• Geotechnical Engineering
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• v.7 no.2
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• pp.83-86
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• 1991

• 방재와보험
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• s.30
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• pp.48-49
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• 1986

• 환경사랑
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• s.59
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• pp.4-5
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• 2011

• Geotechnical Engineering
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• v.10 no.3
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• pp.149-172
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• 1994

• Polymer(Korea)
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• v.27 no.4
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• pp.377-384
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• 2003

High impact polystyrene/organically modified layered silicate (HIPS/OLS) nanocomposites by in situ polymerization were synthesized to investigate the effect of clay on the particle size and properties of rubber. In the OLS, the montmorillonite having benzyl group showed best dispersion in polystyrene phase. With the addition of clay, the intercalated peak from XRB was confirmed, but the peak gradually shifted to lower angle as rubber concentration increased. Thus, it is speculated that the organoclay disperses better in rubber phase than in polystyrene phase. The average rubber particle size increased and the particle size distribution widened as the amount of clay increased, which may be caused by the increase of the viscosity ratio of rubber to polystyrene phases and the unstable dispersion. The materials having clay showed improved thermal properties from thermogravimetric analysis. Rheological properties such as complex viscosity and storage modulus increased as the amount of clay increased.

• Analytical Science and Technology
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• v.24 no.6
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• pp.435-442
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• 2011

Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants (BFRs) which have taken much interest recently due to their potential hazardous effects to human body and ecosystem. Many countries and European community prohibits the usage of certain BFRs in electronics and electronic devices (e.g. RoHS). In this perspectives, Korea Research Institute of Standards and Science (KRISS) has designed and practiced proficiency testing programs based on the ISO/IEC 17043 in order to assist laboratory accreditation activities. The programs for interlaboratory comparisons include congeners of PBDE (PBDE-154, 183, 206, 209) in high impact polystyrene (HIPS). A sample bottle that contains 10 g granular HIPS was distributed to 35 participating laboratories and the test results were calculated by the statistical procedure using z-scores to evaluate performance of each laboratory. The results and the laboratory's performance were discussed.

• Polymer(Korea)
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• v.26 no.3
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• pp.307-315
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• 2002

Major factors affecting the impact resistance of high impact polystyrene (HIPS), the rubber-toughened grade of polystyrene, are rubber-phase particle size and size distribution, molecular weight, morphology, and degree of grafting. Accordingly, it is important to control or investigate these factors. In this study, the effect of solvent content was analyzed by the morphology and particle size distribution of rubber phase, and final properties in bulk-solution polymerization of HIPS. The prepolymerization time was, first, determined by measuring the evolution of particle size distribution of dispersed phase to explain the phase inversion with time. As the solvent content increased, the size of rubber particle increased and then gradually decreased. Rubber-phase morphology was likely to have higher degree of grafting as the solvent content increased. Rheological and mechanical properties decreased as the solvent content increased because of the decrease of matrix molecular weight due to the chain transfer reaction to solvent and the existence of residual solvent. Nevertheless, the impact resistance seemed to increase when the rubber particle size increased.

• Polymer(Korea)
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• v.33 no.5
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• pp.458-462
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• 2009

We have synthesized ABC linear triblock copolymers, i.e., polystyrene-b-poly(ethylene oxide)-b-polylactide, via sequential anionic and ring-opening polymerizations. In the first anionic polymerization step, styrene was polymerized in cyclohexane using sec-butyllithium as the initiator. Poly (styryl) lithium was hydroxylated by the addition of ethylene oxide, and the subsequent protonation with methanolic HCl. In the second anionic polymerization step, potassium naphthalenide was used to deprotonate the hydroxyl group of the PS to generate the macroinitiator of PS-$O^-K^+$. Polymerization of ethylene oxide was performed in THF and terminated with methanolic HCl. In the ring-opening polymerization step, the PS-b-PEO-$AlEt_2$ macroinitiator was prepared from an $AlEt_3$/pyridine system in THF, and the polymerization of lactide was performed at $90^{\circ}C$. The resulting block copolymers showed well-defined molecular weights and narrow molecular weight distributions as revealed by $^1H$- NMR spectroscopy and gel permeation chromatography (GPC).

• Polymer(Korea)
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• v.33 no.1
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• pp.33-38
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• 2009

Monodisperse polystyrene and its copolymer beads containing amine function were prepared for the electroless silver plating using reduction of silver alkylcarbamate complex in organic solvent. Soap-free emulsion polymerization was adopted for the polymerization of styrene, divinylbenzene (DVB), and 2-(N,N-dimethylamino) ethyl methacrylate (DAEMA) in the presence of poly (vinyl alcohol) in a water/methanol solvent. The resulting poly (styrene/DVB/DAEMA), containing 30/0$\sim$1.5/0$\sim$3 wt% in monomer composition, were found to be a sphere-type particle with diameter of 1 ${\mu}m$. Silver Ag-coated polystyrene beads were prepared by in sito reduction of a silver 2-ethylhexylcarbamate (Ag-EHCB) complex solution with hydrazine without pretreatment of polystyrene beads. Robust Ag/polystyrene beads were analyzed by SEM, UV -visible spectrometer and XRD.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.6
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• pp.1056-1062
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• 2004

Migration of low molecular weight components from expanded polystyrene (ESP) to distilled water was measured at different temperature conditions. Overall migration and specific monomer migration were measured. Diffusion model based on Fick's law was used to determine the apparent diffusion coefficients at various experimental conditions. The overall and specific migration levels were estimated to give some practical implications for regulatory guideline development and safe package design. Diffusion coefficients for overall migration in KMnO$_4$ oxidizable extractives and specific migration of styrene monomer from ESP at 6$0^{\circ}C$ were 0.030 and 6.8${\times}$10$^{-5}$ $\textrm{mm}^2$/h, respectively. Their temperature dependence could be explained by Arrhenius equation with respective activation energies of 80.5 and 98.6 kJ/㏖. Experimental conditions ensuring desired migration level were suggested for reliable examination of migration from the packaging material. Some explanatory estimations of migrations were given for some typical conditions of potential usages.