• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.25-32
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• 2021

For developing the durable eco-concrete, water-repellent and hydrophobic emulsion were prepared by stirring and mixing polymethyl hydrosiloxane and polyvinyl alcohol. After adding the PMHS emulsion cement paste, the hydration reaction characteristics and the change in chemical composition were analyzed through BSE and EDS analysis, and the micropores were evaluated by MIP test. Cement mixed with PMHS emulsion was analyzed to increase the hydration reactivity and to decrease the capillary porosity, but it was found that the capillary porosity varies depending on the degree of dispersion of the emulsion in the cement paste. In the case of the emulsion containing metakaolin, there was little difference in hydration degree and porosity from the case of using only the PMHS emulsion. However, when the cement surface was coated with PMHS emulsion, the contact angle was found to increase significantly compared to OPC, and it was analyzed that especially when PVA fiber was used together, it changed to a hypohydrophobic surface.

• Journal of the Korean Applied Science and Technology
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• v.27 no.2
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• pp.183-187
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• 2010

Core-Shell polymers of silicone dioxide-styrene system were prepared by sequential emulsion polymerization. In inorganic/organic Core-Shell composite particle polymerization, silicone dioxide adsorbed by surfactant sodium dioctyl sulfosuccinate (EU-DO133L) was prepared initially and then core silicone dioxide was encapsulated emulsion by sequential emulsion polymerization using styrene at the addition of potassium persulfate (KPS) as an initiator. We found that $SiO_2$ core shell of $SiO_2$/styrene structure was formed when polymerization of styrene was conducted on the surface of $SiO_2$ particles, and the concentration sodium dioctyl sulfosuccinate (EU-DO133L) was 0.5~2.0g. The structure of core-shell polymer were investigated by measuring to the thermal decomposition of polymer composite using thermogravimetric analyzer and morphology of latex by scanning electron microscope(SEM).

• Journal of the Korean Applied Science and Technology
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• v.19 no.2
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• pp.131-136
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• 2002

As model waterborne acrylic coatings, mono-dispersed poly(butyl acrylate-methyl methacrylate) copolymer latexes of random copolymer and core/shell type graft copolymer were prepared by seeded multi-staged emulsion polymerization with particle size of $180{\sim}200$ nm using semi-batch type process. Sodium lauryl sulfate and potassium persulfate were used as an emulsifier and an initiator, respectively. The effect of particle texture including core/shell phase ratio, glass transition temperature and crosslinking density, and film forming temperature on the film formation and final properties of film was investigated using SEM, AFM, and UV in this study. The film formation behavior of model latex was traced simultaneously by the weight loss measurement and by the change of tensile properties and UV transmittance during the entire course of film formation. It was found that the increased glass transition temperature and higher crosslinking degree of latex resulted in the delay of the onset of coalescence of particles by interdiffusion during film forming process. This can be explained qualitatively in terms of diffusion rate of polymer chains. However, the change of weight loss during film formation was insensitive to discern each film forming stages-I, II and III.

• Advanced Composite Materials
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• v.16 no.4
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• pp.385-394
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• 2007

In this study, the effect of molding condition on the tensile properties for plain woven hemp fiber reinforced green composite was examined. The tensile properties of the composite were compared with those of the plain woven jute fiber composite fabricated by the same process. Emulsion type biodegradable resin or polypropylene sheet was used as matrix. The composites were processed by the compression molding where the molding temperature and its heating time were changed from 160 to $190^{\circ}C$ and from 15 to 25 min, respectively. The following results were obtained from the experiment. The tensile property of hemp fiber reinforced polypropylene is improved in comparison with polypropylene bulk. The strength of composite is about 2.6 times that of the resin bulk specimen. Hemp fiber is more effective than jute fiber as reinforcement for green composite from the viewpoint of strength. The molding temperature and time are suitable below $180^{\circ}C$ and 20 min for hemp fiber reinforced green composite. Hemp fiber green composite has a tendency to decrease its tensile strength when fiber content is over 50 wt%.

• Macromolecular Research
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• v.9 no.2
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• pp.122-128
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• 2001

Monodisperse composite latex particles with size of ca. 300 nm, which consist ofn-butyl acrylate as a soft phase and methyl methacrylate as a hard phase with different morphology, were synthesized by seeded multi-stage emulsion polymerization. Three types of composite latex particles including random-, core/shell-, and gradient-type particles were obtained by using different monomer feeding methods during semi-batch emulsion polymerization. Effect of poly(butyl acrylate)-poly(methyl methacrylate) rubber particle morphology on the mechanical and rheological properties of rubber toughened poly(methyl methacrylate) was investigated. Among three different rubber particles, the gradient-type rubber particle showed better toughening effect than others. No significant variation of rheological property of poly(methyl methacrylate)/rubber blends was observed for the different rubber particle morphology.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.133-134
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• 2019

As part of recent low-energy policies, thermal insulation standards for buildings are being tightened every year. The importance of external insulation methods is increasing due to the strengthening of insulation standards. Among the main materials used in the external insulation method, dry bit material is a finishing material composed of an organic binder and aggregate. When the fire occurs, the ignition of the surface part causes a direct fire on the thermal insulation material at the rear side when heat energy is concentrated. Therefore, it is important that the finishing material in dry insulation using a dry bit has a low fire spreading property in case of a fire and does not have a sustained combustion. The purpose of this study was to evaluate the fire spreadability by changing the internal fillers while using alkoxide-based acrylic emulsions, hybrid acrylic emulsions, and general acrylic emulsions in order to suppress the fire spreading properties of exterior finish materials.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1345-1348
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• 2010

Highly monodisperse polystyrene (PS) nanospheres were fabricated by surfactant-free emulsion polymerization in water using styrene, 2,2'-azobis(2-methyl propionamidine) dihydrochloride (AIBA), and poly(vinyl pyrrolidone) (PVP). The size and distribution of the PS nanospheres were systematically investigated in terms of initiator concentration, stabilizer concentration, reaction temperature, reaction time, and reactant concentration. With increasing AIBA initiator concentration, PS particle sizes are raised proportionally, and can be controlled from 120 to 380 nm. Particle sizes were reduced with increasing PVP concentration. This decrease occurs because a high PVP concentration leads to a large number of primary nuclei in the early stage of polymerization. When the reaction temperature increased, the sizes of the PS particles decrease slightly. The particles grew quickly during the initial reaction stage (1-3 h) and the growth rate became steady-state after 6 h. The PS sizes approximately doubled when the reactant (styrene, PVP, azo-initiator) concentrations were increased by a factor of eight.

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.159-166
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• 2012

We have introduced the Pickering emulsion systems to generate novel confining geometries for the selforganization of monodisperse polymer microspheres using nanoparticle-stabilized emulsion droplets encapsulating the building block particles. Then, through the slow evaporation of emulsion phases by heating, these microspheres were packed into regular polyhedral colloidal clusters covered with nanoparticle-stabilizers made of silica. Furthermore, polymer composite colloidal clusters were burnt out leaving nonspherical hollow micro-particles, in which the configurations of the cluster structure were preserved during calcination. The selfassembled porous architectures in this study will be potentially useful in various applications such as novel building block particles or supporting materials for catalysis or gas adsorption.

• Bulletin of the Korean Chemical Society
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• v.34 no.8
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• pp.2451-2454
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• 2013

Poly(methyl methacrylate) coated $BaF_2:Er^{3+}$ nanoparticles were prepared via a novel reverse-emulsion polymerization process using methyl methacrylate as continuous phase and water as dispersed phase. Preparation and coating of $BaF_2:Er^{3+}$ particles were processed in a single step. The resulting polymeric composites show the characteristic $Er^{3+}$ luminescence at excitation of 980 nm and may have potential applications in amplified optical networks.

• Elastomers and Composites
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• v.37 no.1
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• pp.21-30
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• 2002

Core-shell polymers of methyl methacrylate/styrene pair were prepared by sequential emulsion polymerization in the presence of sodium dodecyl benzene sulfonate(SDBS) as an emulsifier using ammonium persulfate(APS) as an initiator. The characteristics of these core-shell polymers were evaluated. Core-shell composite latex has the both properties of core and shell components in a particle, where as polymer blonds or copolymers show a combined properties from the physical properties or two homopolymers. This unique behavior of core-shell composite latex can be used in many industrial fields. However, in preparation of core-shell composite latex, several unexpected phenomina are observed, such as, particle coagulation, low degree of polymerization, and formation of new particles during shell polymerization. To solve the disadvantages, we studied the effects of surfactant concentrations, initiator concentrations, and reaction temperature on the tore-shell structure or PMMA/PSt and PSt/PMMA. Particle size and particle size distribution were measured by using particle size analyzer, and the morphology of the core-shell composite latex was observed by using transmission electron microscope. Glass transition temperature($T_g$) was also measured by using differential scanning calorimeter. To identify the core-shell structure, pH of the composite latex solutions were measured.