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Application of radio frequency heating to accelerate fixation of CCA in treated round-wood
1999 - IRG/WP 99-40133
The potential of radio frequency heating to accelerate the fixation of chromated copper arsenate (CCA) in treated round-wood was assessed. Pre-dried Douglas-fir and western red cedar round-wood sections were pressure treated with CCA in a pilot plant retort, after which they were placed individually in a pilot radio frequency (RF) chamber. Based upon the color reaction of chromotropic acid with hexavalent chromium and the quantitative assessment using diphenyl carbazide, fixation was achieved in less than 6 hours. During heating, the temperature at various locations inside the pole sections was monitored by fiber-optic thermocouples. The moisture profiles before, and after fixation, were also recorded. Further studies will examine other benefit of RF heating, including a) sterilization, and b) rapid drying of round-wood with minimum check formation.
Fang Fang, J N R Ruddick

TBTO absorption and penetration in pine joinery treated by various processes
1989 - IRG/WP 3523
Matched sections of several White pine (Pinus strobus) and Ponderosa pine (Pinus ponderosa) mouldings were treated with TBTO by Double vacuum, modified empty-cell, 15 second dip and several preheating treatments followed by a 15 s dip treatments. As expected the double vacuum and empty-cell (batch) treatments resulted in much greater retentions and penetrations than the dip treatments. The absorptions by the 15 s dip treatments could be improved significantly by preheating the wood to 60-90C° by microwave, radio-frequency or infra-red techniques. Since this approach is amenable to a continuous treatment process, it is being evaluated for potential commercial application.
P A Cooper, Y T Ung

The effect of temperature on the rate of fixation of an alkyl ammonium compound (AAC) wood preservative
1984 - IRG/WP 3293
The rate of fixation of an alkyl ammonium compound wood preservative was measured by soaking samples of wood wool in various preparations of the preservative for arbitrary times followed by immediate leaching in water. The wood wool was then analysed for residual preservative. The results indicated that fixation was very rapid and increased at higher temperatures.
P Vinden

Investigation of microwave as a means of eradicating dry rot attack in buildings
1992 - IRG/WP 92-1545
A microwave-apparatus developed for treatment of building-structures infested by dry rot was tested in the laboratory. The test-conditions simulated treatment of either infested timber or infested brickwork. Sawdust samples, both wet and dry, infested by viable mycelium of Serpula lacrymans were packed in glass-tubes. The tubes were then placed in the middle of either 20 cm thick wooden beams or 35 cm brickwork. The temperature during microwave-treatment was measured both in the tubes using toluene thermometers and in the "construction" using thermo-couples of the copper-constantine-type. The viability after treatment was tested by growth-ability on malt-agar, by ATP-content and by nucleus-staining. The lethal temperature with this specific apparatus was 37-39°C in brickwork and 40-50°C in wood. In comparison with more conventional methods of heat transfer microwaves seem to be more efficient. The variation in temperature within the treated area was undesirably high and in situ treatment above lethal temperature with this specific apparatus would lead to an unacceptably high risk of damage.
C Kjerulf-Jensen, A P Koch

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

Efficiency of wood impregnation processes
1980 - IRG/WP 3151
Many wood impregnation processes have been in use for a very long time, up to 150 years, but they have not been progressively modified. This paper considers impregnation processes in relation to current requirements, particularly impregnation efficiency and energy consumption. The term 'pore' is used throughout in its physical sense and is not confined to botanical 'pores'. SI units are used and, for convenience, atmospheric pressure is assumed to be exactly 100 N/m²; complete vacuum is 0 N/m². These observations and conclusions summarise an extensive programme of investigation at Penarth Research Centre involving creosote and water-borne preservatives, as well as a range of organic solvent preservatives.
B A Richardson

Rapid fixation of Chromated Copper Arsenate (CCA) wood preservatives by microwave treatment
2000 - IRG/WP 00-40184
Rapid microwave heating of freshly chromated copper arsenate (CCA) treated timber indicates that rapid preservative fixation is possible within approximately 40 seconds. The leaching of CCA was evaluated using simulated rainfall. Cost analyses indicates that microwave fixation using an on-line conveyor belt fixation process with an output of 4m3/hour using a microwave power supply of 230 kW costs approximately AU$ 16/m3 for electricity costs of AU$ 0.077/kW-h. When electricity cost are AUS$ 0.017/kW-h the treatment costs are reduced to AU$ 10/m3.
G Torgovnikov, P Vinden, E Mapanda, P R S Cobham

Eradication of wood decay fungi by means of radio frequency
1998 - IRG/WP 98-10292
High frequency electromagnetic fields i.e. radio frequency (RF) are used in wood industry for heating, gluing and bending of wood and are also appropriate for eradicating of wood decay fungi and insects. We investigated the effects of RF exposure on wood samples which were in vitro infected by Coniophora puteana, Gloeophyllum trabeum and Lentinus lepideus. For each fungus, the lethal temperature and time of exposure were determined. The efficacy of RF treatment was visually evaluated from regeneration of mycelia by subsequent exposure of treated wood samples on growth media. The eradication was dependent on the fungus species, temperature and duration of exposure to RF of 4.75 MHz. The most sensitive was Coniophora puteana (destroyed in 4 minutes at 75°C), less sensitive Lentinus lepideus (in 10 minutes at 90°C) and the least, Gloeophyllum trabeum (in 12 minutes at 90°C). At low temperatures, the time of exposure had to be adequately longer.
F Pohleven, J Resnik, A Kobe

Effects of steaming heat treatment of wood on the stimulation of termite feeding
1997 - IRG/WP 97-10212
At the 26th IRG conference, we reported that steamed Japanese larch heartwood samples were suffered a serious attack by subterranean termite, Coptotermes formosanus both in choice and no-choice feeding tests. This is possibly caused by the yield of termites stimulants in the wood samples resulting from the steaming process. Since the steaming heat treatment has often been applied to other several timber species for their drying, dimensional stabilisation, etc., attention should be paid to them on the stimulant effects of this treatment on termite attack. This paper deals with the results of choice and no choice feeding tests of termites using steamed or dry-heated samples of wood for commercial use in Japan. Some steamed wood species were heavily attacked by C. formosanus or Reticulitermes speratus while all dry-heated samples were not attacked more than unheated controls.
S Doi, Y Kurimoto, M Takahashi, T Yoshimura

The kinetics of catalytic acetylation of Pinus radiata (D. Don) using conventional and microwave heating
2010 - IRG/WP 10-40485
This study outlines the effect of catalyst and microwave heating on the degree of acetylation in radiata pine. Samples of radiata pine sapwood were impregnated with potassium acetate (KAc) dissolved in two different solvents (water and methanol). Impregnated samples were dried and subjected to acetic anhydride loading followed by conventional and microwave heating. The degree of acetylation was evaluated by weight percent gain (WPG). Effect of reaction temperature, reaction time on rate of reaction and WPG was investigated. In the initial 30 minutes, the rate of reaction with catalyst was nearly 6 times faster than that of non-catalysed acetylation. A reaction time of 30 minute gave rise to a 25% WPG in a catalysed system while without catalyst, a maximum 23% WPG was obtained after 8 hours of curing. No significant difference in the WPG and rate of reaction was found when water and methanol were used as solvents for KAc. KAc was found to have no adverse effect upon dimensional stability whereas the percentage water uptake was significantly reduced under catalytic acetylation. Microwaves are a potential source of heating and under catalytic conditions a 20 % WPG was obtained after only 5 minutes of curing.
A Kumar Sethy, P Vinden, G Torgovnikov, S Przewloka

Effect of heating on aldehydes emissions from solid wood
2011 - IRG/WP 10-50277
We have found that acetaldehyde, a probable human carcinogen, is produced from wood through reaction with ethanol. Alcohols are increasingly being used in houses and buildings for cleaning purposes. Acetaldehyde emission from solid wood has been attributed to ethanol acidification by enzymes such as ethanol dehydrogenase. Heating could inactivate these enzymes. In this study, the effects of heating and ethanol on acetaldehyde emission from solid wood were investigated. Sugi (Cryptomeria japonica) green wood was used. Specimens of heartwood and sapwood with dimensions of 20 x 20 x 10 mm were prepared, and then dried at 28, 90, and 150 ºC for different treatment times. After treatment, ethanol was added to half of each specimen. Each specimen was then put in a syringe, and placed in an oven at 30 ºC for 24 h. The air in the syringe was sampled, and the amount of acetaldehyde was determined by high-performance liquid chromatography. Significant acetaldehyde production was observed only when ethanol was dropped onto the wood. Experiments clarified that specimens dried at higher temperatures and for longer times emitted lower amounts of acetaldehyde.
A Ishikawa, K Miyamoto, S Tohmura, A Inoue

Thermoplastic Plywood at Moderately Increased Thermal Conditions
2016 - IRG/WP 16-40735
New thermoplastic plywood material so-called GradaTM manufactured by UPM has vast potential in production of wooden products with new approach of manufacturing. This paper examines possibilities of including GradaTM material in skateboard deck production as a large use of plywood type construction in this manufacturing sector. Bending strength (BS) and tensile strength perpendicular to the surface (TS) at the moderate heat up of this material are presented, specifically BS at 30, 40 °C and TS at 30 °C. All increased temperatures are compared to the room temperature (20 °C). Mechanical properties that were obtained from the test are modulus of elasticity (MOE), modulus of rapture (MOR), bending tension (RE) respective to implied fiber prolongation (AE) and stroke strain (AB) respective to tension at the breakage point. The results show the undesirable level of changes of mechanical properties when the material is moderately heated and thus makes it more arduous for an implementation of this material in skateboard industry. However the future research and development of GradaTM may change this claim.
R Réh, M Guoth

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