• Journal of the Korean Chemical Society
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• v.24 no.2
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• pp.167-174
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• 1980

Anionic polymerization of 2-pyrrolidone was carried out via PPBC/KOH catalysis. The effects of PPBC/KOH mole ratio, KOH concentration and temperature on polymerization have been investigated. It was observed that the highest rate of polymerization and maximum conversion were obtained when PPBC/KOH mole ratio was around 0.5. The maximum conversion and the highest viscosity were obtained when the concentration of KOH was 2 mole percent. It was also found that while the rate of polymerization at $50^{\circ}C$ was higher than at $30^{\circ}C$ in the initial stage of polymerization, the conversion and viscosity were decreased as polymerization time was extended. The rate constant $(k_p)$ of polymerization was determined by least square method; the values of $k_p$ obtained were $22.4\;l/mole{\cdot}hr\;at\;30^{\circ}C\;and\;191.9\;l/mole{\cdot}hr\;at\;50^{\circ}C$, respectively.

• Korean Journal of Food Science and Technology
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• v.24 no.2
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• pp.127-131
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• 1992

The effects of chlorine treatment on the rheological properties (farinogram, extensogram, amylogram) of soft white wheat flour were studied by treating flour with different amounts (1, 2 and 4 ounces per 100 pounds of flour) of liquidized chlorine gas. Departure time, water absorption and dough stability increased while mechanical tolerance index decreased as the level of chlorine increased. It was appeared that extensibility and resistance at chlorine level of 1 to 2 oz was appropriate for baking properties of flour compared to those of untreated wheat flour. The temperature at maximum viscosity increased gradually with increasing levels of chlorine. It was noted that maximum viscosity was greatly increased at 4 oz compared to those of lower levels of chlorine treatment.

• Korean Journal of Food Science and Technology
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• v.38 no.2
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• pp.222-231
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• 2006

Deoxynivalenol (DON)-contaminated barley was treated with 0.1 M $Na_2CO_3$ solution to reduce DON content. DON content of barley was reduced from 2.08 to 0.67 ppm. Bread was made with 10, 20, and 30% DON-reduced barley flour added to white wheat flour. Farinogram showed water absorption and arrival time increased, while stability and mechanical tolerance index decreased when DON-reduced barley flour was added to white wheat flour. Gelatinization temperature, temperature at maximum viscosity, and maximum viscosity increased in amylogram with increasing addition of DON-reduced barley flour. Loaf volume of bread decreased with increasing amount of DON-reduced barley flour, while loaf weight increased. Barley flour pH increased by treatment with$Na_2CO_3$, and pH reduction decreased fermentation rate of yeast. Volume and size of gluten matrix decreased and crumb hardened in bread made with DON-reduced barley flour. Acceptabilities for color and texture were low in bread made with DON-reduced barley flour. Addition of DON-reduced barley flour at 30% reduced overall acceptability, whereas no significant difference in overall acceptability was observed when DON-reduced barley flour was added at 10 and 20%.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.6
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• pp.795-800
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• 2009

This study was carried out to investigate the rheological properties of bread dough containing whey ferment cultured by L. acidophilus KCCM 32820 and P. freudenreichii KCCM 31227. Instrumental analysis such as farinograph, amylograph, extensograph, fermentation power, total titratable acidity (TTA) of dough and pH of dough were tested. On farinograph, difference of water absorption between doughs with and without whey ferment was 0.4% and dough containing whey ferment showed long development time of 3.2 min compared to dough without whey ferment, but showed shorter stability of 16.2 min. On amylograph, there was no significant difference on gelatinization and maximum viscosity temperature; however, maximum viscosity of flour with whey ferment revealed low amylograph unit. On extensograph, value of resistance and R/E ratio of dough containing whey ferment were higher than those of dough without whey ferment. On analysis of dough fermentation power by yeast, dough without whey ferment showed higher volume than dough with whey ferment during fermentation of 240 min. However, TTA of dough was higher in dough with whey ferment than that of the control without whey ferment, even though pH value was low.

• Applied Biological Chemistry
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• v.51 no.1
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• pp.6-10
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• 2008

This study was carried out to investigate rheological properties of bread dough by adding hydrocolloids such as arabic gum, pectin and carboxyl methyl cellulose (CMC). 0.2% and 0.5% of each hydrocolloid were added to the dough. Farinograph, pH of dough, extensograph, fermometer and amylograph were analyzed. In farinograph, water absorption rate of dough was increased by adding hydrocolloids and the highest water absorption resulting in 70.8% was shown by adding 0.5% of CMC. Dough development time increased but stability decreased. pH of dough was lowered by adding hydrocolloids and pH of dough with 0.5% of pectin was the lowest. In extensograph, resistance of dough decreased but extensibility increased and R/E value lowered. In fermometer, $CO_2$ gas production increased and dough with 0.2% of CMC showed the largest gas production. In amylograph, initial gelatinization temperature increased by $0.5-1.5^{\circ}C$, but temperature for maximum viscosity was lowered by $1-1.5^{\circ}C$ and maximum viscosity was increased.

• Design & Manufacturing
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• v.14 no.4
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• pp.11-16
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• 2020

In this study, forming of carbon composite parts was performed using an injection/compression molding process. An impregnation of matrix is determined by ability of wet and flow rate between the matrix and reinforcement. The flow rate of matrix passing through the reinforcements is a function of permeability of reinforcement, a viscosity of matrix and pressure gradient on molding, and the viscosity of the matrix depends on the mold temperature, molding pressure and shear strain of matrix. Therefore, compression molding experiment was conducted using a heating mold in order to confirm the possibility of matrix impregnation. The impregnation of the matrix through the porosities between the woven yarns was confirmed by the cross-sectional SEM image of compression molded parts. An injection molding process was also performed at a short cycle time, high molding pressure and low mold temperature than those of compression experiment conditions. Deterioration of impregnation on the surface of molded parts were caused by these injection conditions and it could be the reason of decreasing the maximum tensile strength. In order to improve impregnation of matrix on the surface, injection/compression molding and insert-over molding were applied. As a result of applying injection/compression molding and insert-over molding, it was shown that the improvement of impregnation on the surface and the maximum tensile strength was increased about 2.8 times than the virgin matrix.

• Applied Chemistry for Engineering
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• v.20 no.3
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• pp.322-328
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• 2009

Emulsion polymerization of octamethylcyclotetrasiloxane (OMCTS) was conducted under ultrasonic irradiation. Two sources of ultrasound with different intensities and frequencies of 20 KHz and 40 KHz were used for horn and bath type reactor, respectively. A combined process of horn and bath was also investigated. The effectiveness of the reaction systems was investigated by measuring conversion as well as intrinsic viscosity of the products. The influence of reaction temperature and sonication time on the progress of sonochemical polymerization was examined. It was found that conversion of greater than 80% and high viscosity were achieved within a few minutes of sonication in a horn type reactor, however, conversion and viscosity showed maximum values depending upon the sonication time. In a bath type reactor where a relatively weak intensity was maintained, longer duration time of more than one hour of sonication was required to reach a high level of conversion and viscosity. Compared with the horn type system, the conversion and viscosity in the bath type reactor were increased along with the sonication time. When the polymerization was carried out in a combined system of horn and bath, the evolution of conversion and molecular weight was quite different from the other cases. For the given geometry of reaction system, acoustic analysis using a commercial software was carried out and the results were correlated with experimental observation.

• Journal of the Korean Ceramic Society
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• v.39 no.11
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• pp.1090-1096
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• 2002

Six different composition of water-swellable bentonite rheology modifiers(WSB-1~WSB-6) were prepared by the compounding of peptizers and anionic surfactants as an additives with Bentonite(BEN) of montmorillonite group. Average particle size, particle morphology and water-swellability of WSB and the viscosity with additives were measured, respectively. And the rheological behavior of WSB were investigated using the rheometer. The viscosity of WSB-1 increased with decreasing both pH and average particle size of BEN, WSB-2 treated $Na_2CO_3$ as a peptizer showed the maximum viscosity. These results can be interpretated cause for rearrangment as the edge-to-face structure of BEN particles containing WSB. Also, WSB-4∼WSB-6 containing both peptizer and anionic surfactant was sol phase that their viscosity was not nearly with the shear rate, however, WSB-3 containing Tetrasodium Pyrophosphate(TSPP) as an anionic surfactant showed the thixotropy by the viscosity difference of 1000 times with the shear rate. From this result, the anions of TSPP can be explained to arrange in edge of BEN particles containing WSB-3.

• Journal of the Korean Applied Science and Technology
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• v.33 no.4
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• pp.802-812
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• 2016

Silicone foam is very useful as flame resistant material for many industrial areas such as high performance gasketing, thermal shielding, vibration mounts, and press pads. A silicone foam was prepared through simultaneous crosslinking and foaming by hydrogen condensation reaction of a vinyl-containing polysiloxane (V-silicone) and a hydroxyl-containing polysiloxane (OH-silicone) with hydride containing polysiloxane (H-silicone) in the presence of platinum catalyst and imorganic filler at room temperature. This is more convenient process for silicone foam manufacturing than the conventional separated crosslinking and foaming systems. Funtionalized silicones we used in this experiment were consisted with a V-silicone containing 1,0 meq/g of vinyl groups and a viscosity of 20 Pa-s, an OH-silicone with 0.4 meq/g of hydroxyl groups and a viscosity from 50 Pa-s, and an H-silicone containing 7.5 meq/g of hydride groups and a viscosity of 0.06 Pa.s. The effects of compositions of functionalized silicones and additives, such as catalyst and filler on the structure and mechanical properties of silicone foam were studied. 0.5 wt% of Pt catalyst was enough to accelerate the foaming rate of silicone resins. The addition of OH-silicone with lower viscosity accelerates the initial foaming rate and decreases the foam density, but the addition of V-silicone with lower viscosity reduces the tensile strength as well as the elongation. The final foam density, tensile strength, and elogation of silicone foam prepared under the SF-3 condition increase maximum to $0.58g/cm^3$, $3,51kg_f/cm^2$, and 176 %, repectively. We found out the filler alumina also played an important role to improve the mechanical properties of silicone foams in our foaming system.

• Journal of the Korean Society of Food Science and Nutrition
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• v.15 no.2
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• pp.119-127
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• 1986

The rheological properties of mayonnaise were studied with cylindrindrical viscometer. It was observed that mayonnaise showed pseudoplastic behavior, yield stress and time dependent characteristics. In the initial period of shear time, the decay of viscosity of mayonnaise was followed by a second-order kinetic equation. The influence of temperature on viscosity could be described by Arrhenius equation. The apparent viscosity of mayonnaise markedly increased with an rise in the concentration of egg yolk; and the emulsion was most stable at the concentration of 12%. At the concentration of $65{\sim}75%$ oil, the apparent viscosity was increased; the maximum value was reached at 75% oil, and above 75% oil, the remarkable decreased was observed. The size of oil drops was decreased with an increase in oil concentration of 75% oil. The apparent viscosity of mayonnaise was increased with an rise in water contents, while being decreased with one in the concentration of vinegar.