• Korean Journal of Materials Research
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• v.9 no.4
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• pp.398-403
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• 1999

Studies on the electrical treeing deterioration and dielectric breakdown phenomena in the polymeric insulator of polyethylene and epoxy resin were carried out. Block type samples with needle-plane electrode geometry were electrically stressed and the tree pattern from the needle tip was observed. In LDPE the density of electrical tree was very high and its pattern was bush type. For the case of XLPE, branched tree was observed. As temperature and SN content increased, the dielectric breakdown voltage decreased and the treeing phenomena became more complicated. Fan type cracks were observed around the conducting tree path in the brittle DGEBA/MDA system.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.41-42
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• 2017

In this study, an investigation was made to study the chemical resistance performance of epoxy resin injection type leakage repair material used in the Korean construction market in accordance to the test method outlined in "ISO TS 16774, Part 2; Test Method for Chemical Resistance." This is a new standard document used for quality control method of injection type repair material used for leakage cracking of underground concrete structures. The results of this study can be expected to be utilized as reference data that can be used for quality improvement of the maintenance methods for future construction.

• Polymer(Korea)
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• v.26 no.4
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• pp.501-507
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• 2002

In this work, diglycidylether of bisphenol-S (DGEBS) epoxy resin was prepared by alkaline condensation of bisphenol-S (BPS) with epichlorohydrin (ECH) in the presence of NaOH catalyst. The structure of the synthesized DGEBS epoxy resin was confirmed by IR, NMR spectra, and elemental analysis. The curing reaction and glass transition temperature ($T_g$) of DGEBS epoxy resin cured with phthalic anhydride (PA) and tetrahydrophthalic anhydride (THPA) at curing agents were studied by dynamic differential scanning calorimetry (DSC). The thermal stability of the cured specimen was investigated by thermogravimetric analysis (TGA). As a result, the activation energy ($E_a$) of DGEBS/PA system was higher than that of DGEBS/THPA system, whereas $T_g$, initial decomposed temperature (IDT), and decomposition activation energy ($E_t$) of DGEBS/PA were lower than those of DGEBS/THPA. This was probably due to the fact that the crosslinking density of DGEBS/THPA was increased by ring strain of curing agent.

• Journal of Conservation Science
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• v.27 no.4
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• pp.431-440
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• 2011

The thermal expansion coefficient of epoxy/inorganic additives composites was controlled by changing the amount of the inorganic additives such as talc and fused silica. The epoxy resin comprises hydrogenated bisphenol A (HBA)-based epoxide, difunctional polyglycidyl epoxide (DPE) as a diluent and isophorone-diamine (IPDA) as a crosslinking agent, which was subsequently mixed with inorganic additives (talc and fused silica). The thermal expansion coefficient was decreased by increasing amount of inorganic additives, nearly to fresh granite. Fused silica was more effective than talc in lowering the thermal expansion coefficient. Additionally, lexural and tensile strengths of the composites were getting lower and higher with the amount of the inorganic fillers, respectively. It was thus concluded that an epoxy composite containing inorganic fillers was developed to show much lower thermal expansion coefficient, similar to fresh granite, than the neat epoxy resin, and also proper mechanical strengths for applications.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.2
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• pp.154-160
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• 2009

This paper shows a basic data of the surface discharge characteristics for epoxy resin in Dry-Air as being focused on environmentally friendly insulating Gas. Used electrodes are needle to plane, sphere to plane and KS M3015 electrodes. With the changing electrodes in same condition, we can obtain different creeping lengths, surface discharge voltages and surface dielectric strengths, respectively. Surface dielectric strengths of Needle to plane electrodes are more higher than the others. Moreover, it is considered that the surface discharge characteristics with variation of epoxy resin thickness and diameter. Surface discharge voltage increases as the thickness and the diameter of epoxy resin.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.85-92
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• 2021

The purpose of this study is to investigate the properties of hardener-free epoxy-modified mortars(EMMs) using ground granulated blast furnace slag(GGBFS) and alkali activators. The hardener-free EMMs with a GGBFS content of 20% using 4 types of alkali activators were prepared with various polymer-binder ratios, and tested for strengths, water absorption, carbonation depth, chloride ion and H2SO4 penetration depth. The conclusions obtained from the test results are summarized as follows: The compressive strength of the EMMs with a GGBFS content of 20% attains a maximum at a polymer-binder ratio of 10%. The flexural strength of the hardener-free EMMs using Ca(OH)2 as a alkali activator is improved with increasing polymer-binder ratios. However, the flexural strength of the EMMs using NaCO3, Na2SO4 and Li2CO3 is gradually decreased with increasing polymer-binder ratios. Regardless of the type of alkali activator, the water absorption, chloride ion penetration and carbonation depth are remarkably decreased with increasing polymer-binder ratios due to the epoxy film formed in the EMMs. The H2SO4 penetration depth of the hardener-free EMMs with a GGBFS content of 20% is gradually increased with increasing polymer-binder ratio. In this study, the properties of hardener-free EMMs using Ca(OH)2 as a alkali activator are more excellent than those of other alkali activators.

• Journal of Adhesion and Interface
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• v.14 no.3
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• pp.135-145
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• 2013

Epoxy resin compositions were studied on the view of self-extinguishing properties without retardant additives and suitability as materials of eco-friendly EMC (Epoxy molding compound). Cured epoxy and phenolic resin composition having conjugated double bond of aromatic structure exhibited self-extinguishing properties and low heat release capacity. In this study, the structure of long conjugated double bond of hetero-atom type azomethyne group between conjugated double bonds of aromatic structure showed lower heat release capacity. Low heat release capacity seemed to be related with high reaction enthalpy, $T_g$ and reactivity affected by hetero-atom structure in azomethyne group.

• Composites Research
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• v.30 no.6
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• pp.371-378
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• 2017

In this study, hygroelastic behavior of thermosetting epoxy is predicted by molecular dynamics simulations. Since consistent exposures to humid environments lead to macroscopic degradation of polymer composite, computational simulation study of the hygroscopically aged epoxy cell is essential for long-time durability. Therefore, we modeled amorphous epoxy molecular unit cell structures at a crosslinking ratio of 30, 90% and with the moisture weight fraction of 0, 4 wt% respectively. Diglycidyl ether of bisphenol F (EPON862) and triethylenetetramine (TETA) are chosen as resin and curing agent respectively. Incorporating equilibrium and non-equilibrium ensemble simulation with a classical interatomic potential, various hygroelastic properties including diffusion coefficient of water, coefficient of moisture expansion (CME), stress-strain curve and elastic modulus are predicted. To establish the structural property relationship of pure epoxy, free volume and internal non-bond potential energy of epoxy are examined.

• Elastomers and Composites
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• v.35 no.3
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• pp.196-204
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• 2000

SBR, polyurethane, acryl and epoxy latex were separately mixed with ethylene -vinylacetate emulsion(EVA) in the range of $0{\sim}50wt%$. For the mixtures, the various physical properties such as defoamerability, mechanical property, and water resistance were experimentally examined. The excellent defoamer was BYK-021 and the appropriate use of it was 0.3 phr for the total components. The shrinkage of compounds was influenced by the compatability of resins and the formation of voids. The mechanical properties was related to the cohesive force of resin particles, the coagulation of cement particles and the co-bonding of resin particles with cement particles. Mixing latex separately showed better properties then non-mixing in the shrinkage ratio, flexural strength, adhesive strength, and impact strength. The water resistance of composites mixed with cement was worse than that of EVA resin.

• Korean Journal of Materials Research
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• v.7 no.5
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• pp.386-389
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• 1997

반응성 첨가제로 사용된 HQ-PGE가 DGEBA/MDA계의 기계적 성질에 미치는 영향을 살펴보기 위해서 충격강도와 인장강도를 측정하였다. HQ-PGE의 함량이 25phr일 때 충격 강도는 첨가되지 않았을 때보다 40% 증가하고, 인장강도도 약간 증가하였다. 이것은 HQ-PGE가 합성될 때 생성된 수산기가 자촉매 반응을 하면서 에폭시 수지의 미반응된 에폭시기와 반응한 결과로 사료된다. Young's modulus와 신장율은 HQ-PGE의 함량이 증가함에 따라 크게 변화하지 않았다.