• KIEE International Transactions on Electrophysics and Applications
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• v.12C no.4
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• pp.229-235
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• 2002

The apparent volume resistivity of powders measured by both the tapping and the compressing methods was compared in this study. Factors such as applied voltage, pressure, corona charging, and so on affecting the apparent volume resistivity of polymer powders were also examined experimentally. Powders of polyacrylonitrile and Nylon 11 were mainly used. The values of the apparent resistivity of polymer powders taken by the tapping method turned out to be larger than those taken by the compressing method, which indicates that the apparent volume resistivity of polymer powders depends strongly on the measurement method. The apparent resistivity of polymer powders increased with an increase in applied voltage while it decreased with an increase in pressure, tapping time, and particle size. The influence of the moisture content of powder and corona charging on the resistivity of polymer powders is also discussed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2001.11a
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• pp.88-92
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• 2001

This paper discusses the strength properties of the polymer-modified mortars using redispersible polymer powders, which is widely used for the manufacture of prepackaged-type polymer-modified mortar products at present. The polymer-modified mortars using redispersible polymer powders are prepared with various polymer-cement ratios, and tested for air content, flexural and compressive strengths, and tensile strength. The strength properties are almost the same as those of polymer dispersion-modified mortars, depending on the polymer-cement ratios, and are improved over unmodified mortar. In particular, between tensile strength and glass transition point of polymer powder have a high correlation. It is concluded from the test results that polymer-modified mortars using redispersible polymer powders can be used in the same manner as ordinary polymer dispersion-modified mortars.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.462-463
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• 2006

Monodispersed and nano-sized Ni powders were synthesized from aqueous nickel sulfate hexahydrate $(NiSO_4{\cdot}6H_2O)$ inside nonionic polymer network by using wet chemical reduction process. The sucrose was used as a nonionic polymer network source. The effect of reaction conditions such as the amount of sucrose and a various reaction temperature, nickel sulfate hexahydrate molarity. The influence of a nonionic polymer network on the particle size of the prepared Ni powders was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size analysis (PSA). The results showed that the obtained Ni powders were strong by dependent of the reaction conditions. In particular, the Ni powders prepared inside a nonionic polymer network had smooth spherical shape and narrow particle size distribution.

• Journal of the Korea Institute of Building Construction
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• v.13 no.3
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• pp.235-241
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• 2013

In this study, a mortar was produced using re-dispersible polymer powders that addresses the defects of aqueous polymer and improves the durability of cement mortar. Also, an attempt was made to examine the properties of polymer modified mortars using re-dispersible polymer powders by strength and durability tests between ordinary Portland cement mortars and polymer modified mortars mixed with aqueous dispersion. The test showed that strength and durability are improved considerably compared with ordinary Portland cement mortar, and the performance of aqueous polymer cement mortar was considerably improved. Accordingly, it is expected that high-quality prepackaged polymer modified mortars can be produced using re-dispersible polymer powders.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.252-255
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• 2003

Recently, there is a growing trend in the United States toward replacing latex additives in polymer-modified cement mortars with redispersible polymer powders. This movement is relatively new in the U.S. but is further advanced in Europe due to the more extensive use of cement and concrete in residential construction. Hitherto, in Korea - there is a very diminutive movement towards this growing trend. Thus, there is limited availability of data on redispersible polymer powders. This study investigates the effectiveness of redispersible polymer powder on improvement of the mechanical properties of modified mortar. It was concluded from the results of the experiments that the size of the dispersed polymer particles, variations in glass transition points (Tg), and variations in minimum film formation temperature (MFT) influenced the strength development of the modified mortars, and optimum strength in modified mortars using redispersible powders can be achieved when the Tg which accounts for the degree of powder flexibility is considered.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.464-465
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• 2006

Monodispersed and nano-sized Cu powders were synthesized from copper sulfate pentahydrate $(CuSO_4{\cdot}5H_2O)$ inside a nonionic polymer matrix by using wet chemical reduction process. The sucrose was used as a nonionic polymer network source. The influences of a nonionic polymer matrix on the particle size of the prepared Cu powders were characterized by means of X-ray diffraction), scanning electron microscopy), and particle size analysis). The smallen Cu powders with size of approximately 100 nm was obtained with adding of 0.04M sucrose at reaction temperature of $60\;^{\circ}C$. The particle size of the Cu powders prepared by the reduction inside polymer network was strongly dependent of the sucrose content and reaction temperature.

• Journal of the Korean Chemical Society
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• v.56 no.1
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• pp.102-107
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• 2012

Hollow ITO powders were prepared by using polystyrene powders as a template. The specific gravity of the prepared hollow ITO powders was less than half compared with that of normal ITO spheres. As a result, the mismatch between the specific gravity of ITO and that of polymer solution was reduced. When the prepared hollow ITO powders and the polymer solutions are mixed, some portion of the hollow particles were collapsed and generated lots of small fragments. Thousands of the broken fragments from hollow ITO powders caused the increased contact area between particles and finally resulted in the higher electrical conductivity for the coating solution made of the prepared hollow ITO powders and the polymer solution.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.529-532
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• 2005

The effects of polymer-binder ratio and ceramic powder content on the drying shringage and strength of polymer-modified pastes using redispersible polymer powders and ceramic powder are examined. As a result, the drying shrinkage of the polymer-modified pastes using redispersible polymer powders tend to decrease with increasing polymer-binder ratio and ceramic powder content. Regardless of the type of polymer powder, the tensile strength and adhesion in tension of the polymer-modified pastes with ceramic powder tend to increase with increasing polymer-binder ratio and ceramic powder content.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.438-439
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• 2006

Pure and stable YAG $(Y_3Al_5O_{12})$ powders were synthesized by a PVA (polyvinyl alcohol) polymer solution technique. PVA was used as an organic carrier for the precursor ceramic gel. The precursor gels were crystallized to YAG at relatively a low temperature of $900\;^{\circ}C$. The synthesized powders, which have nano-sized primary particles, were soft and porous, and the porous powders were ground to sub-micron size by a simple ball milling process. The ball-milled powders were densified to 94% relative density at $1500\;^{\circ}C$ for 1h. In this study, the characteristics of the synthesized YAG powders were examined.

• KIEAE Journal
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• v.10 no.5
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• pp.131-137
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• 2010

The building industry must aim at high-durability and sustainability. A holistic life cycle based approach is recommended to reduce the environmental load. In recent years, technical innovations in the construction industry have advanced to a great extent, and caused the active research and development of high-performance and multifunctional construction materials. Nowadays, various polymer powders have been commercialized to manufacture construction materials in the form of prepackaged-type products, which have rapidly been developed for lack of skilled workmen in construction sites. Recently, terpolymer powders of improved quality have been developed and commercialized as cement modifiers. And, hydrocalumite is a material that can adsorb the chloride ions (Cl-) causing the corrosion of reinforcing bars and liberate the nitrite ions (NO2-) inhibiting the corrosion in reinforced concrete, and can provide a self-corrosion inhibition function to the reinforced concrete. The purpose of this study is to ascertain the self-corrosion inhibition function of polymer-modified mortars using redispersible powders with hydrocalumite. Polymer-modified mortars using VA/E/MMA and VAE redispersible powders are prepared with various calumite contents and polymer-binder ratios, and tested for chloride ion penetration depth, corrosion inhibition. As a result, regardless of the polymer-binder ratio, the replacement of ordinary portland cement with hydrocalumite has a marked effect on the corrosion-inhibiting property of the polymer-modified mortars. Anti-corrosion effect of polymer-modified mortars using VA/E/MMA terpolymer powder with hydrocalumite is higher than that of VAE copolymer powder.