
A description is given of the practical application of bifluorides, f. ex. Diffusec in maintaining the adaption of the equilibrium moisture content in timber, as a result of a many years observation of treated timber under outdoor circumstances.
H F M Nijman


Heat treated timber in Finland
2000 - IRG/WP 00-40158
Heat treatment permanently changes the physical and chemical properties of wood by means of high temperatures (150 - 240°C). Heat treatment darkens the colour of the wood. Heat treatment improves the equilibrium moisture content of the wood and the shrinkage and swelling of the wood is reduced. Very high temperatures improve the resistance to rot and also reduce the susceptibility to fungal decay. At the same time the strength properties of the timber are reduced: the bending strength can fall by 30%, depending on the treatment conditions and the cleavage strength (tensile strength perpendicular to fibres) may be reduced to a half, which makes heat treated timber split easily. The improved characteristics of heat treated timber offer the timber product industry many potential and attractive new opportunities. Also wood species having no commercial value as such can be heat treated and in this way new uses can be found for these species.
T Syrjänen, E Kangas


Properties of hot oil treated wood and the possible chemical reactions between wood and soybean oil during heat treatment
2005 - IRG/WP 05-40304
Thermal treatment with hot oil as the heating media based on the original idea from oil-heat treatment in Germany was investigated. The treatment was mainly carried out at 200ºC and 220ºC for 2 hours and 4 hours, and the wood species were mainly spruce and fir. This paper focuses on the difference between soybean oil and palm oil and the possible chemical reactions between wood and soybean oil. Generally palm oil was slightly better than soybean oil in improving the moisture resistance properties of heat-treated wood. But soybean oil treated wood appeared to have better decay and mould resistance. The mass loss of wood treated in soybean oil at 220ºC for 4 hours was below 20 % after exposure to Gloeophyllum trabeum in a soil block test, so the treated wood can be classified as “Resistant” according to ASTM D 2017 standards. Natural weathering exposure also shows that soybean oil treated wood is more mould resistant than palm oil treated wood. In order to investigate the effects of absorbed oil on the properties of treated wood and the possible reactions between wood and oils, extraction of different vegetable oil treated wood with chloroform and other solvents was carried out. The results suggest that part of the soybean oil could undergo chemical reactions with wood that renders it of low extractability.
Jieying Wang, P A Cooper


The Effect on Biological and Moisture Resistance of Epichlorohydrin Chemically Modified Wood
2002 - IRG/WP 02-40224
Southern pine solid wood and fiber were chemically modified with epichlorohydrin to help in understanding the role of moisture in the mechanism of biological effectiveness of chemically modified wood. The solid wood had weight gains from 11% to 34%, while the fiber had weight gains from 9% to 75%. After modification, part of the specimens were water leached for 2 weeks or extracted for 2 hours with a toluene:ethanol (2:1) solution. The equilibrium moisture content (EMC) at 30%, 65%, and 90% relative humidity (RH) and 27 °C was determined on all specimens. Laboratory soil block decay testing using the brown-rot fungus Gloeophyllum trabeum was performed and weight loss calculated. Results show that epichlorohydrin modified specimens did not lower the EMC significantly, yet there was biological effectiveness at 31% weight gain for the solid wood and 60% weight gain for the fiber. This indicates that the mechanism of efficacy may be due to substrate modification rather than moisture exclusion. Energy dispersive x-ray analysis (EDXA) was performed locating the chlorine throughout the wood cell wall.
R E Ibach, B-G Lee


The effect of heat treatment on the properties of spruce
1994 - IRG/WP 94-40032
The effect of high temperature treatment (above 150°C) on the wood quality is studied at the VTT. Improved dimensional stability, lower equilibrium moisture content and increased durability against biodeterioration is achieved, depending on the environmental factors. The biodeterioration resistance of spruce is improved due to changes in chemical composition and lower equilibrium moisture content. As a result of the treatment, darkening of colour and reduction of the strenght of the wood due to changes in microstructure is also observed.
H Viitanen, S Jämsä, L Paajanen, A J Nurmi, P Viitaniemi


The Influence of Extractives on Western Redcedar’s Equilibrium Moisture Content
2006 - IRG/WP 06-40331
The high natural durability of western redcedar (Thuja plicata Donn) heartwood is often attributed to the presence of the thujaplicins, which are toxic to fungi. However, sound, twenty-five year old western redcedar shakes and shingles were found to contain only traces of the thujaplicins, but significant quantities of plicatic acid (which is only weakly toxic to fungi). This suggests that factors other than the presence of thujaplicins, such as western redcedar’s low equilibrium moisture content (EMC), contribute to its natural durability. Western redcedar’s low EMC was confirmed to be attributable to the presence of extractives and through a series of solvent extractions it was found that the lignans, including plicatic acid, were associated with western redcedar’s low EMC. The presence of tropolones did not correspond with lower EMC. Extractives, such as plicatic acid, may contribute to durability through the reduction of EMC.
R Stirling, P I Morris


High Temperature Treated Wood
2008 - IRG/WP 08-40429
High temperature can modify internal structure and physic-chemical properties of wood by a controlled pyrolysis process. Such treatment, among other changes in properties, modifies the wood color in a way that resembles exotic species, increasing its market value. The main objective of this work is to determine the changes in wood properties caused by the effect of temperature and time, in order to establish patterns of time for treatments performed at 220 °C through correlations based in heat transfer concepts. The high temperature treatment will be set at 220 °C during 20, 30 e 40 minutes in body tests of Pinus spp, using an electric wood dryer without steam, while the volume and mass of the wet wood, the dry wood (0%) and after the treatment ends will be controlled and measured. The results of alterations in color, hardness and dimensional stability of the wood and the data (with different temperature treatments) will be useful to set standards for high temperature treatments using theoretical concepts of heat transfer applied to the wood material, considering the wood properties variation, including cost effectiveness of wood products.
C C Borges, A L Barbosa, R Faber de Campos, S T Targas


Estimating the heat treatment intensity through various properties of thermally modified timber (TMT)
2009 - IRG/WP 09-40459
The suitability of different measures for prediction of the heat treatment intensity was investigated. Therefore, the resistance to impact milling (RIM), the lightness L*, the equilibrium moisture content (EMC), the anti swelling efficiency (ASE) and the total amount of soluble carbohydrates (TSC) of heat treated specimens were correlated with corresponding fungal resistance achieved by heat treatments. Heat treatment temperatures of 180°C, 200°C, 210°C, 220°C, and 240°C for various heat treatment durations from 0.25 to 72 h were applied. The results show, that the decrease in mass (dm) by heat treatments is a suitable measurand to describe the treatment intensity, which is a product out of treatment temperature and duration, where the impact of temperature is predominating the impact of time. The properties examined showed a strong reciprocally proportional relationship with the decrease in mass. Thus different correlations were found for the various treatment temperatures: The higher the temperature applied, the lower was the decrease in mass required for an equivalent improvement of certain wood properties, e.g. biological durability, EMC, and dimensional stability. However, mass loss by Poria placenta correlated well with the resistance to impact milling (RIM), lightness L*, EMC, ASE and TSC of the different heat treated specimens, depending on the heat treatment temperature. Consequently, a reliable estimation of improved fungal resistance of TMT, as well as the quality control of TMT in general, strongly requires certain process information.
C R Welzbacher, C Brischke, A O Rapp


Determination of Equilibrium Moisture Content (EMC) of wood in the neighboring Countries of Iran
2011 - IRG/WP 10-40540
The mean value of annual temperature and relative humidity of 33 cities in Azerbaijan, Armenia, Turkmenistan, Afghanistan, Pakistan, Oman, United Arab Emirates, Bahrain, Qatar, Kuwait, Iraq and Turkey were determined using climatic data of the past 11 years. The EMC values were calculated using the Hailwood-Horrobin sorption model and its annual fluctuation, together with Temperature and relative humidity, were determined. The results indicated that EMC Values in the cities were ranged from 5.6% to 15.6%. Comparing annual temperature, relative humidity and EMC curves of these cities and conducting statistical analyses, the cities were classified into five groups with mean EMC values of 6.6, 8.6, 10.6, 12.6 and 14.6 percent. Thus, the results showed that EMC of the cities were below or equal to the allowable moisture content of wood and, wood products and the other hygroscopic materials(leather, textile and related products) in service except Bakoo in Azarbajan (EMC=15.6%). Therefore, if wood and wood products and related hygroscopic materials are processed within the range of the respective moisture content and exported to the neighboring countries of Iran, their quality and durability could be guarantied.
A A Enayati, H Z Hosseinabadi


Relationships between heat treatment intensity and some conferred properties of different European softwood and hardwood species
2012 - IRG/WP 12-40593
Effect of treatment intensity on conferred properties like elemental composition, durability, anti swelling efficiency (ASE) and equilibrium moisture content (EMC) of different European softwood and hardwood species subjected to mild pyrolysis at 230°C under nitrogen for different durations has been investigated. Independently of the wood species studied, elemental composition is strongly correlated with the mass losses due to thermal degradations which are directly connected to treatment intensity (duration). In all cases, an important increase of the carbon content associated with a decrease of the oxygen content was observed. Heat treated specimens were exposed to several brown rot fungi and the weight losses due to fungal degradation determined after 16 weeks, while effect of wood extractives before and after thermal treatment was investigated on mycelium growth. ASE and EMC were also evaluated. Results indicated important correlations between treatment intensity and all of the wood conferred properties like its elemental composition, durability, ASE or EMC. These results clearly indicated that chemical modifications of wood cell wall polymers are directly responsible for wood decay durability improvement, but also for its improved dimensional stability as well as its reduced capability for water adsorption. All these modifications of wood properties appeared simultaneously and progressively with the increase of treatment intensity depending from treatment duration. At the same time, effect of extractives generated during thermal treatment on Poria placenta growth indicated that these latter ones have no beneficial effect on wood durability.
M Chaouch, S Dumarçay, A Pétrissans, M Pétrissans, P Gérardin


Superhydrophobic treatment of Norway spruce wood for improvement of its resistance against brown rot and moulds
2016 - IRG/WP 16-40734
Water repellence of wood can be increased and its some other properties influenced by introduction of hydrophobic chemicals into and on cell walls without affecting the wood’s bulk density due to lumen filling. Herein, a simple dipping method to insert octadecyltrichlorosilane (OTS) into cell walls and to deposit the self-assembled hydrophobic monolayers (SAMs) of OTS is reported. It was found out that the treatment of Norway spruce wood with OTS caused superhydrophobicity of the specimens. At the same time, liquid water uptake was reduced, the equilibrium moisture content lowered and the dimensional stability in terms of the anti-swelling efficiency was increased. Hydrophobicity and lower equilibrium moisture content are believed to be the reason for the observed increased resistance of the treated samples against Coniophora puteana and moulds.
A Kumar, P Ryparová, P Hajek, B Kričej, M Pavlič, A S Škapin, M Šernek, J Tywoniak, J Žigon, M Petrič


Role of cell wall specific moisture content on the brown-rot fungal attack on wood
2016 - IRG/WP 16-40736
Wood is a hydroscopic resource because the cell wall polymers contain hydroxyl and other oxygen-containing groups that attract moisture through hydrogen bonding. Moisture content varies with changing moisture content in its environment. The moisture content in wood is responsible for many of the performance properties we observe. The strength properties of wood are dependent on the moisture content as does dimensional stability and attack by microorganisms. We know that brown-rot fungi does not attack dry wood. We also know that as the moisture content approaches the fiber saturation point, the wood becomes susceptible to attack by brown-rot fungi. Exactly how much moisture is required and where that moisture is located in the cell wall is the subject of this paper. This paper will take a theoretical look at the role of moisture in the brown-rot decay mechanism on acetylated wood.
R M Rowell


The sorption behaviour of wood
2017 - IRG/WP 17-20605
The use of dynamic vapour sorption to determine the sorption properties of wood has become an increasingly popular technique. The method has many advantages when compared with many other gravimetric methods. However, it is necessary to set an equilibrium condition in order to obtain data for an isotherm in a reasonable amount of time. An important recent finding has been that multiple sorption cycles are needed in order to capture the full range of sorption behaviour and the sample history can have an important influence on the results obtained. In addition, the location of the wood in a tree can also be an important consideration when examining sorption behaviour. This paper reviews the recent published data in this area, giving some insights into what affects sorption behaviour and suggests several promising routes for future research.
C Hill


Moisture content levels and decay of hemlock
1986 - IRG/WP 1287
As a model of decay conditions of wooden members in wooden houses, a decay test was set up in which samples of western hemlock (Tsuga heterophylla) under 4 moisture levels were examined. Each week the samples were weighed and if the weights indicated that their moisture contents were lower than the expected levels, distilled water was added. Every 8 weeks 3 samples from each condition were oven dried at 60°C for 48 hours, up to 48 weeks. After 48 weeks, 3 samples from each condition were oven dried every 16 weeks. The results obtained were as follows: After examining the samples for 96 weeks at 27°C, the mean weight loss of the hemlock samples kept at about 50-100% moisture content level was larger than those of the other levels. If the samples were dried every 8 weeks, the amount of decay in them was not significant. Decay was also not significant in the samples kept at approximately 20-30% moisture content level.
K Suzuki


New technique to analyze impregnation processes
1988 - IRG/WP 2304
Equipment has been developed to measure liquid flow in wood during impregnation processes. Basic principles of flow measurements using directly heated negative temperature coefficient thermistors, and some characteristics of the hardware developed are presented in this paper.
J P Hösli


Influence of moisture content of rubber wood on the growth of Botryodiplodia theobromae
1993 - IRG/WP 93-10029
Botryodiplodia theobromae is the main fungus causing sapstain on rubber wood (Hevea brasiliensis). The entry and establishment of the stain fungus is nighly influenced by the moisture content of the wood. To determine the optimum moisture content of wood required for maximum growth of Botryodiplodia theobromae wood blocks at different moisture contents were inoculated with the test fungus and incubated for a period of two weeks. The study showed if the moisture content of the wood was reduced to less than 24%, the wood can be protected from fungal sapstain.
E J M Florence, R Gnanaharan, J K Sharma


Soil virulence tests using Scots pine sapwood
1973 - IRG/WP 222
Following the tests reported in Document No: IRG/WP/210, in which soils from different laboratories were investigated for virulence, supplementary tests have been carried out using Scots pine sapwood and an extended incubation period.
J K Carey, J G Savory


Co-operative research project on L-joint testing. Sampling after 8 months exposure
1983 - IRG/WP 2208
It was anticipated in Document No IRG/WP/2192 that exposure of L-joints by the European co-operators would take place on 1 April 1983. Where L-joints were exposed at this time, sampling after 8 months exposure is due on 1 December 1983. The present document draws attention to relevant previous documents which describe the sampling methods to be adopted. It also provides Tables for recording the results.
J K Carey, A F Bravery


Comparison of the agar-block and soil-block methods used for evaluation of fungitoxic value of QAC and CCA wood preservatives
1994 - IRG/WP 94-20039
The modyfied agar-block and soil-block methods were used for comparing the fungitoxic value of QAC and CCA type preservatives against Coniophora puteana and Coniophora olivacea The mass loss and moisture contents of wood were analysed.
J Wazny, L J Cookson


Collaborative soft rot tests: Programme and test method
1973 - IRG/WP 229
J G Savory, J K Carey


Collaborative soft rot tests: Interim report on PRL tests of Cu/Cr/As preservative using method of Document No: IRG/WP/208
1972 - IRG/WP 211
Preservative: Tanalith CT.106 - Results obtained with beech are given in the table and indicate a toxic limit of 16.7-19.2 kg/m³ - The initial soil moisture content was adjusted to 27.8% (the water holding capacity). Noticeable drying out has occurred in some of the test bottles.
J G Savory


Observations on the failure of anti-sapstain treated timber under non-drying conditions
1990 - IRG/WP 1437
A range of bacteria and yeasts were isolated from antisapstain treated timber and fresh sawdust. Solution samples containing 100 ppm of TCMTB in a nutrient medium were inoculated with these organisms and incubated at 25°C for 5 days. The levels of TCMTB remaining in solution were determined by HPLC analysis after this time. Results indicated high losses of active ingredient for a range of organisms. These results suggest that active biodetoxification of organic biocides could occur in a short period of time during storage of antisapstain treated timber under favourable conditions. The implications of these results are discussed.
G R Williams


Co-operative research project on L-joint testing. Progress report to March 1988
1988 - IRG/WP 2315
Further sets of data received from CTFT (France), BAM (Germany) and PRL (UK) after 46-48 months exposure and STU (Sweden) after 22 months exposure are presented and discussed in conjunction with data reported previously. Colonisation and attack of the L-joints has progressed with increasing exposure period. The new data are generally in agreement with those presented previously and the major difference between Institutes continues to be one of rate of colonisation rather than any relative difference in performance of the treatments. Overall 0.5% TnBTO 1 min dip treatment is providing least protection followed by 1.0% TnBTO 1 min dip treatment. The double vacuum treatments continue to provide better protection than the dip treatments; there are now indications that 0.5% TnBTO double vacuum treatment is less effective than 1.0% TnBTO.
J K Carey, A F Bravery


A standardised procedure for the treatment of timber with test chemicals
1986 - IRG/WP 2257
A procedure is described which allows the standardisation of sample handling and data manipulation during trials invastigating the treatability of timber with test chemicals. The use of computer software allows the data to be handled efficiently.
J Norton, A Zosars, L E Leightley


Diffusion of fused borate rods in top ends of poles
1989 - IRG/WP 3518
Diffusion tests of fused borate rods were carried out on extremities of sapwood poles in service. Rods were set in drills under the cone with or without addition of liquid Boracol 40. After one year of weathering, a good diffusion in the slice under the cone and even below the slice and in the cone itself was observed in Scots pine and spruce poles. The rods were still intacts and constitute, in fact, a reserve of boric acid for the future. This type of treatment would be satisfactory as secondary treatments of poles in service.
D Dirol, J P Guder


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