• 한국의류학회지
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• 제5권1호
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• pp.23-26
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• 1981

In this paper, the extraction mechanism of free formaldehyde in the urea formaldehyde resin finished cotton fabric is discussed. An empirical equation for formaldehyde release has been formulated. $$F=3.7\times10^{-3}\;H\;T^{2.2326}+440$$ in which, F: the amount of free formaldehyde extracted ($\mu$g/g) H: extraction time (min) T: extraction temperature ($^{\circ}C$)

• 한국의류학회지
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• 제3권2호
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• pp.29-36
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• 1979

In order to control free formaldehyde release from fabric finished with urea-formaldehyde precondensate, the resin finished fabric was padded in urea or acylamide solution, dried and cured at $140^{\circ}C$. The effect of aftertreatment with urea or acrylamide on free formaldehyde release and on characteristics of resin finished fabric were examined. It was shown that aftertreatment with urea was effective to control free formaldehyde release, the free formaldelyde content in aftertreated fabric could be reduced from 900 ppm to 200 ppm and formaldehyde release under accelerated storage condition was also reduced from 8000 ppm to 1000 ppm. Polyacrylamide formed in the fiber during aftertreatment appeared to be a formaldehyde capture. Especially by washing the aftertreated fabric, the ability to control formaldehyde release under accelerated condition was not dimimished in contrast with aftertreated with unea. It suggests that polyacrylamide can be used as a formaldehyde capture which withstand diminution from washing.

• 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.

• 접착 및 계면
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• 제7권4호
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• pp.45-52
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• 2006

Five low molar ratio urea-formaldehyde (LUF) resins were synthesized in this study. The effects of molar ratio, free formaldehyde content, and catalysts on the curing characteristics of LUF resins were studied by measuring its free formaldehyde content, pH value change after catalysts added, curing rate, and pot life, observing its cured appearance, and analyzing its thermal behavior. The results indicate that: 1) The LUF resin with lower molar ratio than 1.0 can still cure; 2) Free formaldehyde content is not the main factor in affecting curing rate of LUF resin; 3) Compared with ammonium chloride as a traditional catalyst, persulfate salts markedly accelerate the curing rate of LUF resin, and result in the different appearance; 4) the addition of sodium chloride to catalysts can accelerate the curing rate of LUF resin, but the effect is moderate.

• 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.

• 한국가구학회지
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• 제10권1호
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• pp.43-49
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• 1999

The pH and buffering potential for water extract of seven hardwoods and three softwoods were determined. The pH values ranged from 3.81 to 5.51 for hardwoods and 4.08 to 5.49 for softwoods. The gelation time for a urea-formaldehyde resin for each woods was determined and found to be a range of one minute thirty seven seconds to two minutes thirty nine seconds. Results shows that gelation time of a urea-formaldehyde resin was directly correlated to the pH and inversely correlated with acid buffering potential for seven hardwoods and three softwoods aqueous extracts

• Journal of the Korean Wood Science and Technology
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• 제45권2호
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• pp.223-231
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• 2017

This work was conducted to investigate on the effect of urea-formaldehyde (UF) resin viscosity on plywood adhesion. The viscosity of UF resin was controlled either by adjusting the condensation reaction during its synthesis to obtain different target viscosities (100, 200 and 300 mPa.s) at two levels of formaldehyde/urea (F/U) mole ratios (1.0 and 1.2) or by adding different amounts (10, 20 and 30%) of wheat flour into the resins for the manufacture of plywood. When the viscosity of UF resin increased by the condensation reaction, the adhesion strength of plywood bonded with UF resin of 1.2 F/U mole ratio consistently increased, while those bonded with the 1.0 F/U mole ratio resin slightly decreased, suggesting a difference in the adhesion in plywood. However, the adhesion strength of plywood decreased as the viscosity increased by adding wheat flour, regardless of F/U mole ratio. The manipulation of UF resin viscosity by adjusting the condensation reaction was much more efficient than by adding wheat flour in improving the adhesion performance of plywood. These results indicated that a way of controlling the viscosity of UF resin adhesives has a great influence to their adhesion in plywood.

• 한국잠사곤충학회지
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• 제20권1호
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• pp.15-23
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• 1978

본 연구는 견직물의 촉감을 손상시키지 않는 범위에서 바람직한 방추성을 보유하는 보다 좋은 요소수지가 공법을 개발하기 위하여 수년간에 걸친 보고이다. 특히 본보고는 요소와 결합하는 폴마린양을 극소화한데 특징이 있고 일반요소수지보다도 더욱 우수성을 보이는 반금속성요소수지(Homo Metalic Urea Resin)을 개발하였다는 사실도 첨가하며 본연구에서 얻어진 결과는 다음과 같다. 1. 본보고에 수록된 요소수지조성은 폴마린함량을 극소화하였고 조성된 수지에서 거의 폴마린냄새를 인정할 수 없을 정도였으며 이전에 보고된 어느 것보다 가장 소량의 폴마린으로 요소수지를 만들었다. 2. 필자가 최초로 만든 화합물 즉 uric zincchloride와 폴마린을 원료로 하여 새로운 반금속성요소수지(Homo Metalic Urea Resin)를 개발하였다. 이 방법은 합성수지처리와 중앙처리를 동시에 할 수 있는 특징이 있다. 3. 위의 두가지 수지처리에서 방추도, 강연도 및 발키네스 등이 증가되었는데 신규개발한 수지가 더욱 좋은 결과를 보였다. 4. 견방사나 저연사견직물이 생사나 고연사손직물의 경우보다 좋은 방추개선을 보였다. 5. 두가지 수지처리법이 모두 실용상의 경제성이 좋았다. 6. 강력과 신도가 수지처리후 다소 저하되었는데 이것은 수지처리로 가교작용과 증량작용이 일어났기 때문이었다. 7. 특수한 요소수지처리방법으로 양모와 유사한 견사제조법도 개발했다. 이 방법은 요소용액에 침지한 생사를 폴마린가스로 충만된 밀실에 방치해 둠으로서 생사표면에 스케일을 발생하게 한 것이다.

• Journal of the Korean Wood Science and Technology
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• 제34권5호
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• pp.42-51
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• 2006

The this study, the effect of rice husk flour (RHF) as scavenger on formaldehyde emission rate and formaldehyde content from urea-formaldehyde (UF) resin bonded RHF content wood particleboards (PB). Two type of particle size ($30{\mu}m$ and $300{\mu}m$) of RHF was premixed with the UF resin at 5% and 15% by weight. The performance of UF resins is greatly influenced by the curing characteristics in their curing processing. The curing behavior was monitored activation energy ($E_a$) by DSC and pH variation according to RHF contents. PB with dimensions of $27cm{\times}27cm{\times}0.7cm$ was prepared at a specific gravity of 0.75 using $E_1$ and $E_2$ class UF resins. Formaldehyde emission and formaldehyde content from RHF filled PB bonded with UF resin was measured by 24 h desiccator and perforator method, respectively. RHF causes an increased pH of UF resin. $E_a$ of the modified UF resin decreased independently of RHF particle size. As the pH and the $E_a$ variation of the UF resin containing RHF increased, the amount of formaldehyde content decreased. The formaldehyde emission and formaldehyde content levels of the PB bonded with 15 wt% of $30{\mu}m$ RHF and $E_2$ type UF resin were low and satisfied grade $E_1$, as measured by 24 h desiccator and perforator method. The result of a comparison between 24 h desiccator and perforator test using PB showed that the linear regression analyses show a good correlation between the results for the 24 h desiccator and the perforator tests. The linear regression of a correlation between the desiccator and the perforator was Y=4.842X-0.064 ($R^2=0.989$). RHF was effective at reducing formaldehyde emission and formaldehyde content in urea-formaldehyde adhesives when used as scavenger.

• 한국산림과학회지
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• 제60권1호
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• pp.37-44
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• 1983

요소수지(尿素樹脂)의 변성제(變性劑)로서 열가망성(熱可望性)의 아세톤수지(樹脂)를 첨가(添加)하고 합판(合板)의 접착력(接着力) 및 목파율(木破率)에 미치는 영향(影響)을 조사(調査)하였다. 결론(結論)을 요약(要約)하면 다음과 같다. 1) 합판(合板)의 접착력(接着力)과 목파율(木破率)은 열판온도(熱板溫度) $120^{\circ}C$에서 제조한 것이 가장 좋은 값을 보였으나 아세톤수지(樹脂)의 혼합비율(混合比率)이 증가(增加)함에 따라서 그 값은 점차 감소(減少)되었다. 2) 아세톤수지(樹脂)의 몰비율(比率)은 합판(合板)의 접착력(接着力) 및 목파율(木破率)에 영향(影響)을 미치지 않았다. 3) 아세톤수지(樹脂)를 혼용(混用)한 합판(合板)은 요소수지(尿素樹脂)만으로 접착(接着)된 합판(合板)의 접착력(接着力) 및 목파율(木破率)을 능가하지 못했다. 따라서 아세톤수지(樹脂)는 요소수지(尿素樹脂)의 변성제(變性劑)는 부적당(不適當)하였다.