• KSBB Journal
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• v.22 no.3
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• pp.146-150
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• 2007

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] microspheres were prepared using solvent evaporation technique. P(3HB-co-4HB) with 3.9 mol% 4HB was synthesized by fed-batch culture of Ralstonia eutropha. The effects of concentration and type of surfactant (Tween 80, sodium dodecylsulfate, and polyvinyl alcohol), addition of dispersion stabilizer (Acacia), concentration of polymer and model drug (bovine serum albumin) on particle size of the microspheres and their in vitro drug release characteristics were investigated. The average particle size of the microspheres decreased with the addition of dispersion stabilizer and increased with the concentration of surfactant, drug and polymer. Amount of drug release increased with decreasing particle size of the microspheres.

• Journal of the Korean Graphic Arts Communication Society
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• v.30 no.2
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• pp.1-12
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• 2012

In this experiment, we have manufactured thermal-curable silver pastes for direct printing. And to enhance conductivity, printability, adhesion and hardness during polymer direct-gravure prints, we have manufactured Ag pastes by adding variety of filter contents. Then we have investigated characteristics of rheology in paste according to the gravure printability and the properties of printed conductive patterns. Depending on a variety of Ag powder, there was a big difference in sharpness of printed pattern. And also by the use of carbon, there was a big difference in amount of solvent used, conductivity and in hardness. We could improve doctoring and the sharpness of a pattern by adding Ag paste in carbon particle, but as we have used nano-sized particle, there was an increase in the amount of solvent used and also we have found out that it gives a bad effect as adhesive and hardness becomes weaker. Even though Ag particle has the same spherical shape, the surface treatments could differ from one another. And by the appropriate choice and with the suitable combination of Ag powder, excellent printability and conductivity could be obtained.

• Polymer(Korea)
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• v.36 no.3
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• pp.332-337
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• 2012

The primary objective of this work is to find the properties of sustained release dissolution pattern depending on solubility of drugs, so venlafaxine HCl and carbamazepine tablets were made by using polymer wich various particle size. Hydroxy propyl methyl cellulose (HPMC) has been utilized in this study as an excipient that is one of the most widely used polymers for an oral sustained release formulation, and drug release pattern was strongly influenced by swelling rate depending on particle size of HPMC. Scanning electron microscope (SEM) was employed to investigate the surface of tablets with various HPMC particle size, and differential scanning calorimeter (DSC) was employed to investigate the crystallization of drugs in tablets. The release model equation was applied to analyze the main mechanism of drug release pattern. The results demonstrate that drug release pattern is controlled by the drug solubility and HPMC particle size.

• Polymer(Korea)
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• v.28 no.6
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• pp.524-530
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• 2004

Polystyrene particles (PS) with poly(ethylene glycol) units on surface were formed by an emulsifier-free emulsion polymerization using styrene, poly(ethylene glycol) methacrylate (PEG-MMA) or poly(ethylene glycol) dimethacrylate (PEG-diMMA) at pH 7, and followed by freeze-drying to give the corresponding powders. The structures of PS particles were confirmed by FT-IR spectroscopy, and the particle size and distribution the PS particle were observed by scanning electron microscopy and particle analyzer. Monodisperse polymer particles were obtained at a concentration of PEG-MMA 2∼5 mol% or PEG-diMMA 1 mol% relative to styrene. The highest zeta potential of polymer surface was measured to be 183 mV at a polymer of PEG-MMA 5 mol%, which was measured in dielectric medium by means of ELS-8000 dynamic light scattering.

• Elastomers and Composites
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• v.47 no.2
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• pp.141-147
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• 2012

Silicone resin has no water-absorbing function because it is a strong hydrophobic polymer. However, addition of super absorbent polymer gives much better absorbency than that of conventional silicone resin. In this study, we developed novel silicone materials with water-absorbing function by choosing three types of amorphous acrylic super absorbent polymers with different particle sizes, determining the mixing ratio of the three polymers and applying the mixtures into two-component type silicone material for medical purpose. The change in the mechanical properties such as tensile strength, tear strength, compressive strength and hardness was investigated by varying the particle size and content ratio of the added super absorbent polymers while preparing the silicone resins. The absorbency of the silicone resins was measured over time. Additionally, the particle shape of the super absorbent polymers as well as the distribution within the silicone resin was observed using an optical microscope.

• Microbiology and Biotechnology Letters
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• v.43 no.4
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• pp.343-349
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• 2015

In this study, we applied an increased surface area fractional precipitation with hydrophilic polymer for decreasing the particle size of the anticancer agent paclitaxel from plant cell cultures. The addition of polymer resulted in a considerable decrease in the size of the paclitaxel precipitate. Among the polymers (HPMC 2910, PVP-K90, PVA) used, PVP-K90 was the most effective for the inhibition of precipitate growth. When PVP-K90 (0.2%, w/v) was used, the paclitaxel particles were four to five times smaller, having less than a $20{\mu}m$ radius, than those obtained in the absence of the polymer. In addition, the precipitate size was inversely correlated with the absolute value of zeta potential.

• Elastomers and Composites
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• v.31 no.5
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• pp.327-334
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• 1996

A correlative analysis has been carried out to predict the average particle size of rubber dispersed phase In high impact polystyrene manufactured by bulk polymerization. To do the correlation, a mechanistic model suggested previously by the author was used for describing the size of stabilizing particles agitated under the turbulent viscous shear subranges in a prepolymerization reactor, where the rubber particles were assumed to be formed at the time of phase inversion in the reactor. Viscosities required for the model were postulated to describe the overall behavior of butadiene rubber and polystyrene mixture along the wide range of conversion. The good agreement between the model and the experimental data from a plant was quite satisfactory for the prediction of the average rubber particle size of high impact polystyrene.

• Textile Coloration and Finishing
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• v.17 no.4 s.83
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• pp.15-20
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• 2005

Poly(ethylene-co-vinylacetate)(EVA) microspheres were prepared by thermally induced phase separation in toluene. The microsphere formation occurred by the nucleation and growth mechanism in metastable region. The effects of the polymer or pigment weight percentage and cooling rate on microsphere formation were investigated. The microsphere formation and growth were followed by the cloud point of the optical microscope measurement. The microsphere size distribution, which was obtained by particle size analyzer, became broader when the polymer concentration was higher, the pigment concentration and the cooling rate of EVA copolymer solution were lower.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.23.2-23.2
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• 2010

Researches on the drying of particle/polymer suspensions receive attentions in technical applications such as manufacturing display and batteries. In this study, the effect of polymers on drying behavior of silica/poly(vinyl alcohol) suspension was investigated in terms of suspension stability and stress development during drying. The effect of polymer adsorption was studied by changing pH. More strongly flocculated suspension with lower pH became more dispersed and close-packed film after drying. Evaluation of potential energy allows us to suggest that the adsorbed polymers which bridge the particles introduce steric repulsion and lead flocculated suspension to dispersed film. When the effect of adsorption kinetics was studied by changing the mixing time, the adsorption amount, characteristic stress and dried film density showed a similar behavior in the form of with a single characteristic time. It implies that the drying process can be determined by simple characteristic equation with a single time constant.

• Elastomers and Composites
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• v.28 no.4
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• pp.267-273
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• 1993

A number of hydrophilic acrylic comonomers were incorporated into styrene-butadiene soap-free emulsion polymerization. It was found that reaction rate decreased according to : AN>AA>MMA>EA>IA>AAM>MA>HEMA. It was also observed that reaction rate increased with decreasing H-bonding factor contribution to the solubility parameter of the hydrophilic comonoer. The SBR latexes were very monodisperse with the particle size distribution of $1.03{\times}1.12$. Since growth rate is proportional to polymerization time, the difference in conversion rates between various comonomers was resulted from the particle number density of SBR latexes for the various hydrophilic comonomers. It was also found that the colloidal stability of the latexes was excellent because no external emulsifier was incorporated.