• Journal of the Korean Electrochemical Society
• /
• v.25 no.4
• /
• pp.174-183
• /
• 2022

Polymer electrolyte fuel cells and water electrolysis are attracting attention in terms of high energy density and high purity hydrogen production. The catalyst layer for the polymer electrolyte fuel cell and water electrolysis is a porous electrode composed of a precious metal-based electrocatalyst and an ionomer binder. Among them, the ionomer binder plays an important role in the formation of a three-dimensional network for ion conduction in the catalyst layer and the formation of pores for the movement of materials required or generated for the electrode reaction. In terms of the use of commercial perfluorinated ionomers, the content of the ionomer, the physical properties of the ionomer, and the type of the dispersing solvent system greatly determine the performance and durability of the catalyst layer. Until now, many studies have been reported on the method of using an ionomer for the catalyst layer for polymer electrolyte fuel cells. This review summarizes the research results on the use of ionomer binders in the fuel cell aspect reported so far, and aims to provide useful information for the research on the ionomer binder for the catalyst layer, which is one of the key elements of polymer electrolyte water electrolysis to accelerate the hydrogen economy era.

• Restorative Dentistry and Endodontics
• /
• v.18 no.2
• /
• pp.413-422
• /
• 1993

The purpose of this study was to evaluate the adaptation of light cured glass ionomer cement and composite resin using all- etch technique to tooth structure. In this study, class V cavities were prepared on the buccal surfaces of 10 extracted human premolar teeth with cementum margin and teeth were randomly assigned 2 groups of 5 teeth each. The cavities of glass ionomer cement group were filled with the light cured glass ionomer cement(Fuji II LC) and the cavities of composite resin group were filled with the light cured composite resion(P - 50) using all- etch technique with All- Bond 2. The restored teeth were stored in 100 % relative humidity at $37^{\circ}C$ for 48 hours. And then, the roots of the teeth were removed with the tapered fissure bur and the remaining crowns were sectioned occlusogingivally through the center of restorations. Adaptation at tooth - restoration interface were assessed occlusally, gingivally, and axially by scanning electron microscope. The results were as follows : 1. The adaptation to enamel walls of composite resin restorations using All - Bond 2 showed better than glass ionomer restorations. 2. The adaptation to gingival and axial walls of glass ionomer restorations showed better than composite resin restorations using All - Bond 2. 3. In both groups, occlusal margins of restorations showed better adaptation than gingival margins of restorations.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.25 no.2
• /
• pp.285-291
• /
• 1998

The purpose of this study was to asses the shear bond strengths of 3 types of glass ionomer cement and 1 type of composite resin to dentinal surface with or without ZOE pretreatment. 80 extracted tooth specimens are divided into two groups; the control group (40 specimens) is not treated with ZOE and the other(40 specimens) is ZOE pretreated during 24 hours before bonding procedure. Shear bond strengths were measured with universal testing machine (Instron, Model 4301) and statistically processed by ANOVA and t-test. The results were as follows: 1. Bond strength of the ZOE treated experimental group showed lower than the control group, except chemical cured glass ionomer cement(p<0.05). 2. After ZOE surface treatment, the bond strength of composite resin was superior than glass ionomer cement and all experimental group was decreased (p<0.05). 3. It has nothing to do with ZOE surface treatment, that chemical curing glass ionomer cement was showed lowest bond strength.

• Korean Membrane Journal
• /
• v.10 no.1
• /
• pp.46-52
• /
• 2008

Optimization of ionomer solution was conducted in order to improve the performance of MEAs in PEMPC. The interface between membrane and electrodes in MEAs is crucial region determining fuel cell performance as well as ORR reaction at cathode. Through the modification of Nafion ionomer content at the interface between membrane and electrodes, an optimal content was obtained with Nafion 115 membranes. Two times higher current density was obtained with the outer Nafion sprayed MEA compared with the non-sprayed one. In addition, the symmetrical impedance spectroscopy mode (SM) exhibited that the resistances of membrane area, proton hydration, and charge transfer decreased as the outer Nafion is sprayed. From the polarization curves and SM, the highest current density and the lowest resistance was obtained at the outer ionomer content of $0.15\;mg\;cm^{-2}$.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.23 no.4
• /
• pp.915-924
• /
• 1996

The purpose of this paper is to investigate the surface roughness of glass ionomer cement during initial setting time followed by applying surface coating agent. No other finishing or polishing procedure is done and each surface coating agents (varnish, adhesive, gloss, sealant) are used after filling of glass ionomer cement. Surface roughness indices(Ra) are measured and surface contours are obtained electronically by Surfcorder SEF-30D(Kosaka laboratory Ltd., Japan). The results are as follows: 1. During initial setting time, surface roughness increases slightly regardless of surface coating agents. But it is statistically insignificant. (p>0.05) 2. Among surface coating agents used, Ra indices of group using varnish are high significantly compared to other groups regardless of elapsed time.(p<0.05) Among the groups which has used other surface coating agents except for the varnish group, similar Ra index all over the experiment is obtained, when compared to control group (no agent). 3. If no surface treatment is performed, tri-cure glass ionomer cement (Vitremer) has higher Ra Index than light cure glass ionomer cement (Fuji II LC) (t<0.05). But there is no difference between two groups in Ra index if any kinds of agents are applied except for sealant. (t>0.05)

• Journal of the korean academy of Pediatric Dentistry
• /
• v.26 no.4
• /
• pp.677-687
• /
• 1999

This study was performed to evaluate the effect of aging and thermal cycling on the tensile strength of six commercially available glass-ionomer materials: two chemically set glass-ionomer materials(Fuji II, Fuji IX), two resin-modified glass-ionomer materials(Fuji II LC, Vitremer), and two polyacid-modified composite resins(Compoglass, Dyract). Rectangular tension test specimens were fabricated in a teflon mold giving 5mm in gauge length and 2mm in thickness. All samples were divided into 3 groups. Group 1 was immersed in a $37^{\circ}C$ distilled water for 1 hour. Group 2 was immersed in a $37^{\circ}C$ distilled water for 30 days. Group 3 was subjected to 10,000 thermal cycles between $5^{\circ}C$ and $55^{\circ}C$, and the immersion time in each bath was 15 seconds per cycle. Tensile testing was carried out at a cross-head speed of 0.5mm/min and fracture surfaces were examined with scanning electron microscope. The results obtained were summarized as follows; 1. The polyacid-modified composite resins were stronger than the resin-modified glass-ionomer materials, which were much stronger than the conventional glass-ionomer materials. 2. Tensile strengths were slightly increased after aging treatments for 30days. 3. Tensile strengths of conventional glass ionomers were significantly increased after thermal cycling treatment(p<0.01). 4. The highest tensile strength value of 45.4MPa was observed in the Dyract group and the lowest value of 13.3MPa was observed in the Fuji II LC group after the thermal cycling test, and the strengths of polyacid-modified composite groups were significantly higher than those of other groups. 5. The highest characteristic strength value of 48.6MPa was obtained in the Dyract group, however the highest Weibull modulus value of 8.9MPa was obtained in the Compoglass group after thermal cycling test.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.40 no.8
• /
• pp.808-815
• /
• 1991

The behavior of space charge in PE/ionomer blends has been investigated using the thermally stimulated current (TSC) technique. In the blends, at least two TSC peaks over the temperature range from -50 to 100\ulcorner are observed, one at -5 ~ 10\ulcorner (a peak) and the others at above 60\ulcorner (a peak). The a peak is assigned as the orientation of dipoles from the ionomer component. Two a peaks seem to be related to the charge trapping at sites related to the crystalline phases. One a peak is associated with the ionic interfaces and the other with the ethylene chains without the ionic interfaces. The amount of charges stored in PE/Surlyn 1652 blends increases as the poling field increases over the field range of +8 ~ +30 kV/mm, whereas that in PE/Surlyn 1601 blends increases slightly at low poling fields and then decreases at high poling fields above +10 kV/mm. Exact reasons for such a dirrerence are not known at this point.

• Journal of Yeungnam Medical Science
• /
• v.37 no.3
• /
• pp.169-178
• /
• 2020

Glass ionomer cement (GIC) is a tailor-made material that is used as a filling material in dentistry. GIC is cured by an acid-base reaction consisting of a glass filler and ionic polymers. When the glass filler and ionic polymers are mixed, ionic bonds of the material itself are formed. In addition, the extra polymer anion reacts with calcium in enamel or dentin to increase adhesion to the tooth tissue. GICs are widely used as adhesives for artificial crowns or orthodontic brackets, and are also used as tooth repair material, cavity liner, and filling materials. In this review, the current status of GIC research and development and its prospects for the future have been discussed in detail.

• Proceedings of the KACD Conference
• /
• 2003.11a
• /
• pp.570-571
• /
• 2003

This study was done to evaluate the shear bond strength between light-cured glass ionomer cement base and resin cement for luting indirect resin inlay and to observe bonding aspects which is produced at the interface between them by SEM(Scanning Electron Microscope). 1)Shear bond strength. Light-cured glass ionomer cement base were made in plastic molds(10mm diameter, 5mm thickness). Two type of light cured glass-ionomer cement were uesd.(중략)

• Bulletin of the Korean Chemical Society
• /
• v.19 no.3
• /
• pp.354-358
• /
• 1998

The effect of thermal conditions on the clustering of sulfonated polystyrene ionomers was investigated. It was found that when the zinc-sulfonated ionomer was dried above a matrix glass transition temperature (Tg), the cluster Tg was observed at ca. 310 ℃, which is ca. 45 ℃ higher than that for the ionomer dried below the matrix Tg. This difference is believed to be the result of the increase in chain mobility at higher temperatures, which improves the multiplet formation and clustering; thus the cluster Tg increases. In the lithium ionomer case, however, the increase in the cluster Tg was ca. 6 ℃ upon annealing. From the results, it was suggested that in the zinc ionomer, the zinc ion is soft and divalent, which results in weaker interactions in multiplets, and thus decreases the stability of the multiplets. Therefore, the thermal effect is more significant for the zinc ionomers than for the lithium ionomers.