• Journal of Adhesion and Interface
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• v.19 no.1
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• pp.5-12
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• 2018

The purpose of this study is to evaluate the adhesive properties of polyurethane mixed aqueous dispersions by omitting the primer, dealing with the preparation of skins for synthetic leather with excellent adhesion by omitting the pre-treatment process. The two-component mixed polyurethane water dispersion was prepared by synthesizing an ester-based polyurethane resin (PU-T) and a carbonate-based polyurethane resin (PU-C) to obtain the final resin. As a result of measuring the peel strength of the adhesive specimens omitting the pre-treatment agent, it was confirmed that the state adhesive strength (ethylene vinyl acetate (middle): $4.2kg_f/cm$ and rubber (outsole): $4.4kg_f/cm$) there was. This makes it possible to omit the pre-treatment process which has been indispensably used in the shoe manufacturing process, thereby reducing the process time and reducing the amount of volatile organic compounds (VOCs) generated in the pre-treatment product, resulting in environmentally advantageous.

• Corrosion Science and Technology
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• v.6 no.4
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• pp.206-210
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• 2007

Aerospace aluminum alloys such as Al alloy 2024-T3 and 7075-T6 are subject to localized corrosion due the existence of intermetallics containing Cu, Mg or Zn. Chromate is currently widely used in the aerospace industry as the corrosion inhibitor for these alloys. However, chromate needs to be replaced due to its strong carcinogenicity. In this study, an extensive pigment screening has been performed to find replacements for chromates. Different categories of inhibitors were evaluated by immersion tests, DC polarization tests and other methods. Phosphates, zinc salts, cerium salts, vanadates and benzotriazole were found to be effective inhibitors for AA7075. Among those inhibitors, zinc phosphate was found to be the most effective in our novel, silane-based, one-step aqueous primer system. The performance of this primer is comparable to that of currently used chromate primers in accelerated corrosion tests, while it is completely chromate-free and its VOC is about 80% less than that of current primers. Studies by SEM/EDS showed that the unique structure of the superprimer accounts for the strong anti-corrosion performance of the zinc phosphate pigment. The self-assembled stratified double-layer structure of the superprimer is characterized by a less-penetrable hydrophobic layer at the top and a hydrophilic layer accommodating the inhibitors underneath. The top layer functions as the physical barrier against water ingress, while the lower layer functions as a reservoirfor the inhibitor, which is leached out only if the coating is damaged by a scratch or scribe. The presence of a silane in the primer further improves the adhesion and anti-corrosion performance of the primer.

• The Journal of Korean Academy of Prosthodontics
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• v.53 no.4
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• pp.295-300
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• 2015

Purpose: The aim of this study was to evaluate the shear bond strength between Ni-Cr alloy and composite resin using universal adhesive systems coMPared to conventional method using metal primers. Materials and methods: For this study, a total of 120 cast commercial Ni-Cr alloy (Vera Bond 2V) disks were embedded in acrylic resin, and their surfaces were smoothed with silicon carbide papers and airborne-particle abrasion. Specimens of each metal were divided into 6 groups based on the combination of metal primers (Metal primer II, Alloy primer, Metal & Zirconia primer, MKZ primer) and universal adhesive systems (Single Bond Universal, All Bond Universal). All specimens were stored in distilled water at $37^{\circ}C$ for 24 hours. Shear bond strength testing was performed with a universal testing machine at a cross head speed of 1 m/min. Data (MPa) were analyzed using one-way ANOVA and the post hoc Tukey's multiple comparison test (${\alpha}$=.05). Results: There were significant differences between Single Bond Universal, All Bond Universal, Metal Primer II and Alloy Primer, MKZ Primer, Metal & Zirconia Primer (P<.001). Conclusion: Universal Adhesive system groups indicated high shear bond strength value bonded to Ni-Cr alloy than that of conventional system groups using primers except Metal Primer II. Within the limitations of this study, improvement of universal adhesive systems which can be applied to all types of restorations is recommended especially non-precious metal alloy. More research is needed to evaluate the effect of silane inclusion or exclusion in universal adhesive systems.

• Fisheries and Aquatic Sciences
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• v.7 no.3
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• pp.122-129
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• 2004

Harmful Cochlodinium polykrikoides is a notorious harmful algal bloom (HAB) species that is causing mass mortality of farmed fish along the Korean coast with increasing frequency. We analyzed the sequence of the large subunit (LSD) rDNA D1-D3 region of C. polykrikoides and conducted phylogenetic analyses using Bayesian inference of phylogeny and the maximum likelihood method. The molecular phylogeny showed that C. polykrikoides had the genetic relationship to Amphidinium and Gymnodinium species supported only by the relatively high posterior probabilities of Bayesian inference. Based on the LSU rDNA sequence data of diverse dinoflagellate taxa, we designed the C. polykrikoides-specific PCR primer set, CPOLY01 and CPOLY02 and developed PCR detection assays for its sensitive, accurate HAB monitoring. CPOLY01 and CPOLY02 specifically amplified C. polykrikoides and did not cross-react with any dinoflagellates tested in this study or environmental water samples. The effective annealing temperature $(T_{p})$ of CPOLY01 and CPOLY02 was $67^{\circ}C$. At this temperature, the conventional and nested PCR assays were sensitive over a wide range of C. polykrikoides cell numbers with detection limits of 0.05 and 0.0001 cells/reaction, respectively.

• Korean Journal of Ecology and Environment
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• v.54 no.3
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• pp.199-208
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• 2021

Environmental DNA (eDNA) metabarcoding is effective method with high detection sensitivity for evaluating fish biodiversity and detecting endangered fish from natural water samples. We compared the richness of operational taxonomic units(OTUs) and composition of freshwater fishes according to filters(cellulose nitrate filter vs. glass fiber filter), extraction kits(DNeasy2^® Blood & Tissue Kit vs. DNeasy2^® PowerWater Kit), primer sets (12S rDNA vs. 16S rDNA), and PCR methods (conventional PCR vs. touchdown PCR) to determine the optimal conditions for metabarcoding analysis of Korean freshwater fish. The glass fiber filter and DNeasy2^® Blood & Tissue Kit combination showed the highest number of freshwater fish OTUs in both 12S and 16S rDNA. Among the four types, the primer sets only showed statistically significant difference in the average number of OTUs in class Actinopterygii (non-parametric Wilcoxon signed ranks test, p=0.005). However, there was no difference in the average number of OTUs in freshwater fish. The species composition also showed significant difference according to primer sets (PERMANOVA, Pseudo-F=6.9489, p=0.006), but no differences were observed in the other three types. The non-metric multidimensional scaling (NMDS) results revealed that species composition clustered together according to primer sets based on similarity of 65%; 16S rDNA primer set was mainly attributed to endangered species such as Microphysogobio koreensis and Pseudogobio brevicorpus. In contrast, the 12S rDNA primer set was mainly attributed to common species such as Zacco platypus and Coreoperca herzi. This study provides essential information on species diversity analysis using metabarcoding for environmental water samples obtained from rivers in Korea.

• The Journal of Advanced Prosthodontics
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• v.10 no.5
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• pp.374-380
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• 2018

PURPOSE. The effect of silica-based glass-ceramic liners on the tensile bond strength between zirconia and resin-based luting agent was evaluated and compared with the effect of 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing primers. MATERIALS AND METHODS. Titanium abutments and zirconia crowns (n = 60) were fabricated, and the adhesive surfaces of the specimens were treated by airborne-particle abrasion. The specimens were divided into 5 groups based on surface treatment: a control group, 2 primer groups (MP: Monobond Plus; ZP: Z Prime Plus), and 2 liner groups (PL: P-containing Liner; PFL: P-free Liner). All specimens were cemented with self-adhesive resin-based luting agent. After 24-hour water storage and thermocycling (5,000 cycles, $5^{\circ}C/55^{\circ}C$), the tensile bond strength was measured using a universal testing machine. Failure mode analysis and elemental analysis on the bonding interface were performed. The data were analyzed using Kruskal-Wallis test, Dunn's post hoc test, and Fisher's exact test. RESULTS. The liner groups and primer groups showed significantly higher tensile bond strengths than that of the control group (P<.05). PFL showed a significantly higher tensile bond strength than the primer groups (P<.05). The percentage of mixed failure was higher in the primer groups than in the control group (P<.001), and all the specimens showed mixed failure in the liner groups (P<.001). A chemical reaction area was observed at the bonding interface between zirconia and liner. CONCLUSION. The application of liner significantly increased the tensile bond strength between zirconia and resin-based luting agent. PFL was more effective than MDP-containing primers in improving the tensile bond strength with the resin-based luting agent.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.1
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• pp.49-56
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• 2011

Purpose: The aim of this study was to evaluate the effect of mechanical, chemical surface treatments on the zirconia-to-resin cement shear bond strength (SBS). Materials and methods: Eighty zirconia discs (Lava, 3M ESPE) and eighty zirconia/alumina composite (Zirace, Acucera) were embedded in an epoxy resin base. Zirconia discs were randomly divided in to four treatment groups(10 for each manufacturer): $50\;{\mu}m$ $Al_2O_3$ sandblasting (S50), $110\;{\mu}m$ $Al_2O_3$ sandblasting (S110), $50\;{\mu}m$ $Al_2O_3$ and primer (Z-Prime Plus, Bisco Inc) (S50z) and $110\;{\mu}m$ $Al_2O_3$ and primer (Z-Prime Plus) (S110z). Two resin-based luting cements (Calibra, Panavia F) were used to build 2 mm diameter cylinders onto the zirconia. After 24 h of storage in water, SBS testing was evaluate using a universal testing machine. Bond strength data were analyzed with one-way ANOVA, two-way ANOVA test and post hoc comparison was done using Tukey test (${\alpha}$ = .05). Results: Groups using primer showed the high shear bond strength. The groups that did not use primer presented lower shear bond strengths. Conclusion: The use of primer (Z-Prime Plus, Bisco) had significantly higher shear bond strengths.

• Corrosion Science and Technology
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• v.6 no.5
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• pp.219-226
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• 2007

Pre-construction primer (PCP), or shopprimer, have been applied to steel plates to control temporary corrosion during ship fabrication. For surface preparation at ship block stage, in common shipyard practices, welding beads, burnt and rusted areas shall be blasted or power tool cleaned and the contamination such as zinc salt shall be removed with blasting or power tool. Whereas, the sound film of PCP needs not to be removed or roughened as the paint having good compatibility with PCP is used for the first coat. In many cases, however, full blasting or sweep blasting on the sound PCP treated block assemblies was requested. There still has been argument about the legitimacy of this practice, thus, it is critical to evaluate the quality of the coating system applied on the sound PCP retained condition, comparing with the one applied on the full blasted or sweep blasted condition. In this study, two different epoxy systems for water ballast tank were applied on the surfaces with sound PCP condition, full blasted condition, and sweep blasted condition. Coating performances such as durability, anti-corrosion, cathodic disbondment resistance were evaluated. The test results clearly indicated that the sound film of PCP needed not to be removed or roughened as the paint having good compatibility with PCP based on inorganic zinc silicate.

• Korean Journal of Ecology and Environment
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• v.54 no.3
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• pp.190-198
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• 2021

Human Aichivirus (Aichivirus A; AiV-A) is a positive-sense single-strand RNA non-enveloped virus that has been detected worldwide in various water environments including sewage, river, surface, and ground over the past decade. To develop a method with excellent sensitivity and specificity for AiV-A diagnosis from water environments such as groundwater, a combination capable of reverse transcription (RT)-nested polymerase chain reaction (PCR) was developed based on existing reported and newly designed primers. A selective method was applied to evaluate domestic drinking groundwater samples. Thus, a procedure was devised to select and subsequently identify RT-nested PCR primer sets that can successfully detect and identify AiV-A from groundwater samples. The findings will contribute to developing a better monitoring system to detect AiV-A contamination in water environments such as groundwater.

• Safety and Health at Work
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• v.7 no.1
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• pp.63-71
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• 2016

Background: Construction painters have not been studied well in terms of their hazards exposure. The objective of this study was to evaluate the exposure levels of total volatile organic compounds (TVOCs) for painters in the construction industry. Methods: Activity-specific personal air samplings were carried out in three waterproofing activities [polyurethane (PU), asphalt, and cement mortar] and three painting activities (epoxy, oil based, and water based) by using organic-vapor-monitor passive-sampling devices. Gas chromatograph with flame ionization detector could be used for identifying and quantifying individual organic chemicals. The levels of TVOCs, by summing up 15 targeted substances, were expressed in exposure-index (EI) values. Results: As arithmetic means in the order of concentration levels, the EIs of TVOCs in waterproofing works were 10.77, 2.42, 1.78, 1.68, 0.47, 0.07, and none detected (ND) for indoor PU-primer task, outdoor PU-primer task, outdoor PU-resin task, indoor PU-resin task, asphalt-primer task, asphalt-adhesive task, and cement-mortar task, respectively. The highest EI for painting works was 5.61 for indoor epoxyprimer task, followed by indoor epoxy-resin task (2.03), outdoor oil-based-spray-paint task (1.65), outdoor water-based-paint task (0.66), and indoor oil-based-paint task (0.15). Assuming that the operations were carried out continuously for 8 hours without breaks and by using the arithmetic means of EIs for each of the 12 tasks in this study, 58.3% (7 out of 12) exceeded the exposure limit of 100% (EI > 1.0), while 8.3% (1 out of 12) was in 50e100% of exposure limit (0.5 > EI > 1.0), and 4 tasks out of 12 were located in less than 50% of the limit range (EI < 0.5). Conclusion: From this study, we recognized that construction painters are exposed to various solvents, including carcinogens and reproductive toxins, and the levels of TVOC concentration in many of the painting tasks exceeded the exposure limits. Construction workers need to be protected from chemical agents during their painting works by using personal protective devices and/or work practice measures. Additional studies should focus on the exposure assessment of other hazards for construction workers, in order to identify high-risk tasks and to improve hazardous work environments.