• Food Science of Animal Resources
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• v.30 no.1
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• pp.95-101
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• 2010

Folate loaded WPI (whey protein isolate) nanoparticles were prepared using the cold-induced gelation process. The aim of this work was to investigate the effects of process parameters, such as the concentration of the WPI solution, pH, temperature, etc, on the properties of nanoparticles. The results show that the smallest nanoparticles were obtained when a WPI concentration of 1% was used at a pH of 8.0 (<330 nm). In the case of the concentration of $CaCO_3$, the smallest particles were obtained at a concentration of 5 mM. Alginate produced the smallest mean size with the narrowest particle size distribution, while the largest particles were prepared with k-carrageenan. As the w:o ratio increased, the mean particle size also increased. When the release profile was analyzed, the particles were shown to be stable for more than 6 h at a pH of 1.2, where almost all of the folic acid was released within 2 h in the dissolution media of PBS at a pH of 7.4. Thus, the process parameters appear to be important factors that affect the properties of nanoparticles.

• Clean Technology
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• v.23 no.3
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• pp.270-278
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• 2017

This study introduces a method to easily fabricate highly monodisperse pectin hydrogel microfibers in a microfluidic device by using partial gelation. The hydrodynamic parameters between the pectin aqueous solution and the calcium ions containing oil solution are precisely controlled to form a stable elongation flow of the pectin aqueous solution, and partial gelation of the pectin aqueous solution is performed by the chelating of the calcium ions at the interface between the two phases. The partially gelled pectin aqueous solution is phase-separated from the oil solution in an aqueous calcium chloride solution outside the microfluidic device and is completely gelled to produce monodisperse pectin hydrogel microfibers. The thickness of the pectin hydrogel microfiber is controlled in a reproducible manner by controlling the volumetric flow rate of the initially injected pectin aqueous solution. The pectin hydrogel microfibers were 200 to 500 micrometers in diameter and had a coefficient of variation below 5% under all thickness conditions, indicating that the pectin hydrogel microfibers produced by partial gelation are highly monodisperse. In addition, biomaterials can be immobilized to the pectin hydrogel microfibers produced by a single process, demonstrating the possibility that our pectin hydrogel microfiber can be used as carriers for biomaterials or tissue engineering.

• The Korean Journal of Rheology
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• v.9 no.2
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• pp.47-52
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• 1997

식품유변학은 식품재료로 사용하는 생물체와 세포내외의 생체고분자물질의 물성을 주로 대상으로 하는 학문영역이다. 이들 물질들의 가공적성을 평가하고 공정관리를 수행하 기 위하여 점성, 소성, 점탄성 등유변학적 파라메터들이 사용된다. 또한 제춤의 관능적, 특성 특히 조직감(texture)특성을 나타내는 지표로서 유변학적 성질들이 자주 사용되고 있다. 본 고에서는 식품 유변학의 특징가 발전역사를 개관하고 1990년도 이후 국내에서 연구 발표된 식품유변학 분야의 연구내용을 액상식품, 젤화식품, 식물세포조직으로 구분하여 소개하였다.

• Nuclear Engineering and Technology
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• v.8 no.3
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• pp.145-150
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• 1976

Alkali-treated red algae, Gracilaria sp. was irradiated with various doses of cobalt-60 gamma-rays and the yeild and properties of agar extracted from the seaweed were examined and compared with the quality of commercial agar powder after irradiation. Extraction yield of agar from irradiated seaweed was proportionally increased as the radiation dose was raised up to 2 Mrad whereas it tended to decrease slightly thereafter. Gelation ability, gelation point, gel hardness and specific viscosity of the agar were increased up to 1 Mrad and decreased at higher dose levels while its melting point, total nitrogen, crude ash and total sulfur decreased up to 1 Mrad level and remained unchanged thereafter. Irradiation of commercial agar powder caused remarkable decreases in the gelation ability, specific viscosity and gel hardness and slight decreases in the gelation point and melting point. The pattern of alterations in the properties of agar samples differed whether the polysaccharide was irradiated in free state or bound state in seaweed.

• Polymer(Korea)
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• v.27 no.4
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• pp.349-357
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• 2003

Hydrogels for wound dressing from a mixture of poly(vinyl alcohol) (PVAL), poly(N-vinyl pyrrolidone) (PVP), hexylene glycol (HG) and chitosan were made. The hydrogels were obtained by physical crosslinking of freezing and thawing, chemical crosslinking of irradiation, and irradiation after freezing and thawing of mixture solutions. The solid concentration of PVAL/PVP/HG/chitosan was 15 wt%. The concentration of chitosan was 0.3 wt%, and the ratio of PVAL/PVP was 6:4. The concentration of HG was in the range of 1∼5 wt%. The number of repeated freezing and thawing was in the range of 1∼3 times, and gamma irradiation doses were 25, 35 and 50 kGy. The physical properties such as gelation, water absorption and gel strength of hydrogels were examined. Gel content and gel strength decreased as HG concentration increased, whereas degree of swelling increased. Gel content and gel strength increased as irradiation dose and the number of freezing and thawing increased, whereas degree of swelling decreased. The hydrogels were evaluated for the healing effect for animals and for the antibacterial effect.

• Polymer(Korea)
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• v.27 no.3
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• pp.176-182
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• 2003

The fluorine-containing epoxy resin, 2-trifluorotoluene diglycidylether (FER) was prepared by reaction of 2-chloro-${\alpha}$,${\alpha}$,${\alpha}$-trifluorotoluene with glycerol diglycidylether in the presence of pyridine catalyst. Curing behavior of FER/DDM system was investigated using dynamic and isothermal DSC. Cure activation energy (Ea) was determined by Flynn-Wall-Ozawa's equation. The rheological properties of FER/DDM system were studied under isothermal condition using a rheometer. Cross-linking activation energy (Ec) was determined from the Arrhenius equation based on gel time and curing temperature. As a result, the chemical structure of FER was confirmed by FT-IR, $\^$13/C NMR, and $\^$19/F NMR spectroscopy. The cure activation energy of FER/DDM system was 55.4 kJ/mol and conversion and conversion rate were increased with the curing temperature. The cross-linking activation energy of FER/DDM system was 41.6 kJ/mol and gel time was decreased with the curing temperature.

• Polymer(Korea)
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• v.34 no.5
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• pp.485-489
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• 2010

Poly(lactic acid)(PLA) has been modified by electron radiation in the presence of 5 phr glycidyl methacrylate (GMA) to enhance the melt strength of PLA. The modified PLA was prepared by varying the dose of irradiation and was characterized by observing the thermal properties, the melt viscoelastic properties and the gel fraction. The irradiated PLA with 300 kGy in the presence of 5 phr GMA showed drastically improved complex viscosity and storage modulus properties: a complex viscosity of about 210 times higher and a storage modulus of 14500 times higher than those of virgin PLA when measured at a frequency of 0.1 rad/s. Gel fraction study revealed that a branching reaction was more dominant than a crosslinking reaction when the PLA was irradiated with less than 200 kGy.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.6
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• pp.23-31
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• 2012

Present work deals three families of $SiO_2$ gelling agents which have been used to produce gel fuel based on Kerosene. Jet A-1 is chosen as fuel where power-law rheological model is used to confirm whether or not the gelification is achieved depending on the %wt of gellant. It was confirmed that the produced jelly-like substance have shear-thinning effect, and that its apparent viscosity increases as $SiO_2$ concentration increases. Compared to other gellants, gel with Aerosil(R) R972 fits most to the power-law model, while gels with Silica 230 and Silica 530 deviate from the power-law model. The rheological characteristics behaved differently depending on the mixing method(vortex mixing and manual mixing) when gellant concentration is increased.

• Polymer(Korea)
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• v.35 no.1
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• pp.13-16
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• 2011

In this study, the hydrogels composed of polyvinylpyrrolidone (PVP), ${\kappa}$-carrageenan (${\kappa}C$), and 1,2-hexanediol (HD) were prepared by ${\gamma}$-ray irradiation. The radiation dose was 25 kGy and the concentration of ${\kappa}C$ was 3 wt%. The physical properties of the hydrogels were investigated as a function of the concentrations of PVP and HD. The gel content and the tensile strength increased with increasing PVP concentration due to the crosslinking between the pyrrolidone molecules and decreased with increasing HD concentration. The degree of swelling was inversely proportional to the gel content because the highly crosslinked hydrogels had a tighter structure, hence reducing their water absorption. The antibacterial tests indicated that the hydrogels containing HD had antibacterial activity.

• Korean Journal of Materials Research
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• v.11 no.2
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• pp.137-145
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• 2001

A new process, gelcasting in aqueous medium, to fabricate complex-shaped ceramic core has investigated. The ceramic slurry, mixture of fused silica powder and additives such as zircon and cordierite, was electrosterically stabilizes. The slip was prepared by ball milling of polydispered ceramic suspension with monomer, dimer and dispersant. The rheological behavior of slip was evaluated by viscosity measurement. It was found that the high solid loading of polydispersed ceramic slip, which has low viscosity of 50vol%, is possible to obtained. The viscosity of the slip was significantly dependent upon the amount of polymer dispersant and the formulation of monomer and dimer. The green bodies were fabricated through casting and gelation at room temperature followed by drying at $25^{\circ}C$ for 48hrs under relative humidity of 80~85%. Crack-free green body was successfully fabricated through the above process.