• YAKHAK HOEJI
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• v.38 no.3
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• pp.338-344
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• 1994

This study was carried out to investigate the antifibrotic effects of polysaccharides extracted from Garnoderma lucidum. The biliary cirrhosis was induced by bile duct ligation/scission (BDL/S) in rats. BDL/S rats were dosed 5 mg/rat/day orally for 4 weeks after the operation. Antifibrotic effects were evaluated by serum biochemical values, serum procollagen type III peptide (PIIINP) levels, liver hydroxyproline contents, and light microscopical histology. The results obtained were as follows; 1) PIIINP levels in sera of treated BDL/S group were lowered to 50% of those of untreated BDL/S group. 2) Hydroxyproline contents in the liver of treated BDL/S group were also reduced to 83% of those of untreated BDL/S rats. 3) The hepatic damage such as hepatocellular necrosis, inflammation, bile duct proliferation and fibrosis was less severe in the livers of treated rats. These results suggest polysaccharides extracted from Garnoderma lucidum to be a promising agent for the inhibition of hepatic cirrhosis(fibrosis).

• The Korean Journal of Rheology
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• v.9 no.1
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• pp.6-15
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• 1997

계면활성제용액에 서로 다른 기능을 하는 두 종류의 첨가제를 투입하여 미셀의 미 세구조 전이현상을 규명하였다. 양이온 계면활성제는 CMC 이상의 농도에서 2단계의 미세 구조 전이거동을 나타낸다. 우선 구형 미셀은 첨가제의 투입에 의하여 표면에서의 친수성기 간의 반발력이 감소됨으로써 실린더형 또는 디스크형미셀로 전이가 일어난다. 더욱 농도가 증가하면 이방성을 가지는 실린더형 미셀간의 중첩 또는 hooking 현상에 의한 두 번째 전 이가 일어난다. 이때 미셀 용액은 흔히 점탄성을 나타내거나 확연한 비뉴톤성 유체거동을 나타낸다. 본 연구에선 heptanol의 화확구조적 차이가 물성에 나타내는효과를 규명하고 wormlike 미셀을 형성하는 MaSal에 의한 점탄성 거동을 살펴보았다. Heptanol의 화학구조 의 영향을 보면 약친수성기인 OH기가 알킬그룹과 나란하게 존재하여 밀집된 구조를 가지 기 쉬운 primary heptanol이 가장효과적으로 미세구조 전이를 유도함을 관찰하였다. 다른 이성질 hetanol의 경우 secondary heptanol이 teriary heptanol에 비하여 효과적임을 보이지 만 화학재할수 있는 농도범위가 매우 좁아 대부분 영역에서 비뉴톤성거동을 나타냄을 확인 하였다. 즉 NaSal를 사용한 경우 실린더형 미셀이 존재할 수 있는농도범위가 매우 좁아 대 부분 영역에서 비뉴톤성 거동을 나타냄을 확인하였다. 즉 NaSal 이 첨가된 용액은 선형점탄 성거동을 보이며 몰비가 증가함에 따라 scission 과정이 관찰되었다. 또한 몰농도비에 따라 항복응력과 shear thickening 특징을 보이는데 이는 흐름장의 세기에 따라 미세구조 변화가 일어나기 때문이다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.176-177
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• 2015

본 실험에서 PET 위 무전해 구리 도금을 위한 전처리 방법 중 하나인 UV 조사를 통해 전처리를 한 후 PET 표면의 특성과 염기성 무전해 도금액이 개질된 표면에 미치는 영향에 관한 연구를 하였다. 일반적으로 PET 표면을 개질시키기 위해 UVC(254nm) 파장을 이용하여 PET bond break (Chain Scission)을 이루는 것으로 알려진다. 이때 공기 중의 산소와 UV 조사를 통해 생성된 PET 내의 free radical과 산화 반응을 통해 친수성이 높은 표면을 형성하게 된다. PET 표면의 친수성을 측정하기 위해 접촉각 측정기가 사용되었으며, 표면의 거칠기 및 형상을 관찰하기 위해 AFM과 FE-SEM를 각각 이용하였다. 또한 PET 표면의 구조 변화는 XPS를 통해 분석을 진행 하였다. UV 조사 후 표면의 거칠기 및 친수성은 높아졌지만, 무전해 도금은 이루어지지 않았다. 분석 결과, 이는 표면에 형성된 Low Molecular Weight Oxidation Compound(LMWOC)가 염기성 수용액 내에서 용해되어 모두 씻겨 나가 표면에 형성된 Sn/Pd을 모두 떨어트린 것으로 판단되며, 위와같은 이유로 UV 조사 후 습식 공정에 적용하기 위해 표면개질 된 PET를 염기성 수용액을 통해 전처리가 필요한 것으로 사료된다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.43.1-43.1
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• 2018

Spatial distribution of binding state in depth direction is investigated in a hard skin layer on soft polydimethylsiloxane (PDMS) fabricated by Ar ion beam irradiations. The hard skin layer known as a silica-like homogenous layer was composed of two layers. Impinging Ar ions transfer energy to PDMS as a function of collisional energy transfer rate, which is the maximum at surface and decreases gradually as an ion penetrates. This formed the heterogeneous hard skin layer that consists of a top-most layer and an intermediate layer. XPS depth profiling showed the existence of the top-most layer and intermediate layer. In the top-most layer, scission and cross-linking were occurred simultaneously and Si-O bond showed dissociated status, SiOx (x = 1.25 - 1.5). Under the top-most layer, there was the intermediate layer in which cross-linking is mainly occurred and Si-O bond showed silica-like binding status, SiOx (x = 1.75 - 2). And theoretical analysis which calculates the collisional energy transfer and a displacement per atom explained the thickness variation of top-most layer according to Ar ion energy from 360 eV to 840 eV.

• Textile Coloration and Finishing
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• v.21 no.4
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• pp.33-38
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• 2009

Poly(vinyl acetate) films containing benzophenone were photocrosslinked by continuous UV irradiation.UV irradiation of PVAc film containing 5% benzophenone induced bulk crosslinking of the polymer indicated by 84.1% of gel fraction after ethyl acetate extraction. The crosslinking was attributed to the recombination of tertiary polymer radicals generated upon UV irradiation, which was enhanced by the hydrogen abstraction of benzophenone. Also the UV irradiation resulted in scission of ester linkage and photooxidation of PVAc surface, which was verified by ATR and zeta potential analysis, implying that the PVAc surface became more polar and hydrophilic. The zeta potential proportionally increased from +4.5mV to -26.8 mV with increasing UV irradiation. Also the surface energy of the PVAc film increased with higher UV irradiation upto 56.5 $mJ/m^2$ by the enhanced Lewis acid/base component with larger contribution of Lewis acid parameter. Accordingly the crosslinked PVAc showed higher thermal stability with increasing UV energy.

• Elastomers and Composites
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• v.23 no.4
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• pp.289-298
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• 1988

The thermal degradation of poly(methyl methacrylate)(PMMA) and poly($\alpha$-methylstyrene-co-acrylonitrile)(SAN) mixtures were carried out using the thermogravimetry(TG) and differential scanning calorimetry(DSC) in the stream of nitrogen and air with 50 ml/min at the various heating rate from 4 to $20^{\circ}C/min$ and temperature from 20 to $500^{\circ}C$. The value of activation energies of thermal degradation determined by TG and DSC in the various PMMA/SAN mixtures were 34-54 kcal/mol in the stream of nitrogen. The value of activation energy of SAN 60% mixture were appeared high in comparison with addition rule. PMMA/SAN mixtures by the analysis of infrared spectrophotometer were decomposed by main chain scission in the stream of nitrogen.

• Elastomers and Composites
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• v.38 no.2
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• pp.103-121
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• 2003

The application of powerful ultrasound to rubber recycling is a very recent field of study. An ultrasonic field creates high frequency extension-contraction stresses by acoustic cavitation. The breakdown of rubber network occurs primarily around pulsating cavities due to the highest level of strain produced by high-power ultrasound. Stronger reductions of cross-link density were observed at a higher pressure, indicating an important role of pressure during ultrasonic recycling. Visible bubbles were observed during ultrasonic treatment as a proof of acoustic cavitation. Shearing effect has a significant influence on improving the efficiency of ultrasonic treatment. After the ultrasonic treatment, the cross-link densities of NR/SBR blends were lower than those of NR and SBR due to the reduced degree of unsaturation and chemical reactions. Carbon black fillers increase the probability of bond scission during ultrasonic treatment, due to the restricted mobility. The mechanical properties of ground tire rubber (GRT)/HDPE blends were improved by ultrasonic treatment and dynamic revulcanization. Ultrasonic treatment of GRT in the presence of HDPE matrix was found to give better mechanical properties due to the chemical reactions between rubber and plastic phases.

• Elastomers and Composites
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• v.24 no.1
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• pp.11-18
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• 1989

The thermal degradation of Poly(methyl methacrylate) (PMMA) and poly(acrylonitrile butadiene styrene)(ABS) terpolymer as well as their mixtures were carried out using the thermogravimetry and differential scanning calorimetry(DSC) in the stream of nitrogen and air with 50 ml/min at the various heating rate from 4 to $20^{\circ}C/min$ and temperature from 200 to $300^{\circ}C$ The values of activation energies of thermal degradation determined by TG and DSC in the various PMMA/ABS mixtures were $34{\sim}58Kcal/mol,\;35{\sim}54Kcal/mol$ in the stream of nitrogen. The values of activation energy of ABS20% mixture was appeared high in camparison with addition rule. According to increasing the composition of ABS, the temperatures of glass transition and initial decomposition temperature were increased. PMMA/ABS mixtures by the analysis of infrared spectrophotometer were decomposed by main chain scission in the stream of nitrogen.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.5
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• pp.407-413
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• 2005

Ion implantation provides a unique way to modify the mechanical, optical and electrical properties of polymer by depositing the energy of ions in the material on the atomic scale. Implantation of ions into the polymers generally leads to a radiation damage, which, in many cases, modifies the properties of the surface and bulk of the material. These modifications result from the changes of the chemical structure caused in their turn by changing the chemical bonding when the incident ions cut the polymer chains, breaks covalent bonds, promotes cross-linking, and liberates certain volatile species. We studied the relation among the linear energy transfer (LET) and changes of surface microstructure and surface resistivity on PPS material using the high current ion implantation technology The surface resistivity of nitrogen implanted PPS decreased to $10^{7}{\Omega}/cm^{2}$ due to the chain scission, cross linking, ${\pi}$ electron creation and mobility increase. In this case, the surface conductivity depend on the 1-dimensional hopping mechanism.

• Journal of the Korean institute of surface engineering
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• v.50 no.6
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• pp.480-485
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• 2017

Soft mold imprinting method that uses nanostructured polymer mold was investigated for anti-reflection film fabrication. The nanostructured soft mold was polyethylene terephthalate(PET) irradiated by oxygen ion beams. The collisional energy transfer between oxygen ion and the polymer surface induced cross-linking and scission reactions, resulting in self-organized nanostructures with regular patterns of the wavenumber of $5{\mu}m^{-1}$. Post processes including ultra-violet curable resin coating and delamination fabricated anti-reflection films. The imprinted resin surface also showed the consistent wavenumber, $5{\mu}m^{-1}$. Pristine PET, oxygen ion beam treated PET, and imprinted replica sample showed total transmittance of 91.04, 93.25, and 93.57-93.88%, respectively.