• Journal of the Korean Wood Science and Technology
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• v.43 no.1
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• pp.1-8
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• 2015

Relationship between annual ring width and physical properties of 24-year old alder woods (Alnus glutinosa L.) that had different seed origins from four provenances such as Bulgary, Italy, United Kindom, and Yugoslavia was investigated. No difference among different origins of seeds was found for the moisture content, density, and shrinkage or tangential radial (T/R) ratio. These properties had also no relationship with the growth rate. As important parameters among wood quality indices, no difference in the density or shrinkage on wood that has different growth rates was detected among alder woods from four different origins of seeds. Therefore, it is considered that higher growth rate might be a key factor for selecting the seed origin of the alder tree.

• Journal of the Korean Wood Science and Technology
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• v.47 no.1
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• pp.40-50
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• 2019

The aim of this study was to investigate the effects of density, temperature, size, and grain direction on measurement of moisture contents (MC) of wood materials non-destructively. The MC of different sizes of solid wood, glulam, and CLT from larch (larix kaempferi, $560kg/m^3$) and pine (pinus koraiensis, $430kg/m^3$) were measured using the dielectric type and resistance type meters. The specimens were conditioned in the environmental chamber to be equilibrium moisture content (EMC) of 12 % and 19 %. When density setting in dielectric type meter was increased from $400kg/m^3$ to $600kg/m^3$, the MCs of specimen (S-L-100-E) were decreased from 13.4 % to 11.3 %. However, when wood group (WG) setting in resistance type meter was changed from WG1 to WG4, the measured MCs were increased from 9.2 % to 12.3 %. When temperature setting in resistance type meters was changed from 0 to $35^{\circ}C$, the MC was decreased from 17.0 % to 13.0 %. The MCs measured by dielectric type meter for larger specimens (S-L-100-E_11.3 %, G-L-240-E_11.7 % and C-L-120-E_12.8 %) were higher than those of small size specimens (S-L-30-E_8.7 %, G-L-150-E_10.3 %, and C-L-90-E_9.7 %). The MCs measured by resistance type meter for larger specimens (G-L-240-E_11.6 % and C-L-120-E_13.3 %) were also higher than those of small size specimens (G-L-150-E_10.4 %, and C-L-90-E_11.8 %). The resistance type meter was not affected by the grain direction but the dielectric type meter were affected by the grain direction. The MC measured by resistance type meter for G-L-120-E perpendicular to grain direction was 11.5 % and the measured MC parallel to grain direction was 11.3 %. The MC measured by dielectric type meter parallel to grain direction (12.1 %) was higher than that measured perpendicular to grain direction (10.7 %).

• Journal of the Korean Wood Science and Technology
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• v.32 no.1
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• pp.67-72
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• 2004

Wood/polyethylene panels were manufactured from Populus alba × glandulosa particles and low density polyethylene particles at three mixing rates, 50:50, 60:40, and 70:30. A total of 15 wood/polyethylene panels was made at 145℃ and 5 minutes hot-press time. Wood/polyethylene panels were tested for internal bond, bending, and dimensional stabilities such as thickness swell and water absorption. Panel performance data were analyzed using the SAS programing package. The test results of the wood/polyethylene panels showed that as the polyethylene mixing rates were increased, the panel property values increased. Based on panels' dimensional stabilities, the optimum wood/polyethylene mixing ratio appeared to be 60:40.

• Journal of the Korean Wood Science and Technology
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• v.25 no.3
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• pp.58-65
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• 1997

This research was carried out to evaluate the effect of process variables on mechanical properties of the wood fiber-thermoplastic fiber composites by turbulent air mixing method. The turbulent air mixer used in this experiment was specially designed in order to mix wood fiber and thermoplastic polypropylene or nylon 6 fiber, and was highly efficient in the mixing of relatively short plastic fiber and wood fiber in a short time without any trouble. The adequate hot - pressing temperature and time in our experimental condition were $190^{\circ}C$ and 9 minutes in 90% wood fiber - 10% polypropylene fiber composite and $220^{\circ}C$ and 9 minutes in 90% wood fiber 10% nylon 6 fiber composite. Both in the wood fiber - polypropylene fiber composite and wood fiber- nylon 6 fiber composite, the mechanical properties improved with the increase of density. Statistically, the density of composite appeared to function as the most significant factor in mechanical properties. Within the 5~15% composition ratios of polypropylene or nylon 6 fiber to wood fiber, the composition ratio showed no significant effect on the mechanical properties. Bending and tensile strength of composite, however, slightly increased with the increase of synthetic fiber content. The increase of mat moisture content showed no significant improvement of mechanical properties both in wood fiber - polypropylene fiber composite and wood fiber nylon 6 fiber composite. Wood fiber - nylon 6 fiber composite was superior in th mechanical strength to wood fiber-polypropylene fiber composite, which may be related to higher melt flow index of nylon 6 fiber(22g/10min) than of polypropylene fiber(4.3g/10min).

• Journal of the Korean Wood Science and Technology
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• v.41 no.1
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• pp.42-50
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• 2013

Since 1990's, a plywood for flooring base has gotten customers' demand. Costs of raw material and production increased because of changed environment of industry. Tropical timber such as Red Meranti (Shorea acuminate) used for raw material of the floor has been depleting beside countries in South Eastern Asia changed species of afforestation. As a result, it gets hard to secure good quality of raw material for plywood. Moreover plywood price is increased suddenly after earthquake in Japan. Eucalyptus (Eucalyptus globulus) in china has been using for raw material as a countermeasure of changed environment of industry. In this study, possibility of using flooring consisted of Eucalyptus veneer as crossband layers was checked by deflection experiments. Flooring consisted of Red Meranti was used for comparison. Two factors which impact on deflection are a type of density gradient and density difference between Long-grain veneer and Short-grain veneer. Red Meranti samples are M type of density gradient on the other hand Eucalyptus samples are W type of density gradient. The more samples have high density difference, the more deformation was checked. A sample which has big density difference between core and cross bands layer warp more also deform. Flooring was deformed smaller than plywood and samples which have big density difference was deformed more.

• Journal of the Korean Wood Science and Technology
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• v.44 no.2
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• pp.231-240
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• 2016

The change in chemical compositions of leachate and medium density fiberboard (MDF) from a laboratory-scale simulated landfill which constructed in a plastic container containing alternating layers of soil and MDF was investigated to evaluate decomposing of MDF in soil. Four treatments were conducted: 1) MDF in soil, 2) MDF only, 3) cured UF resin in soil, and 4) soil only. Molecular weight (MW) distribution of compounds in leachate from soil only treatment did not change over time. In UF resin in soil treatment, the MW distribution shifted to a lower MW distribution over time, while the peak shifted to the left indicated changing to higher MW distribution in leachate from treatment 1 and 2 contained MDF. Higher percent nitrogen in leachate was observed in MDF containing treatments due to the UF resin in the MDF. The percent carbon slightly increased in MDF only while that greatly decreased in MDF in soil treatment maybe due to bacterial activity. The percent of extractable materials from the MDF decreased greatly on day 35 compare to day 0, and subsequently did not change much on day 77. In contrast, percent holocellulose and lignin did not change much over time. No structural change of the wood fiber in MDF occurs during the study. Water-soluble materials from MDF in soil contributed the change in chemical composition of leachate.

• Journal of the Korean Wood Science and Technology
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• v.36 no.2
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• pp.29-38
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• 2008

It is well-known that the strength properties of wood connections depend on the density of the wood members, the diameter of the fasteners, the number of fasteners, and the arrangement of the fasteners, etc. In this study, the connection with inserted steel plates and drift pins was made in different configurations. The specimens were Larch and Sugi glulam connections. The specimens were loaded in tension, and the yield loads of the connections were obtained. The values obtained from the tests were compared with the predicted values. Good agreement between the yield loads obtained from the tension failure tests and the predicted yield loads were shown. It was shown that the density of the wood member barely affected the strength properties of the connections. The strength decreases of the Sugi glulam connections by the group effect were less than those of the Larch glulam connections.

• Journal of the Korean Wood Science and Technology
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• v.42 no.3
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• pp.251-257
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• 2014

For new use development of miscanthus sinensis var. purpurascens, which investigated properties of ceramics made from different carbonization temperature ($600{\sim}1,200^{\circ}C$) and percentage of resin impregnation(30~60%) using a mincanthus board. As the carbonization temperature increased, the density, thickness shrinkage, linear shrinkage, weight loss were increased. As the percentage of resin impregnation increased, the density, linear shrinkage and weight loss were increased. On the other hand, thickness shrinkage decreased.

• Journal of the Korean Wood Science and Technology
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• v.49 no.4
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• pp.360-370
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• 2021

For the purpose of finding new uses for Miscanthus sinensis var. purpurascens, this study first constructed boards with the particles of the plant and impregnated them with phenolic resin at resin impregnation rates of 30 ± 2%, 40 ± 2%, 50 ± 2%, and 60 ± 2%. The impregnated boards were then carbonized at the carbonization temperature of 800℃, after which their density and mechanical properties were examined according to the different resin impregnation rates. The results showed that density, flexural strength performance, Brinell hardness, and compressive strength increased as the resin impregnation rate increased, thus affecting the physical and mechanical properties of the ceramics made of M. sinensis var. purpurascens particles.

• Journal of the Korean Wood Science and Technology
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• v.34 no.1
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• pp.23-31
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• 2006

X-ray transit materials with straight path and the its intensity is proportional to the density of materials. Therefore, X-ray has been extensively used as a nondestructive evaluation (NDE) method in various fields. This study was carried out for development of a portable X-ray CT (computed-tomography) system to detect deteriorations of wood members in buildings. Based on the results of our previous study, a procedure of CT image reconstruction was established In order to verify the applicability of developed system, CT images of three wood disks were reconstructed by newly developed procedure and compared with the prototypes. From the results of this study, it was shown that the newly developed system could be used not only to determine the shape, size, and position of defects, but also to find the density distribution in cross section of wood structure members. The density distribution may be utilized to clarify the reason of wood deterioration and to provide the preventive method on how to treat or repair wood buildings. Because it was initial stage of system development, there were some limitations concerned with measuring equipment and image reconstruction algorithm. Especially, measuring time including equipment setup time was longer and measuring accuracy was lower than we expected. Therefore, we planned some additional studies on improvement of equipment and algorithm to enhance the capability of X-ray CT system.