• Journal of the Semiconductor & Display Technology
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• v.14 no.1
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• pp.1-5
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• 2015

This paper deals with the residual stresses developed in an epoxy film deposited on Si wafer. First, chemically induced residual stresses due to the volumetric shrinkage in cross-linking resins during polymerization are treated. The curvature measurement method is employed to investigate the residual stresses. Then, thermally induced stresses are investigated along the interface between the epoxy film and Si wafer. The boundary element method is employed to investigate the whole stresses in the film. The singular stress is observed near the interface corner. Such residual stresses are large enough to initiate interface delamination to relieve the residual stresses.

• Journal of the Korea Safety Management & Science
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• v.3 no.3
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• pp.231-241
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• 2001

The epoxy resin materials used in outdoor high voltage equipments are required to have the high electric performance because of the miniaturization. The frequence dependence of the permittivity and the loss tangent have important information. In this paper we describe the frequency dependence of the permittivity and the loss tangent for epoxy resin filled with silica and the influence of filler shapes on the dielectric properties. The increment of tan $\delta$ in the low frequency region is caused by the increment of both the electrical conductivity and the polarization due to the shape of filler and the water absorbed in and near the interface between fillers and resins. The result of charge current and discharge measure, electric conduction is increased according to voltage.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.58-63
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• 1999

Almost all concrete structures have many inevitable cracks for various reasons such as drying shrinkage, heat liberation of cement, fatigues or repeating loads and movements. Conventionally, they are repaired with epoxy materials. The Epoxy resins used by repair materials are different from properties of the base concrete materials such as thermal and mechanical properties - thermal expansion coefficients, bending strength. And the epoxy resin cannot release the water inside the concrete structure and cause corrosion of the steel bars. In this study, before the experiment got launched, we had analyzed cement and slag. Then We blended the two grades of ultra fine cement using high blaine cement and slag. And the cement slurry was produced by water and suprplasticizer to each blended ultra fine cement in various conditions. The slurry produced by each conditions was evaluated with flow properties such as viscosity, dropping time, segregation and observation of dry surface after injection.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.411-413
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• 1995

Porcelain insulators have been used for the almost all of the suspension insulators in distribution line. However, Puncture breakdowns in porcelain insulators caused by westing cement between metal fitting and porcelain material. There is little puncture breakdown in Epoxy casting insulator. This paper presents a new design technique for the development of suspension insulator used Cycloaliphatic Epoxy resin. The design was performed on the basis of two conditions (weather conditions for the past 30 years and the existing installation conditions of KEPCO) and was proven of its adaptability by FEM method.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.1
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• pp.88-93
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• 2004

Electrochemical impedance spectroscopy was used to evaluate the anticorrosive properties of resin(alkyd, epoxy, urethane) and pigment(hydroxy apatite(HAp), zinc potassium chromate(ZPC). red lead(RL)). The corrosion behavior of coatings applied on steel has been investigated during exposure to 0.5M-NaCl The anticorrosive performances of resins were found to depend on their chemical nature and decreased in the order of urethane > epoxy > alkyd resin coating. Hydroxy apatite and zinc potassium chromate pigment which have property to passivate the substrate showed relatively high anticorrosive performance.

• Electrical & Electronic Materials
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• v.10 no.7
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• pp.651-658
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• 1997

In this paper, effect of interpenetrating polymer network(IPN) introduction on the dielectric properties, heat proof properties, internal structure and defects of the Epoxy/SiO$_2$composite materials, were investigated. we reported a relation between network structures and electrical properties, especially dielectric characteristics with variation of network structures for epoxy composite materials. According to experimental results, the specimens which have single network structures have lower dielectric constant than interpenetrating polymer network(IPN) specimens, but have relatively larger dependency to variation of temperature and frequency. It was confirmed that change of structures is attained by introducing of IPN to insulating materials. Therefore it is counted that introduction of multiple structure including IPN is necessary to improve heat proof and electrical properties.

• Journal of the Korean Applied Science and Technology
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• v.31 no.2
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• pp.329-336
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• 2014

The conductive polymer composites have attracted considerable attention in the field of industry due to their electrical properties. To understand electrical properties of the composites, their volume specific resistance was measured. Electrical conductivity results showed percolation phenomena. Percolation theories are frequently applied to describe the insulator-to-conductor transitions in the composites composed of conductive filler and insulating matrix. It was found that the percolation threshold strongly depends on the aspect ratio of filler particles. The critical concentration of percolation formed is defined as the percolation threshold. The purpose of this study was to examine electrical properties of the epoxy resins filled with nickel. The sample was prepared using vehicle such as epoxy resin replenished with nickel powder, and the evaluation on their practical use was performed in order to apply them to electric and electronic industry as well as general field. The volume specific resistance of epoxy resin composites was 4.666~13.074 when using nickel powder. Weight loss of the conductive composites took place at $350^{\circ}C{\sim}470^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.334-338
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• 2009

Trifunctional epoxy resin triglycidyl paraaminophenol (TGPAP)/$CaCO_3$ nanocomposites were prepared using the melt blending method. The effects of nano-$CaCO_3$ content on the thermal behaviors, such as cure behavior, glass transition temperature ($T_g$), thermal stability, and the coefficient of thermal extension (CTE), were investigated by several techniques. Differential scanning calorimetry (DSC) results indicated that the cure reaction of the TGPAP epoxy resin was accelerated with the addition of nano-$CaCO_3$. When the nano-$CaCO_3$ content was increased, the $T_g$ of the TGPAP/$CaCO_3$ nanocomposites did not obviously change, whereas the crosslinking density was linearly increased. The nanocomposites showed a higher thermal stability than that of the neat epoxy resin. This result could be attributed to the increased surface contact area between the nano-$CaCO_3$ particles and the epoxy matrix, as well as the high crosslinking density in the TGPAP/$CaCO_3$ nanocomposites. The CTE of the nanocomposites in the rubbery region was significantly decreased as the nano-$CaCO_3$ content was increased.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.2_2
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• pp.371-375
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• 2024

Epoxy resins are widely used in various fields due to their high adhesion, mechanical strength, and solvent resistance. However, as the volume decreases during the hardening process and the cooling process after hardening, stress is generated and when an external force is applied, the brittle material exhibits destruction behavior. To complement this, research has been conducted using inorganic nanofillers such as halloysite nanotube(HNT). HNT has a nanotube structure with the chemical formula of Al₂Si₂O₅(OH)₄·nH₂O and is a natural sediment of aluminosilicate. It has been used as additive to improve the mechanical properties of epoxy composites with exchange of amine group as a terminal functional group. In order to simplify complicated procedures of common wet method, a dry coating machine was designed and used for amine group exchange in previous research. In this study, they were applied as filler in epoxy composites, and mechanical properties such as tensile strength and flexural strength of composites were examined.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.960-966
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• 1997

The effects of epoxy resins and content of catalyst on the cure characteristics were studied by FT-IR, DSC and dynamic viscometer for the thermal properties and rheological properties of the catalytic (N-Benzylpyrazinium hexafluoroantimonate, BPH) epoxy thermosetting system. Compared with DSC results of DEGBF containing 0.5wt% BPH, the DSC thermograms of DGEBA containing 0.5wt% BPH indicated that the reaction was faster than that of DGEBF/BPH and the conversion rate of DGEBA/BPH was high in the initial stage of the reaction. As the concentration of BPH increases, the reaction and conversion rates show similar value in both the cases. The influence of hydroxyl group of epoxy resin on gel point defined from the crossover point of storage modulus (G') and loss modulus (G") could be explained by the formation of 3-dimensional network in the initial stage owing to the curing reaction between epoxides and hydroxyl groups of epoxy resin. This was consistent with the gel point obtained from DSC, FT-IR and moduli crossover. The activation energy (Et) obtained from the crossover point (G'/G"=1) are $31-39kJ.mol^{-1}$ for various BPH compositions in case of two epoxy systems.