Kyeong Taek Jung

Scratch Resistant and Transparent UV-Protective Coating on Polycarbonate

UV-protective coating material has been developed to improve the scratch resistance and transparency of polycarbonate substrates. Acetyl acetone (AcAc) chelated silanes and 3-glycidoxypropyl-trimethoxysilane (GPTMS) modified nano-titania sols were used for the UV-protective hard coating materials by the sol-gel technique. The hybrid network is formed as a result of the controlled hydrolysis and condensation of the MTMS (Methyl Tri Methoxy Silane) and DMDMS (Di Methyl Di Methoxy Silane). Surface modified TiO2 nano particles were dispersed in sterically stabilized in the hybrid network by the chelating agent. The coatings dried at 130°C after spray coating were shown to have excellent scratch resistance and adhesion and in addition, it roles as efficient UV-protector under UV irradiation. The long time UV test resulted in no crack formation, without loss of adhesion within the test period of 20 weeks.

Synthesis of mesoporous silica fiber using spinning method

Abstract A very simple procedure for the synthesis of fibrous mesoporous silica using a spinning method was developed. It was based on the sol–gel process and solvent evaporation process using cetyltrimethylammonium chloride as a template. Fibrous mesoporous silica was drawn by using a viscous solution which consisted of a surfactant (cetylmethylammonium chloride) and hydrolyzed silica alkoxide (TMOS). Fibrous mesoporous materials have two distinct pores, 0.9 and 1.9 nm, with a specific surface area of about 580 m 2 /g in 1000 rpm of spinning speed. The intensity of the X-ray diffraction pattern of the mesoporous fibers was increased after both the fiber spinning and calcination process. Increasing the spinning speed from 500 to 2000 rpm in the spinning process increased the specific surface area of the mesoporous fibers from 547 to 605 m 2 /g, and simultaneously decreased the diameter of the fibers from 80 to 20 μm.

The preparation of isotactic polyacrylonitrile using zeolite

Abstract Isotactic polyacrylonitrile (PAN) has been prepared by using a zeolite as a host. After introduction of acrylonitrile monomers, they were subsequently polymerized with radical initiators in Na–Y and Na–β zeolite channels, followed by extraction with hydrofluoric acid. 13C-NMR results show that the isotacticity of extracted PAN is higher than that of bulk PAN prepared under the same reaction conditions and is also affected by the pore structure of host. Thermal and physical properties of extracted PAN were also investigated using GPC, DSC and XRD.

Preparation of transparent ts-1 zeolite film and its photocatalytic isomerization under uv irradiation

TS-1 zeolite film has been prepared by using nano sized TS-1 zeolite particles for the photocatalytic isomerization of cis-2-butene. TS-1 zeolite film showed optical transparent property and the thickness of film was 0.7 μm. UV irradiation of TS-1 zeolite film in the presence ofcis-2-butene leads to the photocatalytic isomerization ofcis-2-butene intotrans-2-butene at the temperature of 275 K. The yield oftrans- 2-butene was linearly increased with UV-irradiation time.

Effect of Organic Additive on the Preparation of Rutile TiO2 by Steam Treatment

Low temperature phase transformation of alkoxide-derived titania was studied under an oxygen flow containing water vapor. The addition of hexylene glycol to the titanium alkoxide solution was effective in transforming rutile phase at low temperature (300°C). Hexylene glycol seems to form a bidentate ligand structure with TEOT in solution state. This bidentate structure promoted the rutile phase at low temperature, under O2-steam treatment. This modification of TiO2 gel structure could be monitored by FT-IR and XANES.

Capillary hydrodynamic fractionation studies on the crystal growth of TS-1 zeolite

Abstract Capillary hydrodynamic fractionation (CHDF) was used, for the first time, to gain information about the particle growth mechanism of TS-1 zeolite. The particle size and the particle size distribution (PSD) of the mother solution were directly and easily monitored by CHDF during crystallization. The effects of the reaction temperature, and the ratios of H2O/Si and TPAOH/Si on the particle growth were studied. During crystallization of zeolite particles, bimodal PSD and an abrupt increase in the number average particle size (30 to 60–80 nm) were observed. It is suggested that zeolite particles of 60–80 nm formed by the aggregation of several particles of 30 nm (i.e. particle intergrowth mechanism). The apparent activation energy for particle intergrowth was 30 kJ/mol. The maximum intergrowth time decreased with increasing reaction temperature, whereas it increased with increasing H2O/Si ratio. The proposed particle growth mechanism was also compared with SEM and TEM results.

UV STUDY ON THE THERMAL STABILITY OF DISPERSE RED 1 FILMS INCORPORATED WITH REACTIVE SILICA

Abstract The thermal stability of thin DR1/PMMA, DR1/silica, and DRS/silica systems was studied by UV spectroscopy. DRS which can covalently bind with reactive silica was synthesized between 4-[ethyl(2-hydroxyethyl) amino]-4′-nitro azobenzene (disperse red 1, DR1) and 3-isocyanatopropyl triethoxy silane The characterization of chemicals and incorporated films were carried out by UV/VIS spectroscopy, DTA, 1H-and 13C-NMR, and FT-IR. After poling of DR1 and DRS incorporated at various temperatures, the UV absorbance decreased due to the alignment of DR1 and DRS by electric field. The second harmonic generation response was obtained by using Nd:YAG laser. The thermal stability of DRS and DRS/silica system was enhanced, compared to that of DR1 and DR1/silica system, respectively.

Performance of ceramic composite membrane for the separation of VOCs

Zeolite composite membranes were prepared for the separation of VOCs by the pressurized coating method. On the top of the composite membrane, TiO2, polyimide or polyethersulfone were coated by the same tech-100 nm-sized nique.ZSM-5 coated membranes show higher selectivity for n-hexane in n-hexane/benzene mixture than 500 nm sized ZSM-5 coated membrane. Composite membrane coated with 100 nm zeolite and polymer showed the highest selectivity (44) for n-hexane/benzene.

Nonlinear Optical Properties of Modified Dr1/Silica Films with Highly Ordered Structures

Abstract Crosslinkable organic NLO chromophore (DRS) has been prepared and chemically incorporated into silica matrices using a sol-gel process. By monitoring the decay of UV absorbance as a function of time and temperatures, a number of electrically poled DRS/silica matrice system has been investigated to elucidate the relaxation behaviors of the oriented organic chromophore by the poling. The value of the second order NLO coefficient d33 was 47 pm/V for the DRS/silica matrice films with 0.4 μm thickness. In addition, from the result of dramatic decreasing of UV absorbance after poling, it is speculated that the DRS may act as a liquid crystalline mesogenic groups and effectively oriented by the poling at the phase (nematic) transition temperature (80°C) and locked in by the crosslinking. The crosslinking reactions between silica matrices and DRS chromophores have been proved using 29Si solid NMR measurement.