• Journal of Environmental Science International
• /
• v.12 no.11
• /
• pp.1145-1157
• /
• 2003

The surface sediments inside Hallim Harbor, one of the major harbors of Jeju Island, were sampled three times (June, September and December, 2001) and analyzed for 16 polycyclic aromatic hydrocarbons (PAHs), recommended by US-EPA as priority pollutants, to assess their distribution levels and to suggest their possible origins. The concentrations of PAHs ranged from 19 to 496 ng/g on a dry weight basis with a mean value of 245 ng/g, and the levels were low to moderate in comparison with other areas in the world. Based on comparisons of individual and total PAH concentrations with effects-based and equilibrium partitioning-based on sediment quality guidelines, the potential for the biological effects were expected to be low. The sedimentary PAHs may be correlated with organic carbon and mud contents to some extent. From the examinations of the four PAH origin indices, such as LMW/HMW (low molecular weight 2-3 ring PAHs over high molecular weight 4-6 ring PAHs), phenanthrene/anthracene ratio, fluoranthene/pyrene ratio, chrysene/benzo〔a〕anthracene ratio, it can be concluded that the sediment PAH contaminations were ascribed to both pyrolytic and petrogenic origins.

• Transactions of the Korean hydrogen and new energy society
• /
• v.27 no.5
• /
• pp.612-619
• /
• 2016

Pitch synthesis reaction was studied based on the effect for chemical composition of feedstock. Feedstock was selected as pyrolyzed fuel oil (PFO) and coal-tar (CT), which are by-products in petroleum and steel industry. Pitch was prepared at $420^{\circ}C$ for 180 minutes on atmospheric pressure by thermal treatment. Thermal stability and softening point (SP) of the prepared pitches were investigated and their molecular weight distribution was analyzed by MALDI-TOF. PFO has various aliphatic compounds and coal-tar has high aromaticity with 3 wt% of primary quinoline insolubles. The thermal property of PFO was enhanced with polymerization reaction during the thermal treatment with increased molecular weight range. But CT was inferior to PFO because of side reaction by hetero elements. CTP was appeared molecular weight by 0~200 m/z.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.33 no.3
• /
• pp.24-28
• /
• 2001

The utilization of wastepaper as a papermaking raw material is everlastingly required for the environmental protection of earth. However the recycling of wastepaper for this purpose cause another problem such as the increasing of the load of wastewater treatment, lower strength properties of paper, and poor printability, etc. The interest in the development of the environmentally friendly deinking technology is increased continuously. Thus, our research team have tried to apply the ozone to the deinking of white ledger and ONP, and obtained the positive results which can be considered as an alternative method for the conventional deinking method. The purpose of this study is to investigate the mechanism of ozone deinking. Styrene acrylate and polystyrene were treated with ozone and measured the change of molecular weight with the GPC. The molecular weight distribution obtained with GPC showed only slight increase by the ozone treatment, and gel formation by the polymerization was observed. Therefore the removal of ink particles with ozone treatment seems to be facilitated by the increase of the brittleness and decrease of adhesive property.

• Journal of Microbiology and Biotechnology
• /
• v.19 no.3
• /
• pp.299-306
• /
• 2009

Dissolved oxygen (DO) has a significant effect on the molecular weight of hyaluronic acid (HA) during the fermentation of Streptococcus zooepidemicus. Therefore, to further investigate the effect of DO on the yield and molecular weight of HA, this study compared the metabolic flux distribution of S. zooepidemicus under aerobic conditions at various DO levels. The metabolic flux analysis demonstrated that the HA synthesis pathway, considered a dependent network, was little affected by the DO level. In contrast, the fluxes of lactate and acetate were greatly influenced, and more ATP was generated concomitant with acetate at a high DO level. Furthermore, the has gene expression and HA synthase activity were both repressed under anaerobic conditions, yet not obviously affected under aerobic conditions at various DO levels. Therefore, it was concluded that the HA molecular weight would seem to depend on the concomitant effect of the generation of ATP and reactive oxygen species. It is expected that this work will contribute to a better understanding of the effect of the DO level on the mechanism of the elongation of HA chains.

• Journal of the Korean Ceramic Society
• /
• v.42 no.8 s.279
• /
• pp.593-598
• /
• 2005

Polycarbosilane was synthesized by the Kumada rearrangement of polydimethylsilane in the presence of zeolite (ZSM-5) as a catalyst at $350^{\circ}C$. The prepared polycarbosilane had very low molecular weight ($M_w=500$), so that it was not suitable to fabricate SiC fiber by melt spinning. Further polymerization of PCS was conducted around $400^{\circ}C$ to obtain spinnable polycarbosilane. After polymerization, the polycarbosilanes were isolated by distillation according to the molecular weight distributions. The PCS with a controlled molecular weight distribution was spun into continuous polycarbosilane green fibers. The PCS green fiber was successfully transformed into silicon oxycarbide fiber. The room temperature strength of the SiC fiber was around 1.5 - 1.8 GPa. The oxidation behavior and the tensile strength after oxidation were also evaluated.

• Carbon letters
• /
• v.15 no.2
• /
• pp.129-135
• /
• 2014

Spinnable pitch for melt-electrospinning was obtained from pyrolized fuel oil by electron beam (E-beam) radiation treatment. The modified pitch was characterized by measuring its elemental composition, softening point, viscosity, molecular weight, and spinnability. The softening point and viscosity properties of the modified pitch were influenced by reforming types (heat or E-beam radiation treatment) and the use of a catalyst. The softening point and molecular weight were increased in proportion to absorbed doses of E-beam radiation and added $AlCl_3$ due to the formation of pitch by free radical polymerization. The range of the molecular weight distribution of the modified pitch becomes narrow with better spinning owing to the generated aromatic compounds with similar molecular weight. The diameter of melt-electrospun pitch fibers under applied power of 20 kV decreased 53% ($4.7{\pm}0.9{\mu}m$) compared to that of melt-spun pitch fibers ($10.2{\pm}2.8{\mu}m$). It is found that E-beam treatment for reforming could be a promising method in terms of time-savings and cost-effectiveness, and the melt-electrospinning method is suitable for the preparation of thinner fibers than those obtained with the conventional melt-spinning method.

• Polymer(Korea)
• /
• v.36 no.4
• /
• pp.513-518
• /
• 2012

Polyamide 12 (PA12) oligomers (oPA1) were prepared by dispersion polymerization of ${\omega}$-amino carboxylic acid and dibasic acid in a dispersion medium, thermally stable hydrocarbon liquid paraffin, YK-D130 (a step polymerization). The molecular weight and various properties of other oligomeric PAs (oPA2) obtained by bulk polymerization without the medium were compared with those of oPA1s. The oPA1s showed lighter white color and narrower molecular weight distribution than oPA2s at the same molecular weight. Moreover elastomeric poly(ether-block-amide) (PEBA)s were synthesized with oPA1 and oPA2 as hard segments and poly(tetramethylene glycol) (PTMG) as a soft segment. The molecular weight distribution, and mechanical property of the PEBA originated from the both oligomeric PAs were characterized.

• Journal of the Korean Applied Science and Technology
• /
• v.34 no.4
• /
• pp.857-865
• /
• 2017

This study was conducted to analyze and characterize the properties of polyethylene wax polymerized and polymerized using various metallocene catalysts based on Indene and Cyclopentadien, which are different from Ziegler-Natta catalysts used in polyethylene polymerizatio n. The polymerization of polyethylene wax was carried out under various conditions by adjusting the polymerization temperature and the ratio of hydrogen gas used as a chain transfer agent and ethylene gas to metallocene catalysts containing ligands of different structures. The molecular weight and molecular weight distribution, The catalyst yields were compared and analyzed. As a result, the structure of a metallocene catalyst suitable for having a low molecular weight and a narrow molecular weight distribution was proposed and the ideal polyethylene wax could be polymerized.

• Journal of the Korean Vacuum Society
• /
• v.6 no.3
• /
• pp.213-219
• /
• 1997

The plasma polymerized styrene films were prepared by using an inter-electrode capacitively coupled gas-flow-type reactor, and the effects of plasma polymerization condition on the molecular weight distribution were investigated by Fourier Transform Infrared (FT-IR), Pyrolysis Gas Chromatography(PyGC), Differential Scanning Calorimetry(DSC) and Gel Permeation Chromatography(GPC). From the above results, the very cross-linked films different from chemical characteristics of the starting monomer were taken out, and it is realized that the molecular structure, cross linking density, and molecular weight distribution could be controlled by changing the parameters such as deposition pressure, deposition power and gas flow rate. Accordingly, it is suggested that plasma polymerization method performed by inter-electrode capacitively coupled gas-flow-type reactor has good characteristics for manufacturing the functional organic thin films which can be applied in sensors, opto-electric device, photo-resist by changing the polymerization parameters.

• Journal of Environmental Health Sciences
• /
• v.33 no.2 s.95
• /
• pp.158-165
• /
• 2007

본 연구는 근원에 따른 용존 유기물의 특성을 평가하기 위해 하천수, 호소수, 하수 2차 처리 유출수의 자연수 및 Aldrich, Wako 사에서 공급된 휴믹산을 대상으로 분자량 분포에 따른 물리 화학적인 수질 특성, 생분해도, 소독, 부산물의 생성 등을 고찰하였다. SUVA를 이용해서 자연수의 생분해 가능성을 평가한 결과 호소수, 하수, 하천수 순으로 예측되었으며 이는, 실제 생분해도 실험 결과와 유사하였다 생분해 반응 중 저분자 영역대의 용존 유기물은 점차 감소하였고 반면에 고분자 영역대의 용존 유기물은 증가하였다. SMP는 전체 용존 유기물의 0.7-5.5%정도 관찰되었으며 고분자 물질을 많이 함유한 시료에서 높게 나타났다. THM 생성은 대체로 고분자 물질이 높을수록 증가하였으며 THMFP도 Wako 휴믹산을 제외한 샘플에서 이와 유사한 경향을 나타냈다.