• The Journal of Korean Academy of Prosthodontics
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• v.43 no.4
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• pp.438-452
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• 2005

Statement of problem: The use of Ceromer is increasing in dentistry. But, the research of Ceromer has not been conducted much. Purpose : This study was to evaluate the marginal fidelity and internal adaptation according to marginal position. Materials and Methods: In this study 60 resin crowns were fabricated. The measurements of the marginal fidelity were carried out using stereomicroscope $SZ-40^{(R)}$ (Olympus, Japan) and the measurements of fracture strength were done using Instron $8871^{(R)}$ (Instron Co., U.S.A.) at a cross head speed of 1mm/min. All of the measurements were statistically analyzed by ANOVA test, multiple range test and Weibull analysis. Statistical significance was set in advance at the probability level of less than 0.05. All of the measurements were analyzed with Window $SPSS^{(R)}$ Version 10.0 soft ware for the personal computer. Results : 1. There were no statistical differences of the marginal fidelity between $Targis^{(R)}$ and $Tescera^{(R)}$, but difference between these two and $BelleGlass^{(R)}$ according to materials. 2. There were no statistical differences of the marginal fidelity between no fiber group and fiber group. There were no interactions between each maerial and with/without fiber group in the marginal fidelity 3. There were statistical differences of the fracture strength between $Tescera^{(R)}$ and $BelleGlass^{(R)}$ but no statistical differences of the fracture strength between $Targis^{(R)}$ and $Tescera^{(R)}$, $Targis^{(R)}$ and $BelleGlass^{(R)}$ according to materials. 4 There were statistical differences of the fracture strength between no fiber group and fiber group. There were no interactions between each material and with/without fiber group in the fracture strength. 5. When comparing the fracture surface, no fiber group showed the resin which were fractured at the labial surface and separated from the adhesion surface. In fiber group, the fractures took a place in resin compartments. Conclusion. The marginal fidelity and the fracture strength were clinically acceptable. From these results, $Targis^{(R)}$ and $Tescera^{(R)}$ were superior than $BelleGlass^{(R)}$ in the marginal fidelity But, when applying these resin crowns in clinic, more careful consideration is needed and further study is recommended.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.118-125
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• 2017

In this study, we examined the bond performance of FRP Hybrid Bars. FRP Hybrid Bars are developed by wrapping glass fibers on the outside of deformed steel rebars to solve the corrosion problem. The surface of the FRP Hybrid Bars was coated with resin and silica sand to enhance its adhesion bonding performance with concrete. Various parameters, such as the resin type, viscosity, and size of the silica sand, were selected in order to find the optimal surface condition of the FRP Hybrid Bars. For the bonding test, FRP Hybrid Bars were embedded in a concrete block with a size of 200 mm3 and the maximum load and slip were measured at the interface between the FRP Hybrid Bar and concrete through the pull-out test. From the experimental results, the maximum load and bond strength were calculated as a function of each experimental variable and the resin type, viscosity and size of the silica sand giving rise to the optimal bond performance were evaluated. The maximum bond strength of the specimen using epoxy resin and No. 5 silica sand was about 35% higher than that of the deformed rebar.

• Tunnel and Underground Space
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• v.28 no.1
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• pp.97-110
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• 2018

The application of sprayed waterproofing membrane with high adhesion and ductility is considered to be promising as a measure for repair and reinforcement of a tunnel structure. Therefore, a powder-type and one-component membrane prototype with high tensile and bond strengths was made in this study. Then, its reinforcement effect on a shield segment was evaluated by carrying out a series of full-scale loading tests of segment specimens on which the membrane was sprayed. From the tests, it was confirmed that the initial cracking loads increased by approximately 34% due to cracking retardation by membrane coating. Even though the increase of failure loads were not so high as cracking loads, the strain-softening behaviors were observed from specimens coated by the membrane. Therefore, it is expected that the membrane coated on the inner surface of a lining might be effective in preventing its brittle failure.

• Journal of the Korean Wood Science and Technology
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• v.37 no.1
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• pp.56-64
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• 2009

The purpose of this study was to investigate and develop an eco-friendly wood adhesive based on vegetable oil (especially soybean oil), the renewable and sustainable natural resources, using ozonification technology for the chemical structure modification. The soybean oil (SBO) was reacted with $O_3$ at the rate of 7.13 g/h for different times, 15 minutes, 30 minutes, 60 minutes, and 120 minutes. The investigation of the modified chemical structure of the ozonized SBOs were conducted using FT-IR, $^1H$-NMR, MALDI-TOF MS, and GC/MS. As ozonification time increased, the peak of the unsaturated double bonds was disappeared and aldehyde or carboxyl peak appeared because ozonification broke the oil into small molecules. The plywoods were made at $110^{\circ}C$ with 30 seconds/mm hot-press time using the different ozonized SBO/pMDI adhesives and were tested for the dry, wet, cyclic boil test according to the Korea Industrial Standard F3101 Ordinary plywood. The bond strengths gradually increased with increasing ozonification time. The weight ratio 1:1 (ozonized SBO/pMDI), all strengths in 15, 30 and 60 minuets, exceeded constantly the dry, wet, cyclic boiling standard requirement. The range of ozonification time and weight ratio can fulfil1 the requirment of the wet test standard were 30~60 minutes and more than 0.5 pMDI. From the comprehensive view on the results of above experiments, it could be confirmed through experiments that ozonized SBO/pMDI has characteristics of effective reactivity and wet stability showed as an excellent candidate of wood adhesive applications.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.2
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• pp.157-169
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• 2009

The aim of this study was to evaluate effect of implant abutment screw coating treatment on joint stability, investigating mechanical properties of these. For this study used $ExFeel^{(R)}$ external hexed implant system and $15mm{\times}1mm$ discs. Experimental group was $1{\mu}m$ TiN, TiCN, TiC coated abutment screws and discs. To know mechanical property, i evaluated adhesion strength, surface hardness, using disc, corrosion test using screw. The results were as follows : rotation angle of coated screws increased than that of non-coated screw because of lower friction coefficient, especially TiC coated screw group had the largest value, but removal torque decreased in all coated screws (p<0.05). Torque loss before and after fatigue test was the smallest in TiC-coated screws, and the largest in non-coated screws (p<0.05), and there was no statistically significant difference between dry condition and wet condition of screws because of higher surface hardness and lower friction coefficient. From the above results, TiN, TiCN, TiC coating group had high abrasion resistance, especially TiC coated group which had low torque-consuming, high rotation angle as low friction coefficient will be considered to influence on implant abutment screw joint stability positively.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.3
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• pp.45-54
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• 2000

The effect of electropolishing far stamped leadframe on the removal of the edge burr and residual stress relief was examined. The present study showed that the electropolishing could be used for enhanced surface quality of stamped leadframes. The electropolishing was performed at the condition of 60% phosphoric acid electrolyte, 5 ampere of current and 3 cm electrode gap at $70^{\circ}C$ for 2 minutes for Alloy42 type leadframe, and $50^{\circ}C$ for 1.5 minutes for C-194 type leadframe. The FWHM values from X-ray diffraction showed that residual stress of electropolished leadframe recovered to the level of as-received raw materials and surface roughness measured by using AFM tuned out to be improved by 0.079 $\mu\textrm{m}$ and 0.014 $\mu\textrm{m}$ ($R_{rms}$) far alloy 42 and C-194 type leadframes, respectively. The plated thickness using XRF showed the improved uniformity in thickness variation by 0.4~0.5 $\mu\textrm{m}$ and grain growth, which is favorable for interface adhesion, was also observed from the bake test samples. We could certify dimensional stability of leadframe with inspection by means of 3D-topography and hardness measurements.

• Elastomers and Composites
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• v.46 no.3
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• pp.218-222
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• 2011

The effect of cycled temperature change on the mechanical properties of wood flour(50 wt.% and 70 wt.%) polypropylene WPC(Wood Plastic Composites) was investigated in this study. Flexural modulus and flexural strength of the WPC showed a decrease due to the degradation of interfacial adhesion between polymer matrix and wood flour by the freeze-thaw test regardless of the cycled number. At the higher loading level of wood flour, the reduction of the flexural modulus was remarkable. After the cycled heat-freeze test, it was found that the flexural modulus and flexural strength of the WPC were lower at the high temperature ($60^{\circ}C$) and higher at the low temperature ($-20^{\circ}C$). At the low temperature ($-20^{\circ}C$) which is below glass transition temperature of polypropylene ($-10^{\circ}C$), WPC is in a glassy state which brings about the high stiffness and strength. At the high temperature ($60^{\circ}C$), the flexural modulus and flexural strength of the WPC with 50 wt.% wood flour were lower because of the increase of polymer ductility.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.124-134
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• 2013

This study investigated the effect of surface water on concrete substrate on adhesive strength in tension of very high flowable SBR-modified cement mortar. The specimens were prepared with proportionally mixing SBR latex, ordinary portland cement, silica sand, superplasticizer and viscosity enhancing agent. Polymer cement ratio (P/C) were 10, 20, 30, 50 and 75% and the weight ratio of fine aggregate to cement were 1:1 and 1:3. The specimens obtained with different P/C and C:F were characterized by unit weight, flow test, crack resistance and adhesion test. After basic tests, two mixtures of P/C=20% and 30% in case of C:F=1:1, and one mixture of P/C=50% in case of C:F=1:3 were selected, respectively. These three selected specimens were studied about the effect of surface water evenly sprayed on concrete substrate by a amount of 0, 0.006, 0.012, 0.017, 0.024g per unit area ($cm^2$) of concrete substrate surface The results show that surface water on concrete substrate increases the adhesive strength in tension of high flowable SBR-modified cement mortar and improve the flowability compared to the non-sprayed case.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.1
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• pp.39-47
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• 2007

It is investigated how KOH and Rthylenediamine(EDA) treatment conditions on Polyimide film surface affect the interfacial fracture energy between electroless plated Ni and Polyimide film by $180^{\circ}$ peel test. Estimated values of interfacial fracture energy were 24.5 g/mm and 33.3 g/mm for the KOH treatment times under 1 and 5 minutes, respectively, while, those were 31.6 g/mm and 22.3 g/mm for EDA treatment times under 1 and 5 minutes, respectively. Interfacial bonding between electroless plated Ni and Polyimide seems to be dominated by chemical bonding effect rather than mechanical interlocking effect. It is found that chemical treatment produces carboxyl and mine functional groups which are closely related the interfacial bonding mechanism. Finally, it is speculated that interfacial fracture energy seems to be controlled by O=C-O bonding near cohesive failure region.

• Korean Chemical Engineering Research
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• v.49 no.4
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• pp.465-469
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• 2011

In this study, poly(ethyleneoxide) and poly(ethylene imine) polymer blends containing fumed silica fillers were studied in order to enhance the ion conductivity and interfacial properties. Lithium perchlorate ($LiClO_4$) as a salt, and silica($SiO_2$) as the inorganic filler were introduced into the polymer composite electrolyte composites and the composites were examined to evaluate their ionic conductivity for a possibility test of electrolyte application. As the diameter of semicircle in an impedance test became smaller, ionic conductivity of composite electrolytes had been enhanced by addition of 20 wt% silica filler. However, the conductivity was not greatly changed over 20 wt% content because the silica was sufficiently saturated in the polymer electrolytes. Diffraction peaks of PEO became weaker with the addition of inorganic fillers using XRD analysis. It showed that a crystallinity was proportionally reduced by increasing filler contents. The morphology of composite electrolyte films has been investigated by SEM. The heterogeneous morphology which silica was evenly dispersed by the strong adhesion of PEI was shown at higher contents of silica.