• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.973-978
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• 1997

The toughness and morphology of epoxy resin based on diglycidyl ether of bisphenol A(DGEBA) cured with of tris (dimethylaminomethy]) phenol(DMP-30) and castor oil (CO) as a toughening modifier have been studied. Mixtures of CO and an epoxy resin showed a higher miscibility than the classical CTBN modified epoxy resin. The glass transition temperature($T_g$) was decreased with the CO content and the cure temperature. It is interpreted that the networks of epoxy matrix obtained at high temperature are apparently looser and more flexible due to the lower crosslinking density. The toughness was slightly increased with the CO content at $40^{\circ}C$ of curing temperature. The toughness increased with increasing the cure temperature and CO content.

• Applied Chemistry for Engineering
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• v.4 no.1
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• pp.125-131
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• 1993

The state of water in various modified cellulose membranes such as [carboxymethyl cellulose(CMC)-gelatin] polyelectrolyte complex, methylcellulose(MC) grafted with acrylic acid(AA), [(MC-g-AA)-gelatin] polyelectrolyte complex, were determined by differential scanning calorimetric technique. The amounts of freezing(free) and nonfreezing(bound) water were estimated to determine the permeability coefficient of solutes through membranes. The state of water in membranes were influenced by the states of the composition, morphology, and their water content. The difference in diffusive permeability through the water-swollen membranes can be explained by the difference in the free and bound water content.

• Applied Chemistry for Engineering
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• v.4 no.1
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• pp.178-187
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• 1993

Degradation of the starch-polyethylene composite film by an activated sludge treatment and a soil burial test was examined. The treated films had deformed structures which were resulted from the removal of starch during the treatments. The added auto-oxidant caused the degradation of the polyethylene matrices and the crosslinking reactions after the oxidation of polyethylene chains as well. As a result of soil burial test, the degradation reaction of the composite film containing corn oil as an auto-oxidant was, however, prevalent : number- and weight-average molecular weight of polyethylene decreased, while the molecular weight distribution increased.

• Applied Chemistry for Engineering
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• v.4 no.1
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• pp.188-195
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• 1993

Polyelectrolyte complexes and graft copolymers as biomaterials were synthesized from the water soluble cellulose derivatives. Polyelectrolyte complexes have been prepared from carboxymethyl cellulose (CMC) and gelatin. Graft copolymers(Mc-g-AA) were synthesized by grafting acrylic acid (AA) onto methyl cellulose(MC). (Mc-g-AA) and gelatin polyelectrolyte complexes were also prepared. The optimum conditions of each sample were investigated after chemical crosslinking or heat treatment. The preliminary results show that these materials might be interesting for biomedical applications.

• Polymer(Korea)
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• v.35 no.1
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• pp.94-98
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• 2011

Poly(2-hydroxyethyl methacrylate), PHEMA, hybrid gels containing Pluronic and acrylic acid (AAc) were prepared as new biocompatible and stimuli-responsive hydrogels by photo-polymerization technique. The prepared hybrid gel showed reversible, temperature-responsive swelling behavior due to the presence of Pluronic component, which underwent sol-gel transition at an elevated temperature to cause gel shrinkage. The hydrogel also exhibited increased swelling degrees and pH-sensitivity due to the AAc component with ionizable carboxylic acid groups. The microporous gel morphology and its changes upon stimuli was observed by scanning electron microscopy.

• Polymer(Korea)
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• v.38 no.5
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• pp.620-625
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• 2014

The effect of polyvinyl alcohol/polyamide-epichlorohydrin (PVA/PAE) complex strengthening additive on dry and wet strength and surface properties of paper was investigated. The enhancements of dry and wet strength and dimensional stability were found when PVA/PAE was applied as a complex strengthening additive compared with the cases of applying individual PVA or PAE. This was understood as physical crosslinking between PVA and PAE in the PVA/PAE complex strength additive. This complex strengthening additive also lowered surface roughness and increased sizing. As a result, PVA/PAE complex strengthening additive provided the distinctive gain dot in printed papers.

• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.55-59
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• 1998

The water absorption in protective coatings, which may greatly influence the durability of these coatings, was studied using quartz crystal microbalance and electrochemical impedance technique. The water absorption in protective coatings and the change of coating capacitance with concentration of electrolyte were measured. The water absorption in coatings seems to be driven by osmotic pressure, and larger amount of water was absorbed in thinner coatings at initial stage of absorption. The amount of water absorbed in coatings changed with the type and crosslinking density of resin used in coating formulation. When water absorption and desorption of coating occured by exposing the coatings to electrolyte solutions of different concentration, increase in impedance caused by desorption of water was found to be higher in the case of thinner film.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.281-282
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• 2008

고압절연용 에폭시-나노콤포지트의 전기적, 기계적, 열적특성이 동반적 물성의 상승을 가져오기 때문에 활발한 연구가 진행 중에 있다. 에폭시 메트릭스 내에서 유기화된 층상구조를 갖는 나노입자의 분산정도에 따라 여러 가지 물성에 영향을 나타내고 있다. Centrifugal 분산기법으로 나노콤포지트제조시 에폭시분자의 층간내로 충분한 삽입으로 박리가 발생하였다. 전기적 특성로서 기본적 구조적 특성인 X-RD특성과 TEM의 관찰로 분산을 확인할 수있었고, DSC의 측정으로 가교도를 알 수 있는 Tg값이 원형수지에 비하여 $11^{\circ}C$향상된 여러종류의 나노콤포지트를 개발하였다. 유전특성 및 절연파괴 특성으로도 원형수지에 비하여 나노콤포지트의 향상된 특성을 얻을 수 있었다.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1608-1610
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• 2000

In this work, the effect of annealing on physical and electrical properties of XLPE cable insulation was investigated. One sample was non-annealed and the other two samples were treated under air circulated oven at 80$^{\circ}C$ for five and ten days. In the DSC patterns of annealed specimen, new peaks appeared at near 80$^{\circ}C$ as a proof of thermal history. The degree of crystallinity increased by annealing effect. In the FT-IR spectrums, the change of absorbances to acetophenone and cumyl alcohol were observated according to the radial direction of cable insulation. They slowly diffused into both semi-conductive layer of the cable in proportion to annealing time and lastly led to near equilibrium state through cable insulation. The AC breakdown strength did not increased but the values were stabilized by effects of crystallinity and diffusion of by-products.

• Membrane Journal
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• v.31 no.4
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• pp.282-292
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• 2021

In this work, we tested commercial organic solvent nanofiltration (OSN) membranes using both in-house dead-end and crossflow systems. Four different crosslinked polyimide Duramem (DM) OSN membranes with various MWCO (molecular weight cut off) values were tested in organic solvents such as ethanol, N,N-dimethylformamide, acetone and acetonitrile. The membranes exhibited more reliable and reproducible performance in the crossflow system, and the performance changed significantly depending in the physical properties of the testing solvent. This is due to the initial stabilization period via pressure-induced compaction phenomenon, which can be vastly different between membrane samples. Hence, to obtain reliable and reproducible results, crossflow system is the preferred choice.