• Journal of the Korean Wood Science and Technology
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• v.25 no.4
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• pp.99-107
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• 1997

This study was executed to test the possibility of replacement for domestic Japanese larch(Larix leptolepis) for hardwoods and to acquire the information about the effects of drying temperature on internal temperature, moisture content and drying defects. In high-temperature drying, internal temperature increased rapidly to boiling point, immediately after that point the internal temperature rising rate was reduced. In the case of drying at temperature of $125^{\circ}C$, internal temperature could reach at boiling point in a very short time. Moisture content in high-temperature drying showed constant drying rate period and first period of falling rate drying together in 4 hours since experiment begun. There was no strong correlation between initial moisture content and final moisture content. Average drying rate at $115^{\circ}C$, $120^{\circ}C$ and $125^{\circ}C$ was 1.42%/hr, 1.88%/hr and 2.02%/hr, respectively; the case of drying temperature of $125^{\circ}C$ showed most rapid drying rate. Drying rate of $125^{\circ}C$ was so rapid that it showed more severe shrinkage, bow, collapse, end check, and internal check development than in other drying conditions. The result of this study showed the strong possibility of high-temperature drying for Japanese larch, and to dry Japanese larch optimally, dry bulb temperature should not exceed $120^{\circ}C$.

• Journal of the Korean Wood Science and Technology
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• v.48 no.5
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• pp.608-617
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• 2020

For efficient use and expansion of domestic small- and medium-diameter woods, cross-laminated wood panels composed of tropical hardwoods and domestic temperate woods were fabricated, and the bending creep behavior under long-term loading was investigated. The bending creep curve of the cross-laminated wood panels showed an exponential function graph with a sharp increase at the top right side. The wood panel composed of a teak top layer and larch core and bottom layers recorded the highest initial deformation, and that composed of a merbau top layer and tulip core and bottom layers showed the lowest initial deformation. Creep deformation of the cross-laminated wood panels showed the highest value in that composed of a teak top layer and larch core and bottom layers and showed the lowest value in that composed of a merbau top layer and tulip core and bottom layers. The obtained creep deformation is 3.1-4.3 times that of merbau, however, it is remarkably lower than that of tulip and larch. The highest relative creep was recorded by the wood panel composed of merbau top layer and larch core and bottom layers, whereas that composed of the teak top layer and tulip core and bottom layers showed the lowest relative creep.

• Journal of the Korean Wood Science and Technology
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• v.31 no.1
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• pp.27-31
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• 2003

This paper presents the results of air-drying processes and mositure content (MC) distribution of red pine (P. densiflora) and Japanese larch (L. leptolepis) square timber with 14 cm and 16.5 cm of face size, respectively. The air-drying rates of square timber were comparatively high during the first 8 weeks, after that gradually decreased. The time to air dry square timber from initial MC to specified MC of 18 percent required about 26 weeks for 14.0 cm and 32 weeks for 16.5 cm square of red pine, and 32 weeks for 14.0 cm and 48 weeks for 16.5 cm square of Japanese larch. The longitudinal- and transverse MC distribution of these air-dried squares showed slight moisture gradient. The effect of face size on moisture gradient of Japanese larch square was more pronounced comparing with red pine one.

• Journal of the Korean Wood Science and Technology
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• v.36 no.3
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• pp.61-69
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• 2008

To examine the compression properties of structural members, the compression and bearing tests were conducted in parallel- and perpendicular-to-grain loading using domestic Japanese larch (Larix kaempferi (Lamb.) Carriere). Compression (bearing) properties with the length of a specimen and the contact length of the bearing plate were investigated, and deformations at each specimen length from the point of bearing force were measured to evaluate the effective end distance tabulated in the present practice (Korean Building Code). Compression (bearing) properties varied with the size of the bearing plate, and the end distance for dowel-type fastener taken into consideration of the specimen's deformation, for the safe design, should be applied with over 7 D.

• Journal of Korean Society of Forest Science
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• v.84 no.2
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• pp.207-217
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• 1995

Various factors reducing seed yield in 4 Larix species throughout the whole reproductive cycle were investigated and partitionate losses attributed to them were determined. Pollen quality, lack of pollination, and degeneration of female gametophyte played minor roles in reducing seed yield. Failure of pollinated ovules to be fertilized was an important factor causing seed loss. Embryo degeneration was also a major factor causing seed loss in all 4 species. Strobili abortion, which causes loss of all potential seeds in a cone, was the most important factor in reducing seed loss in this study. Based on the results obtained from this studs, hybridizations in either direction between European larch and Japanese larch are likely to resulting viable seed. However, hybridization between tamarack as a mother tree and European larch are not likely to result in viable seeds being produced.

• Journal of the Korean Wood Science and Technology
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• v.25 no.1
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• pp.37-41
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• 1997

Hot-water soluble extracts were prepared from medium-sized barks of Siberian larch (Larix gmelineii). The extracts were fractionated by ultrafiltration method for producing uniform quality of adhesives. Molecular weight distribution of the extracts was ranged of 100 to 300.000. pH of the extracts affected amounts of flux, and the range of pH 6~pH 8 was proper for wood adhesives, because of easy concentration and fast gelation time. Removal of particles greater than $0.45{\mu}m$ from the extracts increased both filtration speed (flux) and yields of solids in the filtrates. In ultrafiltration process. operating pressure, filtrate temperature, and flow rate significantly increased with the increase of individual condition. Ultrafiltration using PM10 membrane was very effective to fractionate and concentrate the extracts. Removal of large particles greater than 0.45 m from the extracts increased filtration speed(flux) and yields of solids in the filtrates. A gelation time was accelerated with the increasing pH of the extracts and its concentration. The Stiasny precipitate(26%) from the filtrate obtained by PM 10 membrane was very lower than that(78%) of the retentates. This ultrafiltration method was efficient for obtaining high yield purified phenolic compounds.

• Journal of the Korean Wood Science and Technology
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• v.24 no.2
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• pp.20-25
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• 1996

Wood chips of oak(Quercus mongolica) and larch(Larix leptolepis) were exploded with the optimum condition. Main components of exploded wood were separated with hot hot water and methanol. The hemicelluloses were purified from hot water extracts and alditol complexs were prepared from purified hemicellulose. And also, cellulose nitrate was prepared from extractive residue and characterized. The results can be summarized as follows. 1. Amounts of carbohydrate(72~79%) in the crude hemicellulose of larch wood was more than those of oak wood(55~66%). 2. The crude hemicelluloses were mainly composed of oligosaccharides in oak wood but those in larch wood contained about 50% monosaccharides. 3. Decolorization of hemicellulose was successful with activated charcoal and ion-exchange resin treatment. The alditol yields were 56.3~82.9%. 4. The degree of substitution(D.S.) of cellulose nitrate was 1.95~2.87 and it showed a good acetone solubility.

• Journal of the Korea Furniture Society
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• v.14 no.2
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• pp.21-29
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• 2003

This study was carried out to investigate characteristics of plywood overlaid with softwood veneers densified by resin impregnation and compression. The resin impregnability of Korean pine veneer under atmospheric pressure soaking was greater than that of larch, and impregnability of melamine resin was slightly greater than phenolic resin. It was suggested that resin impregnation ratio was affected by density and thickness of veneer. The largest melamine resin impregnation ratio of 50.7% was obtained with 1.26mm thick Korean pine veneer, and the lowest phenolic resin impregnation ratio of 11.7% with 3.41mm thick larch veneer. Therefore, it was suggested that the vacuum-pres sure-soak treatment is required at thick larch veneer. In densifying resin-impregnated veneers, densification ratio from 13.4 to 31.2% was obtained by high pressure from 15.6 to $20.8kgf/cm^2$. Impregnation of melamine resin also showed relatively greater at densification than that of phenolic resin. So it showed the degree of densification of about 20% or greater. It was seemed that adhesive bonding strength of plywood(base panel) which was directly pressed and overlaid with resin-impregnated veneer was affected by resin tackiness after resin impregnation followed by semi-drying. In laboratory scale, melamine resin impregnation was more favorable for the development of adhesive bonding strength owing to moisture control.

• Journal of the Korean Wood Science and Technology
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• v.28 no.4
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• pp.41-50
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• 2000

Cement-bonded particleboard is being used as outdoor siding material all over the world, because this composite particularly bears a light weight, high resistance against fire, decay, and crack by cyclic freezing and thawing, anti-shock property, and strength enhancement. Construction systems are currently changing into a frame-building style and wooden houses are being constructed with prefabrication type. Therefore, they require a more durability at outdoor-exposed sides. In this study, the cement hydration property for Korean pine particle, Japanese larch particle and face- and middle layer particles (designated as PB particle below) used in Korean particleboard-manufacturing company was investigated, and the rapid manufacturing characteristics of cement-bonded particleboard by supercritical $CO_2$ curing was evaluated. Korean pine flour showed a good hydration property, however, larch flour showed a bad one. PB particle had a better hydration property than larch flour. The addition of $Na_2SiO_3$ indicated a negative effect on hydration, however, $MgCl_2$ had a positive one. Curing by supercritical $CO_2$ fluid gave a conspicuous enhancement in the performances of cement-bonded particleboards compared to conventional curing. $MgCl_2$ 3%-added PB particle had the highest properties, and $MgCl_2$ 1%-added Korean pine particle had the second class with the conditions of cement/wood ratio of 2.7, a small fraction-screened particle and supercritical curing. On the contrary, the composition of non-hammermilled or large fraction-screened particle at cement/wood ratio of 2.2 was poorer. Also, the feasibility for actual use of 3%-added, small PB particle-screened fraction was greatest of all the conventional curing treatments. Relative superiority of supercritical curing vs. conventional curing at dimensional stability was not so apparent as in strength properties. Through the thermogravimetric analysis, it was ascertained that the peak of a component $CaCO_3$ was highest, and the two weak peaks of calcium silicate hydrate and ettringite and $Ca(OH)_2$ were present in supercritical treatment. Accordingly, it was inferred that the increased formation of carbonates in board contributes to strength enhancement.

• Journal of the Korean Wood Science and Technology
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• v.35 no.6
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• pp.23-30
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• 2007

Round piles of Korean larch were excavated from the foundation of ex-Chosunchongdokbu (ex-Chosun Governer-General Building), which was constructed in 1916 and dismantled later in 1996. By the record (Huh, 1996), the Korean larch logs were logged from the Yalu river area near Mt. Baekdu in North Korea. At present, however, Korean larch is not so popular in South Korea. The latewood ratio profiles and strength properties (longitudinal compression, shear, longitudinal tensile, and bending) were obtained. The ratio of latewood from pith to bark increased up to 25 years, and then it showed constant tendency at 40% with some variances. From the microscopic observation, however, the latewood ratio decreased from the heartwood to the sapwood. Compression strength was greater and bending strength was a little lower than the previous reports (references 13~15), which might be attributed to the strength reduction of old structural members by aging or damage in the compression specimens than the bending ones. The flat-grained specimens for the shear and tension test showed higher coefficient of variation (COV) than the edge-grained ones. For the better comparison of results, in case of shear and tensile strength tests, the strength values of the edge-grained specimens were thought to be adopted rather than those of flat-grained ones.