• Journal of the Korean Wood Science and Technology
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• 제26권4호
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• pp.92-97
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• 1998

Four urea-formaldehyde (UF) resins were synthesized as a particleboard (PB) binder with the four different initial formaldehyde/urea mole ratio and the final mole ratio of 1.15. The UF resins were characterized according to the standard method of resin adhesive analysis. PBs were manufactured using liquid UF resins at 5 minutes press time and 6% resin solids levels on an ovendry particle weight basis. A total of 20 PBs was fabricated for 5 panel replication per UF resin types. The panels were tested for physical strength properties per the procedure ASTM D 1037. The formaldehyde emission levels from the PBs bonded with the UF resins were tested according to 2-hour desiccator test method ASTM D 5582. There were no significant differences among UF resin types for internal bond strength of PBs. But there were significant differences among UF resin types for formaldehyde emission level of PBs. The results showed that the formaldehyde emission level was influenced by the UF resin types without reducing the adhesive performance.

• Journal of the Korean Wood Science and Technology
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• 제42권5호
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• pp.605-614
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• 2014

This study investigated microstructural changes of cured urea-formaldehyde (UF) resins mixed with aqueous rubber latex emulsion after intentional acid etching. Transmission electron microscopy (TEM) was used in order to better understand a hydrolytic degradation process of cured UF resins responsible for the formaldehyde emission from wood-based composite panels. A liquid UF resin with a formaldehyde to urea (F/U) molar ratio 1.0 was mixed with a rubber latex emulsion at three different mixing mass ratios (UF resin to latex = 30:70, 50:50, and 70:30). The rate of curing of the liquid modified UF resins decreased with an increase of the rubber latex proportion as determined by differential scanning calorimetry (DSC) measurement. Ultrathin sections of modified and cured UF resin films were exposed to hydrochloric acid etching in order to mimic a certain hydrolytic degradation. TEM observation showed spherical particles and various cavities in the cured UF resins after the acid etching, indicating that the acid etching had hydrolytically degraded some part of the cured UF resin by acid hydrolysis, also showing spherical particles of cured UF resin dispersed in the latex matrix. These results suggested that spherical structures of cured UF resin might play an important role in hindering the hydrolysis degradation of cured UF resin.

• Current Research on Agriculture and Life Sciences
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• 제32권3호
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• pp.125-130
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• 2014

This study used transmission electron microscopy (TEM) to investigate the micro-morphological features of two formaldehyde to urea (F/U) mole ratio liquid urea-formaldehyde (UF) resins with three hardener levels as a function of the curing time. The micro-morphological features of the liquid UF resins were characterized after different curing times. As a result, the TEM examination revealed the presence of globular/nodular structures in both liquid UF resins, while spherical particles were only visible in the low F/U mole ratio resins. The high F/U mole ratio liquid UF resins also showed extensive particle coalescence after adding the hardener, along with the appearance of complex filamentous networks. When the resins were cured with a higher amount of hardener and longer curing time, the spherical particles disappeared. For the low mole UF resins, the particles tended to coalesce with a higher amount of hardener and longer curing time, although discrete spherical particles were still observed in some regions. This is the first report on the distinct features of the crystal structures in low F/U mole ratio UF resins cured with 5% hardener and after 0.5 h of curing time. In conclusion, the present results indicate that the crystal structures of low F/U mole ratio UF resins are formed during the curing process.

• Journal of the Korean Wood Science and Technology
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• 제16권3호
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• pp.17-21
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• 1988

In order to investigate the extending effects on urea-formaldehyde resin- or phenol- formal- dehyde resin- glued keruing plywood, hot pressing temperatures were controlled to 110, 140, 170 and $200^{\circ}C$. As the extender, wheat flour, persimmon bark powder, chestnut bark powder, the equivalently- extended with the above three powders, and diatomite powder were respectively mixed with 5, 10, 15 and 20% ratios to the resin liquid, and also with these the no- extended was allowed. Based on the measured bonding strength, the conclusions were drawn: 1. In the urea- formaldehyde resin, extending effects on the bonding strength were in the order of wheat flour, the equivalently- extended with the wheat flour, persimmon- and chestnut bark powder, persimmon bark powder, chestnut bark powder. In the phenol- formaldehyde resin, the effects in the order of wheat flour, persimmon bark powder, diatomite powder, chestnut bark powder were resulted in. Specifically, superior bonding strength to the no-extended were given with the wheat flour and persimmon bark powder. 2. On the whole, the bonding strength decreased gradually, as the hot pressing temperature increased except for the diatomite powder extending.

• 한국가구학회지
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• 제22권3호
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• pp.219-229
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• 2011

Sick building syndrome symptoms that are experienced by building occupants may be caused by toxic substances such as formaldehyde and VOCs, which are known to be emitted from building materials and wood composite products such as wood-based panel, furniture, engineered flooring and construction adhesive. In Korea, the use of wood composite products for indoor environments has increased over the last decade. Recently, wood composite products have been installed in approximately 95% of newly constructed residential buildings. The use of these products has resulted in problems related to human health, and consequently a realization about the importance of indoor air quality. In addition, consumer demand is increasing for natural materials because conventional building materials and wood composite products are made by adding urea-formaldehyde resin or they contain formaldehyde-based resin. More recently, many efforts have been made to reduce formaldehyde emission from building materials that laid in the indoor environment. Especially, if conventional formaldehyde-based adhesives are replaced with green adhesives for residential spaces, it is possible to reduce most of the emission amounts of formaldehyde in indoor environments. In line with this expectation, many researches are being conducted using natural materials such as tannin and cashew nut shell liquid (CNSL). This study discussed the affects and possibilities of green adhesives to reduce formaldehyde emission in indoor environments.

• Journal of the Korean Wood Science and Technology
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• 제34권4호
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• pp.31-36
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• 2006

본 연구는 UF resin의 접착성능을 개선하여 그 사용처의 확대하기 위하여 각 F/U 몰비별로 제조된 UF resin에 접착성능이 우수한 지방산-글리세롤-pMDI 당량비 1:1:4인 비교적 저가의 isocyanate prepolymer접착제를 선정하여 UF resin의 수지고형분 기준으로 0 wt%(대조구), 2 wt%, 5 wt%, 10 wt%, 25 wt%, 50 wt%로 첨가 혼합하여 접착 성능을 조사하였다. 그 결과, 상태 접착력(Type 2)은 F/U 몰비 1.4에서 가장 우수한 접착력을 준내수 접착력(Type 1.5)은 FGMDI첨가량이 25% 이상에서 KS 합판 접착성 기준인 $7.5kgf/cm^2$를 모두 상회하는 $11kgf/cm^2$ 이상을 나타내었다. 상태접착력대비 준내수 접착력의 평균 감소율은 F/U 몰비가 높아질수록, 지방산-글리세롤-pMDI접착제의 첨가량이 많아질수록 그 감소의 폭이 둔화되었다.

• 한국잠사곤충학회지
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• 제27권2호
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• pp.47-53
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• 1985

요소-formaldehyde 수지를 여러 가지 조건에서 견직물에 처리하여 다음과 같은 결과를 얻었다. 1. 수명수지의 생성 조건은 요소 1mol에 대하여 formaline을 2mod 이상 사용하여 pH 4∼5로 수지욕을 만들어야 한다. 2. 수지농도가 증가하는데 비례적으로 수지부착율도 증가한다. 상대적으로 수분율을 감소하는 경향을 보였다. 3. wet pick 70%, 80%, 90%, 100% 중에서 70%일 경우가 수지잔존율이 가장 높았다. 4. curing 조건에 따른 수지의 부착율은 온도가 높을수록 탈락율은 감소하며 부착율은 증가된다. 5. 촉매의 양은 (NH4)2SO4 경우는 수지에 대하여 2.5%, HCI 경우는 1%, tataric acid 경우는 10%가 적당하였고 나머지 NaHCO3, Zn(NO3)2·6H2O인 경우는 분석이 곤란하였다. 6. 촉매의 종류에 따른 부착율은 산성 혹은 (NH4)2SO4와 같은 잠복성 촉매가 뛰어난 효과를 나타냈다. 7. 촉매에 따른 세탁견뢰성은 산성 촉매일수록 뛰어난 효과를 나타냈다.

• 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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• 제30권1호
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• pp.11-17
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• 2002

본 연구는 요소수지(고형분함량 60%)를 사용, 분죽 3개월생 국산 대나무를 이용하여 대나무 파티클 3층 보드를 제조하고 3년생과 그 보드의 물리 기계적 성질을 비교 검토하였다. 분죽의 수령이 파티클 보드의 비중과 기건 함수율에 미치는 차이는 없었고, 제품의 두께 팽윤율은 함지율 11%부터 KS기준을 만족시켰으며 3개월생 보드가 3년생 보드보다 높은 수치를 나타냈다. 3개월생 파티클 보드의 휨강도가 함지율 3수준(9%, 11%, 13%)에서 모두 3년생보다 훨씬 높게 나타났고, 박기강도도 3개월생 보드가 3년생 보드보다 월등히 높았다. 3개월생, 3년생 보드 모두 KS기준강도보다 월등하였다. 보드의 포름알데히드 방산량값은 모두 E2 등급을 만족시켰다.

• 한국가구학회지
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• 제11권2호
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• pp.45-53
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• 2000

This study was carried out to determine the suitability of 3 months old bamboo species of Phyllostachys bambusoides S. et Z., Phyllostachys Pubescens Mazel and Phyllostachys nigra var henonis Stapf as raw materials for the manufacture of strandboard. Total of 108 strandboards were made using urea-formaldehyde resin content level of 12% and one percent of liquid wax emulsion. The strandboard consisted of three layers the top and the bottom layer of which were oriented to the same direction and weighted 25% of the strandboard each. The middle core layer weighed 50% of the board and was perpendicular to the outer top and bottom layers. Analysis was performed to determine the effect of strand lengths and Uowing years of 3 months, 2 years and 3 years on strandboard properties. The physical and mechanical properties of bamboo species and boards were measured and compared to the standard requirements of strandboards. The results are as follows; 1. The more the growing years the higher the density of bamboo. Top part of bamboo indicated higher density value than that of bottom part. 2. Bamboo showed higher static bending strength compared to the main wood species. Longer growing years of bamboo generally inclosed the static tending strength out there were no statistical significancies for Phyllostachys bmbusoides S. et Z. and Phyllostachys pubescens Mazel. 3. Strand length indicated no difference on density and moisture content of strandboard. 5 cm of strand length gave the best static bending strength and internal bonding strength. Bamboo strandboard exhibited lesser extents of thickness swelling than that of CSA standard. 4. 3 months old bamboo gave higher static bending strength of strandboard than those of 2 years and 3 years old bamboo. In case of Phyllostachys nigra var henonis Stapf, 3 months old bamboo indicated higher internal bonding strength than those of 2 years and 3years old bamboo. but in Phyllostachys bambusoides S. et Z., Phyllostachys pubescens Mazel, there were no difference among growing years. Growing years showed no different physical properties of bamboo strandboard.