• Elastomers and Composites
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• v.33 no.3
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• pp.193-200
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• 1998

It is well known that EPDM(ethylene propylene diene monomer) rubber has inherently excellent resistance to the weathering, ozone, heat, cold and moisture, whereas crosslinked IIR (isobutylene isoprene divlnyl benzene terpolymer) shows proper resistance to the water and gas permeation. Various characteristics of EPDM blend with crosslinked IIR such as curing characteristics, mechanical properties, dispersion of minor component and gas impermeability were explored. The optimum curing time $(t_{90})$ examined with peroxide was decreased by adding small amount of crosslinked IIR to the EPDM rubber. Mechanical properties of blends such as tensile strength, hardness and elongation at break were enhanced by increasing EPDM content. These results might be explained with the affinity of carbon black to the EPDM rubber. On the other hand, the physical properties were not changed significantly after aging, and the increase of crosslinked IIR fraction caused the decrease of compression set to small rate. EPDM rubber shows different behavior with crosslinked IIR in oxygen permeability. By adding 30wt.% crosslinked IIR to the EPDM rubber, the resistance to the oxygen permeation was improved up to three times than that of pure EPDM rubber. Conclusively, EPDM blend containing 30wt.% crosslinked IIR might be commercially applied to the o-ring and electric parts because of its proper resistance to the weathering, ozone and oxygen permeability.

• Asian Journal of Atmospheric Environment
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• v.11 no.1
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• pp.29-32
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• 2017

Ozone concentration in Tokyo Metropolitan area is one of the most serious issues of the local air quality. Tropospheric ozone is formed by radical reaction including volatile organic compound (VOC) and nitrogen oxides ($NO_x$). Reduction of the emission of reactive VOC is a key to reducing ozone concentrations. VOC is emitted from anthropogenic sources and also from vegetation (biogenic VOC or BVOC). BVOC also forms ozone through $NO_x$ and radical reactions. Especially, in urban area, the BVOC is emitted into the atmosphere with high $NO_x$ concentration. Therefore, trees bordering streets and green spaces in urban area may contribute to tropospheric ozone. On the other hand, not all trees emit BVOC which will produce ozone locally. In this study, BVOC emissions have been investigated (terpenoids: isoprene, monoterpenes, sesquiterpenes) for 29 tree species. Eleven in the 29 species were tree species that did not emit BVOCs. Three in 12 cultivars for future planting (25 %) were found to emit no terpenoid BVOCs. Eight in 17 commonly planted trees (47%) were found to emit no terpenoid BVOC. Lower-emitting species have many advantages for urban planting. Therefore, further investigation is required to find the species which do not emit terpenoid BVOC. Emission of reactive BVOC should be added into guideline for the urban planting to prevent the creation of sources of ozone. It is desirable that species with no reactive BVOC emission are planted along urban streets and green areas in urban areas, such as Tokyo.

• Journal of the Korean Society of Tobacco Science
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• v.25 no.2
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• pp.144-153
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• 2003

This study was carried out to determine the relationship between smoke components and sensory evaluation by changes tobacco leaf blending. Seven different cigarettes were made by adding different types of oriental, reconstituted and expanded tobacco leaves. 62 kinds of smoke components which were 6 of general components, 34 of semi-volatile and volatile components, 9 of acid components, and 13 of phenolic components were analyzed. Eight kinds of sensory item were evaluated and also electronic nose system data was collected. All smoke components and sensory characteristics of mainstream smoke were changed by the different blending. To determine the relationship between smoke components and sensory test, the correlation and regression analysis were carried out by using SPSS statistical program. Tar, pH, and CO showed a high correlation with sensory evaluation item. As tar related to hotness, CO have a high correlation with offensive aroma. Semi-volatile and volatile components of smoke related to sensory characteristics such as aroma, taste, irritation, hotness and smoothness. When propylene, l,3-butadiene, butane, isoprene, and 2-methylfuran showed a high correlation with aroma; methyl chloride, methanol, toluene, ethyl benzene showed a high correlation with irritation. Some acidic components and phenolic components of smoke also had a high relation to smoke volume. Especially the acidic components such as 2-furoic acid, 2-hydroxybutyric acid, phenylacetic acid and palmitic acid; the phenolic components such as 4-vinyl phenol, pyrocatechol, 3-methyl catechol, hydroquinone showed a high correlation with smoke volume. As using regression analysis, it was possible to estimate the results of sensory evaluation from the smoke analysis data. From the results of electronic nose system analysis, we can find the different pattern by adding expanded tobacco leaf.

• Journal of the Korean Society of Tobacco Science
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• v.31 no.1
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• pp.18-28
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• 2009

This study describes the manufacturing method of antioxidant filter and evaluate the reduction of free radical and biological activity from mainstream smoke. When we used spray-brush for the application of antioxidant solution to the filter, cv(coefficient of variation) levels of antioxidant added to filter ranged within 3 %, which means stable and constant feeding process. 0.3~0.5mg per cigarette of antioxidant were sprayed to acetate and active carbon part in the filter plug, respectively. It was considered that the use of antioxidant added filter resulted in the reduction of the gaseous compounds of free radicals from 17 % to 19 % in the mainstream smoke. Variation for removal efficiency of free radical in antioxidant filter added to acetate part was more pronounced than that of filter added to active carbon part. Smoking deliveries of tar, nicotine for the antioxidant added filters were similar when comparing to the non-antioxidant added filter, but the delivering amounts of isoprene were significantly reduced. The estimation of consumed GSH(glutathion) showed that the gaseous toxicity of the antioxidant added filter was 14 % ~ 23 % lower than that of non-antioxidant added filter. No significant differences were observed for the total taste quality in sensory evaluation.

• Journal of the Korean Society of Tobacco Science
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• v.29 no.2
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• pp.90-97
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• 2007

This study was conducted to evaluate the effect of additives (antioxidants for free radicals reduction) in cigarette filter treated with various antioxidants (three types of proanthocyanidins and ascorbic acid) and various concentrations of ascorbic acid and loaded with activated carbon on the delivery of free radicals of mainstream smoke (MS) by ESR. Also, we analyzed Hoffmann's analytes andscavenger activity according to the storage time and in vitro cytotoxicity. The analysis of spin number of vapor and particulate phase free radicals in MS are decreased to $14{\sim}24\;%$ and $16{\sim}40\;%$, respectively. As aresult of antioxidant potential for inactivity of vapor and particulate phase free radicals, natural antioxidants were more effective than ascorbic acid. Based on the result of the analysis of Hoffmann's analytes for various antioxidantstreated cigarette filters during the smoking, cigarette filter treated with ascorbic acid showed the lower amount of the deliveries of hydroquinone, isoprene and quinoline in MS than those treated with the other antioxidants. In the significant t-test on the difference of the cytotoxicity among the various antioxidants treated-cigarette filters, there are no significant differences at the 95 % confidence level. Those results indicated that the antioxidants were useful for reducing free radicals in MS because of the fast reaction between antioxidant and free radicals.

• Journal of Microbiology and Biotechnology
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• v.16 no.10
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• pp.1537-1543
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• 2006

A bacterial strain named HY-3 that produces a highly active extracellular protease was isolated from the digestive tract of a spider, Nephila clavata. The bacterium was a Gram-negative, oxidase-negative, catalase-positive, nonhalophilic, nitrate-reducing, facultative anaerobe. Transmission and scanning electron microscopies demonstrated that the isolate was non-spare-forming, straight, rod-shaped, and motile by peritrichous flagella. The G+C content of the DNA was 57.0 mol%. The isoprenoid quinone type was ubiquinone with 8 isoprene units (Q-8). The morphological and biochemical characteristics including the predominant fatty acid and phospholipids profiles placed the isolate HY-3 in the family Enterobacteriaceae. Further biochemical characterization and phylogenetic studies including determination of an almost complete 16S ribosomal DNA sequence suggested that the bacterium was closely related to the genus Serratia. DNA-DNA hybridization analysis revealed that this extracellular protease-producing strain belongs to Serratia proteamaculans, which is also known far its association with insects.

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.3
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• pp.320-328
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• 2016

Among biogenic volatile organic compounds (BVOCs) in the natural ecosystem, monoterpenes, along with isoprene, play important roles in atmospheric chemistry and make significant impacts on air pollution and climate change, especially due to their contribution to secondary organic aerosol production and photochemical ozone formation. It is essential to measure monoterpene concentrations accurately for understanding their oxidation processes, emission processes and estimation, and interactions between biosphere and atmosphere. Thus, traceable calibration standards are crucial for the accurate measurement of monoterpenes at ambient levels. However, there are limited information about developing calibrations standards for monoterpenes in pressured cylinders. This study describes about developing primary standard gas mixtures (PSMs) for monoterpenes at about 2 nmol/mol, near ambient levels. The micro-gravimetric method was applied to prepare monoterpene (${\alpha}$-pinene, 3-carene, R-(+)-limonene, 1,8-cineole) PSMs at $10{\mu}mol/mol$ and then the PSMs were further diluted to 2 nmol/mol level. To select an optimal cylinder for the development of monoterpene PSMs, three different kinds of cylinders were used for the preparation and were evaluated for uncertainty sources including long-term stability. Results showed that aluminum cylinders with a special internal surface treatment (Experis) had little adsorption loss on the cylinder internal surface and good long-term stability compared to two other cylinder types with no treatment and a special treatment (Aculife). Results from uncertainty estimation suggested that monoterpene PSMs can be prepared in pressured cylinders with a special treatment (Experis) at 2 nmol/mol level with an uncertainty of less than 4%.

• Asian Journal of Atmospheric Environment
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• v.11 no.4
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• pp.300-312
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• 2017

To improve the understanding of secondary organic aerosol (SOA) formation from the photo-oxidation of anthropogenic and biogenic precursors at the regional background station on Baengnyeong Island, Korea, gas phase and aerosol chemistries were investigated using the Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-ToF-MS) and the Aerodyne High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS), respectively. HR-ToF-AMS measured fine particles ($PM_1$; diameter of particle matter less than $1{\mu}m$) at a 6-minute time resolution from February to November 2012, while PTR-ToF-MS was deployed during an intensive period from September 21 to 29, 2012. The one-minute time-resolution and high mass resolution (up to $4000m{\Delta}m^{-1}$) data from the PTR-ToF-MS provided the basis for calculations of the concentrations of anthropogenic and biogenic volatile organic compounds (BVOCs) including oxygenated VOCs (OVOCs). The dominant BVOCs from the site are isoprene (0.23 ppb), dimethyl sulphide (DMS, 0.20 ppb), and monoterpenes (0.38 ppb). Toluene (0.45 ppb) and benzene (0.32 ppb) accounted for the majority of anthropogenic VOCs (AVOCs). OVOCs including acetone (3.98 ppb), acetaldehyde (2.67 ppb), acetic acid (1.68 ppb), and formic acid (2.24 ppb) were measured. The OVOCs comprise approximately 75% of total measured VOCs, suggesting the occurrence of strong oxidation processes and/or long-range transported at the site. A strong photochemical aging and oxidation of the atmospheric pollutants were also observed in aerosol measured by HR-ToF-AMS, whereby a high $f_{44}:f_{43}$ value is shown for organic aerosols (OAs); however, relatively low $f_{44}:f_{43}$ values were observed when high concentrations of BVOCs and AVOCs were available, providing evidence of the formation of SOA from VOC precursors at the site. Overall, the results of this study revealed several different SOA formation mechanisms, and new particle formation and particle growth events were identified using the powerful tools scanning mobility particle sizer (SMPS), PTR-ToF-MS, and HR-ToF-AMS.

• Analytical Science and Technology
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• v.31 no.1
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• pp.14-22
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• 2018

After signing the WHO FCTC in 2003, South Korea ratified the FCTC in 2005. This study was conducted to provide data on toxic constituents that can be used as useful information for the level of exposure to Korean smokers. Emissions data from five brands of cigarettes were tested under the ISO and "Canadian Intense (HCI)" smoking regimes, respectively. We conducted an analysis of 25 compounds containing nicotine, tar, carbonyls, phenolics, volatile organic compounds (VOCs), and semi-VOC cigarette smoke. Tar and nicotine showed levels of 4.3 to 5.8 mg/cig and 0.4 to 0.5 mg/cig, respectively, which are within the range of tolerance presented in ISO 8243. In the case of carbonyls, formaldehyde was detected within a range of 8.2 to $14.3{\mu}g/cig$, and acetaldehyde was present within a range of 224.7 to $327.2{\mu}g/cig$ under the ISO smoke regime. Crotonaldehyde was not detected under the ISO regime, and all of the carbonyls showed values 2.3 to 4.5 times higher under the HCI regime than those under the ISO regime. Catechol, which showed a level of 47.0 to $80.5{\mu}g/cig$ under the ISO regime and 117.5 to $184.7{\mu}g/cig$ under the HCI regime, was the highest constituent among the phenols. The amount of isoprene was 91.7 to $158.3{\mu}g/cig$ under the ISO regime and 221.0 to 377.0 under the HCI regime. To summarize, most of the constituents showed a tendency to be detected at levels 2 to 4 times higher under the HCI regime than under the ISO regime. Above all, these results represent the first analysis in Korea from an independent institute of tobacco companies under accreditation of ISO 17025.

• Journal of Adhesion and Interface
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• v.8 no.2
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• pp.15-21
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• 2007

To prepare a natural rubber-based pressure-sensitive adhesive (PSA) for protection film of opto- functionalized sheet, natural rubber (NR) was blended with a DCPD type tackifier and three types of aliphatic hydrocarbon resins, respectively. Also, to supply low cohesion strength of NR, in the fixed ratio of tackifier, synthetic rubber, styrene-isoprene-styrene (SIS) block copolymer was blended with NR as a function of SIS contents. PSA performance of prepared PSAs was evaluated using probe tack and peel strength. Probe tack of NR/tackifier blends was increased with increasing tackifier contents, and showed maximum peak. In addition, probe tack of NR/tackifier blends slightly increased with increasing softening point of aliphatic hydrocarbon resins. Their peel strength increased up to 50 wt% of tackifier contents, but in the over contents of tackifier, they showed stick-slip failure mode. Finally, probe tack of NR/SIS/tackifier blends showed the maximum values at 20~40 wt% of tackifier contents, but at 20 wt% of tackifier contents, they showed fibrillation. For this reason, peel strength showed maximum values at 40 wt% of tackifier contents.