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Barefoot-heat-impact of oil-heat-treated wood: An important thermal property of decking boards
2009 - IRG/WP 09-40458
In this study the phenomenon of sensual heat impression was examined, when walking with bare feet on sun exposed wood based decking boards. A suitable method for measuring the heat flux from decking boards into an artificial foot was developed. The method and measuring device is described as well as results from measuring three different decking board materials: Oil-heat-treated spruce (OHT), untreated Bangkirai, and solid Wood Polymer Compound (WPC). The spruce OHT decking boards showed the lowest surface temperature after exposure to light (OHT 67°C, Bangkirai 76°C, WPC 85°C) and also caused the lowest temperature in the artificial foot (OHT 39.8 °C; Bangkirai 47.5 °C; WPC 52.3 °C). The measured heat flow density of the OHT decking boards was the lowest; the heat flow density of Bangkirai was three times and of WPC four times higher. The data obtained mirrored well the subjective sensation when walking on the three different materials with bare feet. After exposure to artificial solar radiation the OHT-spruce decking caused a feeling, which can be described as “conveniently warm”, whereas Bangkirai and in particular the solid WPC caused pain to the bare skin.
A O Rapp, C R Welzbacher, C Brischke


Thermally modified timber (TMT) for decking applications – determination of relevant surface properties
2011 - IRG/WP 11-40544
In recent years thermally modified timber (TMT) entered various market segments. It is used for facades, horticultural equipment, garden furniture, and also for kitchen and bathroom cabinets. However, flooring turned out to be the most important application for TMT, either as interior parquet or as exterior decking. Besides durability and dimensional stability, which had been the initial target properties of TMT, research activities need to focus also on flooring relevant properties. The performance of flooring is mainly characterized by its optical appearance, thermal behaviour and different mechanical properties, e. g. hardness and bending strength. Consequently, in the frame of a worldwide inter-laboratory test on quality measures for TMT, which was initiated in the frame of IRG in 2008, studies on the sensitivity of TMT on typical flooring loads were considered. Within this study color and heat flux density measurements were conducted to determine the suitability of TMT in terms of thermal comfort. The heat flux density was barely affected by the heat treatment, because it is mainly determined by the material density. Thermal modification did not lead to a remarkable loss, neither in density nor in heat flux. However, timber turned out to be preferential compared to mineral or polymer-based flooring materials suffering from less thermal comfort. The most important mechanical load for flooring was regarded in static and dynamic hardness tests. As TMT is known to be especially susceptible to dynamic loads, a method for determination of dynamic hardness was developed and applied to differently severe treated TMT. The development based on the Brinell hardness principle and aimed on examining differences between static and dynamic loads on hardness as well as on the possibility to convert both hardness values into each other. Extensive hardness tests with 24 different native wood species and TMT were conducted. The dynamic hardness decreased with increasing treatment intensity (in maximum by 20 %), whereby the axial hardness was significantly less affected compared to radial hardness. Furthermore, the reduction in hardness was found to be reliably predictable by color measurements.
L Meyer, C Brischke, C R Welzbacher


Selection of heat flux value for wood fire retardants testing using MLC
2018 - IRG/WP 18-40846
One of more crucial elements of investigating treated wood combustion properties with the use of a cone calorimeter is a proper selection of heat flux (HF). The HF level is directly reflected in time to ignition and a thermal degradation degree. The ignition of raw wood or of wood ineffectively protected against fire occurs at a low HF level, i.e. 10-20 kW/m2. By contrast, the ignition of wood which is effectively protected against fire, may occur no sooner than at HF 50 or even at 75 kW/m2. The aim of the paper was to analyse the problem of the selection of heat flux intensity in both experimental and standard fire testing with the use of a mass loss calorimeter (MLC). The subject of the analysis was wood treated with protective agents of various durability and fire resistance. On the one hand, the high HF value for wood samples of low fire resistance restricts or even excludes practical applications of an MLC as a tool for the evaluation of fire protection efficiency. On the other hand, too low value of HF prevents wood either from ignition or from determination of its thermal degradation degree. It especially applies to the situation when wood is effectively protected against fire. In both cases, the problem arises at the interpretation stage of obtained results. The identified problem was presented on the example of wood treated with chemical compounds which are ingredients of commonly used fire retardants, i.e. MAP – monoammonium phosphate, DAP – diammonium phosphate and PC – potassium carbonate, well known for their fire retardant properties. They are also known for their high solubility, which proves their high leaching from wood resulting consequently in a significant decrease in fire retardant properties. Unfortunately a versatile research procedure was not proposed in the performed study. However, the necessity for the individual selection of physical properties of a combustion process was emphasised. The above forces an unconventional method of result interpretation.
B Mazela, W Perdoch, W Grześkowiak, A Batista


Proposal for further work on accelerated ageing
1988 - IRG/WP 2314
M-L Edlund


Thermal treatment of wood: European Processes and their background
2002 - IRG/WP 02-40241
Recent efforts on thermal treatment of wood lead to the development of several processes introduced to the European market during the last few years. The total production capacity of heat treated wood in 2001 is estimated as approx. 165.000 m3. In the paper the different heat processes are presented. The general technology as well as scientific data on the chemical transformation of the cell wall polymers, on the biological performance, on the physical and mechanical properties of the treated wood are presented and discussed
H Militz


Durability of pine modified by 9 different methods
2004 - IRG/WP 04-40288
The decay resistance was studied for pine modified by nine methods of wood modification: 1) Acetylation, 2) Treatment with methylated melamine resin (MMF), 3) Acetylation followed by post-treatment with MMF-resin, 4) Thermal modification, 5) Furfurylation, 6) Maleoylation (using water solution of MG or ethanol solution of maleic anhydride), 7) Succinylation, 8) NMA-modification and 9) modification with reactive linseed oil derivative (UZA), Wood blocks of Scots pine (Pinus sylvestris L.) sapwood were modified in pilot plants. Methods 1-5 were performed by the authors at Chalmers University of Technology or at BFH in Hamburg. Methods 5-9 were part of a European research project (the Chemowood project, FAIR-CT97-3187) and therefore each of these modifications was performed by the project participant responsible for the method. For laboratory testing in TMCs (modified European standard ENV 807) and pure basidiomycete culture bioassays, smaller test specimens were cut from the modified wood blocks. Most of the modification methods were applied on test specimens for marine field testing (EN 275) and some methods to produce mini-stakes for field tests in five Swedish fields. Some modification methods result in modified wood with poor durability, whereas other methods (acetylation, furfurylation and MMF-treatment) seem to provide excellent resistance to microbial decay.
M Westin, A O Rapp, T Nilsson


Corrosion of fasteners in heat-treated wood – progress report after two years’ exposure outdoors
2005 - IRG/WP 05-40296
The corrosion of common fastener materials now in use - mild steel, zinc-coated steel, aluminium and Sanbond Z-coated steel – has been evaluated after two years’ exposure outdoors in untreated and heat-treated spruce (Picea abies) respectively. Spruce from South-western Sweden was used. The heat-treatment was carried out in Finland according to the ThermoWood process at a maximum temperature of 220 °C for five hours. The results so far show that the corrosion of fasteners in heat-treated wood according to the particular specification is more severe than in untreated wood. Mild steel and zinc-coated steel has been most susceptible. Stainless steel is hardly attacked at all.
J Jermer, B-L Andersson


Accelerated ageing of preservatives in treated wood
1988 - IRG/WP 3476
New preservatives are tested in the laboratory and often in field tests before they are used commercially. Some preservatives, however, tested in the laboratory do not show the expected stability when used in service. The differences between laboratory tests and practical use can never be completely eliminated but must be minimized as far as possible by relevant testing methods. Studies of the effect of different accelerated ageing procedures on the chemical degradation and the wood preserving capacity of six different fungicides or combinations thereof have been carried out. Chemicals tested were tributyltinoxide (TBTO), tributyltin naphthenate (TBTN), furmecyclox, benzalkoniumchloride (AAC) + guazatin and pentachlorophenol. The ageing procedures included exposure of test specimens in a wind tunnel (according to EN 73), in an oven at 40°C, 60°C and 70°C, leaching (according to EN 84) and combinations of these procedures. The influence of the different accelerated ageing procedures on the chemical degradation and toxic effect of different fungicides was obvious and, for some procedures and chemicals, comparable with experiences from practice.
M-L Edlund, B Henningsson, B Jensen, C-E Sundman


Plastic-coated marine piling in Los Angeles Harbour
1984 - IRG/WP 4105
G Horeczko


Developments in wood preservation processing techniques in New Zealand
1980 - IRG/WP 3143
P Vinden, A J McQuire


The Effect of Heat on the Retention of Ammoniacal Copper Quat (ACQ-AB) onto Scots Pine (Pinus Sylvestris L.) Wood
2008 - IRG/WP 08-40390
In this study, the sapwood of Scots pine (Pinus sylvestris L.) were treated with ammonical copper quat type (ACQ-AB), which is one of the environmentally friendly wood preservatives, by using soaking method as a functions of various temperatures and time. The results indicated that the retention behaviour of ACQ onto the wood was considerably affected by temperature of ACQ solution and treatment time.
M Hakki Alma, A Mukremin Kara


Radio frequency heating times for sterilization radiata pine solid piles
2017 - IRG/WP 17-40815
In this work was sterilized wood packaging material of radiata pine, stacked as solid piles without stickers, for determining the heating times using radiofrequency treatment. The experiments were performed in a radio frequency semi-industrial equipment. The results showed that the radio frequency heating times increases with wood volume and that radio frequency treatments were faster than conventional vapour heat treatment.
H Esquivel, V Sepúlveda, J Torres, L Salvo, R A Ananías


Evaluation of wood treated with copper-based preservatives for Cu loss during exposure to heat and copper-tolerant Bacillus licheniformis
1999 - IRG/WP 99-20155
Copper-based wood preservatives need to be effective against exposure to all types of microorganisms. Wood treated with six copper-based preservatives was exposed to 121°C and 20 psi pressure for 15 minutes under standard autoclave conditions and the copper-tolerant bacterium, Bacillus licheniformis CC01, for 10 d at 28°C and 150 rpm. Sixteen to 37 percent of the copper was released from the wood during autoclaving, with copper citrate demonstrating the highest percent loss. Forty-four to 82 percent of the copper remaining in the samples following autoclaving was removed during exposure to the bacterium in liquid culture; copper naphthenate in oil and ACQ-D had losses of eighty percent or greater of the remaining copper. The bacterium removed as much or more total copper in 4 of 6 gas-sterilized samples (85-94%) than the cumulative effects of steam-sterilization and the bacterium on treated samples. Copper loss from in-service treated wood compromises the efficacy of copper-based wood preservatives.
D M Crawford, C A Clausen


Improved resistance of Scots pine and Spruce by application of an oil-heat treatment
2000 - IRG/WP 00-40162
Spruce (Picea abies L. Karst.) and Scots pine (Pinus sylvestris L.) were subject to a heat treatment which was carried out in an oil-bath. The aim was to improve the dimensional stability of the treated wood and its resistance against fungi. The bath of vegetable oil provides a uniform heat transfer at temperatures of 180°C, 200°C and 220°C and protects the submersed wood from oxygen. Heat treatment in air atmosphere was also carried out at the same temperatures for comparison. Wood treated in hot oil was more equal in its appearance than wood heated in hot air. The treatment of spruce and pine in the oil-bath resulted in a better resistance against Coniophora puteana in a lab test according to EN 113 compared to the treatment in air atmosphere. In order to achieve the wanted upgrading effect, certain changes of mechanical properties and colour must be accepted. However, the strength loss caused by the heat-treatment in oil was less severe than in air atmosphere. Since all materials and the energy used in the process originate from renewable resources, the oil-heat-treatment appears to be environmentally friendly. All in all, the heat treatment in oil might be a promising approach to upgrade wood for outdoor use.
M Sailer, A O Rapp, H Leithoff


Heat treatment of bamboo
2001 - IRG/WP 01-40216
Bamboo is a fast growing material with remarkable mechanical properties. In many tropical and subtropical countries bamboo is available in suitable dimensions for a reasonable price. Therefore it is used for many purposes which range from the basket production up to the industrial production of parquet or paper. However, bamboo is known as susceptible to fungal or insect attack and it is difficult to treat with preservatives. Therefore BFH investigated the possibility to protect bamboo by other methods and tested the application of a heat treatment. European grown bamboo (Phyllostachys viridiglaucescens) and Asian grown bamboo (Phyllostachys pubescens) were heat treated and were subsequently inoculated with the basidiomycetes Coniophora puteana, Coriolus versicolor and Schizophyllum commune in an agar block test. Further the durability of treated specimens against soft rot fungi was tested. The changes of the mechanical properties (MOE and shock resistance) caused by the heat treatment were determined too. The application of temperatures above 200°C caused a clearly enhanced durability against a basidiomycete as well as against a soft rot attack but the shock resistance was intensely reduced. Further investigations are still ongoing. The study has been carried out with financial support from the Commission of the European Communities, specific INCO programme INCO-DC 961344.
H Leithoff, R-D Peek


The effects of heat treament on the specific gravity of beech and spruce wood
2003 - IRG/WP 03-40254
The effects of heat treatment on specific gravity of beech (Fagus orientalis) and spruce wood (Picea orientalis) naturally grown and intensively used in forest products industry in Turkey were studied. The wood samples were cut into 2 x 2 x 3 cm. Heat treatment was than applied to the wood samples at four different temperatures (130 °C, 150 °C, 180 °C and 200 °C) and three different durations (2 h, 6 h and 10 h) under air atmospheres. The results indicated that the specific gravity values treated by heating generally exhibited a decrease with increasing the exposure durations and temperatures compared to the untreated wood samples.
S Yildiz, Ü C Yildiz, G Colakoglu, E D Gezer, A Temiz


Durability of different heat treated materials from industrial processes in ground contact
2005 - IRG/WP 05-40312
In this study the durability of heat treated wood originating from four different European industrial heat treatment processes in ground contact was examined. The manufacturers of heat treated material were: PLATO Hout B.V./Netherlands, Thermo Wood/Finland, New Option Wood/France and Menz Holz/Germany where Oil-Heat treated Wood (OHT) is produced. All heat treated materials showed significantly increased durability against decay in ground contact compared to untreated Scots pine (Pinus sylvestris L.), independent from the different heat treatment processes. After four years of field testing, heat treated material appears to be not suitable for in ground contact application, since long service life is required. In analogy to the classification of natural durability (EN 350-1, 1994), durability classes in the range from 2 (durable) to 4 (slightly durable) were achieved by the different heat treated materials. This stands in contrast to statements of suppliers, who promote their material as suitable for in ground applications.
C R Welzbacher, A O Rapp


The effects of heat treatment on the toughness of beech wood
2004 - IRG/WP 04-40283
The effects of heat treatment on toughness of beech (Fagus orientalis) wood naturally grown and intensively used in forest products industry in Turkey were studied. The wood samples were cut into 5 x 5 x 5 cm. Heat treatment was than applied to the wood samples at three different temperatures (130 °C, 150 °C and 180 °C) and three different durations (2 h, 6 h and 10 h) under air atmospheres. The results indicated that the toughness values treated by heating generally exhibited a decrease with increasing the exposure durations and temperatures compared to the untreated wood samples.
S Yildiz, Ü C Yildiz, E D Gezer, Ali Temiz, E Dizman


The effects of heat treatment on anatomical changes of beech wood
2004 - IRG/WP 04-40284
The effects of heat treatment on anatomical changes of beech wood (Fagus orientalis) naturally grown and intensively used in forest products industry in Turkey were studied. The wood samples were cut into 2x2x3 cm and than conditioned at 25 °C and 65 % relative humidity for 3 weeks. Heat treatment was than applied to the wood samples at four different temperatures (130 °C, 150 °C, 180 °C and 200 °C) and three different durations (2 h and 10 h) under air atmospheres. The anatomical changes were determined for each heat treatment variation.
Ü C Yildiz, Z Gerçek, B Serdar, S Yildiz, E D Gezer, E Dizman, A Temiz


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


Heat treatment of wood strands for OSB production: Effect on the mechanical properties, water absorption and dimensional stability
2002 - IRG/WP 02-40238
The effect of heat treatment on the mechanical and physical properties of commercial OSB strands was evaluated. Heat treatment was applied under inert atmospheric conditions to wood strands. The aim of this study was to examine the heat treatment parameters to achieve significant reduction of thickness swelling (upon exposure to moisture in service) without causing excessive reductions in strength. Heat treatments of 200, 210, 220, 230, 240, 250, and 260°C for 20 minutes were applied and swelling tests were performed. Subsequently the modulus of rupture and modulus of elasticity were measured in wood strands. High temperature treatments resulted in significant reductions in thickness swelling of wood strands but resulted in 20% reductions of modulus of rupture and modulus of elasticity.
G J Goroyias, M D C Hale


Investigation of some technical properties of heat-treated wood
2003 - IRG/WP 03-40266
The objective of this study was to investigate some technical properties of heat-treated wood. Wood heat-treated according to a process intended for wood in above-ground end-uses (European hazard class 3) was subject to the following: · A delamination test according to EN 391 with glulam beams made of heat-treated pine (Pinus sylvestris) and spruce (Picea abies) laminations, assembled with PRF and PVAc adhesive respectively. · Determination of the withdrawal load for screws and nails. · Determination of the emission factor for VOC and the identification of major compounds. Results: · PRF adhesive performed very well whereas PVAc adhesive showed an unacceptable percentage of delamination and thus seems to be unsuitable for gluing heat-treated wood. · There is an indication that the withdrawal load for heat-treated wood is generally lower than for untreated wood. However, the number of tests carried out was quite small and definitive conclusions are difficult to draw. · The emission factor for the heat-treated wood, expressed as TVOC, was less than 10 µg/(m2 x h) and this was less than for untreated reference.
C Bengtsson, J Jermer, A Clang, B Ek-Olausson


Fungal resistance of smoke-dried Cryptomeria japonica wood
1998 - IRG/WP 98-40118
Performance of smoke dried wood on fungal resistance was studied. The maximum temperature of the smoke seasoning was 80-90°C in the drying room and 70-80°C within the wood for 6 days during the treatment for 15 days. Decay resistance of smoke-dried Cryptomeria japonica wood was evaluated using a brown rot fungus, Tyromyces palustris. Weight losses of untreated wood, smoke-dried wood, and smoke-dried wood followed by surface removal of 3 mm in thickness were 53%, 16%, and 21% respectively. After leaching for ten days, their weight losses were 38%, 51%, and 46% respectively. Smoke-dried wood had decay resistant some extent against the brown rot fungus, however its effectiveness disappeared completely during leaching. Smoke-drying did not have any effect on preventing the mould growth.
K Yamamoto, I Momohara, T Nishimura


Novel wood modification processes for window and cladding products
2004 - IRG/WP 04-40285
Because of the low natural durability and low dimensional stability of European wood species, the usage of wood for window frames has decreased dramatically during the last decade. In a joint project of several German research institutes and the window industry, following wood modification systems were compared. heat treatment (3 different materials from 2 companies) acetylation (pine sapwood and beech wood acetylated with acetic anhydride) polymerisation (melamine resin treated pine sapwood, Interlace treatment, furfurylation) wax treatment (pine sapwood, which was impregnated with natural resin and waxes) Investigated was the moisture content, dimensional stability, capillary water uptake and the durability. The dimensional stability show a high increase for following materials: heat treated wood, acetylated pine, interlace treated wood and furfurylated wood. The melamine resin treated wood and the wax treated wood show no significant increase in the dimensional stability. The biological durability against different basidiomycetes was tested according to the EN 113. As test fungi, Coniophora puteana, Poria placenta and Coriolus versicolor were used. The results show a very high increase in the durability for most of the treated wood. The wax treated wood shows no significant increase in durability. A novel window frame consists of several functional layers. Different wood properties are demanded for the single layers to achieve optimal window properties. Every modified wood shows a special potential for the use in a functional layer.
A Krause, C Hof, H Militz


Effects of artificial UV weathering and soft rot decay on heat treated wood
2005 - IRG/WP 05-40302
Oil and inert gas oven heat treated pine wood strips 100 µm thick were mildly heat treated (200°C, 30 mins linseed oil, 120 mins oven). Following treatment, specimens were exposed to UV weathering (300 hours) and decay by the soft rot fungus, Chaetomium globosum. The effects of each treatment were assessed by zero span tensile testing, microscopy and by FTIR. Tensile testing of heat treated strips showed greater strength losses in the oil treated samples (73%) than in the oven treated samples (26% loss). Heat treatment darkened the wood strips but this was photo-bleached on exposure to UV artificial weathering. The UV exposure caused some loss in tensile strength (35%) but the additional effects of UV on the tensile strength were less in heat treated wood (oil 15%, oven 18%). The combined effects of UV and fungi on the tensile strengths were less severe for treated wood than in untreated wood, (oil 4%, oven 18%) thus some protection was afforded by the heat tretaments. Exposure of untreated wood strips to the soft rot fungus caused some loss in tensile strength (32%), but heat treated wood showed small but not statistically significant gains in tensile strength after fungal exposure (oil, gain 30%, oven, gain 3%). Microscopic examination confirmed that a soft rot was minimal in heat treated samples, i.e. it was mainly confined to wood cell wall penetration. The combined effects of UV and fungi caused further losses of tensile strength in both oven and oil heat treated samples, but this loss was less severe than that which occurred in untreated controls. However, due to the severity of the initial losses caused by the oil heat treatment, the highest losses overall were in those oil heat treated samples exposed to UV (82%) and UV and decay (78%). Microscopic examination revealed that decay was more advanced in UV exposed samples. The FTIR spectra of oven heat treated samples did not show any change, while the oil heat treated samples increased absorbance at 1737cm-1 and 1450cm-1 relating to the presence of oil. Following fungal decay, no changes were observed, this corresponds with the cavity attack by soft rot fungi, which leave adjacent portions of cell wall material untouched. The ultra violet exposure affected the spectra of all specimens, increasing the absorbance at 1737cm-1. This relates to photo-degradation of the hemicelluloses, forming new carbonyl groups. In the UV exposed untreated wood there were also increases in absorbance at 1510 and 1160cm-1 relating to alterations in lignin structure.
M D C Hale, S C Ghosh, M J Spear


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