• International Journal of Industrial Entomology and Biomaterials
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• v.27 no.1
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• pp.180-184
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• 2013

Recently, silk sericin has attracted the attention of researchers owing to its useful properties as a biomaterial including 1) good wound healing and cell activities, 2) fast gelation character, and 3) high water retention property. In the present study, silk sericin was prepared using different extraction times in hot water and the effect of extraction time on the rheological properties of sericin solutions and gels was examined. It was found that the production yield of sericin increased with extraction time. The shear viscosity of sericin solutions and gels decreased with increasing extraction time due to a decrease in sericin molecular weight. When the sericin solution transformed to a gel, the viscosity increased and the shear thinning behavior was more evident. In addition, the shear stress measurements indicated that the slip between the sericin samples and the measuring plate of the rheometer was increased by the gelation of sericin. The compression strength of sericin gel could be increased remarkably (by more than 100 fold) by preparation using the freezing and thawing method.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.252-252
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• 2006

Utilizing the existence of the induction period in photo-polymerization, we propose a new injection method of photo-polymerizable, thermocrosslinking hydrogels made of di-acrylated Pluronic F127 (DA-PF127). This method can solve the problem of fast dissolution of thermal gelation as a scaffold and the disadvantages of the existing injection method that photo-polymerize di-acrylated Pluronic polymer after injection using optical fiber. Injectable gelation of DA-PF127 by the proposed method was demonstrated both in vitro and in vivo. The enhanced stability by this novel photo-polymerization strategy was confirmed by the more sustained release of loaded protein as well as the prolonged degradation time of the hydrogels.

• The Journal of the Acoustical Society of Korea
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• v.21 no.3E
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• pp.126-131
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• 2002

Ultrasonic measurements are made in egg white to study the properties of the solution of the natural protein. The high-Q ultrasonic resonator method is used to get the ultrasonic absorption spectra over the range 0.2-10 ㎒ at 20℃. It is proportional to the 1.25th power of the frequency. The gelation process caused by heat is studied from the change in the velocity and the absorption. at 3 ㎒ using the pulse echo overlap technique over the range of 10-80℃. The absorption decreases with increasing temperature up to 60℃ where it turns up sharply and rapidly increases thereafter. The strong absorption in the gel region is described by the interaction between the solution and the network structure made of protein. Very slow variation in time elapse is observed after the temperature is quickly raised. It would be a real-time observation of the network building process and the characteristic time for the process is shown to be 400 min. A hysteresis phenomenon with respect to the temperature is observed. This phenomenon is associated with the memorizing effect of the network structure of protein of the gel.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3267-3273
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• 2011

Ag(I) carboxylate gelators with mixed-ligands were systemically investigated to understand the mechanism of the organic gel formation. The gelators constructed 3-D networks of nanometer-sized thin fibers which facilitated gel formation in various aromatic organic solvents, even at very low concentrations. The loss of reflection peaks in the X-ray diffraction data indicated the reduction of strong interactions between the long alkyl chains as the Ag(I) carboxylates formed gels by maximizing their interactions with the organic solvents. The gelation temperature ($T_{gel}$) was measured to explore the interaction between the gelator molecules and solvents depending on their composition and concentration. Based on the gelation phenomena, a dissociation/re-association mechanism was proposed.

• Food Science of Animal Resources
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• v.30 no.5
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• pp.746-754
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• 2010

Response surface methodology was adopted to model and optimize the effects of microbial transglutaminase (TG) and calcium alginate (CA) systems of various ratios on the gelation characteristics of porcine myofibrillar protein (MP) at various salt levels. The CA system consisting of sodium alginate (SA), calcium carbonate (CC) and glucono-$\delta$-lactone (GdL) showed no remarkable changes in the salt-soluble fraction, and only minor effects on electrostatic interactions were observed. Increasing CA concentration caused acid-induced hydrophobic interactions in MPs, resulting in increased MP gel strength. The TG system, containing TG and sodium caseinate (SC), induced cold-set MP gelation by formation of covalent bonding. The main advantage of the combined system was a higher cooking yield when the MP gel was heated. These results indicated that 0.7% TG combined with 0.8% CA system can form a viscoelastic MP gel, regardless of salt levels.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.11
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• pp.561-565
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• 2004

SiO₂ thin films are fabricated using sol-gel method and dipping method. Gelation time is faster according to increasing the amount of H₂O except H₂O/Si(OC₂H/sub 5/)₄=4. Initial viscosity is highest at H₂O/Si(OC₂H/sub 5/)₄=6. Gelation time is faster according to increasing the amount of CH₃COOH. The relative dielectric constant of thin films decreases a little according to increasing the measuring frequency. The dielectric dissipation factor of thin films increases a little below 100kHz and it increases rapidly over 100kHz.

• Journal of the Korean Ceramic Society
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• v.26 no.4
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• pp.471-478
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• 1989

In this study we investigated the gelation time of sol which containing mixtures of TEOS with H2O, ethanol, HCl in the preparation of monolithic silica glass through Sol-Gel method. In this case apparent activation energies were observed by Arrhenius equation. We investigated the conversion from gel to glass in drying and heat treatment stages using DT-TG, FT-IR, XRD analysis and dried gel conversed to glass by heat treatment up to 85$0^{\circ}C$. The results of this experiment showed that the gelation time of solutions were promoted when increasing the amount of addition of H2O and HCl catalyst for TEOS and high reaction temperature of solution.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.12
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• pp.573-577
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• 2005

[$TiO_2$] sol and $SiO_2$ sol were prepared using sol-gel method. As $H_{2}O$/Alkoxide ratios increased, sol had cluster structure and as $H_{2}O$/Alkoxide ratios decreased, sol had linear structure. Gelation time of $TiO_2$ sol was faster than that of $SiO_2$ sol according to the time. In comparison with initial viscosity between $TiO_2$ sol and $SiO_2$ sol, $TiO_2$ sol was highest at $H_{2}O/Ti(OC_{3}H_{7})_{4}=5$, $SiO_2$ sol was almost constant according to $H_{2}O/Si(OC_{2}H_{5})_{4}$ ratios.

• Macromolecular Research
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• v.14 no.3
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• pp.365-372
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• 2006

Poly[styrene-b-(ethylene-co-butylene)-b-styrene](SEBS) triblock copolymer was studied by dissolving the ethylene butylene midblock in selective hydrocarbon oils. These oils differ in their aromatic, paraffinic and naphthenic content. Dynamic rheological studies showed that the storage modulus (G') exceeded the loss modulus (G') for all the gels over the entire range of frequency, thereby confirming them as physical gels. However, the behavior of G' and G' as a function of frequency depended primarily on the oil type. The gelation melting temperature decreased drastically with increased oil aromaticity. Small angle X-ray scattering studies revealed that the maximum interdomain interference shifted to a higher angle depending on the composition and type of hydrocarbon oil.

• Journal of the Korean Ceramic Society
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• v.28 no.8
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• pp.635-639
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• 1991

Monolithic gels in the ZrO2-SiO2 system containing up to 30 mol% ZrO2 were prepared from the mixed solutions of Zr(O.nC3H7)4 and partially prehydrolyzed Si(OC2H5)4 (Tetraethyl orthosilicate) by the sol-gel method. The effect of parameters such as the hydrolysis temperature, the amount of water and HCl on the hydrolysis condensation process was investigated and the obtained gels were studied by the IR spectra and TG-DTA. The results showed that the gelation time becomes shorter with increasing content of HCl, H2O and gelation temperature, and that the polymerization was more easily completed with the higher water volume causing the elimination of unreacted organic groups.