• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.9
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• pp.1407-1413
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• 2015

The objective of this study was to investigate the rheological and pasting properties of potato flour dispersions at different concentrations (3, 4, 5, 6, and 7%, w/w). A potato cultivar 'Goun', used in this study, was developed by Highland Agriculture Research Center, RDA. Potato flour dispersions showed shear-thinning behaviors (n=0.44~0.51) at $25^{\circ}C$. Apparent viscosity (${\eta}_{a,100}$), consistency index (K), and yield stress (${\sigma}_{oc}$) significantly increased with an increase in potato flour concentration. Storage modulus (G') and loss modulus (G") significantly increased, whereas complex viscosity (${\eta}^*$) was significantly reduced with increasing frequency (${\omega}$) from 0.63 to 63.8 rad/s. Magnitudes of G' and G" were significantly increased with elevation of potato flour concentration. G' values were considerably greater than G" over the entire range of frequency (${\omega}$) with a high dependence on ${\omega}$. Cox-Merz rule was not applicable to potato flour dispersions. Rapid Visco Analyzer data showed that peak viscosity, trough viscosity, breakdown viscosity, final viscosity, and set back viscosity of samples significantly increased with an increase in potato flour concentration.

• Journal of Adhesion and Interface
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• v.18 no.3
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• pp.109-117
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• 2017

Poly(N-vinyl carbazole) (PVK) homopolymer, poly(4-vinylpyridine) (PVP) homopolymer, and PVK-b-PVP block copolymer were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and the polymers were used to prepare non-aqueous graphene dispersions with four different solvents, ethanol, N-methyl-2-pyrrolidone (NMP), dichloromethane (DCM), and tetrahydrofuran (THF). $^1H-$ and $^{13}C-NMR$ spectroscopy, size exclusion chromatography (SEC), and differential scanning calorimetry (DSC) were carried out to confirm the chemical structure of the polymers. Stability of graphene dispersions was measured by on-line turbidity measurement. Time-dependent Turbiscan Stability Index (TSI) values were interpreted in terms of surface tension (${\sigma}$) and solubility parameter (${\delta}$) among solvents, polymers, and graphene. It was confirmed that the solubilities of polymer and surface tension between solvent and graphene affected the dispersion stability of graphene. PVK-b-PVP block copolymer could effectively maintain the low TSI values of graphene dispersions in ethanol and THF, which have been known as poor solvents for graphene dispersions. It can also be noted that DCM shows good dispersion stability comparable to NMP, which has been known as the best solvent for graphene dispersion.

• Polymer(Korea)
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• v.35 no.4
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• pp.277-283
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• 2011

Solid dispersion is mainly used for improved dissolution of poorly water-soluble drugs. Solid dispersion of pranlukast was prepared by spray-drying with plasdone S-630. When pH of water was high, pranlukast was highly soluble in the solubility experiment of solid dispersions with varying pH. The particle size of pranlukast particles in solid dispersions was measured to be in nanometers scale based on particle size analysis. Zeta-potential analysis confirmed the negative charge of solid dispersion. SEM was used to observe the surface of solid dispersion, which confirmed spherical morphology, DSC and XRD confirmed the amorphous nature of solid dispersions. The in vitro test was carried out to find improved dissolution rate of pranlukast solid dispersion in simulated juice gastric and a controlled experiment was carried out to compare pranlukast solid dispersions with a conventional drug (Onon$^{(R)}$), These results showed the dissolution properties of pranlukast solid dispersions prepared by spray drying proper for the oral pharmaceutical formulation.

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.34-35
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• 2002

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.11
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• pp.1060-1071
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• 2005

Passive gas dispersions over a 1/1000 scale terrain model at Eiffel type wind tunnel were reproduced by numerical simulation. Large eddy simulation was used to treat the sub-grid scale turbulences. The terrain features were represented by millions of point forces densely distributed over the solid surface using the virtual boundary method. The model simulations agreed very well with the experiments in a consistent fashion for all wind directions. The measured profiles of the wind speeds as well as the tracer gas concentrations were nicely simulated by the CFD model at most locations scattered over the model terrain. With scale factor adjusted and the thermal stratification effects incorporated, the CFD model was expected to provide reliable information on pollutant dispersions over the real complex terrains.

• Journal of the Korean Society of Food Science and Nutrition
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• v.23 no.5
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• pp.822-826
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• 1994

Effects of concentration(6-9%, db) , heating temperature (80-95$^{\circ}C$), cooking time (10-50min) and heating method (continuous and instantaneous) on the apparent viscosity of cowpea sediment dispersions at 6$0^{\circ}C$ were investigated. The instantaneous heating resulted in higher apparent viscosity than continuous heating regardless concentrations and heating temperatures. The activation energy of the increase rate constant of the apparent viscosity was about 8 kcal/mole. The apparent viscosity of the cowpea sediment dispersion heated to 95$^{\circ}C$ and held for 20 min showed a linear relation with the 20 min height at 92.5$^{\circ}C$ by viscoamylograph.

• Macromolecular Research
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• v.15 no.1
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• pp.22-30
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• 2007

High water vapor permeable coating materials were prepared by blending aqueous poly(vinyl alcohol) (PVA) solution with waterborne polyurethane-urea (WBPU) dispersions synthesized by prepolymer mixing process. Stable WBPU/PVA dispersions were achieved at PVA content below 30 wt%. As the water soluble polymer PVA content increased, the number and density of total micro-pores (tunnel-like/isolated micro-pores) formed after the dissolution of PVA in water increased, and the water vapor permeability of coated Nylon fabric also increased significantly. Using WBPU/water soluble polymer PVA blends as a coating material and then dissolving PVA in water was confirmed to be an effective method to obtain prominent breathable fabrics.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.201-206
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• 2002

The purpose of this study is to improve the anti-corrosive properties of coated reinforcing bar using polymer cement slurry. Poymer cement slurry are prepared with three types of polymer dispersions and corrosion inhibiting admixture. And tested for corrosion accelerating tests such as immersion in NaCl 10% solution NaCl 10% solution spray, high temperature and pressure steam in condition of 8cycles, carbonation before and after, penetration of NaCl solution. From the test results, it is concluded that the anti-corrosive properties are considerably improved by coating using polymer cement slurry at surface of reinforcing bar. And this trend is marked by adding of corrosion inhibiting admixture. The difference of the anti-corrosive properties is hardly recognized according to types of polymer dispersions. The anti-corrosive properties of coated reinforcing bar using polymer foment slurry are improved to a great extent compared to those of plain reinforcing bar accordiy to increasing content of chloride ion in cement concrete.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.230-230
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• 2006

Density functional theory (DFT) calculations using the B3LYP hybrid functional and the 6-311++G(d,p) basis set have been performed to predict the wavelength dispersion of optical absorbance and refractive indices for organic compounds and polymers in the range between the vacuum UV (${\sim}157\;nm$) and near-IR (${\sim}850\;nm$). The DFT calculations can reproduce the experimental dispersions of absorbance and refractive indices with high accuracy and low costs. The calculated dispersions demonstrate that the judicious introductions of $-F\;and\;-CF_{3}$ into alicyclic and heterocyclic compounds are effective in reducing the absorption at shorter wavelengths. In addition, the calculated Abbe numbers that represent the refractive index dispersion in the visble region are linearly proportional to the calculated refractive indices at 589 nm.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.133-134
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• 2006

In contrast to paints, the surface appearance of adhesive materials is of minor importance, because the adhesive is invisible between the two substrates. Therefore, the rheological properties needed to apply an adhesive dispersion by spray coating can be quite different. The influence of three different kinds of thickeners on the spraying behaviour of polyurethane adhesive dispersions was investigated. The associative thickener showed only minor changes, whereas the higher molecular weight soluble thickeners dramatically changed the spraying angle and the amount of overspray. Determination of the elongational viscosity by means of the CaBER rheometer proved to be of limited use for thickened dispersions.