• Journal of Environmental Science International
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• v.14 no.6
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• pp.525-532
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• 2005

Polyelectrolyte titration, which was called colloid titration is based on the stoichiometric reaction between oppositely charged polyelectrolytes, This can be used, for instance, to determine the charge density of a cationic polyelectrolyte, using an anionic polyelectrolyte of known charge density, such as potassium polyvinyl sulfate (PPVS). The technique requires a suitable method of end-point detection and there are several possibilities. In this work, two methods have been investigated: visual titrimetry based on the color change of a cationic dye (o-toluidine blue, o-Tb) and spectrophotometry based on the absorbance change corresponding to the color change of the same dye. These have been applied to several cationic polyelectrolytes with different charge density and molecular weight. In all cases, the cationic charge was due to quaternary nitrogen groups. In the case of cationic dye, it was shown that the sharpness depends on the charge density of cationic polyelectrolyte. With the polyelectrolytes of lower charge density, the binding to PPVS is weaker and binding of the dye to PPVS can occur before all of the polyelectrolyte charge has been neutralized. However, by carrying out titrations at several polyelectrolyte concentrations, good linear relationships were found, from which reliable charge density values could be derived. Effects of pH and ionic strength were also briefly investigated. For cationic polyelectrolytes (copolymers of acrylamide and dimethylaminoethy] acrylate), there was some loss of charge at higher pH values, probably as a result of hydrolysis. Increasing ionic strength causes a less distinct color change of o-Tb, as a result of weaker electrostatic interactions.

• Journal of the Korean Applied Science and Technology
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• v.22 no.2
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• pp.191-199
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• 2005

Removable protective adhesives for automobiles were synthesized by an emulsion polymerization of monomers such as n-butyl acrylate (BA), n-butyl methacrylate (BMA), acrylonitrile (AN), acrylic acid (AA) and 2-hydroxyethyl methacrylate (2-HEMA), in which AA and 2-HEMA were functional monomers. Potassium persulfate (KPS) was used as an initiator and sodium lauryl sulfate (SLS) was used as an emulsifier, and polyvinyl alcohol (PVA) was used as a stabilizer. Emulsion polymerization was carried out in a semi-batch type reactor. Tensile strength, extension, peel strength, viscosity and solid content of the synthesized adhesives were tested. The optimum physical properties of the removable protective adhesives for automobiles were obtained with the composition of 0.43 mole BA, 0.57 mole AN, 0.21 mole BMA, 0.03 mole AA, and 0.03 mole 2-HEMA.

• Journal of the Korean Applied Science and Technology
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• v.23 no.2
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• pp.169-176
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• 2006

Acrylic adhesives for automobiles protection were prepared by emulsion polymerization. Monomers used were n-butyl acrylate(BA), acrylonitrile (AN), butyl methacrylate(BMA), glycidyl methacrylate(GMA), and acrylic acid (AA). Emulsifiers used were sodium lauryl sulfate and polyoxyethylene lauryl ether, which are an anionic emulsifier and a nonionic emulsifier respectively. Potassium persulfate was used as an initiator and polyvinyl alcohol was used as a stabilizer. Emulsion polymerization was carried out in a semi-batch reactor at $70^{\circ}C$ and agitation speed was kept at 200 rpm. Water resistance, heat resistance, acid resistance, alkali resistance and smoke resistance were examined. As a result, when each 0.03 mole of GMA and AA was introduced, the adhesion properties and various above mentioned resistances of the prepared adhesives were satisfied the standard for automobiles.

• Journal of the Korean Applied Science and Technology
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• v.22 no.4
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• pp.332-338
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• 2005

This study was conducted to prepare acrylic removable protective coatings by emulsion polymerization. Monomers used were n-butyl acrylate, acrylonitrile, butyl methacrylate. Emulsifiers used were sodium lauryl sulfate and polyoxyethylene lauryl ether, which are an anionic emulsifier and a nonionic emulsifier respectively. Potassium persulfate was used as an initiator and polyvinyl alcohol was used as a stabilizer. Emulsion polymerization was carried out in a semi-batch reactor at $70^{\circ}C$ and agitation speed was 200 rpm. Tensile strength, extension, peel strength, viscosity, and solid contents of the synthesized coatings were examined. The coatings prepared with BA:AN = 60:20 (in weight ratio) satisfied the standard for automobile in terms of extension and peel strength. When the concentration of BMA was in a range of $18{\sim}23$ wt%, the prepared coatings satisfied the standard for automobile in terms of peel strength and water resistance.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.5
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• pp.377-382
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• 2007

Porous mineral coating have been fabricated and applied for basic research on their slow release action to a fertilizer. Feldspar was selected as raw mineral for the coating and two different particle sizes of powder were prepared. Slow-release action was estimated by using a potassium sulfate fertilizer. Spherical pellets were prepared with a pan-type pelletizer and then screened into sizes ranging 1.4 to 2.35mm. While the fertilizer pellets were rotated in the pelletizer again, the feldspar powder and 0.5% polyvinyl alcohol solution were simultaneously sprayed on the pellets. The fertilizer pellets coated with feldspar powder were fabricated. The pellets were heated to increase their strength and screened to sort by coating thickness. Potassium releasing tests were conducted for 40 days and the performance for slow-release action was estimated as functions of the heating temperature, coating thickness and raw mineral powder size. The Burst effect caused high initial releasing rate. Releasing kinetics was proportional to concentration of potassium in pellets. The pellet that was fabricated with $27.4{\mu}m$-sized feldspar and heated at $1050^{\circ}C$ showed a releasing rate of 43% on the 40th day.