• Journal of the Korean Magnetics Society
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• v.23 no.3
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• pp.83-88
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• 2013

The soft magnetic Fe-Si-Cr flakes with the thickness of about 1 ${\mu}m$ were annealed at 500 and $700^{\circ}C$ for 1 h, and the composite sheets for electromagnetic wave noise absorber available for quasi-microwave band were fabricated by using these annealed flakes and polymer. Further the power loss characteristics of the composite sheets was investigated to clarify the annealing effect on electromagnetic wave absorption properties. The power loss decreased in the frequency range of several GHz when the annealed flakes were used as compared to the sheet using the as-milled FeSiCr alloy flakes. Moreover the sheets using annealed flakes exhibited lower value of real and imaginary part of complex permeability. These inferior electromagnetic wave absorption properties of the composite sheets using annealed alloy flakes were considered to be obtained by the enhanced eddy current effect upon annealing-induced recovery of microstructure and resulted low complex permeability.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.888-893
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• 2003

The purpose of this study is to make clear the durability of the polymer films formed in the autoclaved polymer-modified mortars and concretes. The polymer films prepared with polymer dispersions such as a styrene-butadiene rubber (SBR) latex, a poly (ethylene-vinyl acetate)(EVA) emulsion and a polyacrylic ester (PAE) emulsion for polymeric admixtures are exposed to autoclaving at 18$0^{\circ}C$ in temperature and 1.01 MPa in vapor pressure, and subjected to tensile test and infrared spectroscopy. The durability of the polymer films is evaluated from the application of autoclaving to the polymer films under saturated Ca(OH)$_2$ solution immersion causes no degradation for SBR films and a significant degradation due to the saponification of the polymers for EVA and PAE films. Accordingly, in the application of autoclaving to polymer-modified mortars and concretes, it is suggested that SBR-modified mortars and concretes are hardly degraded but EVA- and PAE-modified mortars and concretes are markedly degraded by the saponification of the polymers.

• Ecology and Resilient Infrastructure
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• v.7 no.4
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• pp.262-273
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• 2020

Amending biopolymers such as β-glucan (BG) and Xanthan gum (XG) generally enhances soil strength by ionic and hydrogen bonds between soil particles. Thus, biopolymers have been studied as eco-friendly construction materials in levees. However, physiological responses of plants grown on soil amended with biopolymers are not fully understood. This study focuses on the effects of biopolymers on the growth of Camelina sativa L. (Camelina) under excess zinc (Zn) stress. The optimal concentrations of BG and XG were confirmed to have a 0.5% ratio in soil depending on the physiological parameters of Camelina under excess Zn stress. The Zn binding capacity of biopolymers was investigated using 1,5-diphenylthiocarbazone (DTZ). The reduction of Zn damage in Camelina was evaluated by analyzing the Zn content and expression of heavy metal ATPase (HMA) genes under excess Zn stress. Amendments of BG and XG improved Camelina growth under excess Zn stress. In DTZ staining and ICP-OES analysis, Camelina grown on BG and XG soil showed less Zn uptake than normal soil under excess Zn stress. The Zn-inducible CsHMA3 gene was not stimulated by either BG or XG amendment under excess Zn stress. Moreover, both BG and XG amendments in soil exhibit Zn-stress mitigation similar to that of Zn-tolerant CsHMA3 overexpres sed Camelina. These results indicate that biopolymer-amended soils may influence the prevention of Zn absorption in Camelina under excess Zn stress. Thus, BG and XG are proven to be suitable materials for levee construction and can protect plants from soil contamination by Zn.

• Applied Chemistry for Engineering
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• v.20 no.1
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• pp.67-74
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• 2009

Nowadays, recycling of recycled aggregates from the waste concrete is seriously demanded for the protection of environment and the shortage of aggregates owing to the large scale construction project. In this study, for the development of polymer composite recycling recycled aggregates from the waste concrete, twenty five specimens of the polymer composite were prepared with the five levels of replacement ratios of recycled aggregates (0, 25, 50, 75, 100%) and polymer-cement ratios (0,5, 10, 15, 20%), respectively. For the evaluation of the performance of polymer composite specimens, various physical properties such as compressive and flexural strengths, water absorption, hot water resistance, total pore volume and porosity were investigated. As a result, physical properties of polymer composite were remarkably improved with an increase of polymer cement ratios, but greatly decreased with the replacement ratios of recycled aggregates.

• Journal of Korean Ophthalmic Optics Society
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• v.1 no.1
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• pp.65-72
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• 1996

The general property of plastic ophthalmic lens has been reviewed by the optical property and polymer structure. A PMMA which is synthesized by the polymerization of monomers of two or more kinds is termed a copolymer, and the main chain composes a skeleton of molecular structure in the polymer. Refraction index of polymer was governed mainly by the polarization of molecular and was followed to increase it conspicuously as Cl, Br, and Iodine was substitude to hydrogen. Thermal dependence of refraction index of polymer show that the higher distinctive characteristic than glass material.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.88-96
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• 2020

In this study, the effect of cyclic wetting-drying on the self-healing of cementitious materials containing superabsorbent polymers (SAPs) were experimentally evaluated. In each cycle, cracked cement paste specimens containing various SAP dosages were exposed to wet conditions for 1 h, during which the capillary water absorption tests and water flow tests were conducted, and then exposed to dry conditions for 47 h. The capillary water absorption test results showed that the sorptivity values of the specimen without SAPs, SAP 0.5%, SAP 1.0%, and SAP 1.5% specimens were decreased by approximately 22.9%, 36.8%, 42.8%, and 46.3%, respectively, after 8 cycles. In addition, the water flow test results showed that the amount of water runoff through the cracks of all cracked specimens gradually decreased over wet/dry cycles, especially the reduction ratio of the amount of water runoff increased with increasing SAP dosage. Furthermore, the swelling behavior of SAPs in cracks by in gress water was con firmed via X-ray computed tomography (CT) analysis. These results indicate that the effective crack width can be reduced as SAPs absorb water and swell, while the water absorbed in SAPs can be released to crack surfaces under dry conditions, further promoting healing product formation. This study demon strates that the in corporation of SAPs can in crease the water tightness of cracks, thereby improving the self-healing efficiency of cementitious materials.

• Journal of the Korean Magnetics Society
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• v.20 no.4
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• pp.143-148
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• 2010

This study examined the effects of sheet thickness on electromagnetic wave absorption characteristics and internal microstructure in 92.6%Fe-6.5%Si-0.9%Cr (wt%) alloy flakes/polymer composite sheets available for quasi-microwave band. The composite sheets with the thickness of 0.3, 0.4 and 0.5 mm were prepared by tape casting. A significant decrease in transmission parameter $S_{21}$ and a large increase in power loss were observed for the thick composite sheet in the frequency range of 1~5 GHz. However the permeability properties were not affected by thickness variation, while the imaginary part of complex permittivity increased with the increase of sheet thickness at 1~5 GHz. The enhanced electromagnetic wave absorption characteristics in the thicker composite sheets was attributed to the changed microstructure and the higher dielectric loss.

• The Korean Journal of Mycology
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• v.28 no.1
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• pp.16-21
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• 2000

Super water absorbent (CPAM-AS-hyd-1) was prepared by polymerization of acrylamide and allyl sulfonate salt with N,N'-methylene-bis-acrylamide as crosslinking agent, followed by alkaline hydrolysis and the effect on mycelial growth and sporophore production of edible mushrooms in the artificial cultivation was examined. The mycelial growth of edible mushrooms did not depend on the addition of super water absorbent upto 200 g of hydrated polymer gel per 100 cc medium. The proper hydrated polymer gel concentration for sporophore production of Pleurotus sajor-caju and Hericium erinaceus were 200 g and $200{\sim}250\;g$ per 100 cc medium, respectively. The proper hydrated polymer gel and puffed rice hull concentration for sporophore production of Flammulina velutipes was 200 g per 100 mm medium and 10% (v/v), respectively.

• Polymer(Korea)
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• v.28 no.1
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• pp.18-23
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• 2004

Superabsorbent poly(potassium acrylate-co-acrylamide)s were synthesized in particle form using inverse suspension polymerization technique. Mean diameter of the prepared polymer particles decreased from 300 to 50 $\mu\textrm{m}$ with increasing surfactant concentration. The dynamic and equilibrium swelling behaviors during water absorption and drying process were investigated by weight measurement. The swelling ratio of polymer particles in water changed according to not only polymer crosslinking density, but particle size, saline concentration of aqueous medium, and copolymer compositions. Water sorption amount was increased with decreasing particle size, crosslinking agent concentration, and ion concentration in bulk solution. Being different from the water sorption process, the drying process was not significantly affected by particle size, polymer composition, or crosslinking amount.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05b
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• pp.15-18
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• 2004

피뢰기에 뇌 또는 이상전압과 같은 정격이상의 고장전류가 유입되어 발생하게 되는 순간적인 열 충격과 내부압력 상승은 폭탄이 내부에서 터지는 것과 같은 엄청난 양의 충격에너지이다. 본 연구에 있어서 폴리머 피뢰기의 제조에 사용된 모듈용 브레이드 복합재료는 압력해소 및 폭발 비산하지 않도록 하는 기능을 수행하도록 설계되어있다. 기존의 폴리머 피뢰기에 적용된 복합재료보다 충격에너지를 흡수하는 구조물에 유리한 브레이드 복합재료를 피뢰기 모듈의 제조에 도입한 것은 매우 의미 있는 일이라 판단된다. 따라서 본 연구에서는 열경화성 브레이드 복합재료를 제조하기 위하여 프리폼을 먼저 제작한 다음 금형에 삽입한 후 진공상태에서 수지를 주입하여 경화시키는 RTM공법을 이용하였다. 본 연구의 목적은 브레이드 패턴 및 방압개소 설계 등의 기초적인 자료조사 및 실험을 통하여 폴리머 피뢰기의 폭발 비산을 방지할 수 있는 압력해소 성능을 위한 기초 자료를 확보하고자 하는 것이다. 브레이드 복합재료의 기본적인 경화거동을 등온 및 동적 DSC를 이용하여 고찰하였고, 기본적인 전기적 특성을 평가하였으며, 방압개소를 가진 폴리머 피뢰기 모듈의 고장전류시험시 예상되는 열 충격에 대한 성능을 검증하기 위하여 열팽창계수를 측정하였다.