• Korean Journal of Heritage: History & Science
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• v.49 no.4
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• pp.114-125
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• 2016

Lacquer is one of the most widely used natural resin in East Asia since Neolithic Age. As a major ingredient of lacquerware, lacquer is waterproof, insect-proof and rot-proof to be durable and anti-abrasion, generally utilized for mainly painting purpose. According to lacquerware excavated from several sites of Japan and China, lacquerware seems to appear in Neolithic Age. On the other hand in case of excavation research in Korea, lacquerwares are found after the Bronze Age. The initial purpose of lacquer is estimated to be adhesive, regarding the literatures mentioning bitumen(Yeoksceong ), animal glue(Kyeo) and egg alumen(Nanbaek). Especially piece of jar coffin unearthed in Pyeongtaek Daechu-ri site had trace of restoration by lacquer and hemp as an evidence of lacquer for adhesion in Pre-Three Kingdoms period. Since then a trend to restore the broken ceramics with lacquer and decorate with golden foil lasted especially in Joseon Dynasty. In the field of gold plated lacquer method, mother-of-pearl inlaying technique for lacquerware and restoration of buildings, lacquer is still used as adhesive. Due to matter of reversibility lacquer is being avoided for conservation and restoration of cultural heritage. Lacquer as a traditional material for adhesive since ancient times, however, has advantage in adhesion strength and durability. Because synthetic resin adhesive has problem of emission of volatile organic compounds and aging over time, lacquer receives attention recently. On the contrary, by combination adhesive from mixing lacquer and animal glue, already proved the possibility of applicability and chemical modification. A research to utilize lacquer as modern paint or functional material is also conducted continuously also in China and Japan. To put traditional material into practical use and modernize, chemical research from the molecular level of the lacquer is necessary in the near future.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.77-78
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• 2018

Form-work is a must for construction work. In order to secure the best condition of the form surface and to increase the number of times, the form releasing agent is applied during the process of the form-work. The base oil of the form release agent which has been used already uses the oil which directly or indirectly affects the natural environment and the concrete. In this study, the basic study on the form release agent for concrete was carried out only for the effect of adhesion. The adhesive force of the tile is measured by the mortar to determine the change of the releasing agent and the adhesive strength.

• Journal of the Korean Wood Science and Technology
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• v.26 no.4
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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.

• Wind and Structures
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• v.29 no.5
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• pp.361-369
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• 2019

The modal frequency responses of adhesive bonded T-joint structure have been analyzed numerically and verified with own experimental data. For this purpose, the damped free frequencies of the bonded joint have been computed using a three-dimensional finite element model via ANSYS parametric design language (APDL) code. The practical relevance of the joint structure analysis has been established by comparing the simulation data with the in-house experimental values. Additionally, the influences of various geometrical and material parameters on the damped free frequency responses of the joint structure have been investigated and final inferences discussed in details. It is observed that the natural frequency values increase for the higher aspect ratios of the joint structure. Also, the joint made up of Glass fiber/epoxy with quasi-isotropic fiber orientation indicates more resistance towards free vibration.

• Journal of the Korean Wood Science and Technology
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• v.45 no.4
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• pp.432-443
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• 2017

Maltodextrin and citric acid are two types of natural materials with the potential as an eco-friendly binder. Maltodextrin is a natural substance rich in hydroxyl groups and can form hydrogen bonds with lignoselulosic material, while citric acid is a polycarboxylic acid which can form an ester bond with a hydroxyl group at lignoselulosic material. The combination of maltodextrin and citric acid as a natural binder materials supposed to be increase the ester bonds formed within the particleboard. This research determined to investigate the bonding properties of a new adhesive composed of maltodextrin/citric acid for nipa frond particleboard. Maltodextrin and citric acid were dissolved in distillated water at the ratios of 100/0, 87.5/12.5, 75/25 and 0/100, and the concentration of the solution was adjusted to 50% for maltodextrin and 60% citric acid (wt%). This adhesive solution was sprayed onto the particles at 20% resin content based on the weight of oven dried particles. Particleboards with a size of $25{\times}25{\times}1cm$, a target density $800kg/m^3$ were prepared by hot-pressing at press temperatures of $180^{\circ}C$ or $200^{\circ}C$, a press time of 10 minute and board pressure 3.6 MPa. Physical and mechanical properties of particleboard were tested by a standard method (JIS A 5908). The results showed that added citric acid level in maltodextrin/citric acid composition and hot-pressing temperature had affected to the properties of particleboard. The optimum properties of the board were achieved at a pressing temperature of $180^{\circ}C$ and the addition of only 20% citric acid. The results also indicated that the peak intensity of C=O group increased and OH group decreased with the addition of citric acid and an increase in the pressing temperature, suggesting an interreaction between the hydroxyl groups from the lignocellulosic materials and carboxyl groups from citric acid to form the ester groups.

• Journal of the Korea Convergence Society
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• v.9 no.7
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• pp.149-154
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• 2018

This article intended to examine the anti-plaque activity of 4 essential oils of Lavender, Tea tree, Eucalyptus, Lemongrass against Streptococcus mutans. In the results of measuring the anti-plaque effect against Streptococcus mutans, Minimum anti-adhesive concentration of Lavender oil was 1.0% and that of Tea tree, Eucalyptus, lemongrass essential oils was 0.5 %. Also, it was confirmed that the essential oils have the effect of inhibiting acid generation by Streptococcus mutans. It was confirmed that pH of the concentration was lowered by the acid generation under the MAC by measuring pH of the solution after incubating Streptococcus mutans and the essential oils in the thermostatic bath varying their concentration. From these results, the essential oils, particularly, Tea tree, Eucalyptus, Lemongrass essential oils are the natural material inhibiting the plaque generation and the potential that they can be used to develop the oral care products was confirmed.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.2
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• pp.195-204
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• 2008

Orthodontic brackets often need to be bonded to porcelain such as porcelain fused to metal crowns and porcelain jacket crowns. The purpose of this study was to evaluate the clinical usability of direct bonding system on porcelain teeth by measuring shear bond strength according to various conditions and observing adhesive failure patterns. The specimens, 20 maxillary premolars and 80 porcelain teeth that were produced by duplication of the labial surface of a maxillary first premolar were used and randomly divided into four groups of twenty teeth each. The 5 different preparation procedures tested: (1) application of 37% phosphoric acid on natural teeth, (2) sandblasting on porcelain surfaces, (3) sandblasting and application of 9.6% hydrofluoric acid on porcelain surfaces, (4) sandblasting and application of silane on porcelain surface, (5) sandblasting and application of 9.6% hydrofluoric acid and silane on porcelain surfaces. The metal brackets were bonded with Transbond $XT^{(R)}$ bonding material. The shear bond strength was tested by the micro universal testing machine(Kyung-Sung, Korea) and the amount of residual adhesive on the tooth surface after debonding was examined by stereoscope and assessed with an adhesive remnant index. The results of this study suggest that the direct bonding system on porcelain teeth with sandblasting, HF and porcelain primer is clinically useful.

• Journal of the Korean Wood Science and Technology
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• v.38 no.5
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• pp.385-390
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• 2010

This study was carried out to manufacture very thin natural elm veneer overlaid charcoal board for enhancing aesthetic value of charcoal board for the indoor application, and to use the advantageous properties of the charcoal as a building material for solving the sick house problem. The thin elm veneer had 26.9% opening ratio. The experiment results showed that the spreading area and the nonvolatile content of adhesive did not affect the gas adsoprtion of fancy veneer overlaid charcoal board. The natural thin elm veneer overlaid charcoal board enhanced not only the aesthetic beauty but also showed the same gas adsorption by the charcoal board.

• The korean journal of orthodontics
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• v.30 no.4 s.81
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• pp.483-490
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• 2000

The dental gold alloy shows a lower bond strength than the natural teeth in bracket bonding, and this can be a possible source of subsequent bond failure. This study aims to evaluate the effect of various gold alloy surface treatment techniques on shear bond strength between the orthodontic adhesives and the gold alloy and to find ways of increasing the bond strength. Two hundred and forty specimens made of the dental fold alloy were divided into twelve groups based on the combination of surface treatment methods(non-surface treatment, sandblasted, sandblasted plus tin-plated, and sandblasted plus intermediate adhesive) and adhesive systems (Ortho-one, Panavia 21, Superbond C&B). The specimens with bonded brackets were placed in distilled water at $37^{\circ}C$ for 24 hours and shear bond strength was measured by a universal testing machine. The results were as follows: 1. All surface-treated groups showed a significantly higher shear bond strength than non-surface-treated groups. 2. The sandblasted plus tin-plated group showed a significantly higher shear bond strength than the sandblasted group only when Panavia 21 was involved. 3. The sandblasted plus intermediate adhesive group showed a significantly higher shear bond strength than sandblasted group regardless of the type of adhesive used. 4. Of the three resin adhesive types, the Superbond C&B showed the highest bond strength, followed by Panavia 21 and Ortho-one. These findings suggest that a combination of sandblasting and intermediate resin treatment is desirable in order to enhance bracket bond strength regardless of adhesive types.

• Korean Journal of Heritage: History & Science
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• v.54 no.4
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• pp.78-89
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• 2021

Organic residues analysis is an analysis method that reveals the types of organic material samples by using the characteristic that main components constituting substances are different depending on the species of animals and plants. In this study, scientific analysis of the organic residues attached to wood coffins in the Joseon Dynasty Hoemyo excavated from the site of Singok-dong, Uijeongbu was used to identify the types of remnants and to use them as information to restore the uses of organic materials and the way they lived in the past. As a result of FT-IR analysis of the residue attached to the inside of the wood, it was estimated to be a natural plant resin material. In addition, as a result of analysis by GC-MS to confirm the characteristic factors of natural resins, diterpenoids (abietane) and pimaran (pimarane), such as dehydroabietic acid and pimaric acid (diterpenoid) compounds, and saturated and unsaturated fatty acid components were detected together. Diterpenoid compounds are components mainly found in Pinaceae resins. It is confirmed in the literature that rosin, a representative material of Pinaceae resin, was used as an adhesive material. Considering the situation where an organic material remained at the joint of the wood, the organic material attached to the wood is judged to be an adhesive material made of Pinaceae resin. In addition, the fatty acid component detected together is a component derived from plant oil, and it is presumed to be made by mixing rosin and oil as recorded in previous studies. This study confirms that organic residues remain in the burial environment without losing their characteristics. It is expected that scientific analysis of organic residues will be conducted in the future to accumulate information necessary for the interpretation of past living culture.