• Journal of the Korean Wood Science and Technology
• /
• 제12권2호
• /
• pp.3-9
• /
• 1984

This study was carried out to examine the practicality of DAP[$(NH_4)_2HPO_4$] as fire retardant for plywood by static bending test the redried plywoods which had been soaked in 20% $(NH_4)_2HPO_4$ solution. Being hot/cold soaked in the solution for 3/3, 6/3, 9/3 and 12/3 hours and redried by cyclic press-drying method at the platen temp. of 130, 145, 100 and $175^{\circ}C$, the treated plywoods were tested to offer the mechanical data, that is, $S_{pl}$(stress at proportional limit), MOE(modulus of elasticity), MOR(modulus of rupture) and $W_{pl}$(work per unit volume to proportional limit ) in flexure. The results obtained were summarized as follows. 1. $S_{pl}$ of fire retardant treated plywoods ("FRP" would be used hereinafter) decreased as the platen temperature increased, but it was superior to that of non-treated plywoods(Control) at $160^{\circ}C$ or higher. 2. MOE of FRP decreased roughly with the increase of temperature, hut this tendency was not constant. And the value of FRP was higher than that of Control even at $175^{\circ}C$. 3. MOR of FRP showed same temperature-dependent tendency as MOE, but it was influenced more sensitively at the higher temperature. 4. $W_{pl}$ of FRP also decreased gradually with the increase of platen temperature and the value in DAP 9/3 treatment was Jess than 70% of control plywoods. 5. In view of redrying time and mechanical properties, the most reasonable platen temperature for DAP treated FRP was $160^{\circ}C$ in this study.

• Journal of the Korean Wood Science and Technology
• /
• 제11권3호
• /
• pp.31-38
• /
• 1983

This experiment was carried out to improve the physical and mechanical properties of sawdust-board by combining with reinforce material, that is, plastic wire screen and steel wire screen. In experiment results, the density of sawdust-board reinforced with three steel wire screens was highest and its bending strength was also highest. Wastepaper-5% mixed sawdust-board showed as high bending strength as other boards, and therefore the possibility of using wastepaper as raw materials for boards. The sawdust-board with steel wire screen was not ruptured immediatedly after having been deformed by static loading. However, plywood showed higher bending strength than the reinforced sawdust-boards.

• Journal of agriculture & life science
• /
• 제46권2호
• /
• pp.43-48
• /
• 2012

This study was investigated on the properties of board made from Miscanthus sinensis var. purpurascens particles differed in density of board and mixed ratio of powder type- and liquid type-phenolic resin. As the board density increase, thickness swelling and bending strength increased while water absorption decreased. With increasing the resin content, water absorption and thickness swelling decreased while MOR and internal bond strength increased. The board made of liquid type phenol-formaldehyde resin was low in water absorption and thickness swelling, and there were similar bending strengths between power type- and liquid type-phenol resin in resin cont of 11% and 13% at the board density $0.4g/cm^3$ and internal bond strength was higher with liquid type-phenolic resin in its bending strength.

• Journal of agriculture & life science
• /
• 제46권2호
• /
• pp.9-17
• /
• 2012

In this study, in addition to the green tea - wood fiber hybrid composite boards of previous researches, to make effective use of saw dust of domestic cypress tree with functionalities and application as interior materials, eco-friendly hybrid composite boards were manufactured from wood fiber, green tea and saw dust of cypress tree. We investigated the effect of the component ratio of saw dust and green tea on dynamic MOE (modulus of elasticity). Dynamic MOE was within 1.41~1.65 GPa, and showed the highest value in wood fiber : green tea : saw dust = 50 : 40 : 10 of the component ratio, and had the lowest value in 50 : 30 : 20 of component ratio. These values were 1.4~1.6 times higher than static bending MOE of wood fiber - saw dust - green tea hybrid composite boards, and were 2.0~2.9 times lower than those of green tea - wood fiber hybrid composite boards reported in the previous researches. From the results of correlation regression analyses between dynamic MOE and static strength performances, a very high correlation coefficients were obtained, therefore it was found that static bending strength performances can be estimated with a high reliability from dynamic MOE.

• Journal of the Korean Wood Science and Technology
• /
• 제38권1호
• /
• pp.1-10
• /
• 2010

In this study, to study an effective use and improve strength performances of woods and wood-based materials, three-ply hybrid laminated woods which are composed of spruce in the face and three kinds of wood-based boards (MDF, PB, OSB) in the core were manufactured, and the effect of constitution elements used for the core laminae on bending creep performances was investigated. The shape of creep curves showed exponential function plots which the upper right side was increased, and differed among the kinds of wood-based boards used for the core laminae of hybrid laminated wood. The creep deformation perpendicular to the grain of faces of hybrid laminated woods was in order $C_{\perp}$(P) > $C_{\perp}$(M) > $C_{\perp}$(O) with PB, MDF and OSB in the core, respectively. It was found that the creep deformation arranged with OSB in the core had 2 times smaller than those arranged with MDF and PB in the core. By hybrid laminating, the creep deformation of spruce perpendicular to the grain was markedly decreased. On the other hand, the creep deformation parallel to the grain of the faces ($C_{\parallel}$ type) of hybrid laminated woods was in order $C_{\parallel}$(P) > $C_{\parallel}$(O) > $C_{\parallel}$(M) with PB, OSB and MDF in the core. The ratios among three hybrid laminated woods were considerably decreased, especially the difference between $C_{\parallel}$(P) and $C_{\parallel}$(O) hybrid laminated woods arranged with PB and OSB in the core was very small. These values showed 0.108~0.464 times smaller than creep deformation of three wood-based boards and it was found that creep deformation of three wood-based boards was considerably decreased by hybrid laminating. Creep anisotropy of hybrid laminated woods was greater in creep deformation than in initial deformation, whereas it was found that the values was much smaller than that of spruce parallel laminated woods.

• Journal of the Korean Wood Science and Technology
• /
• 제40권4호
• /
• pp.257-267
• /
• 2012

In this study, the method for heat treating wood using superheated steam (SHS) was designed and applied. The physical and mechanical properties of Korean Pine (Pinus koraiensis Siebold & Zucc.) lumber heat-treated by SHS at $170^{\circ}C$ and 0.4 MPa for 10 hours were compared with those of non-treated and normal heat-treated wood. The amount of adsorbed water and equilibrium moisture content of the SHS treated wood were lower than non-treated wood. On the other hand the compressive strength parallel to grain and the bending strength of SHS treated wood were higher than those of non-treated wood. The hygroscopicity of SHS treated wood was similar to normal heat treated wood at $220^{\circ}C$. Internal checks that often occur during normal heat treatment were not developed at SHS treatment. Also, SHS treatment are effective in control of internal checks occurrence and resin exudation.

• Journal of the Korean Wood Science and Technology
• /
• 제45권5호
• /
• pp.519-524
• /
• 2017

Physical, mechanical and deteriorating properties of Phellodendron amure were investigated. Air dried density located indoor was 0.41 but $0.43g/cm^3$ outdoor. In oven dry shrinkage, T/R ratio for located indoor was 1.40 but 1.32 outdoor. Hygroscopic property at $40^{\circ}C$ with 90% relative humidity was 16.30% for indoor and 15.80% for outdoor. Compressive strength for outdoor conditioned sample was 43.81 MPa but 40.33 MPa for indoor conditioned. Also bending strenght for outdoor conditioned was 84.63 MPa but 68.80 MPa for indoor conditioned. Impact strength was 3.43 and $4.00J/cm^2$ indoor and outdoor, respectively. Hardness at cross-section was 47.92 and 49.20 MPa indoor and outdoor, respectively. With one-year conditioning at indoor or outdoor, there was no significantly different in strength properties, which came from strong resistance for deterioration. Also Phellodendron amure wood showed dimensionally stable raw material based on low T/R ratio.

• Journal of the Korean Wood Science and Technology
• /
• 제41권3호
• /
• pp.211-220
• /
• 2013

The nailed joints in wood construction are commonly designed to resist and carry the lateral load but also subject to withdrawal force like uplift load due to the wind. This research was conducted to evaluate the performance of nailed joint composed of dimension lumber and sheathing materials through the nail withdrawal and unsymmetric double shear joint test, and then compared to current design values. The withdrawal strength was greatly dependant on wood specific gravity, and the withdrawal strength of I-joist with OSB showed higher value in spite of low specific gravity. The maximum withdrawal loads were greater than that of derived current design values about 5 times. The lateral resistance of Japanese larch/OSB nailed joints was higher than that of SPF/OSB nailed joint, and derived allowable lateral strength of nailed joints in this study exceeded the current design values. The failure mode of nailed joints was primarily due to the nail bending and this tendency was notable in SPF/OSB nailed joint.

• Journal of the Korean Wood Science and Technology
• /
• 제41권1호
• /
• pp.33-41
• /
• 2013

This study was performed to analyse cause of quality deterioration using byproduct of plywood and to determine physical and mechanical properties of particleboard used new bonding condition we found. The result of bending strength of Com-Ply board using EMDI is 57.7 $N/mm^2$ on linear direction and 25.1 $N/mm^2$ on vertical direction. EMDI has better water-resisting qualities than Urea formaldehyde adhesive according to result of thickness swelling and water absorption test. Pre-treatment soaked particle 72 hours in water caused increase of HCHO emission.

• Journal of the Korean Wood Science and Technology
• /
• 제43권4호
• /
• pp.429-437
• /
• 2015

It has been known that acetylation improves the dimensional stability of wood. Liquid phase acetylation is more popular than gas-phase acetylation for the effectiveness of weight gain of wood. In this study domestic red and Korean pine specimens were liquid phase acetylated and their physical properties, such as density, bending strength, dimensional stability etc., were investigated. Acetylation increased the average weights of red and Korean pine specimens by 10.4% and 9.2%, respectively, and their average oven-dry densities were increased by 6.9% and 4.6%, respectively. Acetylation did not influence on modulus of rupture (MOR), modulus of elasticity (MOE) and dynamic MOE (DMOE). The average percentage reduction in hygroscopicity (PRH) of red and Korean pine specimens were respectively 20.6% and 13.8%, while the average percentage reduction in water soaking (PRW) were respectively 20.0% and 8.5%. Thus it can be concluded that the liquid acetylation improved the dimensional stability of red pine specimens more than that of Korean pine specimens.