• Journal of the Korean Wood Science and Technology
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• 제25권4호
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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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• 제48권5호
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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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• 제31권1호
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• pp.27-31
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• 2003

이 논문은 소나무와 일본잎갈나무의 변장 14.0 cm와 16.5 cm인 큰 정각재의 천연건조과정과 함수율분포에 관한 내용으로서 건조속도는 건조개시 첫 8주 동안 비교적 컸었으나, 그 이후부터 점차 감소하였다. 생재에서 규격함수율 18% 수준까지 건조시간은 소나무 14.0 cm와 16.5 cm가 각각 26주와 32주이고, 일본잎갈나무의 경우는 각각 32주와 48주이었다. 이들 정각재의 재장방향과 두께방향의 수분경사는 비교적 완만하였다. 일본잎갈나무의 수분경사는 소나무의 것보다 컸었고, 일본잎갈나무의 변장의 크기가 수분경사에 미치는 영향은 소나무의 것보다 컸었다.

• Journal of the Korean Wood Science and Technology
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• 제36권3호
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• pp.61-69
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• 2008

구조부재의 압축성능을 검토하기 위하여 낙엽송 소재에 대해 섬유방향 및 섬유직각방향 압축시험을 행하였다. 시험편의 길이와 가압판의 크기에 따른 압축성능을 검토하였으며 현행 기준의 최소끝면거리의 적정성에 대해 검토하기 위하여 다우얼 지압지점으로부터 시험편의 섬유방향에 대해 변형율 변화를 측정하였다. 가압판의 크기에 따라 압축성능은 다르게 나타났으며, 다우얼형 파스너의 최소끝면거리(end distance)는 내부변형을 고려할 경우 현행 7 D보다 높게 적용하여야 안전한 것으로 나타났다.

• 한국산림과학회지
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• 제84권2호
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• pp.207-217
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• 1995

4가지 낙엽송(구주낙엽송, 일본낙엽송, 시베리아낙엽송, tamarack)의 종자결실에 영향을 미치는 요인과 각각의 요인들에 의한 종자손실율을 조사하였다. 화분의 질, 수분의 실패, female gametrophyte의 퇴화 등은 종자결실에 큰 영향을 미치지 않았으나, 수정실패, 배의 퇴화 등은 조사된 4개의 수조에서 모두 주요한 종자손실요인으로 조사되었다. 조사된 요인들 중 종자수확에 가장 큰 영향을 미치는 것은 수분후 strobilus자체가 퇴화되는 것이었다. 조사된 4가지 교배조합중 구주낙엽송 또는 일본낙엽송을 모수로 하는 것이 종자생산측면에서는 가장 바람직한 것으로 나타났으며, tamarack을 모수로 하는 교배조합은 건전한 종자생산을 하지 못할 것으로 판단된다.

• Journal of the Korean Wood Science and Technology
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• 제25권1호
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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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• 제24권2호
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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.

• 한국가구학회지
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• 제14권2호
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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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• 제28권4호
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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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• 제35권6호
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• pp.23-30
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• 2007

구 조선총독부 청사의 기초 말뚝으로 사용된 원주는 1916년 건물 기초를 다지기 위해 사용되었던 것으로 1996년 청사의 철거와 함께 건축 당시 사용되었던 만여 개 중 백여 개가 발굴되었다. 이 말뚝은 문서 및 수종 식별결과 잎갈나무(Larix gmelini var. principis-ruprechtii Pilger)로 확인되었으며 현재 남한에서는 축적량이 매우 적은 수종으로 청사 건립 당시 백두산 압록강변에서 벌채한 것으로 기록되어 있다. 발굴된 잎갈나무 말뚝에 대해서 만재율 분포와 강도 특성을 알아보기 위해 주사(scanning)에 의한 횡방향 만재율 분포와 압축, 전단, 휨, 인장 시험을 행하여 그 강도 성능을 검토하였다. 만재율은 수로부터 수피 방향으로 연륜의 증가에 따라 증가하다가 약 25연륜 이후에는 40% 정도로 안정적인 경향을 나타냈다. 그러나 현미경에 의한 관찰에서는 심재부, 심변재 경계부, 변재부로 수령이 증가되면서 만재율은 감소하였다. 종압축강도는 높게 나타났으나 휨강도는 오히려 다소 낮게 나타나 고부재의 경우처럼 열화, 손상 등에 의한 강도적 감소는 압축형 시험보다 인장형 시험에서 영향을 크게 받는 것으로 밝혀졌다. 전단강도와 인장강도에 있어서는 접선단면 시험편의 변이계수가 높게 나타나 안정적인 강도 성능 비교를 위해서는 방사단면 시험편에 의한 강도 값이 채택되어야 할 것으로 검토되었다.