• Journal of the Korean Wood Science and Technology
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• v.40 no.5
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• pp.343-351
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• 2012

A large diameter roundwood is an important element of Korean traditional buildings, Hanok, and is hard to be dried without surface cracks. Four different pretreatments, such as pre-cracking, oil heating, kerfing-oil heating and PEG impregnation, were investigated for reducing the surface cracks of large-diameter roundwood specimens during heat treatment. The roundwood specimens of pre-cracking, oil heating and kerfing-oil heating showed surface cracks during pretreatment, but that of PEG impregnation did not. It was confirmed that kerfing reduced the total crack width. Among the four pretreatments and control only the PEG impregnation roundwood specimen had no crack on both outer and inner surfaces after heat treatment. The PEG impregnation specimen shrank only 1.6% in the tangential direction while the pre-cracking did 8.0%.

• Journal of the Korean Wood Science and Technology
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• v.40 no.5
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• pp.335-342
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• 2012

To prepare the eco-friendly fire retardant wood, Japanese red pine (Pinus densiflora), Hemlock (Tsuga heterophylla), and Radiata pine (Pinus radiata) were treated with inorganic chemicals, such as sodium silicate, boric acid, ammonium phosphate, and ammonium borate. Different combination and concentration of those chemicals were impregnated by vacuum/pressure treatment methods. The electron-beam treatment was used to increase the chemical penetration into the wood. The fire performance of the fire retardant treated wood was investigated. The penetration of chemicals into the wood was enhanced after electron beam treatment. Ignition time of the treated wood was the most effectively retarded by sodium silicate, ammonium phosphate, and ammonium borate. The most effective chemical combination was found at 50% sodium silicate and 3% ammonium borate, which satisfied flammability criteria for a fire retardant material in the KS F ISO 5660-1 standards.

• Journal of the Korean Wood Science and Technology
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• v.19 no.4
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• pp.52-61
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• 1991

In this paper, the difference of the property of absorption and desorption for five species in semi-steady state are studied. The species used are listed in Table 1 and the dimension of specimen was $8\times8{\times}T$(Tangential direction)cm and tested in various conditions. A change of average moisture content with time were measured in each cycles. The results obtained are summarized as follows. When the relative humidity in air was maximum or minimum, the distribution of moisture In wood of all specimens were illustrated by exponential curves of decrease or increased from lace 10 center of wood. From the consideration of coefficient of decrease(C), the amount of moisture change of spruce was larger than the others. The pheonomenon was considered no relation to the specific gravity in air dry, but the wood structures. The velocity of the absorption and desorption for species decreased in the order spruce(Picea sitchensis) neodobam(Fagus crenata), solsong(Tsuga heterophylla), meranti(Shorea sp.) and kaesoo(Cercidiphyllum japoicum). In case of constant temperature and water vapor pressure is changed. the amount of absorbed moisture was larger than that of constant water vapor pressure and temperature vaned. In this fact, it is considered that the property of sorption of wood is strongly influenced by vapor pressure gradient than temperature gradient.

• Journal of the Korean Wood Science and Technology
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• v.29 no.1
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• pp.9-15
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• 2001

Specific energy curves for water removal in vacuum-press drying of different thick softwoods of red pine (Pinus densiflora), white pine (Pinus koraiensis), larch (L. leptolepis) and Western hemlock (Tsuga heterophylla) were split into three sections: increased slowly, fairly constant, and increased rapidly. Calculated specific energy for 3, 5, 7, 9 and 11cm thick lumber was a value of 0.483, 0.649, 0.814, 0.977 and 1.138kWh/kg of water, respectively. Specific energy almost linearly increased as lumber thickness increased, and specific energy for severe schedule was less than that for mild schedule. Average specific energy was 0.712kWh/kg and vacuum-press drying consumed less energy as compared with any other drying methods.

• Journal of the Korean Wood Science and Technology
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• v.29 no.1
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• pp.1-8
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• 2001

Red pine (Pinus densiflora), white pine (Pinus koraiensis), larch (Larix leptolepis) and Western hemlock (Tsuga heterophylla) lumber were vacuum-press dried under three drying schedules to investigate current moisture contents (MC), drying rates and drying time factors related to five lumber thicknesses of 3, 5, 7, 9 and 11cm. Current MC could be estimated by drying factors such as lumber thickness, initial Me and drying time. Average drying rate from 30% to 15% Me was the highest for Western hemlock below fiber satuartion point, red pine, white pine and larch in the order of their magnitude. Drying rate curvilinearly decreased as lumber thickness increased. Drying time factor curvilinearly increased as lumber thickness increased.

• Journal of the Korean Wood Science and Technology
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• v.12 no.3
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• pp.15-24
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• 1984

The $3{\times}3{\times}30\;cm^3$ sized specimens of Douglas-fir(Pseudotsuga menziesii) and western hemlock(Tsuga heterophylla) in this study were soaked in four fire-retardant solutions of ammonium sulfate, monoammonium phosphate, diammonium phosphate, and aluminium chloride for 1, 24, 72, 168, and 336 hours. Subsequently they were air-dried and burned at high temperature of ca. $1,800^{\circ}C$ and for short time of 5 minutes. This study estimated the relationship between the adsorbed chemicals and the residual weight ratio or residual bending strength of these partly burned lumbers. The results were as follows; 1) In average amount of chemical adsorption, diammonium phosphate showed the largest and aluminium chloride the smallest regardless of species but monoammonium phosphate was larger in Douglas-fir than that of western hemlock. 2) The amount of chemical adsorption was larger in western hemlock than Douglas-fir on the whole. 3) The amount of chemical adsorption was increased with the increase of soaking time but the rate of increase began to decrease at 200hrs. 4) Residual weight ratios showed no difference between species but showed differences among the chemicals treated i.e. monoammonium phosphate, diammonium phosphate, ammonium sulfate and aluminium chloride in turn from the largest to the smallest. 5) MOR values showed linear increase with the increase of residual weight ratios but showed no difference in species and chemicals respectively. 6) In the relationship between amount of chemical adsorption and MOR, only diammonium phosphate showed the curve of secondary degree with significance in Douglas-fir. 7) The MOE value of burned Douglas-fir lumber increased and showed significance of 99% as the adsorbed chemical amount increased, but among the chemicals only monoammonium phosphate showed significance. The MOE value of burned western hemlock lumber didn't show significance. 8) In only Douglas-fir, the correlation between adsorbed chemical amount and work to proportional limit showed significance in only monoammonium phosphate. And in both Douglas-fir and western hemlock, the correlation between adsorbed chemicals and work to maximum load showed significance in monoammonium phosphate.

• Journal of the Korean Wood Science and Technology
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• v.41 no.3
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• pp.173-180
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• 2013

This study was carried to provide basic data for the research of the effect of PEG impregnation on preventing wood from cracking during heat treatment. Three popular softwood species were selected for investigating the PEG penetration rate and retention depending on PEG molecular weight, PEG retention after heat treatment and their EMCs. The average retentions of PEG400 were reversely proportional to the basic densities of three species and those of the other PEGs showed similar behaviour as well. It is obvious that PEG retention decreased as PEG molecular weight increased with a species. PEG impregnation increased or decreased the moisture contents of the specimens within 2%, and increased their basic densities by 16.8% as a maximum. The Weight Percentage Losses of PEG400 during heat treatment were the largest among three PEG levels, which implied that lower molecular weight PEG leached more than the highers. There was less difference in EMC between PEG impregnated and control specimens at low RH, but their difference increased at high RH.