• Transactions of the Korean hydrogen and new energy society
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• v.29 no.1
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• pp.111-116
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• 2018

The environmental impacts of a 1 kW polymer electrolyte membrane fuel cell (PEMFC) system are quantitatively assessed by performing a Life Cycle Assessment (LCA) study. A PEMFC system produces electricity and heat simultaneously, so an appropriate allocation of associated inputs and outputs is performed between the electricity and heat produced. The environmental impacts of the PEMFC system on the impact categories such as global warming (GW), abiotic depletion (AD), acidification (AC), and eutrophication (EU) are assessed from the life cycle impact assessment. The impact indicator results of the impact assessment on these impact categories are obtained as $3.70E-01kg\;CO_2\;eq./kWh$, 1.86E-03 kg Sb eq./kWh, $4.09E-04kg\;SO_2\;eq./kWh$, and $1.88E-05kg\;PO_4{^{3-}}/kWh$, respectively. For all impact categories studied the most influential stage is the operation stage, which accounts for 98.8%, 98.7%, 70.3%, and 62.3% of the total impact on GW, AD, AC, and EU, respectively. For the impact categories of AD, AC, and EU, most of the environmental impacts during the operation stage is attributed to the production of city gas. However, for the impact category of GW, $CO_2$ emission from the reforming process of city gas is the main reason for the largest contribution of the operation stage to the total impact results.

• Journal of the Korean Chemical Society
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• v.34 no.4
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• pp.377-383
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• 1990

Three kinds of hydrogel membranes were prepared by the copolymerization of 2-hydroxyethylmethacrylate (HEMA) with acrylamide, N, N-dimethylamide and methylmethacrylate in the presence of solvent and crosslinker respectively. The equilibrium water content, relative permeability and partition coefficient of the membranes for alcohol solutes were measured. It has been found that the permeation of organic solute occurs through the water-filled regions in the hydrogel membrane, and that the gpermeability coefficient of organic solute depends on the molecular size. But the permeability of organic solute was controlled by the interaction of solute-membrane at the low water content. By the partition data, it has been shown that the partition of solute is only controlled by hydrophobic interaction between solute and membrane. The diffusion coefficient data were interpreted on the basis of water-solute interaction. It has been found that the diffusion of organic solute is determined by the free volume of water in the membrane, and that hardly depends on polarity-polarizability and hydrogen bonding ability between water and solute.

• Journal of the Korean Applied Science and Technology
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• v.30 no.2
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• pp.215-224
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• 2013

Recently, many cosmetic researchers have been focused on the development of high functional cosmetics including anti-wrinkle and whitening. In these studies, they couldn't afford to pay a deep attention to stable encapsulations for unstable materials and efficient drug deliveries for them. Particularly, in order to show a degree of instant effects as cosmetics, they can't also ignore moisturizing effect enough to satisfy customers just after applying and its maintenance by improving the function of skin barrier as well as above two effects. Therefore, skin analogue systems have attracted considerable attention in the view of structural and compositional similarity to intercellular membrane in stratum corneum. And, some models for skin analogue composition were developed to improve the function of skin barrier, stably encapsulate unstable materials such as retinol, vitamin B, C, E, etc., and control their skin penetration in order to show good effects as cosmetics. In this study, we suggest the new skin analogue model having the compositional similarity as well as conventional structural ones. Our skin analogue membrane(SAM) is mainly composed of ceramide/ cholesterol/phosphatidylcholin/fatty acids and its structural defects are compensated by including cholesterol amphiphile and controlling the ratio of ceramide/cholesterol. It was possible to confirm the formation of skin analogue membrane having highly-densed multilamella structure and compare them according to the change of each ratio with a polarized microscope, X-ray diffraction. More detaily, we observed their structures with a electron microscope(TEM). Finally, we dispersed them in excess of continuous water phase, observed the formation of maltese-cross liquid crystalline and measured the efficiency of drug deliveries and moisturizing effects.

• Membrane Journal
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• v.24 no.4
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• pp.259-267
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• 2014

PEBAX[poly(ether-block-amide)-ZIF-8(zeolitic imidazolate framework) composite membranes were prepared with different amounts of ZIF-8; 0, 1, 3, 7, 10, and 20 wt%. Gas permeation experiment were performed by varying the temperature of 25, 35, $40^{\circ}C$ under condition $6kgf/cm^2$. Gas permeability of $C_3H_6$, $C_3H_8$ and selectivity ($C_3H_6/C_3H_8$) were investigated by increasing the amount of ZIF-8 in the PEBAX. The gas permeability of $C_3H_6$ and $C_3H_8$ increased as ZIF-8 content increased among 0 to 7 wt% range and decreased among 7 to 20 wt% range. When the ZIF contents of PEBAX-ZIF composite membrane were 7 wt%, the selectivity ($C_3H_6/C_3H_8$) was taken between 3.6 and 3.8 value and also had the lowest activation energy.

• Membrane Journal
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• v.30 no.4
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• pp.242-251
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• 2020

Computer simulation tools mainly used for polymer materials and polymeric membranes are divided into various fields depending on the size of the object to be simulated and the time to be simulated. The computer simulations introduced in this review are classified into three categories: Quantum mechanics (QM), molecular dynamics (MD), and mesoscale modeling, which are mainly used in computational material chemistry. The computer simulation used in polymer research has different research target for each kind of computational simulation. Quantum mechanics deals with microscopic phenomena such as molecules, atoms, and electrons to study small-sized phenomena, molecular dynamics calculates the movement of atoms and molecules calculated by Newton's equation of motion when a potential or force of is given, and mesoscale simulation is a study to determine macroscopically by reducing the computation time with large molecules by forming beads by grouping atoms together. In this review, various computer simulation programs mainly used for polymers and polymeric membranes divided into the three types classified above will be introduced according to each feature and field of use.

• Journal of the Korean Chemical Society
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• v.35 no.1
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• pp.51-58
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• 1991

A new tubular poly(vinyl chloride) membrane type of nitrate selective electrode was prepared and its characteristics were evaluated. The response slope, detection limit, and response time (t$_{99}$) under the optimum membrane composition (5${\%}$ aliquat-NO$_3$ solution + 32${\%}$ poly(vinyl chloride) + 63${\%}$ dibutyl sebecate) of the electrode were 58.5 ${\pm}$ 0.1 mV/decade, 2.0 ${\times}$ 10$^{-5}$ M, and 25 seconds, respectively. The nitrite ion was determined by the continuous-automated method using the new electrode. 10$^{-2}$ M phosphate buffer solution (pH 7.6) was used as a recipient solution. And also hydrogen peroxide (0.3${\%}$) was added to the recipient as an oxidant. The linear response range and response range and response slope for the standard nitrite solution under the optimum condition of this electrode system were 8.0 ${\times}$ 10$^{-5}$ M ∼ 5.0 ${\times}$ 10$^{-2}$ M and 56.8 ${\pm}$ 0.2 mV/decade, respectively.

• Membrane Journal
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• v.27 no.6
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• pp.528-535
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• 2017

In this study, halogen element was introduced into polyphenylene oxide polymer using bromination reaction, and then halogen element was replaced with imidazolium. Imidazolium corporated polyphenylene oxide polymer was synthesized and the synthesis was confirmed by various instrumental characterization. In addition, gas permeation properties of $O_2$, $N_2$, $CO_2$ were studied with different imidazolium contents. As the content of imidazolium increased, the ion exchange capacity increased and the mechanical strength decreased. The gas permeance showed a tendency to decrease slightly with increaing imidazolium contents. Whereas, it was confirmed that the tendency of $CO_2/N_2$ ideal selectivity increased as the imidazolium contents increased.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.252-260
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• 1996

In this article, we investigate into the structural changes of liposome to design its functional membranes by the synthesis of two types of liposomes, DPPC liposome and DTAB of hydrocarbon substance/DPPC liposome. The changes of membrane structures are evaluated by the CF fluorescent intensity measured above and below the phase transition temperature of the membrane, $t_c=41^{\circ}C$. CF fluorescent intensities are enhanced by the CF leakage from DPPC liposome at $45^{\circ}C$, while no changes are observed at $20^{\circ}C$. Under the same conditions, it is observed that the intensity enhanced by CF leakage from DPPC/DTAB liposome is larger than that of DPPC liposome alone, which suggests that DPPC/DTAB liposome has irregular arrangement. Under the presence of $Ca^{2+}$, Quin 2 fluorescent intensity in either DPPC liposome or DPPC/DTAB liposome is significantly increasing at $45^{\circ}C$, while almost none of the changes are observed at $20^{\circ}C$. The fluorescent intensity of DPPC liposome turns out to be larger than that of DPPC/DTAB liposome, which suggests that the DPPC/DTAB liposome is structurally more stable than the DPPC liposome. Additionally, when the analysis is done to observe changes in the shapes of membrane surfaces with ANS fluorescent, ANS fluorescent under DPPC or DPPC/DTAB liposome shows each of different appearances at $45^{\circ}C$ and $20^{\circ}C$ respectively. This result indicates that its respective membrane fluidity is changing above and below of the designated temperatures in phase transition. As to the magnitude of change of its membrane fluidity, DPPC liposome is much larger than DPPC/DTAB liposome. As far as the temperature in phase transition measured by DSC are concerned, it is $41^{\circ}C$ and $32^{\circ}C$ for DPPC and DPPC/DTAB liposome respectively, which suggests that DPPC/DTAB liposome has an irregular molecular arrangement in its structure. That is, it is summed up that DPPC/DTAB turns out to be structurally stable, even so, its structure is irregularly arranged.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.870-877
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• 1998

With impedance spectrum measurements, impedance was studied in the interface between sample solutions for $K^+-ion$ selective PVC membrane electrode containing neutral carriers [dibenzo-18-crown-6 (D18Cr6) and valinomycine (Val)]. Response characteristics of electrode were examined by measuring AC impedance spectra that were resulted from the chemical structure and the content of carrier, variation of plasticizer, membrane thickness, doping of base electrolytes, and concentration variation of sample solution. Transport characteristics of PVC membrane electrode were also studied. It was found that the equivalent circuit for the membrane in $K^+$ solution could be expressed by a series combination of solution resistance and a parallel circuit consisting of the bulk resistance and geometric capacitance of the membrane system. But the charge transfer resistance and Warburg resistance were overlapped a little in the low concentration and low frequency ranges. The carrier, D18Cr6 was best for electrode and impedance characteristics, and ideal electrode characteristics were appeared especially in case of doping of the base electrolyte[potassium tetraphenylborate(TPB)]. The optimum carrier content was about 3.23 wt% in case of D18Cr6 and Val. DBP was best as a plasticizer. As membrane thickness decreased the impedance characteristics was improved, but electrode characteristics were lowered for membrane thickness below the optimum. In the case of D18Cr6, the selectivity coefficients by the mixed solution method for the $K^+$ ion were the order of $NH_4{^+}>Ca^{2+}>Mg^{2+}>Na^+$.

• Membrane Journal
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• v.25 no.2
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• pp.191-201
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• 2015

We have studied on the preparation of $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloy, the characteristics of $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloy by X-ray diffractometer (XRD), pressure composition temperature (PCT) curve, scanning electron microscopy (SEM) and the $H_2-N_2$ gas mixture separation of $TiCo_xFe_{1-x}$(x=0.50~1.00)- stainless steel (SS) composite membranes. The formation of $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloys with cubic crystal same as TiCo was confirmed by X-ray diffractometer. $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloys showed the hysteresis at $120^{\circ}C$. As the Fe content of $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloys increased, the hysteresis was increased both range x=0.90~1.00 and x=0.55~0.60, and the range x=0.55~0.90 gave decreased hysteresis. $TiCo_{0.55}Fe_{0.45}$ alloy was the one showed the lowest hysteresis among them. The lowest value of hydrogen permeation pressure of $TiCo_xFe_{1-x}$(x=0.50~1.00)-SS composite membrane was $TiCo_{0.55}Fe_{0.45}$-SS composite membrane with the value of 2.5 atm at $120^{\circ}C$; otherwise, $TiCo_{0.90}Fe_{0.10}$-SS composite had the highest pressure value among the membranes with the value of 10 atm. $TiCo_{0.55}Fe_{0.45}$-SS composite membrane was the best to separate the $H_2-N_2$ gas mixture excellently among the $TiCo_xFe_{1-x}$(x=0.50~1.00)-SS composite membranes since $TiCo_{0.55}Fe_{0.45}$ had the least hysteresis, and hydrogen permeation pressure was the lowest with value of 2.5 atm.