• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.359-365
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• 1999

We have evaluated the performance and some physical properties of 25 automotive engine oils (21 domestic and 5 imported products) which are purchased on the market to verify the API(American Petroleum Institute) or ILSAC(International Lubricant Standardization and Approval Committee) certification marks attached on the products and to determine the necessity of the quality control of the engine oils on the market. 12 test items are chosen according to API engine oil specification, which are flash point, pour point, cold cranking simulator apparent viscosity, pumping viscosity, gelation index, HTHS(High Temperature High Shear viscosity), foam, high temperature foam, filterability, volatility, high temperature deposit(TEOST), phosphorus content. We have found one product which did not meet the API specification on gelation index, one on HTHS, four on foam, and one on volatility, which implies that the quality control system is in need to check the fidelity of the certification marks attached on the engine oils being marketed. In addition, this works raises the necessity of the upgrade of the present Korean engine oil specification.

• Journal of Pharmaceutical Investigation
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• 제38권4호
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• pp.229-234
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• 2008

In the present study, chitosan-glycerophosphate sodium salt solution as a thermosensitive system (TSS) was used to formulate a temperature-sensitive drug delivery system (TSDDS) containing acetaminophen (AAP). The optimized TSS was prepared by measuring gelation temperature, gelation time and rheological properties of TSS. The optimized gelation temperature and time of TSS were $36^{\circ}C$ and 100 seconds, respectively. The viscosity of TSS was also suitable for maintaining gel structure at $37.2^{\circ}C$. The release profiles of TSDDS in PBS/pH 7.4 with various apparatuses and mass loss of TSDDS were investigated. The time required to release 50% of AAP from TSDDS ($t_{50%}$) was 120 min with the formation of pore on the surfaces, which was 2 times longer than that from AAP-chitosan gel. In addition, TSDDS was degraded approximately 80% within 4 hr and then degraded slowly for 20 hrs. In conclusion, AAP-TSS (TSDDS) formulated in this study might be suitable for some specific uses such as subcutaneous injection and rectal formulation.

• 한국식품조리과학회지
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• 제12권4호
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• pp.571-576
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• 1996

The moisture-dependent gelation characteristics of five different proteins are evaluated to understand the modification of gel strength when they are added in surimi gel. Compressive force and penetration force of protein gels gradually decreased with increase of moisture level, with showing markedly decrease at certain point of moisture level called critical moisture level. The critical moisture level for gelation of SPI-1, SPI-2, EW, WPC and LA were 79.4%, 81.6%, 91.4％, 87,8% and 84.7%, respectively. Beyond this critical level of water, protein gel matrix begins to lose its water binding and structural integrity. The mnisture that was not re tained by a protein was available to diluting the protein matrix and eventually weakened the overall gel strength. EW and MPI showed higher water retention than those of SPI, WPC and LA. The compressive force of SPI, WPC and LA-incorporated surimi gel at the varying moisture levels strongly correlated with the amount if water retained at corresponding moisture level within those protein (r=0.99).

• 한국세라믹학회지
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• 제36권9호
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• pp.893-900
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• 1999

Silica films were prepared on Si single crystal substrates by sol-gel process using TEOS as starting materials. Films were fabricated by a spin coating technique. Sol solutions were prepared by varying the compositions of CH3OH, H2O and DMF with fixed molar ratio of TEOS=1, HCl=0.05(mol). Wetting behavior viscosity of solutions gelation time thickness of films and cracking behavior were investigated with the various solution compositions. Wetting behaviors of solutions depended on the solution compositions mixing method and mixing rate. The optimum composition of sol was TEOS : DMF ; CH3OH: H2O :HCl=1:2:4:4:0.05(mol) and the mixing rate of solution was optimized at 1 ml/min. Viscosity of solutions were controlled by choosing a reaction time(elapsed time after mixing) at a room temperature so that we could get up to 800nm thick film The surface roughness was getting poor when thickness of films was thicker than 500nm. Thickness of coated films were increased with decreasing amount of CH3OH. The best surface roughness was obtained at the content of CH3OH 4 mol. The shortest gelation time was obtained with the content of CH3OH 8 mol. Crack-free filkms were fabricated when sintered at 500$^{\circ}C$ for 1 hr with heating rate of 0.6$^{\circ}C$/min.

• Asian-Australasian Journal of Animal Sciences
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• 제17권1호
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• pp.131-136
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• 2004

The effects of salt concentration and heating conditions on the thermal gelation properties of surimi produced from mechanically deboned chicken meat (MDCM) were investigated. Chicken surimi was manufactured by washing (MDCM: 0.5% NaCl=1:4), standing, straining and centrifuging. The fat, water-soluble protein and heme pigment in the MDCM were removed by increasing washing cycles. The compressive force of the chicken surimi increased as the concentration of salt was increased from 0% to 5%. Total gel strength of the surimi measured by texture profile analysis showed a maximum in the range 3-5% NaCl. Microstructural analysis showed that the unfolding network structure of the surimi gel began to appear at NaCl concentrations>2%. The optimum heating condition for gelation was $90^{\circ}C$ for 40 min as this resulted in maximum values for measures of gel strength including compressive force, hardness, fracturability, adhesiveness, springiness, gumminess, chewiness and resilience. Chicken surimi gel formed by cooking at a heating rate of $1^{\circ}C/min$ to $90^{\circ}C$ showed better a texture than gels produced at $1.85^{\circ}C/min$. Our result show that a lower rate of heating improves chicken surimi gelation.

• 한국전기전자재료학회논문지
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• 제17권9호
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• pp.953-959
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• 2004

BaTiO$_3$ powder has been applied in so much electronic ceramics. Therefore, as recent, the method to add or coat additive will be needed BaTiO$_3$ powder. As a kind of the method, the coating of BaTiO$_3$ powder was considered. In this study, during BaTiO$_3$ powder was coated by BaTiO$_3$ sol, gelation path was experimented. Standard coating condition was set for homogeneous coating. The phase of the gel was deferent by gelation path. It was confirmed the amorphous gel was made in BaTiO$_3$ phase easily at low temperature. In the amorphous gel, particle growth was shown at 900$^{\circ}C$, because crystallization temperature was low. The optimal ratio of sol and powder was at 10 vol% for the homogeneous coating.

• 한국축산식품학회지
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• 제18권3호
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• pp.209-215
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• 1998

Effects of protein concentration, ionic strength, pH, and temperature range on the heat-induced denaturation of salt soluble protein extracted from spent layer meat were investigated. Viscosity of salt soluble protein heated at 65$^{\circ}C$ for 30 min began to increase sharply above 7 mg/ml of breast protein concentration, and above 21 mg/ml of leg protein concentration, respectively. Both turbidity and viscosity showed the highest value in cooked protein solution with pH 6.0 and 1% NaCl. The turbidity of salt soluble protein started to increase continuously from 40$^{\circ}C$ to 80$^{\circ}C$. The viscosity increased rapidly from 45$^{\circ}C$ to 60$^{\circ}C$ in breast protein, and increased from 50$^{\circ}C$ to 55$^{\circ}C$ in leg protein, respectively, and then kept relatively constant. Breast protein had higher viscosity than leg protein during heat-induced gelation. Therefore, salt soluble protein from spent layer meat was associated with denatured protein (turbidity change) prior to gelation (viscosity change) during heating. Breast protein showed lower thermal transition temperature, and better gel formation than leg protein during heating.

• Macromolecular Research
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• 제10권6호
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• pp.325-331
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• 2002

Phase behavior of a PEO-PPO-PEO (Pluronic P103) triblock copolymer in water is investigated using small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), dynamic light scattering (DLS) and rheology. Pluronic P103 shows apparent two gel states in different temperature regions. The first sol-to-gel transition at a lower temperature (i.e., the hard gel I state) turns out to be the hexagonal microphase as evidenced by the combined SANS and SAXS and the frequency dependence of both G′ and G" in rheology. In contrast to the hard gel I, the second sol-to-gel transition (i. e., the hard gel II state) at a higher temperature represents the block copolymer micelles in somewhat disordered state rather than the ordered state seen in the hard gel I. Moreover, turbidity change depending only on the temperature with four distinct regions is observed and the large aggregates with size larger than 5,000 nm are detected with DLS in the turbid solution region. Based upon the present study, two different gelation mechanisms for aqueous PEO-PPO-PEO triblock copolymer solutions are proposed.

• Bulletin of the Korean Chemical Society
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• 제18권6호
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• pp.588-594
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• 1997

Gelation time, gel structure and volatility of by-products during gelation of PZT sol-gel processing were investigated by FT-IR spectroscopy. FT-IR spectroscopic study was performed on PZT gels with the various H₂O contents (1, 2 and 3 mol) and the several types (HNO₃, NH₄OH) and amounts (0.1, 0.2 mol) of catalysts, monitoring temporal (0, 1, 3, 10 weeks, 3 months and 3 years) and thermal (100-700 ℃) changes of FT-IR spectra. The interpretation of temporal change of the spectra revealed two trends. One is under the condition of 1 mol H₂O, 1 mol H₂O+0.1 mol HNO₃, 3 mol H₂O and the other is for 1 mol H₂O+0.1 mol NH₄OH, 2 mol H₂O, 1 mol H₂O+0.2 mol HNO₃. The gel structures and the gelation times for these conditions were discussed in comparison with the reported results of SiO₂, and we suggested the reaction mechanisms for these structural characteristics. Thermal variation of FT-IR spectra was interpreted as the evolution processes of gel by investigating the evaporation of solvent and the decomposition of organic residues.

• 폴리머
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• 제38권1호
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• pp.108-112
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• 2014

도파민 및 에틸렌디아민의 폴리숙신이미드(polysuccinimide)와의 연속적인 개환 아미놀리시스 반응을 통해 카테콜 및 1차 아민기를 곁가지에 함유한 접착성 폴리아스팔트아미드를 합성하고, 산화제로서 $NaIO_4$를 사용한 상기 고분자 수용액의 산화적 젤화 반응을 관찰하였다. FTIR, UV-vis과 oscillatory rheometry를 이용하여 산화성 가교반응을 통한 젤 형성을 규명하고, 제조된 젤의 수팽윤도, 열중량분석(TGA) 및 SEM 모폴로지를 조사하였다.