• Journal of the Korea Furniture Society
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• v.21 no.1
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• pp.62-71
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• 2010

This study was carried out to investigate the physical and mechanical properties of 6 hardwoods before and after heat treatment in an effort to produce the high quality industrial lumber product. The object of the research was to design living products with heat treated woods. The results were as follows. Specific gravities of green woods were in range from 0.87 to 1.12. The specific gravities of never treated woods showed higher than those of the heat treated woods. The shrinkage of heat treated woods when green to air & oven dry was significantly low, compared to never treated woods. The compression strengths parallel to grain of heat treated woods showed higher than those of never treated woods. The moduli of rupture (MOR) of never treated and heat treated woods were $170.37N/mm^2~107.07N/mm^2$ and $122.78N/mm^2~61.27N/mm^2$ respectively. MORs of heat treated woods showed lower than those of never treated woods. The modulus of elasticity (MOE) of heat treated woods showed higher than those of never treated woods.

• Journal of the Korea Furniture Society
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• v.20 no.5
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• pp.457-466
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• 2009

This study was carried out to investigate the physical and mechanical properties of 6 hardwoods before and after heat treatment in an effort to produce the high quality industrial lumber product. The results were as follows. Specific gravities of green woods were in range from 0.90 to 1.10. The specific gravities of never treated woods showed higher than those of the heat treated woods. The shrinkage of heat treated woods when green to air & oven dry was significantly low, compared to never treated woods. The compression strengths parallel to grain of heat treated woods showed higher than those of never treated woods. The moduli of rupture (MOR) of never treated and heat treated woods were $176.4N/mm^2{\sim}102.8N/mm^2$ and $100.1N/mm^2{\sim}61.2N/mm^2$ respectively. MORs of heat treated woods showed lower than those of never treated woods. There was no significant change in the modulus of elasticity (MOE) before and after heat treatment.

• Journal of the Korean Wood Science and Technology
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• v.46 no.6
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• pp.726-734
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• 2018

In this study, for using effectively domestic (temperate) small and medium diameter logs as a wooden floorboard, cross-laminated wood panels were manufactured using domestic larch and tulip woods as a base material for teak and merbau wood flooring, and static bending strength performances were measured to investigate the applicability as the base materials of wooden flooring in place of plywood. Static bending MOE was much influenced by the strength performances of the top layer lamina than that of the laminae for base materials. Bending MOR showed the higher values in tulip wood that was hardwoods than in larch wood that was softwoods regardless of the strength performances of the top layer laminae, and it was found that the values were much influenced by the strength performances of the base materials used in the core and bottom layers. However these values were 1.4-2.5 times higher values than the bending strength of the wooden floorboards specified in KS, it was found that it can be sufficiently applied to the base materials of wooden floorboards in place of plywood.

• Journal of the Korean Wood Science and Technology
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• v.29 no.3
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• pp.36-46
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• 2001

This study was to find a way of reusing wood and plastic wastes, which considered as a troublesome problem to be solved in this age of mass production and consumption, in manufacturing wood fiber-polypropylene fiber composite panel. And the feasibility of this composite panel as a substitute for existing headliner base panel of automobile was also discussed, especially based on physical and mechanical performance. Nonwoven web composite panels were made from wood fiber and polypropylene fiber formulations of 50 : 50, 60 : 40, and 70 : 30, based on oven-dry weight, with densities of 0.4, 0.5, 0.6, and 0.7 g/$cm^3$. At the same density levels, control fiberboards were also manufactured for performance comparison with the composite panels. Their physical and mechanical properties were tested according to ASTM D 1037-93. To elucidate thickness swelling mechanism of composite panel through the observation of morphological change of internal structures, the specimens before and after thickness swelling test by 24-hour immersion in water were used in scanning electron microscopy. Test results in this study showed that nonwoven web composite panel from wood fibers and polypropylene fibers had superior physical and mechanical properties to control fiberboard. In the physical properties of composite panel, dimensional stability improved as the content of polypropylene fiber increased, and the formulation of wood fiber and polypropylene fiber was considered to be a significant factor in the physical properties. Water absorption decreased but thickness swelling slightly increased with the increase of panel density. In the mechanical properties of composite panel, the bending modulus of rupture (MOR) and modulus of elasticity (MOE) appeared to improve with the increase of panel density under all the tested conditions of dry, heated, and wet. The formulation of wood fiber and polypropylene fiber was considered not to be a significant factor in the mechanical properties. All the bending MOR values under the dry, heated, and wet conditions met the requirements in the existing headliner base panel of resin felt.

• Journal of the Korean Wood Science and Technology
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• v.11 no.3
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• pp.39-48
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• 1983

This research was performed to investigate the manufacturing possibility of the particleboard treated with commercial fire retardant chemicals. Laboratory test boards at this investigation were made from particles treated by soaking into 5, 10, 15, and 20 percent concentration solutions of ammonium sulfate and Minalith before resin was applied. According to the results, MOR (modulus of repture) and MOE (modulus of elasticity) in flexure exceeded type 100 (100 kgf/$cm^2$, $1.5{\times}10^4\;kgf/cm^2$) of the Korean Industrial Standard (KS F 3104). Except for 15 and 20 percent chemicals concentrations of Minalith, every internal bond stress values met type 100 (1.5 kgf/$cm^2$) of KS F 3104. However thickness swelling values of fire retardant treated particleboards were not reached in the Standard (12%).

• Journal of Korea Foresty Energy
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• v.25 no.2
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• pp.1-8
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• 2006

The physical, mechanical and chemical properties of old and new Korean red pine (Pinus densiflora) were analyzed. The old woods were from dismantled timbers of Bonjungsa temple. The crystallized resin in the latewood was observed by microscopic analysis. Also, reduction of specific gravity, occurrence of microscopic cleavage of tracheid was observed in the old wood. The angle of microscopic cleavage of tracheid is estimated with the same angle of micro-fibril angle of 52 layer. The bending, compression and shear strength of old world were decreased about 35-27% than those of new wood. Dynamic modulus of elasticity measured by ultrasonic nondestructive test has the tendency of reducing by the time elapse of the wood usage. Therefore, deterioration of wood could be measured by reduction of specific gravity and dynamic MOE. The static MOE and mechanical properties of old wood could be predictable by measuring dynamic MOE in the longitudinal direction. Extractives of the old wood in 1-% NaOH solution are larger quantity than new wood. Therefore the decay of the wood could be evaluated by analyzing the chemical compound, especially 1-% NaOH solution. The results of this research could be used for understanding and prediction of the changing properties with elapsing time of wood.

• Journal of agriculture & life science
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• v.46 no.6
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• pp.75-86
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• 2012

In this study, eco-friendly hybrid composite boards were manufactured from green tea, 3 kinds of charcoals and wood fiber for developing interior materials to reinforce the strength performances and the functionalities in addition to performances of the hybrid composite boards composed of green tea and wood fiber. The effects for the kind and the component ratio of raw materials on dynamic MOE (modulus of elasticity) were investigated, and static bending strength performances were nondestructively estimated. Dynamic MOEs were highest in the hybrid composite boards composed of green tea, fine charcoal and wood fiber on the whole. However, the difference caused by the kind of charcoals was small. These values decreased with increasing component ratios of green tea and charcoals. The hybrid composite boards using $E_1$ grade urea resin had the higher values than those using $E_0$ grade urea resin, however the difference between them markedly decreased than that of hybrid composite board composed of green tea and wood fiber, and it was found that these values were markedly improved than those of the hybrid composite boards composed of green tea and wood fiber. There were mostly high correlations with significance at 1% level between dynamic MOEs and static bending strength performances, and this means that the static bending strength performances can be estimated from dynamic MOE.

• Journal of the Korean Wood Science and Technology
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• v.27 no.1
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• pp.37-49
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• 1999

The effect of fire-retardant treatment and redrying on the mechanical properties of radiata pine sapwood were evaluated. Small, clear specimens were treated with three different fire-retardant(FR) chemicals, borax-boric acid(BRX), minalith(MIN), and pyresote(PYR), with target retentions of 30 and 60kg/$m^3$, and then redried at maximum dry-bulb temperature of $25^{\circ}C$, $60^{\circ}C$, $80^{\circ}C$ or $110^{\circ}C$. Each specimen, including untreated and water-treated controls, was tested in static bending and in compression parallel to grain. The extent of strength reduction was dependent on the type of FR chemicals, retention, and redrying temperature, and a highly significant interaction existed between FR treatment and redrying temperature. Modulus of rupture(MOR) and work to maximum load(WML) were significantly decreased by FR treatment and redrying. None of three FR chemicals adversely affect modulus of elasticity (MOE) and maximum crushing strength(MCS). MOE of BRX treatment and MCS of both BRX and PYR treatment increased significantly compared to untreated controls. No significant differences existed between retention levels except for MOE and MCS of some combinations of FR chemicals and redrying temperatures. Although MOE and MCS was not significantly affected by any of the redrying temperatures, these properties were generally decreased with the increase in redrying temperature. The significant reduction in MOR and WML was observed in BRX treatment when dried at temperatures of $60^{\circ}C$ and above, and in MIN and PYR treatment when dried at temperatures of $80^{\circ}C$ and above. Consequently, BRX-treated radiata pine should not be redried at temperatures >$60^{\circ}C$, and MIN- and PYR-treated radiata pine should not be redried at temperatures > $80^{\circ}C$ where bending strength and energy-related properties are important design considerations.

• Journal of the Korean Wood Science and Technology
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• v.27 no.2
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• pp.31-37
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• 1999

This study was carried out to develop the Korean paper(Hanji) sludge-wood fiber composite boards utilizing the relinquished sludges occurring from the making process of Korean classic paper Hanji. The bark of paper mulberry(Broussonetia kazinoki Sieb.) has been used as a raw material since past hundreds and thousands years. Korean paper(Hanji) sludge was divided into two kinds, the one was the white sludge from the first stage and the other was the black sludge occurring from the final stage of Korean paper(Hanji) making. Four levels of the mixed ratio of each white or black sludge to wood fiber(10:90, 20:80, 30:70 and 40:60), three levels of the resin adhesives(PMDI, urea and phenol resin) and three levels of the density(0.60, 0.75 and 0.90) were designed to investigate the mechanical properties of Korean paper(Hanji) sludge-wood fiber composite boards. From the results and discussion, it could be concluded as follows : 1. In the white and black sludge-wood fiber composite boards, bending modulus of rupture showed the clear decreasing tendency according to the increase of sludge additive, but it was clearly increased with the increase of specific gravity. Modulus of elasticity showed the same tendency as in the modulus of rupture, and also tensile and internal bonding strength had the same tendencies as in these bending properties. 2. Among the resin adhesives, PMDI or urea resin showed great values in MOR of white sludge-wood fiber composite board, but urea resin was greater than PMDI in MOR and MOE of black sludge-wood fiber composite board. Tensile and internal bonding strength showed the same tendencies as in white sludge-wood fiber composite board. 3. It is suggested that the white sludge-wood fiber composite boards bonded with PMDI or black sludge-wood fiber composite boards bonded with urea resin were able to made similar boards to general fiberboard by the mixed ratio 20:80 of sludge to wood fiber.

• Journal of the Korean Wood Science and Technology
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• v.38 no.6
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• pp.470-479
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• 2010

In this study, the visual grading based on the visual characteristics and structural timber bending test were conducted for domestic yellow poplar dimension lumber. Structural performance of domestic yellow poplar dimension lumber was conducted through the evaluation of strength and stiffness. Visual grading rule of yellow poplar dimension lumber did not exist in Korea. Visual grading of yellow poplar dimension lumber was performed according to the NSLB (Northern Softwood Lumber Bureau) standard grading rules including several hardwood dimension lumber. The allowable bending stress was calculated from the results of a visual grading. Compared with NDS (National Design Specification), the yellow poplar dimension lumber showed enough strength for structural uses. In addition, the visual grading was performed according to the KFRI (Korea Forest Research Institute) grading rule to calculated allowable bending stress and to evaluated the feasibility. The yellow poplar was classified into the pine groups by the KFRI criteria regulated by specific gravity. Allowable bending stress based on weibull distribution had became highly than KFRI criteria, as No. 1 (10.0 MPa), No. 2 (7.4 MPa) and No. 3 (4.1 MPa). And the availability of yellow poplar dimension lumber for structural uses had been confirmed. The Modulus of Elasticity (MOE) of domestic yellow poplar dimension lumber had not met the NDS and KFRI criteria. However, for the use of domestic yellow poplar, average values of MOE which obtained through this test were suggested as design value for domestic yellow poplar. Design values were supposed No. 1, 2 (9,000 MPa) and No. 3 (8,000 MPa).