Byung Hyun Ahn

Synthesis of polystyrene beads loaded with dual luminophors for self-referenced oxygen sensing

Dispersion polymerization has been successfully applied to synthesize monodisperse polystyrene beads loaded with SiOEP and PtOEP for self-referenced oxygen sensing. The polystyrene beads became larger in size as the concentration of initiator was increased due to the reduction of primary particles precipitated from the polymerization medium. The dual luminophors showed similar absorption spectra but two distinctive emission spectra with peaks at 580 and 650nm for SiOEP and PtOEP, respectively. While the emission of SiOEP exhibited no response to oxygen, the luminescence intensity of PtOEP was monotonically dependent on the concentration of oxygen. From the Stern-Volmer plot, we observed a linear correlation between the intensity ratio of SiOEP at 580nm to PtOEP at 650nm and the concentration of oxygen, which could be used to reliably monitor the partial pressure of oxygen in a system.

Photocatalytic decomposition of 4-nitrophenol over titanium silicalite (TS-1) catalysts

Abstract Titanium silicalite zeolites (TS-1) having Si/Ti ratios of 3.3, 13.7, and 26.3 were synthesized and used as photocatalysts for decomposition of 4-nitrophenol (4-NP) in aqueous solution. In the dark, the adsorption of 4-NP on TS-1 changed greatly depending on the Si/Ti ratio in TS-1 and the pH of the solution. The amount of 4-NP adsorbed on TS-1 increased with increasing Si/Ti ratio and decreasing pH of solution. The photocatalytic activities of TS-1 zeolites for the decomposition of 4-NP were found to be greatly affected by H 2 O 2 . In the absence of H 2 O 2 , the TS-1 having lower Si/Ti ratio, and consequently containing a larger amount of extra framework titanium, exhibited higher photocatalytic activity. In contrast, in the presence of H 2 O 2 , the TS-1 with higher Si/Ti ratio, in which the titanium content is lower while the fraction of framework titanium is higher, showed a higher increase in photocatalytic activity. Especially in acid conditions, the addition of H 2 O 2 to the reaction solution results in a remarkable enhancement of the photocatalytic activity of TS-1; the apparent rate constant increased with increasing Si/Ti ratio. Such results suggest that, upon UV illumination, OH radicals can be formed easily from the titanium-hydroperoxide species that are formed by the interaction of framework titanium in TS-1 with H 2 O 2 . The enhancement of photocatalytic activity of TS-1 for the decomposition of 4-NP by the addition of H 2 O 2 can be attributed to both the efficient formation of OH radicals and the close proximity of OH radicals to the reactant molecules.

PLATING OF COPPER LAYERS ON POLYIMIDES USING ELECTROLESS PLATING BY SURFACE MODIFICATION

This work describes electroless deposition of copper layers onto a polyimide (PI) film. The film was modified by etching with 1.0 M KOH solution treatment, and an activated Ag thin film was developed on this surface using 0.1 M AgNO3. The Cu layers were coated on the activated surface of polyimide films by electroless plating method. The thickness and surface morphology of Cu layers on the PI films were characterized with atomic force microscopy. The surface properties of PI film were identified with contact angle measurements.

Synthesis and Photo-Polymerization of Poly(Alkyl Urethane) Acrylate Oligomers Using 2-Isocyanatoethyl Methacrylate for UV Curable Coating

The poly(alkyl urethane) acrylate oligomers (AUAOs) were obtained by the reaction of alkyl acrylate oligomers and 2-isocyanatoethyl acrylate. Synthesis of AUAOs were done with 2-mercaptoethanol (2-MEOH), alkyl (methyl, butyl, 2-ethylhexyl) acrylate, 2,2′-azobisisobutyronitrile (AIBN, initiator) and dibutyltin dilaurate as a catalyst. Then 2-MEOH was used for functional chain transfer agent. The oligomers were characterized by FT-IR, FT-NMR, rheometer, and DSC. Each oligomer was blended and photopolymerized by UV light, and their ball tack, adhesiveness, and thermal resistance were confirmed by ball tack tester and so on. Photo-polymerized AUAOs can be used for UV curable coatings, inks and adhesives.

Synthesis And Characterization Of Polyurethane Acrylates For Uv Curable Coating Agents

The single hydroxyl-terminated urethane acrylate oligomers were synthesized from 2-mercaptoethanol (2-MEOH), alkyl (methyl, butyl, and 2-ethylhexyl) acrylate, and 2,2-azobisisobutyronitrile (AIBN, initiator), with dibutyltin dilaurate (DBTDL) as a catalyst. 2-MEOH was used as a functional chain transfer agent. Poly(alkyl urethane) acrylate oligomers were obtained by the reaction of single hydroxyl-terminated polyalkyl acrylates and 2-isocyanatoethyl acrylate. They were characterized by NMR, FT-IR spectroscopy, rheometer, and DSC. Because poly(alkyl urethane) acrylate oligomers have lower Tg and viscosity than hydroxyl-terminated polyalkyl acrylate oligomers (HTPAO) non-containing urethane groups, they can be used for ultraviolet (UV) curable coatings, inks, and adhesives.

Study on the durability of E-glass fiber/vinylester resin composites in various environment

The effect of various environmental conditions on durability of E-glass fiber/vinylester resin composites has been investigated with tensile test specimen of strand type. The durability test method performed by strand type specimen was more convenient and reliable than other conventional test method. The weight gain of E-glass fiber reinforced composites increased with the immersion time in both water and alkali solutions, and the weight gains at 80°C were a little greater than ones at 20°C. The tensile strength decreased with the immersion time in all aqueous solution, and the tensile strength in 80°C of alkaline solution decreased most rapidly. The decrement of tensile strength in various environmental conditions was mainly caused by the degradation of interface and damage of glass fiber surface.

Preparation and Characterization of Anti-Fogging Low Density Polymer Film

In this work, low density polyethylene (LDPE) was grafted with trifluoroacetic acid allyl ester using γ-ray irradiation from a Cobalt-60 source at different adsorbed doses. It was found that the grafting degree increases with the absorbed doses. The highest grafting degree was obtained at 100 kGy of absorbed dose and with 30 wt% of trifluoroacetic acid allyl ester. The grafting was identified with fourier transform infrared (FT-IR) using a calibration curve reported in literature. Thermal properties of the functional polymers were studied by thermogravimetric analysis (TGA) and the surface morphology was investigated by scanning electron microscope (SEM).

Grafting of Trifluoroacetic Acid Allyl Ester onto Linear Low Density Polyethylene by γ-Ray Irradiation

Grafting of linear low density polyethylene (LLDPE) is an important method used in the modification of functional group. The method of γ-ray irradiation grafting of trifluoroacetic acid allyl ester onto LLDPE was studied. The γ-ray irradiation causes molecular bond scission and produces free radical sites on the LLDPE. This process was carried out at 500 kGy γ-ray irradiation doses from a 60Co source and the optimum concentration (30 wt%) of trifluoroacetic acid allyl ester. The microstructure of modified polymer film has been characterized by fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR). Thermal properties of the grafted products were also studied by thermogravimetric analysis (TGA).