• Journal of the Korean Society of Safety
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• v.14 no.2
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• pp.83-89
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• 1999

The electrical properties due to mixture ratio of linear low density polyethylene(LLDPE) and ethylene vinyl acetate(EVA) films are studied. An experimental specimen is selected as LLDPE/EVA of thickness 200${\mu}{\textrm}{m}$ produced by mixture ratio of 50 : 50, 60 : 40, 70 : 30 and 80 : 2 wt%. In temperature range from $25^{\circ}C$ to 12$0^{\circ}C$, the measurement of volume resistivity using a highmegohm meter is performed within 10 minutes since each voltage of DC 100 V, 250 V, 500 V and 1000 V is applied, according to the step voltage method. From FT-IR spectrum for an analysis of physical properties, it can be confirmed that LLDPE blended with EVA shows an absence of carbonyl groups(1735 $cm^{-1}$, C=0) and ether groups(1242 $cm^{-1}$, C-O). The peak of LLDPE and EVA made of mixture ratio of 70 : 30 at 2$\theta$ =21.4$^{\circ}$ in the results of XRD is higher than the others. In the experiment for volume resistivity characteristics in order to investigate the electrical properties of specimen, it is confirmed that volume resistivity is decreased with the increase of the molecular motion and temperature.

• Korean Journal of Veterinary Research
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• v.60 no.3
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• pp.145-153
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• 2020

This study aimed to evaluate the effects of a bioabsorbable bone hemostatic agent comprising poly (ethylene glycol-propylene glycol) copolymers (PEG-PPG) on hemostasis and osteogenesis. Bilateral 3 mm diameter calvarial defects were created in 99 male Sprague-Dawley rats. The defects were filled with PEG-PPG or bone wax. The defects of control group were left unfilled. Virtual autopsy was performed to evaluate bioabsorption. The calvaria were subjected to x-ray microtomography (microCT) and histological examination. Bone volume fraction (BV/TV) and bone mineral density (BMD) were measured using microCT; furthermore, white blood cell count and histological examination were performed. After application of PEG-PPG and bone wax, immediate hemostasis was achieved. Autopsy revealed that PEG-PPG disappeared within 48 h at the application site; in contrast, bone wax remained until 12 weeks. The PEG-PPG and control groups showed significantly more osteogenesis than the bone wax group with respect to BV/TV and BMD at 3, 6, and 12 weeks (p < 0.05). Histology revealed that the bone wax group exhibited little bone formation with inflammation. In contrast, PEG-PPG and control groups showed significantly more qualitative osteogenesis than the bone wax group (p < 0.01). In conclusion, PEG-PPG showed immediate hemostasis and was absorbed to allow progressive osteogenesis.

• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.901-905
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• 2003

The lower critical solution temperature (LCST) of thermosensitive poly(organophosphazenes) with methoxypoly(ethylene glycol) (MPEG) and amino acid esters as side groups was studied as a function of saccharide concentration in aqueous solutions of mono-, di-, and polysaccharides. Most of the saccharides decreased the LCST of the polymers, and the LCST decrease was more prominently observed by saccharides containing a galactose ring, such as D-galactose, D-galactosamine and D-lactose, and also the polysacccharide, 1-6-linked D-dextran effectively decreased the LCST of the polymers. Such an effect was discussed in terms of intramolecular hydrogen bonding of saccharides in polymer aqueous solution. The saccharide effect was found to be almost independent on the kinds of the amino acid esters and MPEG length of the polymers. Such a result implies that the polymer-saccharide interaction in aqueous solution is clearly influenced by the structure of sacchardes rather than by that of the polymers. The acid saccharides such as D-glucuronic and D-lactobionic acid increased the LCST, which seems to be due to their pH effect.

• Journal of Korean Society of Forest Science
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• v.103 no.3
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• pp.368-374
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• 2014

This study was investigated the changes of storability and quality characteristics of 'Autumn Sense' hardy kiwifruit according to ethylene treatment and storage condition. In the results of investigation of changes in hardy kiwifruit quality during storage period, hardness of ethylene treated hardy kiwifruit during 48 and 96 hours was rapidly decreased, but soluble solid content was rapidly increased with the passing of storage period in all treatment groups. The total acid was estimated from 0.7 to 1.4% with storage period in all treatment groups. In the results of investigation of the weight loss rate, ethylene treated hardy kiwifruit during 48 hours was the highest 30.9% in storage at $20^{\circ}C$ and lowest 5.9% in storage at $2^{\circ}C$ with a relative air humidity of about 90% during storage at 24 days. Ethylene treated hardy kiwifruit during 96 hours was decrease 29.4% in storage at $20^{\circ}C$, 20.7% in storage at $4^{\circ}C$, 12.1% in storage at $2^{\circ}C$, and 6.0% in storage at $2^{\circ}C$ with a relative air humidity of about 90% during storage at 22 days. The taste of hardy kiwifruit during storage was reduced to increase in all treatment groups. Particularly, storage at $20^{\circ}C$ was rapidly reduced to increase in the early storage and storage at $2^{\circ}C$ with a relative air humidity of about 90% was decrease after storage at 18 days. The rotten rate during storage was increased in all treatment groups, storage at $20^{\circ}C$ was after storage at 2 days and storage at $2^{\circ}C$ with a relative air humidity of about 90% was rapidly increased after storage at 16 days. Thus, it can be recommended that storage at $2^{\circ}C$ with a relative air humidity of about 90% is good to maintain quality. Also, we will decide optimal storage condition and after-ripening time of 'Autumn Sense' hardy kiwifruit.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.195-198
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• 2002

Poly(crown ether)s as a functional polymer materials have powerful and selective complexation properties with a large number of metal cations and have advantage of facility of their recovery and modification of their complexation properties in contrast to their monomeric analogues. Poly(crown ether)s having pendant macrocyclic groups can easily form 2:1-type crown ether ring-to-cation complexes with particular metal ions which are a little larger than the cavity of the crown ether ring. (omitted)

• Proceedings of the Korean Environmental Health Society Conference
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• 2005.11a
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• pp.150-153
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• 2005

A gas chromatography/electron impact mass spectrometric assay method was developed for the determination of Hb-adduct, 2-(hydroxyethyl)valine (HEVal), of ethylene oxide(EO). Globin was separated from hemoglobin by acid iso-propanol and ethyl acetate, then HEVal was isolated as PFPITH-HEVal by Edman degradation. PFPITH-HEVal was silylated with N-methyl-N-(tert-butyl-dimethylsilyl)trifluoroacetamide(MTBDMSTFA)-NH4I (1000:4) under catalysis of dithioerythritol. The detection limit of the assay was 5.8 pmol/g based upon assayed hemoglobin of 0.1g. Two groups of mice were exposed to EO for 0.5 and 1.0 hr/day, respectively at 400ppm during 4 weeks. As the result, the adduct levels increased according to the exposure time with the linearity of 0.7011 and 0.8914, respectively, HEVal was very valuable as biomarker for the exposure of EO. In human, HEVal was analyzed until 8.33 pmol/mg.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.12
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• pp.2230-2234
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• 2010

This paper deals with the change of surface potential decay, surface resistivity, contact angle and XPS of ultraviolet-treated PET films. From the experimental results on the surface potential decay of UV degraded-samples, it was found that the accumulation of charge is decreased and the surface potential decay time is shortened. Also, from the result of XPS, it was found that the changes affected by the surface degradation of PET film were caused by the generation of carboxyl groups through the chain decomposition and recombination with oxygen molecules in the air.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.195-198
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• 1998

In this paper, the physical and the volume resistivity properties due to linear low density polyethylene(LLDPE)/ethylene vinyl acetate(EVA) blends are studied. In order to measure the volume resistivity properties. the micro electrometer is used, the range of temperature and applying voltage are 25 to 120[$^{\circ}C$], form 100 to 1000[V] respectively. From FT-IR spectrum, LLDPE blended with EVA shows an absence of carbonyl and ether groups. From the experimental result of the volume resistivity properties, it is confirmed that the volume resistivity is decreased, which was attributed to the increase of molecular motions with the increase of temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.78-83
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• 2001

In this work, the surface of inorganic fillers were modified with some functional groups such as stearic acid, aliphatic long chain, vinylsilane and aminosilane to control the interaction between inorganic fillers and polymer matrix. Ethylene-vinyl acetate copolymers (EVA) with various amount of vinyl-acetate content and copolyether-ester elastomer were used as polymer matrix. The addition of inorganic fillers increases flame retardancy, but results in steep drop of electrical and mechanical properties, which may be caused by the defect in the interface between organic/inorganic hybrid composites. The hybrid composites are found to show better mechanical properties and higher volume resistivities as inorganic fillers are well dispersed and have good adhesion with polymer matrix. Also, the most effective type of functional group coated on fillers depends on the chemical structure of polymer.

• Fibers and Polymers
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• v.7 no.1
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• pp.1-7
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• 2006

Interaction of a representative antibiotic, doxycycline(Doxy), with commercial poly(acrylonitrile) (PAN) and cationic-dyeable poly(ethylene terephthalate)(PET) fiber was studied in development of infection resistant biomedical materials. Regular PET was also employed for a comparison purpose. Their interactions were investigated at different treatment temperatures, times, and pHs. Fibers were also hydrolyzed by 1% NaOH for 1 or 2 hours at $85^{\circ}C\;and\;100{\circ}C$ to study effect of hydrolysis on antibiotic sorption. Infection-resistant characteristics of the substrates were evaluated by zone of inhibition (ZOI) test. Results revealed that a significant chemical change occurred in PAN and cationic-dyeable PET due to hydrolysis. Additional functional groups obtained by hydrolysis not only enhanced sorption of the antibiotics but also provided greater ZOI values, indicating substantial improvement in sustained infection resistance properties.