• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.129-133
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• 2020

The concentration of remaining formaldehyde contained in waste liquid emitted from the process of urea-formaldehyde microcapsule synthesis was analyzed by gas chromatography-mass spectrometry (GC-MS). Three factors that can affect on the reaction of formaldehyde were selected including pH, ammonium chloride input and temperature. The effect of these factors on the concentration of remaining formaldehyde was studied. When ammonium chloride input was 0.025g, microcapsules could not be obtained or core substance leaked out because of weak shell, and therefore this reaction condition would be inadequate. It was confirmed that the concentration of remaining formaldehyde could be minimized when the microencapsulation was conducted at 70℃ and pH 2.5 by using a ammonium chloride input of 0.050g. This study can make contribution to UF microencapsulation in safer working environment.

• The Journal of the Korean dental association
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• v.11 no.3
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• pp.199-203
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• 1973

Various concentration of formaldehyde solution (1%, 5%, 10%) were applied to cut pulp surface, for 3 minutes and the remaining pulp were carefully examined histo-pathologically. The result were as follows, 1. One week survival group which were treated by 1% formaldehyde solution showed seperation of odontoblast layer randomly and the weil's zone was undistinguishable. Deeper portion of this area was necrotic or coagulated. 2. Two week survival group which were treated 1% formaldehyde solution showed necrotic appearance spread from odontoblastic layer to weil's zone. 3. One and two week survival group which were treated 5% formaldehyde solution showed the odontoblastic layer was highly necrotic, under this zone empty net-work was seen. 4. One and two week survival group treated 10% formaldehyde solution showed complete destruction of pulp.

• Restorative Dentistry and Endodontics
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• v.6 no.1
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• pp.27-35
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• 1980

This study was to evaluate the effectiveness of a few disinfectant on amputated pulps of domestic dogs. The materials employed for the purpose were zinc oxide eugenol paste, calcium hydroxide as control groups and guaiacol (1%, 5%, 10% by weight) added zinc oxide eugenol paste and formaldehyde (1%, 5%, 10% by weight) added calcium hydroxide as experimental groups. Following were the results obtained throngh histo-pathological examination. 1) In calcium hydroxide-formaldehyde groups, secondary dentin formation was observed in the 2 weeks, but the remaining pulp tissue was severely atrophied according to the concentration of formaldehyde and the time increased. 2) In zinc oxide eugenol-guaiacol groups, the first evidence of secondary dentin formation was observed in the 3 weeks. It seems that the concentration variety of guaiacol influenced very little to the potential ability of dentin formation. 3) Except 1% formaldehyde containing calcium hydroxide group, every group showed severe pulp degeneration. In all groups of zinc oxide eugenol-guaiacol cases revealed the tendency of recovery.

• Elastomers and Composites
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• v.45 no.3
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• pp.199-205
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• 2010

Medium-density fiberboard (MDF) is widely used as an indoor building materials. However, formaldehyde resins, commonly used to bind MDF together, emit formaldehyde and other volatile organic compounds that cause health risk at sufficient concentration. In this study, condensed tannin having formaldehyde absorption ability was used to solve the problem of formaldehyde emission generated from surface material. The synthesis of melamine-formaldehyde resin and reaction of melamine-formaldehyde and condensed tannin were analyzed by FT-IR spectrum. Also surface properties, such as shear force, impact strength, tape adhesion, pencil hardness and gloss retention were measured. Free formaldehyde analysis was performed to analyze remaining unreacted formaldehyde. According to the results, the optimum shear force and impact strength could be obtained by 10 wt.% usage of condensed tannin. In cases of pencil hardness and gloss retention, the optimum properties could be obtained at 20 wt.% of condensed tannin. The amounts of formaldehyde emission of surface material containing 20 wt.% of condensed tannin was 59 ${\mu}g/m^2{\cdot}h$. The amounts of formaldehyde emission could be reduced 3 times by using 20 wt.% of condensed tannin.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.4
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• pp.403-411
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• 2023

Objectives: Formalin is used as an anthelmintic in farms where flounder are raised. In this study, we aim to identify formaldehyde exposure levels for aquaculture industry workers and provide basic data for managing formaldehyde exposure. Methods: Exposure levels of formaldehyde in the air, including formalin spraying operations, were assessed separately for personal and area samples. In addition, considering the formalin administration method, dermal exposure to the hands was estimated when administering the chemical, and dermal exposure to the legs during water tank work was estimated by collecting water in the water tank and evaluating the amount of formaldehyde remaining. Finally, the respiratory exposure level and the estimated dermal exposure level were added to derive the total exposure level and compared with the maximum allowable human dose. Results: As a result of the airborne evaluation, the formaldehyde concentration of the worker (1 person) who performed the formalin spraying and flounder sorting was 33.61 ppb, and the arithmetic mean of formaldehyde concentrations of the workers (3 people) who only performed the flounder sorting was 3.28 ppb (range: 2.25-4.89 ppb). In the case of dermal exposure, when spraying formalin once, the amount was estimated to be 0.33-2.62 mg when wearing protective gear and 3.27-26.12 mg when not wearing it. Conclusions: There was a difference in the formaldehyde exposure level of workers depending on their operation of handling formalin and whether or not protective gear was worn. In particular, because the level of formaldehyde exposure due to dermal exposure can be significant, there is a need to improve formalin administration methods in a way that avoids skin contact as much as possible.

• Journal of the Korean Wood Science and Technology
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• v.35 no.3
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• pp.61-69
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• 2007

The building materials used for improving indoor air quality, the wood charcoal mixed with cement mortar or natural water paint were examined for their potential removing ability of formaldehyde. After the reaction of samples with formaldehyde in the glass flasks designed in our lab, the remaining formaldehyde was collected using DNPH (2,4-dinitrophenyl hydrazine) cartridges, and their concentration was determined using HPLC. From the results, it was found that the removing amount of formaldehyde per one gram sample containing 5, 10, or 15% of wood charcoal was more than three times compared to that of control (100% cement mortar or water paint). Their elimination percentages from the initial formaldehyde was about 80~90%. The experimental results for wood charcoal-water paint showed a similar trend with those of wood charcoal-cement mortar samples. Their elimination percentages from the initial formaldehyde was about 90%. It is proposed that formaldehyde is adsorbed on the adsorbed 'O' or 'OH' groups in the graphene layers formed through the re-arrangement of lignocellulose in the wood during the carbonization procedure.