Jin-Wook Ha

Molecular weight distribution of syndiotactic polystyrenes prepared over different kinds of catalysts

Abstract The styrene polymerization was carried out with different kinds of homogeneous titanium compounds. The structure of polymers was investigated with 13 C-NMR (nuclear magnetic resonance) spectroscopy, DSC (differential scanning calorimeter) and GPC (gel permeation chromatography). The molecular weight distribution (MWD) of polystyrenes from none-cyclopentadienyl titanium catalysts depended on the aluminoxane/transition metal (Al/Ti) mole ratio and the shape of the MWD was bimodal. Whereas, MWD of polystyrenes from a monocyclopentadienyl titanium catalyst did not depend on the Al/Ti mole ratio and the shape of the MWD was unimodal. From the above results, the MWD of polystyrene depended on the kinds of catalyst and/or the interaction between transition metal and aluminoxane.

Physical properties of the nascent polyethylenes prepared with different kinds of catalysts

From short time kinetic studies using different catalyst systems (Ziegler-Natta catalyst, hybrid catalyst and metallocene catalyst) for ethylene polymerization, the role of methyl aluminoxane (MAO) as a co-catalyst is proposed. The MAO may act as an electron donor, via oxygen, to Lewis acidic sites in the catalyst. From the analyses of the bulk densities and thermal properties, those properties such as bulk density, heat of fusion and melting temperature which depend on the catalyst and co-catalyst systems used in polymerization were determined.

Preparation and Characteristics of Photochromic Plastic Lenses by Hard Coatings

In this study, we have prepared plastic lenses with both photochromic and hard properties by hard coating, and evaluated their optical properties and surface characteristics. Photochromic effects could be observed on the UV spectra of the closed forms and the visible spectra of the open forms. Visible light transmittance of photochromic lenses was from 83.44% for graphite(GP) to 85.15% for blue(BL) in colourless state and from 71.10% for red(RE) to 79.98% for yellow(YE) in colour state. Red photochromic lens was higher in optical density(∆OD) and color difference(△E * ab) than the others. Photochromic lenses applied by hard coating showed good adhesion, hot water resistance, chemical resistance and surface appearance. Also, compared to the uncoated lens, hardness and abrasion resistance were increased. Consequently, this coating system could impart functional properties such as photochromic and hard coating property onto ophthalmic lenses.

Molecular structure of styrene-ethylene copolymers prepared over different kinds of titanium catalysts

Abstract The copolymerization of styrene and ethylene was carried out in the presence of two different catalyst systems; i.e., CpTiCl 3 -methyl aluminoxane and TiCl 4 -methyl aluminoxane. The structure of polymers was investigated with 13 C-NMR (nuclear magnetic resonance) spectroscopy, DSC (differential scanning calorimetry) and XRD (X-ray diffractometry). From the analyses of the 13 C-NMR and XRD data, the molecular structure of the styrene-ethylene copolymer produced over the CpTiCl 3 catalyst system seems to indicate that the ethylene units are randomly distributed in the syndiotactic polystyrene main chain as defects. Whereas the molecular structure of the styrene-ethylene copolymer produced over the TiCl 4 catalyst seems to indicate that the styrene units are randomly distributed in the polyethylene main chain as defects.

A study on the synthesis and characterization of nano-sized metal oxide for conservation treatment of paper records

Abstract Recording materials are the valuable historical and cultural parts themselves as well as the methods for exchanging informations. Therefore, the appropriate conservation treatments should be conducted to the recording materials respectively. In case of the paper records, some particular conservation treatments such as a deacidification and a sterilization are necessary to prevent both bio and chemical deteriorations.In this research, the nano-scaled ZnO and MgO with 10~30㎚ size were prepared for the effective and stable conservation treatment of the paper records. Deacidification and sterilization effect of nano compounds were excellent and since nano compounds had almost 100% purity(free from Pb, Cd, As), the additional damages caused by the heavy and toxic metals should not be occur to the books and papers. Key Words : Nano-sized metal oxide, ZnO, MgO, Deacidification, Sterilization 본 논문은 행정안전부 국가기록원 재원으로 2012년 기록보존기술 연구개발사업의 지원을 받아 수행된 연구임 . * Corresponding Author : Jin-Wook Ha(Soonchunhyang Univ.)Tel: +82-10-9171-5542 email: chejwh@sch.ac.krReceived December 5, 2013 Revised February 4, 2014 Accepted February 5, 2014

Development of IR Reflective Cool Pigment and Paint

Abstract Infrared(IR) reflective black cool pigment and paint which is used for interior/exterior materials(IR reflectance >30%) to prevent heat island effect and to increase energy efficiency were studied. Cool pigment was synthesized using mixture of Fe 2 O 3 and Cr 2 O 3 with calcination from 900 to 1,200 ℃ . Cool paint was prepared byformulation of cool pigment, acrylic resins, and other additives. Results showed that optimum color fixation of pigment obtained by mole ratio of Fe to Cr was 0.9 with calcination temperature at 1,000 ℃ . The cool paint formulated by 20% pigment and 1.5% dispersive additive with 125 ㎛ thickness of coated layer showed optimum IRreflectance. Temperature difference on surface between cool paint and ordinary paint(STD) was 36.5 ℃ and IR reflectance(TSR) was 39.3% at wavelength from 700 to 2,500 ㎚ . And color change was not detected during 500hrs weathering test. Key Words : Ceramic Pigment, Infrared Reflection, Coating, High performance pigments, Cool Paint

Recycling Technique of Nano TiO 2 -Coated Silica-bead

In this study, recycling methods of nano -coated silica-bead were conducted in order to solve a deactivation problem of bead that had been invented for decomposition of pollutants in aqueous solution. Surface cleansing was selected as the recycling method for used beads. The surface cleansing was done with four different solutions such as distilled water, surfactant, acetone, and ethyl alcohol(ethanol). The recycling process consists of cleansing and calcination. After cleaning the used (deactivated) beads, calcination was done at , and for 30 minutes, respectively. This process was repeated three times. The activity of the recycled bead was measured by photo-degradation of methylene blue. The result shows that acetone cleansing and calcination at for 30 minutes was the most efficient recycling method.

Development of Environmental-friendly Nontoxic Organic.Inorganic Complex Pigment

Non-toxic orgarnic inorgarnic complex green pigment using Fluidized Bed Vapor Deposition(FB-VD) process was developed to alternate green pigment used heavy metals chrome and lead in present domestic. Kaolin materials and were used as supporter of pigment and surface and compositions of supporters were characterized by SEM and EDXS, respectively. Various kind of surface active agents(surfactants) were also used to optimize the dry condition or color revelation. Results showed that anion type surfactant is most suitable for dry and color revelation of pigment.

A Study on the Photodegradation of VOC Using High Efficiency System

In this paper, The paste was prepared by changing the ratio of (Degussa, P-25), binder (A-9540) and solvent. The paste was coated on to aluminuim metal plate to investigate the photodegradation of IPA. The best efficiency was obtained with increasing content and decreasing binder content. MEK is preferred to ethanol in terms of efficiency and the lower amount of solvent enhanced the rate. We, however, found the increasing viscosity of the paste and cracking with the lower content of solvent(MEK). In conclusion, the optimum activity was obtained when the ratio of , Organic binder(A-9540) and MEK was 1.75 : 0.25 : 10.

Development of Environmental-friendly Nontoxic Flame Retardant Paint

Environmental-friendly nontocxic flame retardant paint which can overcomes the restriction of harmful materials for human body and environments such as Pb, Hg, Cd, , PBB/PBDE by EU and domestic Ministry of Environment was developed. Developed paint is the water-soluble organic inorganic hybrid material that VOC(volatility organic compound) discharge is low, and that human riskiness and environmental pollution is minimized not using the kinds of halogen materials. , , and Zinc borate were used as flame retardant materials, 2% Micell and water were used as binder and solvent, respectively. Results showed the optimum activity was obtained when the ratio of those frame retardant agents(, , Zinc borate made by 1: 2: 2), binder(2% Micell) and water was 1: 0.5: 0.5.