• Bulletin of the Korean Chemical Society
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• v.22 no.11
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• pp.1255-1260
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• 2001

The expansion of two different kinds of hydrodynamic size of polymethyl methacrylate (PMMA Mw: 1.56- 2.04 ${\times}$ 106 g/mol) has been measured by dynamic light scattering and viscometry above the Flory $\theta$ temperature of the variou s solvents such as n-butyl chloride, 3-heptanone, and 4-heptanone. The expansion of PMMA chains was analyzed in terms of universal temperature parameters and also compared with previous results of polystyrene (PS) system. First it was found that simple $\tau/{\tau}c$ parameter no longer had its universality for the expansion behavior of hydrodynamic size in the chemically different linear polymer chains. However after modifying ${\tau}/{\tau}c$ parameter into $(Mw/Ro2)3}2(\tau/\tauc)$, we observed a much better universality for both PMMA and PS systems. Here Mw, Ro, $\tau[=(T-{\theta}$)/${\theta}$]$, and ${\tau}c[=({\theta}-Tc)/Tc]$ are defined as the weight average molecular weight, the unperturbed end-to-end distance, the reduced temperature and the reduced critical temperature, respectively.

• Journal of the Korean Chemical Society
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• v.39 no.8
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• pp.666-671
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• 1995

The conformational properties of poly(ethylene oxide) (PEO) in aqueous solutions are studied by viscometry with respect to the water structure perturbing capabilities of a series of urea solutes at $16^{\circ}C$, and experiments for the effect of amounts of urea and methylurea on PEO at 16 and $25^{\circ}C$ are also performed. The results show that the chain expansion, by ureas, of PEO of $1.0{\times}10^5$ molecular weight at $16^{\circ}C$ is similar to that of PEO of $8.0{\times}10^3$ molecular weight at $25^{\circ}C$ with respect to the water structure perturbation. Urea and methylurea make the PEO chain expand by the perturbation of water structure around PEO and by the hydrophobic interaction between methylurea and PEO, respectively. PEO of $1.0{\times}10^5$ molecular weight has hydrophobic sites on it, which are roughly classified into two parts; one is the inner hydrophobic groups which can interact between themselves (intramolecular hydrophobic interaction) and prevails at $16^{\circ}C$, and the other is the outer, exposed hydrophobic groups which can interact with the added hydrophobic solute (intermolecular hydrophobic interaction) and prevails at $25^{\circ}C.$

• Korean Journal of Food Science and Technology
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• v.36 no.4
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• pp.547-552
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• 2004

Attempt was made to establish identification methods for irradiated starch. Commercial starches (corn starch/CS, sweet potato starch/SS, and potato starch/PS) were irradiated at 0-6.0 kGy and used to measure viscosity with Brookfield DV-III programmable rheometer. Starch suspensions were prepared at 8.0 (7.2%, d.b.), 8.5 (7.3%, d.b.), and 9.0% (7.3%, d.b.) for CS, SS, and PS, respectively at 100 rpm in spindle speed. Results showed viscosities of samples significantly decreased (p<0.05) as irradiation dose increased, with $R^2$ 0.9754, 0.9618, and 0.9888 for CS, SS, and PS, respectively. Irradiation dose at 1.5 kGy induced decrease in viscosity as compared to non-irradiated control by 34, 57, and 51% in CS, SS, and PS, respectively, suggesting viscometry could lie applied to identify irradiated starches. Solubility and alkali number of irradiated starches significantly increased with irradiation doses, while swelling power decreased (p<0.05). Results suggested solubility, alkali number, and swelling power for irradiated starches complement identification results of viscometry.

• Polymer(Korea)
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• v.33 no.5
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• pp.501-508
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• 2009

The thermal degradation experiment of sodium salt of poly (${\gamma}$-glutamic acid) (PGGNa) has been carried out in both its solid phase and solution phase at the range of $57{\sim}120^{\circ}C$ and their molecular weight decreasing effect was analyzed as a function of time by means of viscometry and light scattering. Based on the solid phase degradation results, it was supposed that the bond scission rate in a polymer chain kept constant and that the bond scission was occurred on a randomly located position in a polymer chain. For the degradation in solution phase, it was also found that all data at various temperatures were dropped on a single master curve when the reduced time $t/t^*$ was used in the plot of the reciprocal intrinsic viscosity (or molecular weight). This degradation curve in solution phase could be expressed as the sum of a single exponential and a linear equation and especially, the single exponential character appeared only at the beginning stage. The activation energy was measured as $107{\sim}115$ kJ/mol in this study and agreed with the literature values.

• Journal of the Korean Applied Science and Technology
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• v.24 no.2
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• pp.167-173
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• 2007

The surface of poly(ethylene naphthalate) film applicable to high temerature insulator for convection microwave oven was modified with silicone coating solutions in the presence of silane crosslinking agent. The structure and properties of the PEN films were investigated by using Fourier transform IR spectroscopy, viscometry, microscopy, and tensile tests. The experimental results showed that the coating with silicone enhanced thermal stability up to $200^{\circ}C$, and slightly lowered the tensile strength and elongation of the PEN films. Judging from dimensional stability results the silicone coated PEN films can not be used for higher temperature insulator above $230^{\circ}C$. Serious dimensional contraction of films was obtained during heat treatment at $250^{\circ}C$ even for 1h. However, the surface of those films still have same chemical structure of silicones. Therefore, If we use PEN film prestretched at $230^{\circ}C$ as base one it will be possible to prepare a high temperature insulator up to $230^{\circ}C$. Conclusively, a silicone coated PEN film can be suitable for the application to convection microwave oven door insulator at high temperature up to $230^{\circ}C$.

• Journal of the Korean Applied Science and Technology
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• v.27 no.4
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• pp.508-514
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• 2010

Regenerated cellulose fibers were prepared from three pulps containing different degree of polymerization(DP) and $\alpha$-cellulose contents by dry-jet wet spinning technique with cellulose dope in N-methylmorpholin N-oxide (NMMO). The effect of antioxidant, n-propyl gallate (PG) on the properties of different regenerated celluloses was studied using X-ray diffraction, copper number calculation, and viscometry. The degradaqtion of regenerated cellulose from pulp containing higher DP and lower $\alpha$-cellulose content was occurred more seriously. The tensile strength and initial modulus of regenerated cellulose fiber obtained from NMMO dope with PG were higher than those of fiber obtained from NMMO dope without PG. All fibers showed the round shape cross section and typical cellulose II crystalline structure.

• Bulletin of the Korean Chemical Society
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• v.7 no.3
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• pp.238-240
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• 1986

Complex formations between syndiotactic poly(methacrylic acid) (st-PMAA) and poly(N-vinyl pyrrolidone) (PVP), and that between st-PMAA and polyethyleneoxide (PEO) through hydrogen bonding were studied by viscometry and potentiometry. Reduced viscosity (${\eta}_{red}$) was measured at various mole fraction of PVP or PEO with respect to a constant amount of st-PMAA. Observation shows a sharp minimum at the 1:1 mole ratio of st-PMAA:PVP or st-PMAA:PEO, which shows that the complexation becomes optimal and the complex has a compact structure in this ratio. Variation of pH also supports this conclusion. This is the case of the system of st-PMAA and PVP in water as well as in DMF. Also the complexation is much enhanced when the molecular weight of PVP is high. Meanwhile, the system of st-PMAA and PEO shows a little different behavior, i.e., this system does not form the complex in DMF and does only in water. It is because the interaction st-PMAA with PEO is weaker than that with PVP.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.715-721
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• 1997

W/O/W multiple emulsions were prepared comprising $MgSO_4$ in the inner aqueous phase as a model drug. The stability and drug release behavior of the multiple emulsions were studied using optical microscopy, viscometry and conductometry. Glucose was introduced in the outer aqueous phase to reduce the osmotic pressure gradient across the oil layer arising from the localization of drug molecules in the inner water phase. It was found that the presence of glucose was effective in stabilization of the multiple emulsions and in control of the release rate of drug more evidently when oil phase was partially hydrophilized with cetostearyl alcohol. This may be attributed to the fact that the migration of water accompanying the hydrophilic surfactant to the inner water phase was limited under a reduced osmotic pressure gradient and thereby slow down the destabilization of the oil/inner water interface.

• Membrane Journal
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• v.28 no.4
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• pp.286-295
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• 2018

A novel multi-valent salt based on polyethyleneimine having molecular weight of 800 (PEI 800) has been synthesized and characterized as forward osmosis draws solute. A reaction intermediate was synthesized by the neutralization reaction of polyethyleneimine and methyl acrylate, and was hydrolyzed with potassium hydroxide to synthesize a water soluble carboxylic acid (potassium salt) polyethyleneimine. NMR spectrometry, viscometry measurements and osmometry measurements was performed to characterize the draw solute. Forward osmosis experiments were done to know whether the solute could be used as a draw solute or not. The result shows comparable water flux and lower reverse salt flux compared with NaCl as a draw solute. We have also demonstrated recycling of the draw solute in the FO-NF integrated process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.1
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• pp.51-56
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• 2015

The object of this study is to obtain the optimum mix proportion of halogen free compound with flame resistance and, for the purpose, thermal/electrical characteristics test are conducted using compatibilizing agents, flame resistance agents, hydroxide aluminum, sunscreen, antioxidant and silicon oil on the base resin of linear low density polyethylene (LLDPE), Ethylene vinyl acetate copolymer (EVA). Existing compound method accompanies many requirements to be satisfied including a lot of addition of flame resistance agents, prohibition of impact on mixing capability with base and property and etc. In this study, different from the existing method, the optimum mix proportion is determined and experimented by adding nano clay. Oxygen index test shows no difference between specimens while T-6, T-9 shows oxygen index of 29[%] and 26[%], respectively. This is concluded that hydroxide aluminum, which is a flame resistance agent, leads low oxygen index. From UL94-V vertical flame resistance test, the combustion behavior is determined as V-0, Fail based on UL94-V decision criteria. Viscometry shows low measurements in specimens with separate addition of compatibilizing agents or nano clay. Volume resistivity test shows low measurement mainly in specimens without compatibilizing agents. Therefore, with the flame resistance compound shows better performance for thermal/electrical property and the optimum mix proportion are achieved among many existing materials.