• Journal of the Korean Wood Science and Technology
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• 제29권3호
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• pp.27-35
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• 2001

Four different sources of wood-fibers from Eucalyptus, Italian poplar, hemlock, and mixed species fibers were used to study the influence of their fiber characteristics on the performance of medium density fiberboard (MDF) panels bonded with both urea-formaldehyde (UF) and phenol-formaldehyde (PF) adhesives. Included fiber characteristics were fiber length, size distribution, bulk density, and acidity. Physical and mechanical properties of MDF panels manufactured by dry process using these different fibers were determined for the comparison of board performance. Two hardwood species had a large fraction of short fibers resulting in a higher bulk density while very long hemlock fibers had lower bulk density. Fiber acidity was revealed to strongly affect the internal bond (IB) strength of MDF panels bonded with UF resins. MDF panels made from mixed species fibers showed highest IB strength of all panels prepared. UF-bonded MDF panels showed poor dimensional stability. In conclusion, the present study showed that wood-fiber characteristics such as fiber length, bulk density, and acidity affect the performance of MDF boards, and also suggested that fiber characteristics be considered for MDF panel manufacture.

• Journal of the Korean Wood Science and Technology
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• 제49권5호
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• pp.453-461
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• 2021

In wood-based composite panels, low-molar ratio (LMR) urea-formaldehyde (UF) resins usually result in reduced formaldehyde emission (FE) at the expense of poor adhesion. However, the FE and adhesion of medium-density fiberboard (MDF) bonded with LMR UF resins were both improved in this study. The modified LMR UF resins with transition metal ion-modified bentonite (TMI-BNT) nanoclay simultaneously improved the FE and adhesion of MDF panels. The modified LMR UF resins with 5% TMI-BNT resulted in a 37.1% FE reduction and 102.6% increase in the internal bonding (IB) strength of MDF panels. Furthermore, thickness swelling and water absorption also significantly decreased to 13.0% and 24.9%, respectively. These results imply that TMI-BNT modification of LMR UF resins could enhance the formation of a three-dimensional network rather than crystalline domains, resulting in improved cohesion.

• Journal of the Korean Wood Science and Technology
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• 제23권4호
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• pp.85-90
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• 1995

목질보드 제조에 있어 매트의 최종함수율은 에너지가 필요한 목질 엘리먼트의 초기 건조공정이나 열압싸이클공정, 목질보드의 균질정합성, 목질재료의 물리 기계적 성질 및 치수안정에 지대한 영향을 주기 때문에 대단히 중요하다. 지금까지 PB에 대한 최종매트의 함수율에 대한 연구는 많이 보고되어 있으나 요소수지로 제조되는 MDF에 대한 연구보고는 없으며 미국과 한국을 위시한 각국이 MDF의 최종함수율을 PB에 준하여 8~11%로 조정하여 MDF를 제조하고 있다. 따라서 본 연구는 미국산 침엽수 혼합수종으로부터 제조된 가압 해섬섬유와 요소수지로 제조된 MDF의 물리 기계적 성질에 관련된 적정 최종매트 함수율을 규명하고자 실시하여 다음과 같은 결론을 얻었다. 1. 혼합 침엽수 원료로부터 제조된 요소수지제조 MDF의 적정 최종 매트 함수율은 13% 부근으로서 현재 MDF공장에서 적용되고 있는 8~11%보다 높았다. 2 평판이 시작되는 최종매트 함수율은 15.4%였다.

• Journal of the Korean Wood Science and Technology
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• 제27권1호
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• pp.64-71
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• 1999

본 연구는 통상적으로 충밀도 섬유판 제조에 사용되고있는 요소수지를 페놀수지로 대체함으로써 그 장단점을 찾아 보기 위해 실행되었다. 페놀수지을 이용해 제조한 중밀도 섬유판의 성능은 표준 요건을 충족시켰으며 높은 내구성을 보였다. 아울러 24 시간 냉수 침적후 두께팽창은 2 퍼센트 이하로 낮게 나타났다. 요소수지를 페놀수지로 대체했을 경우 단점들은 비교적 높은 수지함량 (8% 섬유전건종량기준)과 긴 열압시간 (7 분)으로 판명되었다. 이러한 결과들은 페놀수지을 사용한 중밀도 섬유판제조시 열압공정의 최적화가 되어야함을 시사하였다.

• Korean Chemical Engineering Research
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• 제55권3호
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• pp.385-394
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• 2017

도계부산물인 닭털(CF)의 알칼리 및 산 가수분해물과 폼알데히드계 가교제를 혼합하여 조제한 접착제의 반응기작 및 경화특성을 조사하였다, 또한 이를 적용시켜 제조한 중밀도섬유판(MDF)의 물성 및 폼알데히드 방산량 측정 결과를 토대로 CF 접착제의 목질계 판상재 제조를 위한 분사형 접착제로서 적용 가능성을 확인하기 위하여 본 연구를 수행하였다. 고형분 함량이 40% 이상인 CF 접착제는 상온에서 점도가 높았으나, $50^{\circ}C$에서 측정한 점도는 $300{\sim}660m{\cdot}Pa{\cdot}s$로 측정되어 낮은 점도를 요구하는 분사형 접착제로 적용이 가능하였다. 적외선 분광기 분석을 통하여 폼알데히드계 가교제의 사용에 따른 methylol기의 부가 및 축합반응을 확인하였다. 시차주사 열량계 분석을 통하여 CF 접착제가 현재 목질계 판상재 제조에 사용되고 있는 요소수지(C-UF)와 비교하여 높은 열압온도 또는 긴 경화시간이 필요한 것으로 조사되었다. 5% NaOH 농도의 수용액에서 가수분해된 CF 가수분해물(이하 CF-AK-5%)과 formaldehyde/phenol 몰비가 2.5인 phenol-formaldehyde prepolymer (PF-2.5)로 조제한 접착제를 사용하고 8분간 열압하여 제조한 MDF에서 높은 휨강도(MOR)와 박리강도(IB)를 보였다. 또한 이 접착제로 제조한 MDF의 MOR과 IB는 대부분의 접착제 조제 및 열압 조건에서 C-UF로 제조한 MDF보다 높았다. 이 측정치를 KS 규격과 비교하였을 때, IB는 모든 조건에서 기준을 상회하였으나, MOR은 CF-AK-5%와 PF-2.5로 조제한 접착제를 사용하고 8분간 열압하여 제조한 MDF를 제외하고 그 기준을 만족하지 못하였으며, 24-TS도 모든 조건에서 기준을 만족하지 못하였다. 그러나 MDF 제조시 보드의 목표밀도를 높이거나 내수성 부여를 위하여 접착제에 첨가하는 wax emulsion의 양을 증가시킬 경우 MOR과 24-TS는 충분히 향상될 것으로 생각한다. 한편, MDF 제조에 있어 CF 접착제의 사용은 폼알데히드 방산량을 크게 감소시켰으며, 따라서 적절한 조건에서 조제된 CF 접착제는 목질계 판상재 제조를 위한 분사형 접착제로서 적용이 가능할 것으로 판단된다.

• Journal of the Korean Wood Science and Technology
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• 제40권2호
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• pp.91-100
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• 2012

This study analysis the effect of various temperatures (20, 35 and $50^{\circ}C$) on the formaldehyde emission from wood composites, which were particleboard (PB), medium density fiberboard (MDF), high density fiberboard (HDF) and laminated HDF (L-HDF) by Japanese desiccator method. Also, to reduce formaldehyde emission by wood composites, it has been suggested that undergo a bake-out conditions. On average, the level of formaldehyde emission increased many times with a $15^{\circ}C$ increase in temperature from 20 to $35^{\circ}C$ for PB, MDF, HDF and L-HDF, respectively. Formaldehyde emissions from wood composites could be expected to increase with increasing ambient temperature. At $35$ for 28 days bake-out treatment of boards, the free formaldehyde emission reduced 67.8% (PB), 40.1% (MDF), 37.8% (HDF), and 35.2% (L-HDF). On the other hand, after the bake-out at $50^{\circ}C$ for 28 days, the formaldehyde concentration decreased by 88.2, 66.9, 62.2 and 59.3% of the concentration before the bake-out for PB, MDF, HDF and L-HDF, respectively. An interesting of the bake-out treatment at $50^{\circ}C$ after 14 days, formaldehyde emission grade of PB & MDF down $E_2$ to $E_1$, and HDF & L-HDF down $E_1$ to $E_0$.

• 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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• 제33권2호통권130호
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• pp.29-39
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• 2005

Formaldehyde emissions from wood-based panels bonded with pine and wattle tannin-based adhesives, urea-formaldehyde resin (UF), melamine-formaldehyde resin (MF), and co-polycondensed resin of urea-melamine-formaldehyde (UMF) were measured by the Japanese standard method using a desiccator (JIS A 1460) and the EN 120 (European Committee For Standardization, 1991) method using the perforator value. In formaldehyde emission, all particleboards made using the wattle tannin-based adhesive with three different hardeners, paraformaldehyde, hexamethylenetetramine, and tris(hydroxyl)nitromethan (TN), satisfied the requirements of grade $E_1$. But only those made using the pine tannin-based adhesive with the hexamine as hardener met the grade $E_1$ requirements. Hexamine was effective in reducing formaldehyde emission in tannin-based adhesives when used as the hardener. While the UF resin showed a desiccator value of $7.1mg/{\ell}$ and a perforator value of 12.1 mg/100 g, the MF resin exhibited a desiccator value of $0.6mg/{\ell}$ and a perforator value of 2.9 mg/100 g. According to the Japanese Industrial Standard and the European Standard, the formaldehyde emission level of the MDF panels made with UF resin in this study came under grade $E_2$. The formaldehyde emission level was dramatically reduced by the addition of MF resin. The desiccator and perforator methods produced proportionally equivalent results. Gas chromatography, a more sensitive and advanced method, was also used. The samples for gas chromatography were gathered during the experiment involving the perforator method. The formaldehyde contents measured by gas chromatography were directly proportional to the perforator values.