• Korean Journal of Materials Research
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• v.33 no.8
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• pp.323-329
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• 2023

There are many types of foam molding methods. The most commonly used methods are the pressure foaming method, in which foam resin is mixed with a foaming agent at high temperature and high pressure, and the normal pressure foaming method, which foams at high temperature without pressure. The polymer resins used for foaming have different viscosities. For foaming under normal pressure, they need to be designed and analyzed for optimal foaming conditions, to obtain resins with low melt-viscosity or a narrow optimal viscosity range. This study investigated how changes in viscosity, molding temperature, and cross-link foaming conditions affected the characteristics of the molded foam, prepared by blending rubber polymer with biodegradable resin. The morphologies of cross sections and the cell structures of the normal pressure foam were investigated by SEM analysis. Properties were also studied according to cross-link/foaming conditions and torque. Also, the correlation between foaming characteristics was studied by analyzing tensile strength and elongation, which are mechanical properties of foaming composites.

• Elastomers and Composites
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• v.50 no.1
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• pp.49-54
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• 2015

Dynamically vulcanized PMMA/ACM (80 wt%/20 wt%) blend using DCP as a curing agent was prepared using internal mixer. The morphology, mechanical properties, optical properties, melt viscosity and die swell were characterized by using FE-SEM, tensile test, Izod impact test, dynamic mechanical analysis, ARES and capillary rheometer, respectively. The blends show a phase-separated morphology in which ACM are dispersed in PMMA matrix. Dynamically vulcanized blend exhibits higher mechanical properties, higher melt viscosity, and die swell as compared to simple blend. And, the dynamically vulcanized blend showed total transmittance of more than 75% and haze of higher than 90%, which enable it to find potential applications to fabricate an optical diffuser by extrusion process.

• The Korean Journal of Ceramics
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• v.4 no.3
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• pp.176-182
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• 1998

The effects of temperature, cooling surface tension on the fining were studied in alkali-alkaline earth-silica TV screen glassmelts containing ZnO. Sodium antimonate $(Na_2OSb_2O_5)$ was used as a fining agent. Viscosity and surface tension of the melts were determined. On the basis of these properties, fining tests for several batches were performed by "MF" (Melting and Fining) and "PMF" (Profiled melting and Fining) methods. The results of these tests showed an opposite behavior each other with increase in ZnO content. This hehavior has been discussed in terms of two fining processes-growth of bubbles and shrinkage of seeds. shrinkage of seeds.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.152-157
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• 2002

The cure and rheological behavior of Diglycidyl ether of bisphenol F, catalyzed by four kinds of imidazoles and a Nadic methyl anhydride curing agent were studied using a differential scanning calorimeter (DSC) and rheometer. The isothermal traces were employed to analyze cure reaction. The DGEBF/anhydride conversion profiles showed autocatalyzed reaction characterized by maximum conversion rate at 20~40 % of the reaction. The rate constants obtained from isothermal test showed temperature dependance, but reaction order did not. The order of reaction (m+n) was calculated to be close to 3. The measurements of viscosity and relation time in the presence of inorganic fillers were carried out at different isothermal curing temperatures. The viscosity and gelation time increased with filler content at the same isothermal temperature.

• Journal of the Korean Applied Science and Technology
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• v.15 no.1
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• pp.35-45
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• 1998

Chitin/chitosan be known as biodegradable natural polymer. However, commercial use of chitin has been limited due to highly resistance to chemicals and the absense of proper solvents. Therefore, we was studied that chitin was prepared by the application of Hackman's method from Protunus trituberculatus shells. And another viscosity chitosan were prepared from chitin which were deacetylated under various concentration of alkali, reaction time and temperature by the application of Mima's method. And crosslinked chitin/chitosan was preparaed from chitin/chitosan with crosslink agent followed by crosslinkage. The major parameters for chitosan manufacturing methods were found to be concentration of alkali solution, reaction time and temperature etc. The effects of these parameters on chitin, another viscosity(molecular weight) chitosan and crosslinked chitin/chitosan were investigated by various analysis apparatus.

• Journal of the Korean Applied Science and Technology
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• v.31 no.3
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• pp.517-524
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• 2014

Two key technologies of horizontal drilling and hydraulic fracturing are recognized to achieve the rapid growth of shale gas production, in specific, in the United States during last decade. The claims between environmentalists and oil companies have been debating in terms of water contamination. Nowadays, voluntary publication of chemicals from shale gas players are available in the website, FracFocus. This paper introduces chemicals that are currently used in hydraulic fracturing process. Among chemicals, guar gum and guar derivatives are dominantly consumed to increase the viscosity of hydrofracking fluids. The role of additional additives, such as breakers and biocides, is presented by explaining how they cut down the molecular structure of guar gum and guar derivatives. In addition, crosslinking agent, pH controller, friction reducer, and water soluble polymers are also presented.

• Bulletin of the Korean Chemical Society
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• v.20 no.11
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• pp.1329-1334
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• 1999

The curing characteristics of diglycidyl ether of bisphenol A (DGEBA) with diaminodiphenylmethane (DDM) as a curing agent were studied using differential scanning calorimetry (DSC), rheometrics mechanical spectrometry (RMS), and dielectric analysis (DEA). The isothermal curing kinetics measured by DSC were well represented with the generalized auto-catalytic reaction model. With the temperature sweep, the inverse relationship between complex viscosity measured by RMS and ionic conductivity obtained from DEA was established indicating that the mobility of free ions represented by the ionic conductivity in DEA measurement and the chain segment motion as revealed by the complex viscosity measured from RMS are equivalent. From isothermal curing measurements at several different temperatures, the ionic conductivity contribution was shown to be dominant in the dielectric loss factor at the early stage of cure. The contribution of the dipole relaxation in dielectric loss factor became larger as the curing further proceeded. The critical degrees of cure, at which the dipolar contribution in the dielectric loss factor starts to appear, increases as isothermal curing temperature is increased. The dielectric relaxation time at the same degree of cure was shorter for a sample cured at higher curing temperature.

• Korean Journal of Food Science and Technology
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• v.31 no.2
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• pp.509-515
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• 1999

Lactic acid bacteria (LAB) fermented foods were prepared from egg white powder (EWP), casein and growth stimulating agents (GSA). The effects of GSA on acid production and growth of Lactobacillus were studied. The effects of GSA on sensory properties and viscosity of LAB fermented foods were also studied. Acid production by Lactobacillus was stimulated by addition of GSA (0.3% or 1%, W/V). Although stimulating effect differed among each GSA, some GSA increased the acidity up to the level of fermented milk. However, stimulating effect of GSA on viable cells was not noticeable. Acid production by L. acidophilus was generally higher than other Lactobacilli. The optimum concentration of GSA added to substrate was 1% (W/V). Sensory evaluation showed that the optimum fermentation time was 18hr. The sensory properties of GSA samples were evaluated as slightly lower than that of fermented milk because GSA samples showed whey separation and taste and smell of GSA. Apparent viscosity of GSA samples was significantly lower than that of fermented milk and control sample (p<0.05). There was no significant difference of apparent viscosity among GSA samples. GSA samples, fermented milk and control sample showed thixotropic flow characteristics.

• International Journal of Advanced Culture Technology
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• v.8 no.3
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• pp.211-215
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• 2020

Currently, most of the chlorine dioxide gas is processed at the beginning of storage or distribution. It has the disadvantage of not being able to continuously process gas since there is no system that can continuously process it during the distribution process. Therefore, in order to minimize changes in freshness and quality during the distribution process of agrifood, there is a need for a sustained-release chlorine dioxide gas treatment technology that can be continuously released. Therefore, in this study, the film to be used was examined so that the chlorine dioxide gas can be continuously released for a certain period of time, the concentration of the reactant and the viscosity at the time of the reaction were determined, and a chlorine dioxide gas gel pack was manufactured using this optimal condition. In addition, the gel pack was used to measure the amount of chlorine dioxide gas released and the sterilization effect of food poisoning bacteria.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.661-664
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• 2000

It is known that high flowing concrete performs much higher fluidity, segregation resistibility and better placeability than normal concrete. However, it is hard to apply high fluidity concrete in field because of high manufacturing cost. Therefore, we intend to investigate the validity of segregation reducing type superplasticizer which is made by combining 0.61 of viscosity agent and 0.022 of AE agent for 1 of superplasticizer. Test are conducted on high flowing concrete using fly ash by applying segregation reducing type superplasticizer. According to experimental results, As contents of fly ash increase, fluidity, segregation resistibility and placeability shows favorable results. And also compressive strength at early age shows to be retarded, while it gains high strength at later age.