• Journal of the Korean Ceramic Society
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• v.41 no.7
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• pp.555-559
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• 2004

Ceramic foams were prepared by a self-blowing process of a polysiloxane with A1$_2$O$_3$ as a filler. The release of water and ethanol vapor during the condensation reaction of the polymer triggered the pores in the polymer melt. The size. interconnectivity and shape of the pores in the ceramic foams were strongly dependent on the viscosity of the polymer melt, which could be varied by the content and size oi the filler. When the content of the filler inceased and the size of the filler decreased. the size of the pores were decreased and the thickness between the pores were increased. In the addition, the viscosity of polymer melt increased by the pretreatment at 130$^{\circ}C$ for Ire intermolecular cross linking thereby stabilizing the foam structure. The density and compressive strength of the ceramic foams were affected by the heating rate during the blowing process.

• The Korean Journal of Pesticide Science
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• v.9 no.4
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• pp.401-410
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• 2005

A series of studies involving formulation processes, bubbling activity test, diffusibility test and biological efficacy test was undertaken to develop Jumbo herbicide formulations in paddy rice field. Gas evolution speed from the tablets prepared by different organic acids was in the order of oxalic acid, malonic acid, citric acid, and tartaric acid. The total volume of evolved gas from the tablet and diffusibility of the active ingredient in the submerged water were increased with increase of water temperature; the volume from 1 g of tablet at 10, 15, 25 and $30^{\circ}C$ for 5 minutes after immersion into water was 20, 25, 28, 45, 57 mL, respectively. The concentration of halosulfuron-methyl and pyriminobac-methyl in submerged water at 5, 15, 20 and $30^{\circ}C$ at the 2.4 m distance from the applied spot of the tablet was 20, 48, 85, and 97% of the concentration of treated spot, respectively. The evolved gas volume from the tablets was not affected by pH of submerged water. The concentration of halosulfuron-methyl in different sizes of submerged water within 24 hours after treatment of the tablet was maintained 0.16 ppm, which is ideal concentration at standard dosage regardless of the submerged water area. The concentration of pyriminobac-methyl was also uniformly dispersed in the water within 24 hours after applying it into the submerged water. The wind velocity of 5 m $sec^{-1}$ on concentration distribution of halosulfuron-methyl and pyriminobac-methyl in the submerged water 24 hours after treatment was not influenced; an equal concentration in the up the wind and down the wind from the applied spot was maintained. Spot treatments of one tablet formulations(5 g) including 4 times higher dosage at 4 different spots resulted in even concentration distribution of active ingredient in the water 24 hours after applying it into the submerged water.

• Polymer(Korea)
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• v.26 no.2
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• pp.218-226
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• 2002

For the preparation of high resilience polyurethane (PU) foams with polyether type cell openers which have different ethylene oxide (EO) content, molecular weight and chain structure, the influences of tell opener structure on the kinetics, rheology, structural stability, open cell content and mechanical properties of the obtained foam were investigated. It was observed that urea formation reaction was delayed with the increase of EO content and incorporation of ester linkage in cell opener molecule and was relatively independent on the molecular weight. With the rheological studies, the decreases of viscosity and storage modulus were confirmed for the increase of EO content and molecular weight, so that the resulted foam had low structural stability and high open cell content. The cell opener having ester linkage in molecule exhibited the lowest values of viscosity and storage modulus and the obtained foam has high open cell content. However, the structural stability increased due to the larger intermolecular interaction of ester linkage. The hardness, tensile strength, tear strength and elongation of foam were deteriorated with increase of EO content and molecular weight of tell opener. On the other hand, the cell opener having ester linkage in molecule improved the values of tensile strength, tear strength and elongation.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.73-81
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• 2006

Heat treatment condition for the stabilization of foamed glass block through the foaming process of the hydrolized waste glass was investigated and scale-up test for the manufacturing of foamed glass was also attempted for the actual foaming process. Proper heat treatment condition was quenching from the foaming temperature to $550{\sim}600^{\circ}C$ for stabilization, and then annealing from stabilization temperature to $200^{\circ}C$ and holding up at $200^{\circ}C$ for removal thermal stress, and then annealing to the room temperature with cooling speed of $0.3^{\circ}C/min$. Through this heat treatment conditions, foamed glass block with size of $250mm{\times}250mm{\times}90mm$ was produced successfully. The properties of this foamed glass block showed density of $0.28{\pm}0.06g/cm^3$, thermal conductivity of $0.048{\pm}0.005kcal/hm^{\circ}C$, moisture absorption of $0.5{\pm}0.09vol%$, linear expansion coefficient of $(8.6{\pm}0.2){\times}10^{-6}m/m^{\circ}C$($400^{\circ}C$), flexural strength of $15.0{\pm}0.6kg/cm^2$, and compression strength of $39.5{\pm}0.6kg/cm^2$.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.230-235
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• 2002

엽채류 양액재배용 정식판으로 사용되는 발포스틸로폼을 작기가 끝난 후에 세척할 수 있는 브러시와 물분사방식의 평면 세척기를 제작하여 시험한 결과는 다음과 같다. 가. 정식판을 세척기내로 이송하는 속도에 따라 세칙정도를 측정한 결과, 이송단수 1단 0.15m/s에서 진행저하율이 낮았으며 2단이상에서 진행저하율이 35~40%로 매우 크게 나타났으며, 이대의 명도값은 각각 79~80으로 세척전보다 42~44정도 증가한 것으로 나타났다. 나. 횡브러시 회전속도별 정식판의 이송속도와 진행저하율은 1010rpm에서 17%로 매우 큰 것으로 나타났으나, 이때의 세척정도는 세척전후 명도차가 44.1로 매우 크게 나타났다. 다. 물공급량별 정식판의 이송속도와 진행저하율은 물공급량 80$\ell$/min일 때 11.6%로 가장 적었으며, 세척전후의 명도차도 44.4로 크게 나타났다. 라. 정식판의 세척전후 명도는 대체로 세척전 명도값이 34~40이던 것이 세척후 명도값이 59~81로 크게 개선된 것으로 나타났다. 마. 이상과 같은 결과로부터 정식판 이송속도 0.17m/s, 횡브러시 회전속도 1010rpm, 물분무량 80$\ell$/mim으로 성능 시험한 결과, 300평용을 세척하는데 2.8시간으로 인력보다 20배 능률적으로 나타나 세척기의 사용이 노동력 절감에 크게 기여하는 것으로 판단된다.

• Composites Research
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• v.29 no.3
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• pp.91-97
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• 2016

In this paper, impulse-momentum theory was coupled to a constitutive equation both for implementing quasi-static and impact characteristics of EPP (Expanded polypropylene). Also, parameters which have physical meanings were expressed as functions of relative density. Simultaneous nonlinear Newton-Raphson method was applied to find the proper values for parameters in the constitutive equation along with quasi-static test data. Results from the impulse-momentum theory coupled constitutive equation showed good agreement with experimental data and the potential to be applied to different material type polymeric foam.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.6
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• pp.1056-1062
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• 2004

Migration of low molecular weight components from expanded polystyrene (ESP) to distilled water was measured at different temperature conditions. Overall migration and specific monomer migration were measured. Diffusion model based on Fick's law was used to determine the apparent diffusion coefficients at various experimental conditions. The overall and specific migration levels were estimated to give some practical implications for regulatory guideline development and safe package design. Diffusion coefficients for overall migration in KMnO$_4$ oxidizable extractives and specific migration of styrene monomer from ESP at 6$0^{\circ}C$ were 0.030 and 6.8${\times}$10$^{-5}$ $\textrm{mm}^2$/h, respectively. Their temperature dependence could be explained by Arrhenius equation with respective activation energies of 80.5 and 98.6 kJ/㏖. Experimental conditions ensuring desired migration level were suggested for reliable examination of migration from the packaging material. Some explanatory estimations of migrations were given for some typical conditions of potential usages.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.910-913
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• 2001

Rapid Prototyping(RP) techniques have unique characteristics according to their working principle: the stair-stepped surface of a part due to layer-by-layer stacking, low building speed, and additional post-processing to improve surface roughness. A new RP process, Variable Lamination Manufacturing by using expandable polystyrene foam(VLM-S), has been developed to overcome the unfavorable characteristics. The objective of this study is to investigate the thermal characteristics and skeleton size effects as the hotwire cuts EPS foam sheet in order to improve dimensional accuracy of the parts, which is produced by VLM-S. Empirical and analytical approaches are performed to find the relationship between cutting speed and heat input, and the relationship between maximum available cutting speed and heat input. In addition, empirical approaches are carried out to find the relationship between cutting error and skeleton size, and cutting deviation and skeleton size. Based on these results, the optimal hotwire cutting condition and available minimum skeleton size are derived. The outcomes of this study are reflecting in the enhancement of VLM-S input data generation S/W.

• Journal of the Korean Institute of Gas
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• v.5 no.4 s.16
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• pp.79-84
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• 2001

In this study, the effect of polyol structure(OH-value, functionality) on the reactivity, mechanical property and cell morphology of polyurethane foam and the possibility of replacing HFC-36smfc was examined by evaluating how each blowing agent(CFC-11, HCFC-l4lb, HFC-36smfc) affects the reactivity, mechanical property and cell morphology. Results of the experiment showed that as the functionality and OH-value of polyol increased, there was an increase in the temperature profile, reaction rate, density and compressive strength. However. as the functionality and OH-value increased. the ceil size became smaller The use of different kinds of blowing agents did not appear to have and significant influence on the temperature profile, reaction rate, density and compressive strength. The foam using HFC-365mfc produced more uniform cells compared to the foam using HCFC-l4lb.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.185-194
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• 2000

Rapid Prototyping(RP) techniques have their unique characteristics according to the working principles: stair-stepped surface of parts due to layer-by-layer stacking, low build speed caused by line-by-line solidification to build one layer, and additional post processing to improve surface roughness, so it is required very high cost to introduce and to maintain of RP apparatus. The objective of this study is to develop a new RP process, Variable Lamination Manufacturing using linear hotwire cutting technique and expandable polystyrene foam sheet as part material(VLM-S), and to investigate characteristics of part material, cutting characteristics by using linear hotwire cutting system and bonding. Experiments were carried out to investigate mechanical properties of part material such as anisotropy and directional tensile strength. In order to obtain optimal dimensional accuracy, surface roughness, and reduced cutting time, addition experiments were performed to find the relationship between cutting speed and cutting offset of hotwire, and heat generation of hotwire per unit length. So, adhesion strength tests according to ASTM test procedure showed that delamination did not occur at bonded area. Based on the data, a clover-shape was fabricated using unit shape part(USP) it is generated hotwire cutting. The results of present study have been reflected on the enhancement of the VLM-S process and apparatus.