• Polymer(Korea)
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• v.29 no.6
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• pp.599-604
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• 2005

The hyaluronic acid (HA) with excellent biocompatibility has been combined with lactide, the ester dimer of polylactide, with good biodegradability to produce biocompatible materials which can control the period of degradation in a human body. By freeze frying method, HA and lactide were crosslinked with crosslinking agent, 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC). Degree of lactide and EDC reaction was determined by the analysis of nuclear magnetic resonance spectroscopy. Both lactyl group and EDC conversion increased as the mole ratio of lactide to HA increased from 5 to 13. The membrane swelled less and became more brittle with the more addition of lactyl group resulting from the higher mole ratio of lactide to HA. Swelling ratio decreased and tensile modulus increased due to the more addition of lactyl group as the EDC concentration increased or reaction temperature decreased. Drug release experiment from various membranes with different degree of crosslinking showed that permeability decreased with increasing degree of crosslinking. The degradation became slower with the more addition of lactyl group. Mechanical property and degradation rate of the synthesized membrane were shown to be controlled through adjusting operation parameters such as mole ratio, temperature, and crosslinking agent concentration.

• Polymer(Korea)
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• v.39 no.3
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• pp.394-402
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• 2015

Modification of polyacrylonitrile (PAN) films by using hydroxylamine (HA) and hydrazine to produce hydroxyl and amine groups, respectively, and to introduce cross-linking of PAN polymers was studied. Modified PAN films obtained by HA and/or hydrazine treatment including a successive or a simultaneous process were analyzed by the degree of conversion, water and N,N'-dimethylformamide (DMF) swelling ratio, FTIR spectra, atom content, and thermal analysis data. PAN films reacted with HA showed increased hydrophilicity and low dimensional stability in water. Hydrazine treatment gave PAN films high dimensional stability of low DMF swelling. Although the DMF swelling ratio of the modified PAN films was dramatically decreased by the successive treatment of hydrazine and HA, the introduction of the hydrophilic functional groups was limited due to the cross-linking. Simultaneous treatment of HA and hydrazine was the most effective method to increase hydrophilicity of PAN films with a high dimensional stability.

• The Journal of Engineering Geology
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• v.7 no.2
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• pp.127-137
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• 1997

Bentonites that are used currently for the civil engineering puppose in our country were investigated to reveal their physico-chemical properties such as viscosity, swelling volume, cation exchange capacity (CEC) and chemical composition, and to compare the content of their constituting minerals and their characteristics using the X-ray diffraction and infrared spectrum methods. The content of montmorillonite in the hentonites ranges from 50 to 79%. As the content of montmorillonite in the hentonites increases, the viscosity, swelling volume, water content, methylene blue adsorption, CEC, and the amount of clay-size particles tend to increase in general. Because these properties also show good correlation within them, the results can he used to infer the characteristics of hentonites indirectly. However, a few samples do not show this correlation hetween the properties. This is probably due to the characteristics of constituting minerals of raw ore and manufacturing process. A saraple with lowest content of rnontrnofiiionite was shown to be inferior in the physico-chemical properties that are needed for the civil engineering-purpose bentonites.

• Korean Journal of Food Science and Technology
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• v.37 no.3
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• pp.418-424
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• 2005

The physicochemical properties of raw noodle flours (n = 11) commercially produced from Australian Standard White (ASW) (Group 1, n = 8) and blonds (Group 2, n = 3) of ASW and Australian hard, western white or hard red winter were investigated. Protein and ash contents were lower in Group 1. The tristimulus color values, mean particle size, flour swelling volume (FSV) and rheological parameters of farinograph and extensigraph were not different between two flour groups. Peak viscosity measured with Rapid Visco Analyzer was higher in Group 1. The protein content was positively correlated with mean particle size, dough stability and dough extensibility, and negatively correlated with FSV and peak viscosity. The FSV wag positively correlated with the peak viscosity. The rheological parameters of dough did not show any correlations with FSV and peak viscosity.

• Applied Biological Chemistry
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• v.30 no.1
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• pp.24-30
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• 1987

starches, isolated from Japonica and nonwaxy rites, were analyzed fur gelatinization characteristics. Amylose contents of Taebaeg and Sangpung starch were 16 and 17%, respectively. The portion of large-sized particles was more pronounced in the case of Sangpung starch. Swelling power and solubility increased according to the rise in gelatinization temperature. The decrease of pasting temperature according to the incense in starch concentration in Sangpung starch was higher than that of Taebaeg starch. Most of the increase in light penetration was accomplished between 85 and $90^{\circ}C$. Gelatinization reactions of Taebaeg and Sangpung starch appeared as 2 different stages up to the gelatinization temperature of $90^{\circ}C$.

• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.427-433
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• 2005

The use of the microwave-assisted process for the extraction of effective constituents from ginseng was investigated at various operating conditions. The influence of solvent (ethanol-water, 50% v/v) to ginseng ratio, particle size and applied microwave power on the efficiency of extraction was examined. The microwave extraction system used was custom manufactured so that the intensity of microwave may be varied by using anode-voltage controller. It was found that the ratio of 6 : 1 (vol/mass) gave a good extraction efficiency. Small particle size gave high yield but it caused difficulties in the separation of solvent from the sludge. The higher power was no guarantee of the efficient extraction yield. The more important factor than the employed power was the adequate temperature under sufficient contact time. Using deionized-water as swelling agent, the degree of swelling of ginseng by microwave heating and conventional heating in water-bath was also studied. It was observed that the microwave heating enhanced the swelling much more than the conventional heating. It is believed that this enhanced swelling was responsible for the rapid microwave-assisted extraction rate.

• Korean Journal of Food Science and Technology
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• v.31 no.5
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• pp.1216-1220
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• 1999

The effects of low-temperature blanching on the physical properties of chestnut powder were studied. Chestnuts were blanched in water for 15, 30 and 60 min., each at three temperatures viz. $45^{\circ}C,\;55^{\circ}C$ and $65^{\circ}C$. The particle size of chestnut powder was prepared smaller than 60 mesh$(250\;{\mu}m)$. Higher blanching time and temperature increased water binding capacity(WBC) of chestnut powder. Water soluble index(WSI) was the highest for chestnuts blanched at $65^{\circ}C$ for 30 min. As with water binding capacity(WBC), swelling power of chestnut powder increased with increasing blanching time and temperature but solubility showed an reduction by increasing blanching temperature. In Brabender amylographic examination, peak viscosity of chestnut powder showed great change, but the gelatinization temperature showed no significant differences by blanching conditions.

• Journal of the Mineralogical Society of Korea
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• v.19 no.2 s.48
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• pp.123-128
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• 2006

Beidellite, a member of the dioctahedral smectite group, was synthesized hydrothermally from dickite. Organophilic [DEACOOH]-beidellite intercalation complex was formed by the cation exchange reaction between synthetic Na-beidellite and [DEACOOH]Br. The products dried in high vacuum were treated with various organic solvent such as methanol, ethanol, acetone, ether, acetonitrile and caprolactam in order to determine the swelling behaviour of the prepared complexes. After drying under high vacuum, basal spacing of [DEACOOH]-beidellite shows 15.1 ${\AA}$, and it changed to 19.4, 29.9, 15.9, 16.8, 14.8, 26.5 and 14.8 ${\AA}$ under distilled water, methanol, ethanol, acetone, ether, acetonitrile and caporlactam, respectively. Especially, the characteristics of the intercalation complexes and their swelling behavior of the synthetic beidellite and natural montmorillonite were compared.

• Applied Biological Chemistry
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• v.34 no.4
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• pp.379-385
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• 1991

Morphological changes of starch granules from 12 different varieties of rice were examined by scanning electron microscopy during heating at 2.5% (w/v) concentration. Rice starch granules proceeded through a similar pattern of progressive morphological changes daring heating, regardless of variety. Rice starch granules began to swell radially in the initial stage of gelatinization and then undergo radial contraction and random tangential expansion to form complex structures in the latter stage of gelatinization temperature range. At higher temperatures, starch granules softened and melted into thin flat discs, and then stretched into thin filaments to form three-dimensional networks. These progressive morphological changes were reflected in the changes of swelling power, solubility and amylograph viscosity of starch. During the transition of melting or softening, swelling power, solubility and amylograph viscosity increased rapidly. The time of loss of granular structure of starch depended on gelatinization temperature range. The ratio of amylose to amylopectin was largely responsible fur the rate of melting or softening and the fineness of a three-dimensional filamentous network above the gelatinization temperature range. Therefore, both the gelatinization temperature range and amylose content of starch affect the rate of cooking, and amylose content of starch affects the final texture of cooked starch paste.

• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.691-697
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• 1996

The NR films were prepared with mixing of natural rubber latex(NRL) with various additives, and NR/CR films were prepared by blend ratio of chloroprene rubber latex(CRL). The swelling degree and the mechanical properties of these films were measured according to the procure time. As a result, optimum condition were showed the swelling degree : 80~85%, precure time : 48~60hrs., and tensile strength was reduced but elongation was increased as increasing the blend ratio of CRL. On the mechanical properties of films prepared by different dipping process in these optimum condition, the tensile strength and tear strength of NR/CR films by one dipping process are better than NR-d-CR films by two dipping process. The surface of these films were observed with scanning electron microscopy(SEM). It was found that phase separation was occured as increasing the blend ratio of CRL.