• Polymer(Korea)
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• v.34 no.5
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• pp.434-441
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• 2010

Sodium polyacrylate (PAANa) was synthesized by inverse emulsion polymerization method to absorb excess water in concrete. Liquid paraffin was used as a continuous phase. Acrylic acid (AA) was neutralized by aqueous sodium hydroxide solution (8 M). Different amount of N,N'-methylene bisacrylamide (MBA) was used as a crosslinking agent to change crosslinking density of the synthesized PAANa. The size distribution of synthesized particles was measured by particle size analyzer. Swelling ratio of crosslinked PAANa was evaluated from the equation in D. I. water, cement aqueous solution, and $Ca(OH)_2$ aqueous solution. The FTIR spectroscopy was used to characterize $Ca^{2+}$ ion interaction with PAANa. Incorporation of 1.0 wt% PAANa into cement increased compressive and flexural strength approximately 30% and 10%, respectively, compared with those of ordinary portland cement.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.138-143
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• 2005

Finite Element analysis is widely applied to elevated temperature forging processes and shows a lot of information of plastic deformation such as strain, stress, defects, damages and temperature distributions. In highly elevated temperature deformation processes, temperature of material and tool have significant influence on tool life, deformation conditions and productivities. To predict temperature related properties accurately, adequate coefficients of not only contact heat transfer between material and dies but also convection heat transfer due to coolants are required. In most F.E analysis, too higher value of contact heat transfer coefficient is usually applied to get acceptable temperature distribution of tool. For contact heat transfer coefficients between die and workpiece, accurate values were evaluated with different pressure and lubricants conditions. But convection heat transfer coefficients have not been investigated for forging lubricants. In this research, convection heat transfer coefficients for cooling by emulsion lubricants are suggested by experiment and Inverse method. To verify acquired convection and contact heat transfer coefficients, tool temperature was measured for the comparison between measured tool temperature and analysis results. To increase analysis accuracy, repeated analysis scheme was applied till temperature of the tool got to be in the steady-state conditions. Verification of heat transfer coefficients both contact and convection heat transfer coefficients was proven with good accordance between measurement and analysis.

• Transactions of Materials Processing
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• v.14 no.7 s.79
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• pp.619-623
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• 2005

Lubrication and cooling characteristics are the most important factors of elevated temperature forging lubricants. Usually adopted lubricants in warm forging processes are graphite, synthetic and emulsion lubricants. Most widely and effectively applied lubricants are graphite lubricants, but these have a lot of problems like tool corrosion and dusty environment. In this research, boronite lubricant is considered, because it is able to substitute for graphite. Hot ring compression test, cooling test and mass production test are performed to check the validity of new lubrication pigment.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2007.11a
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• pp.21-33
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• 2007

CPAM has been applied to the paper industry for the purpose of wet-end improvement for a long time. And molecular weight and charge density have been managed most important quality factors to make CPAM for this application. Recently branched CPAM was developed to improve retention and drainage characteristics and we considered branch degree of CPAM as important factor as molecular weight and charge density. In this experiment, we tried to investigate physical and chemical properties to determine branch degree and flocculation efficiency using Arbocell pulp which was recently developed micro size pulp and finally we applied retention and drainage test under the ONP stock condition.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.101-101
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• 2006

We have studied the micellisation of poly(n-butyl acrylate)-block-poly(acrylic acid) and poly(n-butyl acrylate)-graft-poly(acrylic acid) in aqueous solution. The size and structure of the formed micelles was elucidated by scattering and imaging techniques. The micelle structure depends on pH, composition, and topology: graft copolymers form much smaller micelles that block copolymers of similar composition. We have also synthesized block copolymers of acrylic acid and N-isopropylacrylamide (NIPAAm) or N,N-diethylacrylamide (DEAAm). Due to the LCST of polyNIPAAm and polyDEAAm, these block copolymers spontaneously form micelles upon heating and they form inverse micelles upon decreasing pH below 4. If the LCST block is much longer than the PAA one, this presents a very convenient way to prepare crew-cut micelles. The polymers have been successfully used as stabilizers in emulsion polymerization. They also have been conjugated to streptavidin. The conjugates reversibly form mesoscopic particles on heating.

• Macromolecular Research
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• v.14 no.1
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• pp.52-58
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• 2006

A novel fabrication of the patterned surfaces in the polymer films was demonstrated by using the self-organizing character of the block copolymers of polystyrene-b-oligothiophenes and polystyrene-b-aromatic amide dendron. Hexagonally arranged open pores with a micrometer-size were spontaneously formed by casting the polymer solutions under a moist air flow. The amphiphilic character of the block copolymers played the crucial role as a surfactant to stabilize the inverse emulsion of water in the organic solvent, and subsequently the aggregated structure of the hydrophilic oligothiophene or aromatic amide dendron segments remained on the interiors of the micropores. The chemical composition on the top of the surface of the microporous films was characterized by energy-filtering transmission electron microscopy (EFTEM) or a time-of-flight secondary ion mass spectrometer (ToF-SIMS). The characterizations clearly indicated that the patterned surfaces in the self-organized block copolymer films with the hexagonally ordered microporous structures were fabricated in a single step.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2009.04a
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• pp.23-28
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• 2009

The purpose of this study was to improve not only wet-end performances but also paper characteristics by the modification of various factors like molecular design and ionic characteristics of polyacrylamides First of all physical characteristics were observed after modify molecular design of the cationic polyacrylamides to linear, branched and cross-linked. In addition it was found analysis method to confirm branch degree of cationic polyacrylamides to combine ionic titration characteristics and spectroscopic behavior, After application of these structure modified polyacrylamides to the multiple retention systems with inorganic microparticles, it was found adjusting of branch degree of polyacrylamides was very important to optimize wet-end improvement. Second, After polymerization of amphoteric polyacrylamide to have both of cationic and anionic functional group in the polymer, we observed not only physical characteristics but also wet-end improvement to apply recycled pulp and found that the improvement of solution stability to prevent hydrolysis and increase of ash retention dramatically to compare traditional cationic polyacrylamide retention aid, Finally, After polymerization of anionic polyacrylamide, we observed not only wet-end improvement but also paper characteristics to apply preflocculation of PCC and it was found the improvements of flocculation efficiency, retention, ash retention, optical properties of the paper and bursting strength to compare traditional preflocculant of cationic polyacrylamide.

• Polymer(Korea)
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• v.36 no.2
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• pp.208-215
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• 2012

To study the effect of surface crosslinked layer on the crosslinked poly(sodium acrylate) (cPSA) absorbent, we synthesized several surface crosslinked cPSAs with 5, 10 and 20 g of ethylene glycol dimethacrylate (EGDMA) by an inverse emulsion polymerization method to delay the absorption of excess water in concrete. We measured the compressive and flexural strength of mortars having 0.5, 1.0 and 1.5 wt% cPSA-EGDMA. We observed the increase of compressive and flexural strength of the cPSA-EGDMA added cement mortars except for the 0.5 wt% cPSA-EGDMA (20 g) added cement mortar. 1.0 wt% cPSA-EGDMA (5 g) added cement mortar showed about 16% and 10% increased compressive and flexural strength than those of plain cement mortar. To study the effect of porosity on compressive and flexural strength, we used FE-SEM and porosimeter. FE-SEM analysis showed swollen cPSMAEGDMA (5 g) filled between calcium silicate hydrate (C-S-H) crystals. We observed the decreased porosity of the cPSA-EGDMA added cement mortars than that of plain cement mortar. 1.0 wt% cPSA-EGDMA (5 g) cement mortar showed the lowest porosity of 16.5%.