• Corrosion Science and Technology
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• v.9 no.4
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• pp.147-152
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• 2010

Conventional paints for conversion coating applications in steel production derived mainly from water-based polymer dispersions containing several additives actually show good general performance, but suffer from poor scratch and abrasion resistance during use. The reason for this is because the relatively soft organic binder matrix dominates the mechanical surface properties. In order to maintain the high quality and decorative function of coated steel sheets, the mechanical performance of the surface needs to be improved significantly. In fact the wear resistance should be enhanced without affecting the optical appearance of the coatings by using appropriate nanoparticulate additives. In this direction, nanocomposite coating compositions (Nanomer$^{(R)}$) have been derived from water-based polymer dispersions with an increasing amount of surface-modified nanoparticles in aqueous dispersion in order to monitor the effect of degree of filling with rigid nanoparticles. The surface of nanoparticles has been modified for optimum compatibility with the polymer matrix in order to achieve homogeneous nanoparticle dispersion over the matrix. This approach has been extended in such a way that a more expanded hybrid network has been condensed on the nanoparticle surface by a hydrolytic condensation reaction in addition to the quasi-monolayer type small molecular surface modification. It was expected that this additional modification will lead to more intensive cross-linking in coating systems resulting in further improved scratch-resistance compared to simple addition of nanoparticles with quasi-monolayer surface modification. The resulting compositions have been coated on zinc-galvanized steel and cured. The wear resistance and the corrosion protection of the modified coating systems have been tested in dependence on the compositional change, the type of surface modification as well as the mixing conditions with different shear forces. It has been found out that for loading levels up to 50 wt.-% nanoparticles, the mechanical wear resistance remains almost unaffected compared to the unmodified resin. In addition, the corrosion resistance remained unaffected even after $180^{\circ}$ bending test showing that the flexibility of coating was not decreased by nanoparticle addition. Electron microscopy showed that the inorganic nanoparticles do not penetrate into the organic resin droplets during the mixing process but rather formed agglomerates outside the polymer droplet phase resulting in quite moderate cross linking while curing, because of viscosity. The proposed mechanisms of composite formation and cross linking could explain the poor effect regarding improvement of mechanical wear resistance and help to set up new synthesis strategies for improved nanocomposite morphologies, which should provide increased wear resistance.

• Restorative Dentistry and Endodontics
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• v.31 no.6
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• pp.445-451
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• 2006

The purposes of this study were to compare the effects of one or two applications of all-in-one adhesives on microtensile bond strengths (${\mu}$TBS) to unground enamel and to investigate the morphological changes in enamel surfaces treated with these adhesives using a scanning electron microscopy (SEM). Twenty-five noncarious, unrestored human mandibular molars were used. The unground enamel surfaces were cleansed with pumice. The following adhesives were applied to lingual, mid-coronal surfaces according to manufacture's directions; Clearfil SE bond in SE group, Adper Prompt L-Pop$^{TM}$1 coat in LP1 group, 2 coats in LP2 group, Xeno$^{\R}$III1 coat in XN1 group, and 2 coats in XN2 group. After application of the adhesives, a hybrid light-activated resin composite was built up on the unground enamel. Each tooth was sectioned to make a cross-sectional area of approximately 1.0 mm$^2$ for each stick. The microtensile bond strength was determined. Each specimen was observed under SEM to examine the morphological changes. Data were analyzed with one-way ANOVA. The results of this study were as follows; 1. The microtensile bond strength values were; SE (19.77 ${\pm}$ 2.44 MPa), LP1 (13.88 ${\pm}$ 3.67 MPa), LP2 (14.50 ${\pm}$ 2.52 MPa), XN1 (14.42 ${\pm}$ 2.51 MPa) and XN2 (15.28 ${\pm}$ 2.79 MPa). SE was significantly higher than the other groups in bond strength (p < 0.05). All groups except SE were not significantly different in bond strength (p < 0.05). 2. All groups were characterized as shallow and irregular etching patterns.

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.123-132
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• 2000

To overcome problems of conventional glass ionomers, resin components have been added to glass ionomers. On a continuum between glass ionomers and composites are a variety of blends, employing different proportions of acid-base and free radical reactions to bring about cure. Popular groups defined between the ends are resin-modified glass-ionomers(RMGIs), polyacid-modified composite resins(Compomers) and ionomer modified resins. These groups show different clinical properties, and in selecting these materials for a restoration, one should sufficiently understand these different setting properties. In this study, some difference in the setting characteristics of different groups of hybrid ionomers were examined. Two RMGIs (Fuji2 LC,GC / Vitremer, 3M), three Compomers (Dyract AP, Dentsply / F2000, 3M / Elan, Kerr) were involved in this study. The identification of the setting characteristics of different groups was achieved by a two-stage study. First, thermal analysis was performed by a differential scanning calorimeter, and then the hardness of each group at different depth and time were measured by a micro-hardness tester. Thermal analysis was performed to identify the inorganic filler content and to record the heat change during setting process. The setting process was progressed for each material by chemical set mode and light-cured mode. In the hardness test, samples of materials were prepared with a 6mm-diameter metal ring, and the hardness was measured at the top, and 1mm, 2.5mm, 4mm below at just after a 40 second-cure, and after 10 minutes, 24 hours, and 7 days. Statistical analysis was performed by Mann-Whitney rank sum test to assess significant differences between set modes and types of materials, and by ANOVA and T-test to evaluate the statistical meanings of data at different times and depths of each materials. Followings are findings and conclusions derived from this study. Thermal analysis; 1. Compomers show no evidence of chemical setting while RMGIs exhibit heat output during the process of chemical setting. 2. Heat of cure of RMGIs exceed Compomers. 3. The net heat output of RMGIs through light-cured mode is higher than through chemically set mode. Hardness test; 1. Initial hardness of RMGIs immediately after light cure is relatively low, but the hardness increases as time goes by. On the contrary, Comomers do not show evident increase of the hardness following time. 2. Compomers show a marked decrease of setting degree as the depth of the material increases. In RMGIs, the setting degree at different depths does not significantly differ.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.99-105
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• 2022

As the chip size gets smaller, the width of the electrode line is also fine, and the density of interconnections is increasing. As a result, RC delay is becoming a problem due to the difference in resistance between the capacitor layer and the electrical conductivity layer. To solve this problem, the development of electrodes with high electrical conductivity and dielectric materials with low dielectric constant is required. In this study, we developed low dielectric ink by mixing commercial PSR which protect PCB's circuits from external factors and PI with excellent thermal property and low-k characteristics. As a result, the ink mixture of PSR and PI 10:3 showed the best results, with a dielectric constant of about 2.6 and 2.37 at 20 GHz and 28 GHz, respectively, and dielectric dissipation was measured at about 0.022 and 0.016. In order to verify the applicability of future applications, various line-width transmission lines produced on Teflon were evaluated, and as a result, the loss of transmission lines using low dielectric ink mixed with PI was 0.12 dB less on average in S21 than when only PSR was used.

• Restorative Dentistry and Endodontics
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• v.31 no.4
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• pp.263-268
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• 2006

Recently, self-etching adhesive system has been introduced to simplify the clinical bonding proce- dures. It is less acidic compared to the phosphoric acid, thus there is doubt whether this system has enough bond strength to enamel. The purpose of this study was to investigate the influence of additional etching on the adhesion of resin composite to enamel. Ninety extracted bovine permanent anterior teeth were used. The labial surfaces of the crown were ground with 600-grit abrasive paper under wet condition. The teeth were randomly divided into six groups of 15 teeth each. Clearfil SE $Bond^{\circledR},\;Adper^{TM}$ Prompt L-Pop and Tyrian $SPE^{TM}$ were used as self-etching primers. Each self-etching primers were applied in both enamel specimens with and without additional etching. For additional etching groups, enamel surface was pretreated with 32% phosphoric acid (UNI-ETCH, Bisco, Inc., Schaumburg, IL. USA). Hybrid resin composite Clearfil AP-X, (Kuraray Co., Ltd., Osaka, Japan) was packed into the mold and light-cured for 40 seconds. Twenty-four hours after storage, the specimens were tested in shear bond strength. The data for each group were subjected to independent t - test at p < 0.01 to make comparisons among the groups. In Clearfil SE $Bond^{\circledR}$, shear bond strength of additional etching group was higher than no additional etching group (p < 0.01). In $Adper^{TM}$ Prompt L-Pop and Tyrian SPE, there were no significant difference between additional etching and non-etching groups (p > 0.01). In conclusion, self-etching adhesive system with weak acid seems to have higher bond strength to enamel with additional etching, while self-etching adhesive system with strong acid seems not.

• Restorative Dentistry and Endodontics
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• v.33 no.1
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• pp.9-19
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• 2008

The purpose of this study was: (1) to compare nanoleakage patterns of a conventional 3-step etch and rinse adhesive system and two experimental hydrophobic adhesive systems and (2) to investigate the change of the nanoleakage patterns after load cycling. Two kinds of hydrophobic experimental adhesives, ethanol containing adhesive (EA) and methanol containing adhesive (MA), were prepared. Thirty extracted human molars were embedded in resin blocks and occlusal thirds of the crowns were removed. The polished dentin surfaces were etched with a 35 % phosphoric acid etching gel and rinsed with water. Scotchbond Multi-Purpose (MP), EA and MA were used for bonding procedure. Z-250 composite resin was built-up on the adhesive-treated surfaces. Five teeth of each dentin adhesive group were subjected to mechanical load cycling. The teeth were sectioned into 2 mm thick slabs and then stained with 50 % ammoniacal silver nitrate. Ten specimens for each group were examined under scanning electron microscope in backscattering electron mode. All photographs were analyzed using image analysis software. Three regions of each specimen were used for evaluation of the silver uptake within the hybrid layer. The area of silver deposition was calculated and expressed in gray value. Data were statistically analyzed by two-way ANOVA and post-hoc testing of multiple comparisons was done with the Scheffe's test. Silver particles were observed in all the groups. However, silver particles were more sparsely distributed in the EA group and the MA group than in the MP group (p < .0001). There were no changes in nanoleakage patterns after load cycling.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.3
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• pp.456-468
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• 2008

This study was performed to evaluate the quality of newly offered dentin bonding system($AdheSE^{(R)}$ One) by comparing the degree of microleakage measured with those of several conventional adhesive materials(AQ Bond Plus and $Adper^{TM}$ Single Bond 2). The quality of hybrid layer and resin tags was analyzed by observing restoration/ tooth interface under SEM. All-in-one system is in the limelight for having advantage of reducing chair time of children with difficult behavior pattern. Therefore the possibility of clinical application of All-in-one system was evaluated. The results obtained are as follows; 1. At the enamel margin, group II(AQ Bond Plus) showed the highest value of microleakage, and the other groups showed decreased value in order of group III($AdheSE^{(R)}$ One) and I($Adper^{TM}$ Single Bond 2). There was statistically significant difference between group II and the others(p<0.05), and no statistical difference was found between group I and III. 2. At the dentin margin, microleakage value was increased in order of group II, I, III and significant difference between all groups(p<0.05). 3. In group I and III, microleakage value measured at the enamel margin was significantly lower than that seen at the dentin margin(p<0.05), and there was no statistical difference in group II. 4. Resin tags observed under SEM were very weak and tangled in group II and III while the strong and thick tags were observed in group I. In conclusion, careful case selection and accurate clinical application is recommended in using AQ Bond Plus and $AdheSE^{(R)}$ One, giving consideration of the results showing its higher microleakage and weaker strength than $Adper^{TM}$ Single Bond 2.

• Restorative Dentistry and Endodontics
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• v.31 no.4
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• pp.300-311
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• 2006

The purpose of this study is to evaluate prospectively the effect of different bonding systems and retention grooves on the clinical performance of resin restorations in non-carious cervical lesions (NCCLs). Thirty-nine healthy adults who had at least 2 NCCLs in their premolar areas were included in this study. One hundred and fifty teeth were equally assigned to six groups: (A) Scotchbond Multi-Purpose (SBMP, 3M ESPE, St. Paul, MN, USA, 4th generation bonding system) without retention grooves; (B) SBMP with retention grooves; (C) BC Plus (Vericom Co., Anyang, Gyeonggido, Korea, 5th generation bonding system) without retention grooves; (D) BC Plus with retention grooves; (E) Adper Prompt (3M ESPE, Seefeld, Germany, 6th generation bonding system) without retention grooves; (F) Adper Prompt with retention grooves. All cavities were filled with a hybrid composite resin. Denfil (Vericom Co., Anyang, Gyeonggido, Korea) by one operator. Restorations were evaluated at baseline and at 6-month recall, according to the modified USPHS (United States Public Health Service) criteria. Additionally, clinical photographs were taken and epoxy resin replicas were made for SEM evaluation. At 6-month recall, there were some differences in the number of alpha ratings among the experimental groups. But, despite the differences in the number of alpha ratings, there was no significant difference among the 3 adhesive systems (p < 0.05). There was also no significant difference between the groups with or without mechanical retention (p < 0.05). Follow-ups for longer periods than 6 months are needed to verify the clinical performance of different bonding systems and retention grooves.