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Heat transfer and wood moisture effects in moderate temperature fixation of CCA treated wood
1994 - IRG/WP 94-40022
Practical aspects of heat transfer and fixation of wood exposed to drying conditions after CCA treatment are considered. The rates of heat transfer and CCA fixation are substantially influenced by the cooling effect of water evaporating from the wood surface when drying occurs during fixation. At least in the early stages of fixation, the wood temperature approaches the wet bulb temperature, rather than the dry bulb temperature of the fixation chamber. Some drying during fixation is acceptable, but the time to complete fixation will be extended significantly, depending on the dry bulb/wet bulb depression. At above ambient temperatures, complete hexavalent chromium reduction can occur relatively quickly in relatively dry wood. However, CCA deposited under these conditions is more easily leached from wood and fixation conditions must be controlled to prevent wood from reaching fibre saturation point moisture content before fixation is complete.
J Chen, M Kaldas, Y T Ung, P A Cooper

Fire Safety of Wood Floor Assembly: Model and Full-scale Test
2007 - IRG/WP 07-20375
The present paper describes the model for the prediction of fire safety of wood floor assemblies. The model includes heat transfer model for the calculation of the flow of heat in floor assembly and structural model for the analysis of the mechanical performance of wood joists. The floor assemblies considered in this paper are constructed with nominal 2x10 (38x241mm) wood joists lined by Type X (or Type C) gypsum board (12.7mm or 15.9mm thickness, one layer or two layers) as a ceiling membrane, and 15.9mm thick plywood as a sub-floor. The heat transfer model employed two-dimensional heat conduction equation to predict the temperatures in the ceiling (gypsum board), wood joists and sub-floor (plywood) in the floor assembly, when the ceiling is exposed to fire. The structural model, using the temperature distribution in the joists predicted from the heat transfer model, calculated strength of the joists and deflection of joists based on the modulus of elasticity, moment of inertia and rigidity of joists to examine the mechanical performance of floor / ceiling assemblies. The results from the computer model were compared to the results from the full-scale tests. Reasonably good agreement was observed between the results from the model and those from the tests.
H Takeda

Effect of silver nanoparticles on the rate of heat transfer to the core of the medium-density fiberboard mat
2014 - IRG/WP 14-40653
Effect of silver nanoparticles on the rate of heat transferred to the core section of medium-density fiberboard (MDF) mat was studied here. A 400 ppm aqueous nanosilver suspension was used at three consumption levels of 100, 150, and 200 mL/kg based on the weight of dry wood fibers; the results were then compared with the control MDF panels. The size range of silver nanoparticles was 30-80 nm. Results showed that the uniform and even dispersion of nanoparticles throughout the MDF-matrix significantly contributed to the faster transfer of heat to the core section. As to the loss of mat water content after the first 3 – 4 minutes under the hot press, the core temperature slightly decreased in the control panels. However, heat-transferring property of silver nanoparticles contributed in keeping the core temperature rather constant in the NS150 and 200 treatments. As to the de-polymerization of part of the resin in the surface layers of the mat due to the rapid absorption of heat from hot plates by the nanoparticles, it can be concluded that the optimum nano-suspension content should not necessarily be the highest one.
H Reza Taghiyari, O Schmidt, E Bari, P M Tahir, A Karimi, P Nouri, A Jahangiri

Self-regulating heating cables for conductive heat transfer in pest control
2020 - IRG/WP 20-40895
Pest control by means of conductive heating of wooden elements requires considerable measuring and control efforts in order to avoid overheating of wooden surfaces, damage of structural elements and risk of fire. The usage of self-regulating heating cables might overcome such problems. In laboratory tests and under real conditions the applicability of self-regulating heating cables is tested with respect to insect and fungal control. Good prospects are obvious for the application of self-regulating cables for local insect control of structural elements. Fungal control seems to be possible, but only makes sense if strength reduction of the infested wooden elements is not relevant and wood moisture level can be kept low after the heat treatment.
J Müller, E Melcher, J Welling

Significance of the thermal design and the sorption isotherm shape in hygroscopic wood moisture dynamics and service life
2022 - IRG/WP 22-20682
Moisture dynamics are considered important for predicting the service performance of wood in exterior applications. Above a critical moisture content, water acts a softener on the structural polymer matrix of the wood cell wall, enabling the necessary diffusion of molecular species involved in the fungal degradation mechanism of wood. Water may enter solid wood in either liquid form or in vapor form, whereas it can only leave in vapor form. In exterior applications with prolonged exposure to rainwater, wood moisture may quickly accumulate to the critical moisture content for fungal degradation. On the other hand, moisture loss during dry weather conditions proceeds by relatively slow vapor transfer, leaving wood vulnerable to fungal decay for extended periods of time. This conference contribution addresses the latest scientific work, showing the role of heat transfer - associated with moisture changes in wood - as a major physical cause for the slow moisture content change rates in a humid ambient. The results from this work may guide the wood technologist to improve the service performance of wood through thermal detailing in the application design and/or by wood modification of the moisture sorption isotherm.
W Willems

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

A suggested method to test the toxicity of wood preservatives towards the house longhorn beetle
1977 - IRG/WP 275
This method was developed in the Institute for Wood Technology in Sarajevo, Yugoslavia and is used to get quick information on the toxicity of wood preservatives against house longhorn beetle (Hylotrupes bajulus). The method can be used for superficially treated or deeply impregnated wood blocks, and by using small or normal size test material it can be used as a laboratory or field test, and also for accelerated infestation of test material out of ground contact. The paper is given to the International Research Group on Wood Preservation as a suggested method which could possibly be used as a standard. Only the laboratory test method is described.
N Vidovic

Natural durability transfer from sawmill residues of white cypress (Callitris glaucophylla). - Part 3: Full penetration of the refractory sapwood of white cypress
2000 - IRG/WP 00-40167
The heartwood of white cypress, Callitris glaucophylla, is renowned for its termite resistance and durability against decay. The sapwood, which can represent up to 30% of log volume, is non-durable and refractory to conventional preservative treatment. Previous work ascribes the lack of permeability to oily deposits within tracheids and ray cells. Environmental scanning electron microscopy was used to investigate ultrastructural aspects of sapwood permeability. Several pre-treatment processes to improve permeability were tested with limited success. Solvent drying allowed preservative penetration but damaged the structure of the timber. Neither, long term water soaking nor an oscillating pressure/vacuum cycle had any effect on porosity to water-borne treatments. Through extensive modifications to a standard VPI process we can now repeatedly achieve full penetration with organic solvent-based wood preservative solutions into white cypress sapwood. Effects of this process on the strength of the timber are being evaluated. Work is continuing as to the most effective and efficient treatment schedule and the latest results will be presented at IRG 31.
M J Kennedy, L M Stephens, M A Powell

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

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

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

Methodology challenges in developing a transfer of natural durability from sawmill residues, illustrated by experiences with white cypress (Callitris glaucophylla)
2000 - IRG/WP 00-20203
The transfer of durability-conferring extractives from durable to non-durable wood has been accomplished often, but usually as an educational exercise rather than as a commercially oriented process. In the latter environment, many factors previously overlooked become vitally important. How to study them, in the absence of well-developed methodology and given the shorter timeframes being demanded by industry research funding organisations, presents real challenges. These challenges will be illustrated by experiences with the development of such a process for the 'waste' durability components of white cypress. Factors to be considered include: identification of active components; quantification of their individual and collective activities against target organisms; optimisation of source material handling, storage and extraction techniques; extract standardisation and batch-to-batch reproducibility; compatible yet cost-effective carriers for the actives into treated wood; effects on durability and other wood properties such as strength and handling safety; regulatory obstacles including acceptance into wood preservation standards; and quality control methods for penetration and retention of the treated product.
M J Kennedy, M A Powell

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

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