• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.97-102
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• 2018

In this work, the surface of gold nanoparticles (AuNPs) was modified with small molecules including mercaptoundecanoic acid (MUA) and L-lysine for the development of highly sensitive lateral flow (LF) sensors. Uniformly sized AuNps were synthesized by a modified Turkevich-Frens method, showing an average size of $16.7{\pm}2.1nm$. Functionalized AuNPs were then characterized by transmission electron microscopy, UV-vis spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The stable conjugation of AuNPs and antibodies was obtained at pH 7.07 and the antibody concentration of $10{\mu}g/mL$. The functionalized AuNP-based LF sensor exhibited lower detection limit of 10 ng/mL for hepatitis B surface antigens than that of using the bare AuNP-based LF sensor (100 ng/mL).

• Polymer(Korea)
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• v.29 no.4
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• pp.392-398
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• 2005

Self-assembled multilayer thin films of poly(ethylene-alt-maleic anhydride) (PEMAh) and poly(4-vinyl pyridine) (P4VP) were fabricated by layer-by-layer (LbL) sequential adsorption. Fourier transform infrared (FT-IR) spectroscopic analysis of the self-assembled PEMAh/P4VP multilayer films confirms that the driving forces for the multilayer buildup are the intermolecular hydrogen bonding and electrostatic interactions. The linear increase of absorption peak of P4VP at 256 nm with increasing number of PEMAh/P4VP bilayers indicates that the multilayer buildup is an uniform assembling process. We also investigate the effects of polyelectrolyte concenhation variation of the dipping solution and pH variation of the PEMAh solution on the multilayer film formation. Thickness. adsorbed polyelectrolyte mass and surface roughness of the multilayer films were measured by UV-visible spectroscopy, quartz crystal microbalance (QCM), and atomic force microscopy (AFM), respectively.

• Polymer(Korea)
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• v.26 no.2
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• pp.209-217
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• 2002

We studied the mechanism of orientation of polyimide molecules which were irradiated by polarized UU (PUV) using polarized Fourier transform infrared (FT-IR) spectroscopy and ultraviolet (UV) spectroscopy, According to the measured UV spectra, we found PI films mainly absorb UV light less than 350 nm wavelength, therefore, UV light less than 360 nm induces photochemical reaction of PI. PUV irradiation of PI films caused decrease of all peak intensities in the FT-IR spectra. except the newly formed broad peak at $3244 cm^{-1}$, due to degradation of the PI molecules. The remaining PI molecules after photo-degradation showed predominantly perpendicular molecular orientation to the irradiated PUV polarization direction, due to the preferential degradation of PI molecules parallel to irradiated PUV polarization direction. However the rubbing of PI films induced reorientation of the PI molecules parallel to the rubbing direction. We also investigated the alignment of the liquid crystal by rubbing or PUV irradiation. Liquid crystals align perpendicular to the PUV polarization direction and parallel to the rubbing direction.

• Polymer(Korea)
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• v.31 no.5
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• pp.393-398
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• 2007

We studied the mechanism of liquid crystal alignment on polyvinylfluorocinnamate (PVCN-F) films which were irradiated by UV using polarized fourier transform infrared (FT-IR) spectroscopy and ultraviolet/visible (UV/Vis) spectroscopy. UV irradiation of PVCN-F films caused decrease of vinylene -C=C- stretching peak area at $1638cm^{-1}$ and shift of conjugated C:0 stretching vibration at $1712cm^{-1}\;to\;1734cm^{-1}$ which is caused by nonconjugated C=O stretching nitration. To study the orientation direction of 5CB liquid crystal (LC) molecules in the liquid crystal cell with PUV irradiation, rubbing treatment or without any treatment on the PVCN-F alignment layer, we used polarized FT-IR dichroism technique. We successfully measured 5CB LC alignment directions, which are perpendicular to the irradiated PUV polarization direction and parallel to the rubbing direction in the liquid crystal cell without using dichroic dyes.

• Resources Recycling
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• v.29 no.6
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• pp.98-103
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• 2020

In this study, the depression behavior of zinc sulfate on the sphalerite with the addition of potassium butyl xanthate was investigated to clear the relationship between zinc sulfate and xanthate in depression of sphalerite. As a result of the experiment, it was confirmed that the depress effect of zinc sulfate on the sphalerite declined with the increase of its addition amount. From the results of SEM-EDS and FT-IR analysis, it was found out that the amorphous precipitate of metal xanthate (Zn-BX) was formed in sphalerite concentrate, when the solubility product of [Zn+]·[BX] in the pulp solution exceeded 3.71×10-11, which is the solubility of Zn-butyl xanthate. It is considered that the Zn-butyl xanthate had a negative effect on the depression of sphalerite.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.61-69
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• 2009

Statement of problem: Porcelain veneers have become a popular treatment modality for aesthetic anterior prosthesis. Fitting porcelain veneers in the mouth usually involve a try-in appointment, which frequently results in salivary contamination of fitting surfaces. Purpose: An in vitro study was carried out to investigate the effect of silane treatment timing and saliva contamination on the resin bond strength to porcelain veneer surface. Material and methods: Cylindrical test specimens (n=360) and rectangular test specimens (n=5) were prepared for shear bond test and contact angle analysis. Whole cylindrical specimens divided into 20 groups, each of which received a different surface treatment and/or storage condition. The composite resin cement stubs were light-polymerized onto porcelain adherends. The shear bond strengths of cemented stubs were measured after dry storage and thermocycling (3,000 cycles) between 5 and $55^{\circ}C$. The silane and their reactions were chemically monitored by using Fourier Transform Infrared Spectroscopy analysis (FTIR) and contact angle analysis. One-way analysis of variance (ANOVA) and Dunnett's multiple comparison were used to analyze the data. Results: FT-IR analysis showed that salivary contamination and silane treatment timing did not affect the surface interactions of silane. Observed water contact angles were lower on the saliva contaminated porcelain surface and the addition of 37% phosphoric acid for 20 seconds on saliva contaminated porcelain increased the degree of contact angle. Silane applied to the porcelain, a few days before cementation, resulted in increasing the bond strength after thermocycling. Conclusion: Within the limitation of this study, it can be concluded that it would be better to protect porcelain prosthesis before saliva contamination with silane treatment and to clean the contaminated surface by use of phosphoric acid.

• Clean Technology
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• v.27 no.2
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• pp.132-138
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• 2021

Research is being conducted on graphene to provide graphene having both excellent physical as well as electrical properties in addition to unique physical properties. In this study, Hummer's method, which is a representative method for chemical exfoliation, was applied in order to investigate the possibility of the mass production of high-quality graphene oxide. Three types of graphite (graphite, crystalline graphite, and expanded graphite) were used in the preparation of graphene oxide with variations in the amount of potassium permanganate added, reaction temperature, and reaction time. Then a Fourier transform infrared spectroscopy (FT-IR), a Raman spectrometer, and a transmission electron microscope (TEM) were used to measure the quality of the prepared graphene oxide. Of the three types of graphite used in this experiment, crystalline graphite showed the highest quality. The prepared graphene oxide was then purified with an organic solvent, and an analysis conducted using energy dispersive X-ray spectroscopy (EDS). From the results of the residual values, we were able to confirm that both acid wastewater and wastewater were best purified using cyclohexane. The method for manufacturing graphene oxide as well as the method of purification using organic solvents that are presented in this study are expected to have less of an environmental impact, making them environmentally friendly. This makes them suitable for use in various industrial fields such as the film industry and for heat dissipation and as coating agents.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.6
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• pp.88-95
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• 2020

Currently, Fiber-Reinforced Plastic (FRP) composite materials are used in many industrial fields, owing to their superior stiffness and specific strength compared to metals. However, there are issues with FRP inefficiency, due to low productivity of such materials, environmental problems they pose and long curing times needed. Trying to address these issues, research was conducted towards the development of a FRP composite material with excellent properties and short production time, introducing a curing method using a UV lamp. Four types of composite materials were prepared, cured with catalyst or UV (CZ: Catalyst + ZNT 6345, CR: Catalyst + RF 1001 MV, UVZ: Photoinitiator + ZNT 6345, and UVR: Photoinitiator + RF 1001 MV). Examination of the chemical and mechanical properties of these composites showed that UV-cured materials performed better than the catalyst-cured ones. These results indicate that the production process of FRP composite materials can be simplified by using a UV lamp for curing, resulting in composite materials with the same quality, but reduced production time by about 70% compared to currently used practices. This advancement will contribute greatly to the composite material industry.

• Polymer(Korea)
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• v.25 no.5
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• pp.649-656
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• 2001

Miscibility of poly(4-vinylpyridine) (P4VP) blends with poly(vinyl acetate-co-vinyl alcohol) (VAc-VAL copolymers) was investigated as a function of comonomer composition of VAc-VAL copolymers. Differential scanning calorimetry (DSC) and thermo-optical microscopic (TOM) analysis confirmed that P4VP is miscible with VAc-VAL copolymers containing more than 30 mole% VAL. Fourier transform inflated (FT-IR) spectroscopic analysis revealed that the strong intermolecular hydrongen bonding interaction between the vinylpyridine and VAL hydroxyl group was formed. Theoretical phase diagram was constructed by the calculation using the Association model, a thermodynamic model for hydrogen-bonded polymer blend systems developed by Coleman et al. The calculated theoretical binodal phase diagrams were in good agreement with the experimentally determined cloud point curves.

• Polymer(Korea)
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• v.31 no.1
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• pp.68-73
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• 2007

This study is on the synthesis of reactive polymer modifiers by emulsion polymerization to improve properties of asphalt for paving. Styrene, methyl methacrylate (MMA), isoprene and glycidyl methacrylate (GMA) which has epoxy ring to react with carboxyl group of asphaltene were used to synthesize polymer modifiers. Modifiers with various composition were tested miscibility with asphalt. Modifiers which showed good miscibility with asphalt were investigated by DSC for $T_g$. Existence of epoxy rings and their reaction with asphaltene wore investigated by FTIR. Molecular structures of synthesized modifiers were confirmed by $^1H-NMR$. The synthesized modifiers which showed good miscibility had their $Tg's$ in the range of $37.5{\sim}56.5^{\circ}C$ and had isoprene contents of 30 wt%. They showed good miscibility in the 1 and 2 wt% concentrations, but not in the 3 wt% concentration.