• Elastomers and Composites
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• v.48 no.1
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• pp.39-45
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• 2013

Melt grafting of citraconic acid (CCA) onto an ethylene-propylene-diene terpolymer (EPDM) with various peroxide initiators was performed using a Haake Rheocorder. Finding the optimum running condition and concentration is critical for effective grafting and performance of grafted material. Therefore, this study focused on the effects of mixing (reaction) condition and monomer/initiator dosages on the grafting degree, grafting efficiency and crosslinking degree (gel content), melt flow index and mechanical properties of CCA-g-EPDM. As the grafting degree/crosslinking degrees increased, the tensile strength increased significantly, but elongation at break and melt flow index decreased. The initiator 2,5-dimethyl-2,5-di(tert-butyl peroxy)-hexane (T-101) appeared to meet for the best grafting(2.31%). The grafting degree increased markedly with increasing monomer CCA/initiator T-101 contents. The grafting degree also increased with increasing mixing temperature/time, and then leveled off or decreased/increased a little. The optimum monomer/initiator dosages and reaction temperature/time were found to be about 5/0.05 wt% and $180^{\circ}C$/15min, respectively.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.38 no.4
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• pp.350-359
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• 1993

The effect of gibberellic acid ($GA_3) and abscisic acid (ABA) on KCl-enhanced proteolysis of senescing leaves of rice(Oryza sativa L. cv. Chilsung) was studied. Emphasis was given to their effects on KCI-enhanced efflux of amino acids and proteinase activity. When treated singly, $GA_3 affected leaf proteolysis little, while ABA increased proteolysis, the rate of amino acid efflux, and ribulose -1,5 -bisphosphate carboxylase / oxygenase (Rubisco)-degrading endoproteinase activity. An additive increase in all three parameters mentioned above was observed when leaves were treated with ABA and KCl. No such an additive effect was found when $GA_3 was treated with KCl. Both $GA_3 and ABA helped to alleviate the KCI-suppressed activity of Rubisco-degrading exoproteinases. The additive increase in proteolysis of rice leaves in the presence of both ABA and KCl could thus be ascribed to a further increase in the efflux of protein hydrolyzates and Rubisco-degrading endoproteinase activity. An increase in proteolysis was accompanied by a decrease in water absorption, and the combined treatment of ABA with KCl resulted in a further reduction of water absorption.

• Membrane Journal
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• v.22 no.2
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• pp.142-154
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• 2012

In order to remove $CO_2$ from the DME plant process, we investigated the composite membrane with rubbery polymers as the separation layer and its separation performance of $CO_2$ and $H_2$. Hollow fiber membranes for supporting layer were prepared by solution spinning method. In case of using PDMS as a separation layer, the composite membranes showed the permeation rates of $CO_2$ were over 300 GPU and minimum $CO_2/H_2$ selectivitties were 4.3 and in case of using PEBAX as a separation layer, the composite membranes showed the permeation rates of $CO_2$ were over 120 GPU and minimum $CO_2/H_2$ selectivities were 5.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.5021-5028
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• 2015

Previous studies have considered the permeability and construction method of paving materials, thus focusing on more practical issues rather than basic research of their properties. The present study investigated the possibility of using an elastic paving material having lesser thickness in the resurfacing of existing concrete or asphalt paved areas while satisfying the necessary conditions of resilience and water permeability. An alternative to complete reconstruction would reduce the amount of resource wastage and environmental pollution, as well as the cost of projects. This study investigated five variants of thickness (10, 13, 15, 20, 25mm) and three mixing ratios of binder to rubber chips (20, 22.5, 25%) to ascertain the ideal basic properties of each. The obtained test data revealed that a minimum thickness(10~25mm) of the elastic paving materials can be determined from a qualitative point of view, and alternatives should be provided to improve the durability of the paving material on account of the temperature sensitivity.

• Elastomers and Composites
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• v.43 no.4
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• pp.230-240
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• 2008

In order to synthesize polymer particle containing inorganic material, styrene and nbutylmetacrylate were copolymerized with alumina by dispersion polymerization. The ratio in weight of styrene to n-butyl methacrylate was 3:1. Poly(N-vinyl pyrrolidon) and 2,2'-azobis(isobutyronitrile) were added as stabilizer and as initiator, respectively. The change of particle size was investigated with concentration of initiator, the type of medium, the mixed solubility parameter (${\delta}_{mix}$) of medium, and coupling agent. The enhancement in concentration of initiator resulted in slight increase of particle size. The increase of polarizability in medium also yielded the increase of particle size. In case of changing the ratio of isopropanol to distilled water, we could find relationship of $[{\delta}_{mix}]^{-4.01}\;{\propto}$ particle size and $[{\delta}_{mix}]^{-0.83}\;{\propto}$ particle size distribution(PSD). The type and the concentration of coupling agent showed no effect on the particle size and PSD.

• Membrane Journal
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• v.1 no.1
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• pp.34-43
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• 1991

The relationships between affinity of membranes and optimum operation conditions were investigated in the pervaporation of water(1)/ethanol(2) mixture through cellulose acetate(CA) membranes having more affinity to water and silicone rubber(SR) membranes having more affinity to ethanol. CA and SR membranes were prepared and amount of sorption, sorption selectivity, pervaporation separation factor and pervaporation rate in both of membranes were determined and compared. The effects of downstream pressure were analyzed using Thompson diagram and the sorption and pervaporation characteristics with composition of feed and operation temperature were examined in terms of affinity, activity coefficient, plasticizing effect and activation energy of individual species. In the separation of water through CA membranes, high performance of both pervaporation separation factor (water to ethanol, $[\alpha^2_1]_{PV}$) and pervaporation rate was obtained in the conditions of low downstream pressure, middle range of feed concentration and high temperature. In the separation of ethanol through SR membranes, pervaporation separation factor(ethanol to water, $[\alpha^2_1]_{PV}$) increased with downstream pressure and decreased with concentration of ethanol in feed and operation temperature, while pervaporation rate showed opposite trends to those of ($[\alpha^2_1]_{PV}$).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.228-234
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• 2005

A magnetic composite as noise absorber of quasi-microwave band was developed. The Fe-Si-Al alloy powder were forged by attrition mill to get flaky shape. The magnetic composite sheet was fabricated in which powders are dispersed in polymer and aligned in the direction perpendicular to electromagnetic wave propagation. The permittivity of magnetic composite is increased as forging time increasing, while the permeability is decreased slightly. The maximum attenuation peak of reflection loss is shifted to lower fiequency range as milling time increasing, and the value of maximum attenuation peak is to get smaller gradually. From these result, we could designed a noise absorber sheet (t=1.0 mm) for quasi-microwave band, which is impedance matched at 1.4 GHz with respect to -8.2 dB reflection 1055.

• Elastomers and Composites
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• v.48 no.4
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• pp.249-255
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• 2013

Hydroxypropyl terminated PDMS was synthesized by the hydrosilylation reaction with allyl alcohol in the presence of Karstedt's catalyst. And them, an one-pot reaction with HDI isocyanurate trimer and hydroxyethyl methacrylate was conducted to give a silicone-modified urethane acrylate oligomer (PUA oligomer) having 9000 g/mol, weight average molecular weight. The synthesized PUA oligomer was characterized by using FT-IR and GPC. The UV-curable coatings were prepared by PUA oligomer blending with a reactive monomer (phenylthioethyl acrylate) under the different mole ratios. It was found that the refractive index of cured film increased when the reactive monomer was added but there was no relationship between the refractive index and amount of reactive monomer. Also, their transmittance for cured films was not change as increasing the content of reactive monomer.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.2
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• pp.376-381
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• 2008

In mixed dentition there exists many empty spaces in the arch due to eruption of permanent teeth and exfoliation of primary teeth. The empty spaces makes it difficult to apply fixed orthodontic appliances. Horseshoe Appliance can be used effectively at this stage, holding the whole dentition in one piece. It covers every surface of erupted teeth and prevents extrusion and rotation of single tooth. By using intermaxillary elastic force, remodeling of the alveolar bone is opposite in each arch. In patients who were treated with horseshoe appliance, forward growth of maxilla, labioversion of maxillary incisors and linguoversion of mandibular incisors were obtained. Minimum downward and clockwise rotation of mandible was shown, so increasing anterior facial height was minimized.

• Elastomers and Composites
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• v.48 no.2
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• pp.125-132
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• 2013

In this work, we have discussed new engineering systems for preparing carbon master batch composed by carbon black and various organic compounds. In general, polymer resin, which applied for automobile tire, household items, and various industry items, is used with the fillers including carbon black and silica to control the color or properties. Domestic part and material industry has been remarkably developed in that the development of materials including the compounding of raw materials. Meanwhile, the engineering technique for mass production has not reached to a requirement of industry due to slow technique development and high dependence on foreign. Thus, we will focus on the introduction of new engineering technique developed by domestic company for preparing carbon master batch.