• Membrane Journal
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• v.25 no.6
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• pp.496-502
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• 2015

Facilitated transport is one of the possible solutions to simultaneously improve permeability and selectivity, which is challenging in conventional polymer-based membranes. Olefin/paraffin separation using facilitated transport membrane has received much attention as an alternative solution to the conventional distillation process. Herein, we report olefin separation composite membranes based on the polymer blends containing $AgBF_4/Al(NO_3)_3$ mixed salts. Free radical polymerization process was used to synthesize an amphiphilic graft copolymer of poly(dimethyl siloxane)-graft- poly(ethylene glycol) methyl ether methacrylate (PDMS-g-POEM). In addition, poly(ethylene oxide) (PEO) was introduced to the PDMS-g-POEM graft copolymer to form polymer blends with various ratios. The propylene/propane mixed-gas selectivity and permeance reached up to 5.6 and 10.05 GPU, respectively, when the PEO loading was 70 wt% in polymer blend. The improvement of olefin separation performance was attributed to the olefin facilitating silver ions as well as the highly permeable blend matrix. The stabilization of silver ions in the composite membrane was achieved through the introduction of $Al(NO_3)_3$ which suppressed the reduction of silver ions to silver particles.

• Polymer(Korea)
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• v.32 no.4
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• pp.340-346
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• 2008

The aim of this study is to understand the effect of structure on the dispersion of both CNT and GNF in the phase of synthesized polyurethanes matrix. Various CNT/PU and GNF/PU composite films were prepared. Polyurethane having a different hard segment was blended with both CNT and GNF. PU having HDI as hard segment showed good dispersion with both CNT and GNF because of their linear structural character and molecular kinesis while PU having aromatic ring showed poor dispersion with those due to their structural complexity. Structural effect also induced the increase of its electro conductivity. The PU/CNT composite showed a bad dispersion (because of phase separation between PU matrix and CNT) but good electro conductivity at its surface (because CNT was collected on the surface of composite film due to low density of CNT). PU/CNT and PU/GNF composite films have quite low normalized sheet resistance value compared with silver/PU nanocomposite film because the fiber type filler could have much more contact points than that of sphere shaped silver particles have.

• Membrane Journal
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• v.30 no.5
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• pp.326-332
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• 2020

In this study, polymer-fluorinated silica composite hollow fiber membranes were fabricated and applied to a membrane contactor for the recovery of methane dissolved in the anaerobic effluent. To prepare the composite membranes, porous hollow fiber substrates were fabricated with Ultem^®, a commercial polyetherimide (PEI). Subsequently, fluorinated silica particles were synthesized and coated on the surface via strong covalent bonding. Due to the high porosity, our membrane showed a CH₄ flux of 8.25 × 10^-5 ㎤ (STP)/㎠·s at the liquid velocity of 0.03 m/s which is much higher that that of commercial polypropylene membrane designed for degassing processes. This is attributed to our membrane's high porosity as well as a superior surface hydrophobicity (120~122°) resulted from the coating with fluorinated silica nanoparticles.

• Membrane Journal
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• v.21 no.4
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• pp.389-397
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• 2011

In this study, polymer composite membranes based on sulfonated poly(arylene ether sulfone) (SPAES) were prepared using a solution casting method with different amount of vermiculite (VMT) content. The dispersion of VMT particles in the SPAES matrix was confirmed by means of a scanning electron microscopy observation. The composite membrane containing less than 1 wt% of VMT has a smooth skin on the top and bottom, which means there is a good dispersion of VMT in the matrix. The water uptake of the composite membranes gradually increases as the temperature increases, and the results confirm that all the adsorbed water is bound water because VMT has a strong water affinity on account of its high cation exchange value. A composite membrane with a VMT content of less than 1 wt% increases the proton conductivity and reduces the methanol permeability. Of all the composite membranes, the membrane SPAES/VMT 1.0 has the best fuel cell performance in terms of membrane selectivity. The performance value of SPAES/VMT 1.0 is double that of Nafion 112, which suggests that SPAES/VMT1.0 could be an excellent candidate for direct methanol fuel cells.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.888-894
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• 2015

Inorganic composite particles have excellent physical and chemical characteristics and have been applied in various industries. Recently, many studies have examined the optical properties, such as light scattering, refraction, transmission characteristics, by coating organic-inorganic materials on a substrate, such as mica. Mica is widely applied as a pigment, plastics, painted products, and ceramics because of its high chemical stability, durability and non-toxicity. Magnesium oxide has a range of properties, such as high light transmittance, corrosion resistance and non-toxicity, and it is used as an optical material and polymer additives. To use the optical properties of mica and magnesium oxide, mica was coated with magnesium hydroxide by a dissolution and recrystallization process. In this study, the optimal conditions for the haze value of the particles were found by adjusting the amount of precursors and pH. Magnesium hydroxide layers were formed on the surfaces of mica and converted to MgO after calcination at $400^{\circ}C$ for 4 h. The results showed that the value of MgO-coated mica haze can be controlled easily by the amount of the magnesium hydroxide and pH. The optical properties of the inorganic composite powder were analyzed using a hazemeter and the highest haze value was 85.92 % at pH 9. The physicochemical properties of the synthesized composite was analyzed by SEM, XRD, EDS, and PSA.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2005.09a
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• pp.201-212
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• 2005

[ $Epoxy/BaTiO_3$ ] composite embedded capacitor films (ECFs) were newly designed fur high dielectric constant and low tolerance (less than ${\pm}15\%$) embedded capacitor fabrication for organic substrates. In terms of material formulation, ECFs are composed of specially formulated epoxy resin and latent curing agent, and in terms of coating process, a comma roll coating method is used for uniform film thickness in large area. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ composite ECF is measured with MIM capacitor at 100 kHz using LCR meter. Dielectric constant of $BaTiO_3$ ECF is bigger than that of $SrTiO_3$ ECF, and it is due to difference of permittivity of $BaTiO_3\;and\;SrTiO_3$ particles. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ ECF in high frequency range $(0.5\~10GHz)$ is measured using cavity resonance method. In order to estimate dielectric constant, the reflection coefficient is measured with a network analyzer. Dielectric constant is calculated by observing the frequencies of the resonant cavity modes. About both powders, calculated dielectric constants in this frequency range are about 3/4 of the dielectric constants at 1 MHz. This difference is due to the decrease of the dielectric constant of epoxy matrix. For $BaTiO_3$ ECF, there is the dielectric relaxation at $5\~9GHz$. It is due to changing of polarization mode of $BaTiO_3$ powder. In the case of $SrTiO_3$ ECF, there is no relaxation up to 10GHz. Alternative material for embedded capacitor fabrication is $epoxy/BaTiO_3$ composite embedded capacitor paste (ECP). It uses similar materials formulation like ECF and a screen printing method for film coating. The screen printing method has the advantage of forming capacitor partially in desired part. But the screen printing makes surface irregularity during mask peel-off, Surface flatness is significantly improved by adding some additives and by applying pressure during curing. As a result, dielectric layer with improved thickness uniformity is successfully demonstrated. Using $epoxy/BaTiO_3$ composite ECP, dielectric constant of 63 and specific capacitance of 5.1nF/cm2 were achieved.

• 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.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.2
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• pp.54-60
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• 2019

Recently, various composite materials for additive manufacturing are interested to expand the application field of 3D printing. 3D printing technique was mainly developed using polymer, and ceramic materials for 3D printing are still in the early stage of research due to the requirement of high solid content and post treatment process. In this study, silica particles with various diameters were surface treated with silane coupling agent, and synthesized as silica composite with photopolymer to apply DLP 3D printing process. DLP is an additive manufacturing technology, which has high accuracy and applicability of various composite materials. The rheological behavior of silica composite was analyzed with various solid contents. After DLP 3D printing was performed using silica composites, the printing accuracy of the 3D printed specimen was less than about 3 % to compare with digital data and he bending strength was 34.3 MPa at the solid content of 80 wt%.

• Journal of the Korean Society of Safety
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• v.32 no.3
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• pp.1-7
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• 2017

Particle reinforced composites are materials that have enhanced physical properties by adding particle reinforcements to polymer materials and have been applied to a wide range of fields such as the aerospace, bio-technology and automative industry. In this study, particle reinforced composites were prepared by mixing $SiC/Al_2O_3$ to the vinyl ester as the thermoset resin. The purpose of this study is to evaluate mechanical properties and fracture behavior by the tensile test and single edge notch specimen according to the addition ratio of reinforcement. Addition of 1 and 2 wt% of the particle reinforcement to the vinyl-ester resin was effective for the strength improvement. However, when it was more than 3 wt%, its strength was decreased. Also the highest elastic modulus obtained as 3.19 GPa was found at the 2 wt% addition of reinforcement. Futhermore the fracture toughness was evaluated by the energy release rate and the maximum critical energy release rate was obtained when 1 wt% reinforcement. The results show that the limit of adding of $SiC/Al_2O_3$ for improvement of the mechanical and fracture performance is 2 wt% reinforcement particles.

• Applied Chemistry for Engineering
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• v.20 no.5
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• pp.511-516
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• 2009

Photodegradation characteristics of polyolefin composites were studied. Thermogravimetric analysis results suggest that the polyolefin blends used in this study have different amounts of talc. The mechanical behaviors of polyolefin blends, which experienced UV-irradiation in accordance with SAE J1960, are investigated using tensile and Izod impact tests. These results show that as the UV-exposure time increases, a significant drop in the elongation at break and impact strength at a low temperature are observed. This may be explained by the decreases in elastic energy derived from the scission of polymer molecular chains and the low density of entanglement after UV- photodegradation. Scanning electron microscopy observations indicate that no crack and surface damage are observed, while the additional talc particles are exposed, on the UV-exposed surfaces. The exposure of talc particles may be responsible for the discoloration of UV-exposed polyolefin blend surface. Observation using Fourier transform infrared spectroscopy (FT-IR) confirms the presence of photodegradation on the surface of UV-exposed polyolefin blend.