• Polymer(Korea)
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• v.33 no.2
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• pp.175-182
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• 2009

Waterborne polyurethanes (WPUs) based on isophorone diisocyanate and mixed polyols of poly(tetramethylene glycol) (PTMG)/polycarbonate diol (PCD) were synthesized. The variation of mechanical and dyeing properties and alkali resistance of the WPU films were analyzed according to the polycarbonate (PC) content. The tensile strength of the films increased and the elongation at break decreased with the PC content in the WPU film. The incorporation of PC component in the WPU film did not affect the alkaline hydrolysis behavior. The synthesized WPU solutions were used as impregnating resins for the production of PET artificial leathers. The prepared WPU resins showed the good color fastness to washing, rubbing, and light of the artificial leather fabrics. The improvement of the properties became greater with the PC content in the WPU resin.

• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.376-380
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• 2007

Used polyurethane (PU) was chemically degraded by the treatment with flame retardants such as tris(1,3-chloro-2-propyl) phosphate (TCPP), triethyl phosphate (TEP), and trimethyl phosphate (TMP). Analysis of FT-IR and P-NMR showed that the degraded products (DEP) contained oligourethanes. Rigid polyurethane foam was produced using the DEP as flame retardants. The flammability and thermal stability of recycled rigid polyurethane were investigated. The mechanical properties such as compressive strength of recycled polyurethane were also studied. The recycled polyurethane reduced flammability and enhanced thermal stability over intrinsic polyurethane. Mechanical strength of recycled polyurethane also shows as high as that of intrinsic polyurethane. In order to evaluate flame retardant properties of the recycled polyurethane foams with various amounts of DEP, heat release rate (HRR) of the foam was measured by cone calorimeter. Scanning electron micrograph of recycled PU showed a uniform cell morphology as a intrinsic PU.

• Polymer(Korea)
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• v.36 no.6
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• pp.693-698
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• 2012

In this study aluminum isopropyl oxide ($Al(O-i-Pr)_3$) was supported on the amine-functionalized surface of silica to synthesize high molecular weight (MW) polylactide (PLA), and it was tested for PLA polymerization behaviors. A silica was funtionalized with silane compound having amine groups, then in-situ treated with $Al(O-i-Pr)_3$. $Al(O-i-Pr)_3$ attached to amine group on silica showed activity only in the presence of MAO (methyl aluminoxane). At the polymerization temperature of $115^{\circ}C$, the conversion and the MW of PLA were increased as the amount of silane was increased. At the polymerization temperature of $130^{\circ}C$, the conversion was decreased while the MW was increased drastically and reached to MW 44000 g/mol when the amine concentration was 3.0 mmol/g. A bimodal type GPC curve was shown at the polymerization temperature of $115^{\circ}C$. As the amount of amine group increased, the peaks of GPC curve were merged. At the polymerization of $130^{\circ}C$, a unimodal GPC curve was shown. $Al(O-i-Pr)_3$ supported on amine-functionalized silica was able to produce higher MW PLA with enhanced activity compared to homogeneous $Al(O-i-Pr)_3$.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.221-226
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• 2016

Production of eco-friendly and biologically harmless materials is strongly required in all industries. In particular, reducing volatile organic compounds in coating processes is extremely important to secure worker's safety. During recent two decades, extensive research works on water-borne polyurethane dispersion (PUD) have been continuously developed as an alternative to solvent-borne polyurethane. However, PUD was shown inferior mechanical properties to the organic solvent-borne polyurethane due to a limit to the molecular weight increase, which resulted in the limit of applications. To overcome this drawback, several approaches have been examined such as polymer blends and thermal/radiation induced crosslinking. Among these methods, the radiation curing system was suitable for industrialization because of the high crosslinking density and fast curing speed. In this study, we overcame the drawback for PUD via introducing benzophenone radiation curable units to PUD. We synthesized PUD films which possessed good dispersion in water for 30 days, increased Tg and Td more than $5^{\circ}C$ after UV curing film as well as improved young's modulus more than double.

• The Korean Journal of Zoology
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• v.22 no.2
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• pp.81-93
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• 1979

Metabolic changes of early mouse embryos treated with progesterone were investigated in order to elucidate the mode of action of progesterone on embryogenesis in vitro. The embryos were cultured, and labelled with radioactive precursors of macromolecules for certain periods in the absence or presence of various concentrations of progesterone by employing the microtube culture technique. The changes of transport and macromolecular synthesis systems of the embryos were examined by measuring the amounts of uptake and incorporation of the precursors. The results obtained were as follows: 1. Progesterone stimulated markedly the uptake of amino acids, but rather suppressed their incorporation by embryonic cells. 2. Progesterone suppressed both the uptake and incorporation of nucleotide precursors (uridine and thymidine) by embryonic cells. 3. Progesterone penetrated into the embryonic cell membranes and was taken up by them. The present results seem to indicate that the inhibition of the progesterone on the mammalian embryogenesis in vitro may not be directly related to the membrane transport system. They seem to imply that progesterone would penetrate into the embryonic cells and may directly block the biosynethetic pathways of macromolecules, and so lead to the inhibition of the embryogenesis in vitro.

• Polymer(Korea)
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• v.39 no.1
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• pp.169-173
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• 2015

Metallocene was supported on the silica, which was functionalized with aminosilanes such as aminopropyltrimethoxysilane (1NS) or N-[3-(trimethoxysilyl)propyl]ethylenediamine (2NS), and ionic liquids such as 1-butyl-4-methylpyridinium chloride (Cl), tributylmethylammonium chloride (Amm), benzyldimethyltetradecylammonium chloride (Ben), 1-butyl-1-methylpyrrolidinium chloride (Pyr), and then ethylene polymerizations were performed. The Zr contents of $SiO_2/1NS/IL/(n-BuCp)_2ZrCl_2$ and $SiO_2/2NS/IL/(n-BuCp)_2ZrCl_2$ were lower than those of only aminosilane-treated silicas. However, the polymerization activity of $SiO_2/1NS/IL/(n-BuCp)_2ZrCl_2$ was higher than that of $SiO_2/1NS/(n-BuCp)_2ZrCl_2$. The polymerization activity of $SiO_2/2NS/IL/(n-BuCp)_2ZrCl_2$ was lower than that of $SiO_2/2NS/(n-BuCp)_2ZrCl_2$ due to much lower Zr content.

• Journal of the Speleological Society of Korea
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• no.63
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• pp.1-8
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• 2004

The non-magnetic materials with non-conductive showing high structure dispersity were developed on the base of natural quartz and lava-scoria which was collected from Je-ju island in Korea, and treated by methane-chemical technology those were obtained novel properties of magnetization through the analyzing. Depending on the processing conditions and subsequent applications the materials produced by strong methane-chemical reaction (MCR) in alcohol solution showed concurrently magnetic, dielectric and electrical properties. The obtained magnetic-electrical powders classified by aggregate complex of their features as segnetomagnetics, containing a dielectric material as a carrying nucleus, particularly the quartz on that surface one or more layers of different compounds were synthesized having thickness up to 10～50 nm and showing magnetic, electrical and other properties. It was confirmed in magnetizing process that powders of quartz and lava-scoria produced by MCR were better oil adsorbent as of oleophilic and floating matter on water surface although their specific gravities are comparably more than 1 in quartz or less than unity, as that of water, in lava-scoira. Therefore, it will be Possible and very useful to remove low density and light gravity oil spillage in difficult recovery from sea and inland water contamination spread on water surface, by marine accident and ship sinking accident occurring frequently in recent years, by way of magnetic adsorbent conveyer system in continuous, if it could be built up the mass Production system of water-floating magnetizable oleophilic adsorbent materials with use of iow cost and good Qualify lava-scoria spread on volcano district in Je-ju island. And, there will also be urgent advent of necessity with strong possibility to develop useful applications of various magnetic functional materials include oleophilic adsorbent for removal of sea oil-contaminants and maritime pollutants, and other kinds of various utilities in industrial applications and practical uses of novel functional materials in the fields of environments and health care applications with in deep expectation.

• Polymer(Korea)
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• v.36 no.6
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• pp.776-788
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• 2012

Octa[8-{4-(4'-cyanophenylazo)phenoxy}]octyl and octa[8-{4-(4'-cyanophenylazo)phenoxycarbonyl}]heptanoated disaccharide derivatives were synthesized by reacting cellobiose, maltose, and lactose with 1-{4-(4'-cyanophenylazo) phenoxy}octylbromide or 1-{4-(4'-cyanophenylazo)phenoxycarbonyl}]heptanoyl chloride, and their thermotropic liquid crystalline and photochemical phase transition behavior were investigated. All the {(cyanophenylazo)phenoxy} octyl disaccharide ethers (CADETs) formed monotropic nematic (N) phases, whereas all the {(cyanophenylazo) phenoxycarbonyl}heptanoated disaccharide esters (CADESs) exhibited enantiotropic N phases. Compared with CADETs, CADESs showed higher isotropic (I)-to-N phase transition temperatures. Photoirradiation of the disaccharide derivatives in a glass cell or in a cell with a rubbed polyimide (PI) alignment layer at a N phase resulted in disappearance of the N phase due to trans-cis photoisomerization of azobenzene, and the initial N phase was recovered when the irradiated sample was kept in the dark because of cis-trans thermal isomerization and reorientation of trans-azobenzenes. The rates of the photochemical N-I and the thermal I-N phase transition of disaccharide derivatives in a cell with a rubbed PI alignment layer were faster than those in a glass cell, and were significantly different from those observed for the monomesogenic compounds containing cyanoazobenzene and the 4-{4'-(cyanophenylazo)phenoxy}octyl glucose and cellulose ethers. The results were discussed in terms of difference in cooperative motion of azobenzene groups due to the flexibility of the main chain, the number of mesogenic units per repeating units, and the distance between the azobenzene groups.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.625-639
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• 2019

Microplastics are one of the substances threatening the marine ecosystem. Here, we summarize the status of research on the effect of microplastics on marine life and suggest future research directions. Microplastics are synthetic polymeric compounds smaller than 5 mm and these materials released into the environment are not only physically small but do not decompose over time. Thus, they accumulate extensively on land, from the coast to the sea, and from the surface to the deep sea. Microplastic can be ingested and accumulated in marine life. Furthermore, the elution of chemicals added to plastic represents another risk. Microplastics accumulated in the ocean affect the growth, development, behavior, reproduction, and death of marine life. However, the properties of microplastics vary widely in size, material, shape, and other aspects and toxicity tests conducted on several properties of microplastics cannot represent the hazards of all other microplastics. It is necessary to evaluate the risks according to the types of microplastic, but due to their variety and the lack of uniformity in research results, it is difficult to compare and analyze the results of previous studies. Therefore, it is necessary to derive a standard test method to estimate the biological risk from different types of microplastics. In addition, while most of the previous studies were conducted mostly on spheres for the convenience of the experiments, they do not properly reflect the reality that fibers and fragments are the main forms of microplastics in the marine environment and in fish and shellfish. Furthermore, studies have been conducted on additives and POPs (persistent organic pollutants) in plastics, but little is known about their toxic effects on the body. The effects of microplastics on the marine ecosystems and humans could be identified in more detail if standard testing methods are developed, microplastics in the form of fibers and fragments rather than spheres are tested, and additives and POPs are analyzed. These investigations will allow us to identify the impact of microplastics on marine ecosystems and humans in more detail.