• Journal of the Korean Wood Science and Technology
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• 제44권6호
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• pp.913-922
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• 2016

This study attempted to measure molecular weight (MW) of melamine-urea-formaldehyde (MUF) resins prepared by two different synthesis methods: the one-step MUF resins were synthesized in one batch procedure, while the two-step MUF resins were prepared by a physical mixing of urea-formaldehyde (UF) resin with melamine-formaldehyde (MF) resin that had been synthesized in a separate procedure. The properties of medium density fiberboard (MDF) panels bonded with two types of MUF resins were also investigated. MWs of these MUF resins were measured using gel permeation chromatography (GPC). In addition, this study measured the MWs of one-step MUF resin during its synthesis procedure. The performance of two types of MUF resins was evaluated by determining properties of MDF panels prepared in laboratory. As the synthesis procedure progressed, both number average MW ($M_n$) and weight average MW ($M_w$) of one-step MUF resin gradually increased, while the polydispersity index (PDI) decreased. And low Mw species of the resin predominantly decreased as the synthesis step progressed. The one-step MUF resin showed greater $M_n$ and $M_w$ than those of the two-step ones even though the PDI values of both resins were very similar each other. As expected, the one-step MUF resin resulted in better properties of MDF panels than those of two-step resins. In particular, the one-step MUF resin provided better internal bond (IB) strength and thickness swelling (TS) with MDF panels than those of two-step ones, indicating better water resistance of the one-step resin. These results suggest that the preparation method of MUF resins have a great impact on the MW and final panel properties.

• Journal of the Korean Wood Science and Technology
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• 제45권1호
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• pp.62-71
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• 2017

본 연구는 쌀의 도정과정에서 발생되는 농업부산물인 왕겨를 탄화시켜 만든 왕겨숯을 톱밥과 혼합하여 밀도별, 수지첨가율별 및 톱밥첨가율별로 보드를 제조하고 기초물성을 측정하여 보드 재료로서의 이용가능성을 검토하였다. 수분흡수율은 수지첨가량 25%일 때 80.09%로 가장 낮은 값을 나타냈고, 밀도가 증가하고 톱밥첨가량이 감소할 때 수분흡수율이 감소하는 경향을 나타냈다. 또한 측정된 두께팽윤율은 KSF 3104 파티클보드의 품질규정에 만족시키고 있어 치수안정성 부분에서 건축내장재로 활용가능성이 확인되었다. 박리강도는 수지첨가량 25%일 때 $0.244N/mm^2$으로 KSF 3104 파티클보드의 품질기준을 만족시켰지만, 나머지 조건에서는 현저하게 낮은 값을 나타내 조건을 충족시키지 못하였다. 밀도, 수지첨가율, 톱밥첨가율이 증가할수록 경도도 증가하는 경향을 나타냈다.

• 한국가구학회지
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• 제19권6호
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• pp.411-419
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• 2008

Xylia xylocarpa is fast-growing trees that are currently planted on trial basis in Sabah, Malaysia. The wood quality of trees grown in Sabah may differ from those grown in other places due to the environmental factors. Five 9-year-old trees of each species were extracted from their respective plots at Luasong, Tawau. Wood specimens were prepared from three height levels; bottom, middle and top, at the inner and outer radial positions. The within-tree and between-tree variations of physical properties of these species were analyzed. The basic density, oven-dry density and green moisture content(MC) are 0.72g/$cm^3$, 0.78g/$cm^3$ and 49.8% respectively. The shrinkage from green to oven-dry conditions for the radial and tangential directions were 3.35% and 5.76%, respectively. The trends of within-tree variations for most properties were more consistent in radial rather than vertical direction. This suggests diameter growth to be a more important factor contributing to the variations compared to height. Samples from the outer part of the stem were found to have higher density, shrinkage and mechanical strengths. The between-trees variations of some wood properties were found to be significantly different, probably due to genetic and micro-environmental factors. Significant correlation was recorded among the physical properties of the species. The true potential of X. xylocarpa for end-uses would be enhanced by further research such as the study on properties of wood from different sites and other properties like durability, seasoning, processing and machining characteristics. The characteristics of X. xylocarpa are comparable to a number of local popular hardwood species, indicating its suitability for heavy construction uses.

• Journal of the Korean Wood Science and Technology
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• 제41권4호
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• pp.293-301
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• 2013

본 연구에서는 수분 흡착효과가 있다고 알려진 커피박을 첨가하여 중밀도섬유판을 제조한 다음 물성과 강도특성을 조사하여 커피박의 중밀도섬유판 원료로써의 가능성을 확인하고자 하였다. 커피박은 주로 인스턴트커피 제조 시 많이 발생하는 찌꺼기인데 가수분해된 것을 전건무게 기준 3, 6, 9% 수준에서 목섬유와 혼합해 중밀도섬유판을 제조하였으며, 이 때 사용한 접착제는 요소수지접착제였다. 커피박과 목섬유를 섞은 중밀도섬유판에 대해 물성과 강도 특성 및 포름알데히드 방산량을 측정하였다. 커피박과 목섬유를 무작위로 섞어 제조한 중밀도섬유판의 휨강도와 박리강도는 모두 KS 기준보다 높게 나타났으며 커피박을 층으로 구성한 적층 성형구조 경우에는 모두 기준에 미달하였다. 제조된 중밀도섬유판의 흡수 두께팽창률은 시판용 중밀도섬유판보다 낮아 물리적 특성 면에서 현저히 개선됨을 보여주었다. 포름알데히드 방산량은 시판용 중밀도섬유판과 유사한 것으로 나타났으며 모두 KS 기준상의 $E_1$급에 부합하였다. 이런 결과는 커피박이 친환경 중밀도섬유판 제조 시 원재료로 활용될 수 있음을 보여주고 있으며 중밀도섬유판의 성능 향상을 위해서는 접착제와 커피박 간의 상호 접착성 및 커피박의 흡착성능 향상을 위한 전환방법에 대한 추가 연구가 요구된다.

• Journal of the Korean Wood Science and Technology
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• 제48권2호
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• pp.196-205
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• 2020

The purpose of this study was to investigate a method for improving the physical and mechanical properties of laminated board made from oil palm trunk (OPT). The effects of pretreating the lamina with heat-pressure and altering the lamina composition of the laminated board were investigated. The outer third of OPT in cross-section had high-density wood, while the underlying third had low to medium density. The hot press was applied to pretreat the lamina that had low to medium density. The lamina were 1.5 cm in thickness, 5 cm in width, and 65 cm in length. The hot press was applied at 2.94 MPa or 4.41 MPa at 150 ℃ for 60 minutes, and the target thickness of the lamina was 1 cm. The three layers of the laminated board samples were bonded with isocyanate adhesive at a glue spread of 300 g/㎡ and cold pressed at 0.98 MPa for 3 h. The laminated board samples were tested according to Japanese Agricultural Standard (JAS) 234-2003. The results showed that the densification of the inner lamina did not significantly affect the physical-mechanical properties of the laminated board produced. However, the laminated board made with high-density laminas for the outer layers fulfilled the JAS 234-2003 standard for the modulus of elasticity and the modulus of rupture.

• 한국가구학회지
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• 제23권1호
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• pp.68-74
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• 2012

In this study domestic thinning and small diameter woods of Giant dogwood (Cornus controversa Hemsl) was used. To increase the utilizability of wood, the utilizability was proposed after manufacturing laminated wood by pressing and heating. The physical and mechanical characteristics of Laminated wood were investigated and the color change was measured, using a Chromaticity coordinates, after being pressed at 10% (45 mm), 20% (40 mm), 30% (35 mm) for 5 minutes, using Stopper, and then heated at $180^{\circ}C$ for 6, 12, 24 and 48 hours. The results were as follows. Wood density, compressive strength, MOR, MOE are increased with increasing pressing rate but decreased as heating time is increased after pressing. However, Color change is clear, dimensional stability is improved after pressing and heating.

• Journal of the Korean Wood Science and Technology
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• 제31권6호
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• pp.45-54
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• 2003

The density and strength of wood is affected by degradations and defects, such as voids and knots. Old wooden structures such as traditional cultural properties have been deteriorated by these types of defects. They were evaluated by a visual observation that is difficult to evaluate the inner deterioration in structures. In this study, three nondestructive testing techniques were investigated to detect the wooden structural members. Ultrasonic stress wave tests, drilling resistance tests and visual inspections were used to examine the structural wood members. Patterns of Resistograph using by drilling resistance tests could indicate the features of internal wood such as voids, knots, decay, fungi, and so on. The technique just like as ultrasonic stress wave tests, however, difficult to detect exactly area where small amounts of internal deterioration in logs are. In spite of results of ultrasonic stress wave test, the internal deterioration of wooden structural members could be evaluated by the relationship between ultrasonic stress wave tests and drilling resistance tests.

• Journal of the Korean Wood Science and Technology
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• 제47권1호
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• pp.8-20
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• 2019

This study was conducted to analyze the pore structure of Yellow poplar. Cross-sectional surfaces of heartwood and sapwood of Yellow poplar (Liriodendron tulipifera) were observed by SEM, and the true density of the heartwood, intermediate wood and sapwood were measured by gas pycnometery, while gas permeability and pore size of heartwood, intermediate wood and sapwood were measured by capillary flow porometery. The pores were classified as through pore, blind pore and closed pore. It was determined that the permeability was increased due to the content and size of through pore being increased although the total porosity of specimen showed slight difference from pith to bark. The content of through pore porosity was 33.754 % of heartwood and 47.810 % of sapwood, showed an increasing trend from pith to bark, however, those for the blind pore porosity and closed pore porosity were 27.890 % and 19.492 % for heartwood and 19.447 % and 4.660 % for sapwood, showed a decreasing trend from pith to bark. The max pore size of specimens was increased by about 5 times from $5.927{\mu}m$ to $31.334{\mu}m$, and mean flow pore size was increased by about 315 times from $0.397{\mu}m$ to $12.437{\mu}m$ from pith to bark.

• 한국가구학회지
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• 제10권2호
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• pp.55-61
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• 1999

This research was carried out to investigate the fundamental properties such as the structure of annual ring, density distribution, compressive strength with parallel to grain, relative crystallinity, and microfibril angle of Gumgangsong(Pinus densoflora for. erecta Uyeki). The wood specimens, Gumgangsong and Sonamu(Pinus densiflora S. et Z.), for this experiment were prepared at Ulijingoon Sokwangri and Kyungpook university's forest in Kyungpook province, respectively. Average annual ring width is $2.0mm{\pm}0.3$ in heartwood of Gumgangsong. The respectively of heart wood was over 60 percent in Gumgangsong and 20~50 percent in Sonamu. Heartwood density were ranged from 0.5 to $0.8{\;}g/cm^3$ in Gumgangsong and from 0.4 to $0.5{\;}g/cm^3$ in sonamu. Compressive strength in Gumgangsong and Sonamu was about $30{\pm}5MPa$ and $25{\pm}5MPa$, resepectively. But the relative crystallinity and microfibril angle of two species were not different clearly. From these results of Gumgangsong and Sonamu, therefore, it was considered the main difference factors for both species were annual ring width and heartwood percentage.

• Journal of the Korean Wood Science and Technology
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• 제38권3호
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• pp.178-184
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• 2010

인피섬유로 한지를 제조하고 남은 닥나무 목질부를 고부가가치화 하기 위하여 닥나무 목질부로 파티클 보드를 제조하고 페놀수지 함침율 변화에 따른 닥나무재료 우드세라믹을 제조하여 물성을 검토하였다. 밀도, 휨강도성능, Brinell 경도, 압축강도 등은 수지함침량이 증가할수록 증가하였으며 밀도와 휨강도성능, 경도, 압축강도간 및 휨탄성계수와 강도간에는 유의성이 인정되는 밀접한 상관관계를 나타내었다.