• Textile Coloration and Finishing
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• v.34 no.4
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• pp.261-271
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• 2022

Waterborne polyurethane(WPU) is greatly affected by its properties depending on the average particle size. In this study, by analyzing the characteristics of WPUs with different average particle sizes according to the DMPA content and we confirmed that the WPU-Ms have different properties from the physical properties of WPU by mixing two types of WPU with different particle sizes in the same volume. At this time, we mixed WPU at an ideal ratio of 7:3 through literature research. In the thermal characteristic analysis, it was confirmed that the thermal decomposition temperature decreased and Tg increased as the content of DMPA, which is the hard segment, increased. In addition, the average particle size of WPU decreased as DMPA increased, and physical properties and adhesive strength were improved due to increased interaction. When mixed with each other in a weight ratio of 7:3, it was observed that adhesion and mechanical properties were improved compared to only WPU.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.901-906
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• 1997

Ultrafine silicon dioxide($SiO_2$) powder was prepared from tetraethylorthosilicate(TEOS) by the gas-phase reaction. The effects of reaction temperature, flow rate of gas, TEOS concentration, and preheating temperature of reactants on the particle size were investigated. As the reaction temperature increased, average particle size of the silicone dioxide powder became smaller. Smaller particles were also obtained with decreasing the residence time of reactants in the reaction zone. Larger particles having narrow size distribution were produced with the high concentrations of the reactants. The effect of the preheating temperature was not considerable on the average particle size. The range of average particle size was from 30 nm to 58 nm depending on experimental conditions.

• Korean Chemical Engineering Research
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• v.56 no.4
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• pp.461-468
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• 2018

Microspheres were prepared by solvent-evaporation method with Poly-L-lactic acid (PLLA) as a starting material, and the effects of preparation variables on microsphere shape and average particle size were investigated. As the concentration of PVA solution increased from 1 to 5 wt%, the average particle size decreased from $370{\mu}m$ to $160{\mu}m$ and then increased to $240{\mu}m$ at 7 wt%. On the other hand, As the addition volume of PVA solution increased from 10 mL to 50 mL, the average particle size decreased from $370{\mu}m$ to $220{\mu}m$. Also, as the stirring speed increased from 500 rpm to 1,500 rpm, the average particle size decreased from $370{\mu}m$ to $110{\mu}m$. When dichloromethane and chloroform were used as organic solvents, respectively, the average particle size did not show any significant difference. However, when dichloromethane was used, voids were observed on the particle surface, but when chloroform was used, smooth spherical particles were obtained.

• Korean Journal of Materials Research
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• v.30 no.5
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• pp.223-230
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• 2020

As a case study on aspect ratio behavior, Kaolin, zeolite, TiO₂, pozzolan and diatomaceous earth minerals are investigated using wet milling with 0.3 mm media. The grinding process using small media of 0.3 pai is suitable for current work processing applications. Primary particles with average particle size distribution D₅₀, ~6 ㎛ are shifted to submicron size, D₅₀ ~0.6 ㎛ after grinding. Grinding of particles is characterized by various size parameters such as sphericity as geometric shape, equivalent diameter, and average particle size distribution. Herein, we systematically provide an overview of factors affecting the primary particle size reduction. Energy consumption for grinding is determined using classical grinding laws, including Rittinger's and Kick's laws. Submicron size is obtained at maximum frictional shear stress. Alterations in properties of wettability, heat resistance, thermal conductivity, and adhesion increase with increasing particle surface area. In the comparison of the aspect ratio of the submicron powder, the air heat conductivity and the total heat release amount increase 68 % and 2 times, respectively.

• Journal of the Korean Geotechnical Society
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• v.28 no.12
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• pp.77-86
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• 2012

We have carried out a series of numerical experiments to study the effect of average particle size on the mechanical properties of granite-derived weathered soils. A distinct-element method was adopted to study the changes in macro-scale mechanical properties with particle size and maximum-to-minimum particle size ratio. The numerical soil specimen with cohesion values of 0.25 MPa and internal friction angle of 29 degrees was prepared for reference. While keeping the porosity values constant, we varied particle size and size distribution to study how cohesion and internal friction angle changes. The experimental results show that the values of cohesion apparently decrease with increasing particle size. Changes in the values of internal friction angles are small, but there is a trend of increase in internal friction angle as the average particle size increases. This study demonstrates a possibility that the results of numerical experiments of this type may be used for rapid estimation of mechanical properties of granite-derived weathered soils. For example, when mechanical properties obtained through in situ tests and particle size data obtained through lab analysis are available for a site, it is expected that the mechanical properties of weathered granite soils with varying degrees of weathering (thus, varying particle size) may be estimated rapidly only with particle size data for that site.

• Journal of the Korean Ceramic Society
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• v.29 no.9
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• pp.711-718
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• 1992

Pb(Fe1/2Nb1/2)O3 was prepared by the molten salt synthesis method using an equimolar mixture of NaCl-KCl. Initial particle size could be controlled by varying the weight ratio of the NaCl-KCl to raw materials from 0.1 to 1.0, and the initial particle size effects on the sintering and dielectric properties of Pb(Fe1/2Nb1/2)O3 were investigated at the sintering temperature range from 90$0^{\circ}C$ to 105$0^{\circ}C$. As the weight ratio of salt increased, the average particle size decreased and the particle size distributions tended to narrow. As the initial particle size decreased, the linear shrinkage and density increased due to the promotion of densification. Dielectric constant increased with decreasing the initial particle size resulting from the increase of density and grain size.

• 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.

• Resources Recycling
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• v.13 no.6
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• pp.16-25
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• 2004

In this study, nano-sized indium oxide powder with the average particle size below 100 nm is prepared from the indium chloride solution by the spray pyrolysis process. The effects of the concentration of raw material solution, the nozzle tip size and the air pressure on the properties of powder were studied. As the indium concentration of the raw material solution increased from 40 g/l to 350 g/l, the average particle size of the powder gradually increased from 20 nm to 60 nm, yet the particle size distribution appeared more irregular, the intensity of a XRD peak increased and specific surface area decreased. As the nozzle tip size increased from 1 nm to 5 nm, the average particle size of the powder increased from 40 nm to 100 nm, the particle size distribution was much more irregular, the intensity of a XRD peak increased and specific surface area decreased. As the air pressure increased from 0.1 kg/cm$^2$ to 0.5 kg/cm$^2$, the average particle size of the powder varies slightly upto 90~100 nm. As the air pressure increased from 1 kg/cm$^2$ to 3 kg/cm$^2$, the average particle size decreased upto 50~60 nm, the intensity of a XRD peak decreased and the specific surface area increased.

• Elastomers and Composites
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• v.33 no.2
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• pp.110-116
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• 1998

A new technology was introduced to the emulsion polymerization. It is the ultrasonic activation method which replaced a chemical initiator and the environmentally benign process. In this study, free radicals were produced by a pulse type ultrasound energy irradiation, then polystyrene latex was polymerized without chemical initiator. With ultrasonic energy density, the degree of polymerization, average molecular weight, and particle size were increased, but the polydispersity index for the molecular weight and the particle size were decreased. The optimum condition of emulsifier concentration and temperature was found to be 1.0 wt.% SDS and $40^{\circ}C$, respectively. As a result, the emulsion polymerization process without chemical initiator was proved to be comparable to common latex properties such as average molecular weight, molecular weight distribution, particle size, etc.

• Smart Structures and Systems
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• v.24 no.5
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• pp.659-668
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• 2019

In digital image correlation, speckle image is closely related to the measurement accuracy. A practical global evaluation criterion for speckle image is presented. Firstly, based on the essential factors of the texture image, both the average particle size and image sharpness are used for the assessment of speckle image. The former is calculated by a simplified auto-covariance function and Gaussian fitting, and the latter by focusing function. Secondly, the computation of the average particle size and image sharpness is verified by numerical simulation. The influence of these two evaluation parameters on mean deviation and standard deviation is discussed. Then, a physical model from speckle projection to image acquisition is established. The two evaluation parameters can be mapped to the physical devices, which demonstrate that the proposed evaluation method is reasonable. Finally, the engineering application of the evaluation method is pointed out.