• Journal of the Korean Wood Science and Technology
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• v.36 no.6
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• pp.121-129
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• 2008

Environmental friendly UV-curable coatings, having excellent hardness, gloss, mar and chemical resistance, are commonly used for the wooden flooring coatings. Especially epoxy acrylate oligomers are chosen for the wooden flooring coatings, due to their thermal stability and fast curing. In this study, we investigated the effect of the acrylate functionality on the thermal stability and surface hardness. The thermal degradations of monomers, oligomer, photoinitiator and formulated coatings with different acrylate functionality were measured using a thermogravimetric analysis (TGA). And the surface hardness was also measured with a pendulum hardness tester to compare relationship between the thermal stability and the physical property. The cured coatings became thermally stable by crosslinking during UV-curing. Both the thermal stability and surface hardness of cured coatings were improved with increasing acrylate functionality.

• Journal of Microbiology and Biotechnology
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• v.17 no.11
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• pp.1841-1847
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• 2007

We previously identified the origin of replication of p703/5, a small cryptic plasmid from the KBL703 strain of Enterococcus faecalis. The origin of replication contains putative regulatory cis-elements required for replication and a replication initiator (RepA) gene. The replicon of p703/5 is similar in its structural organization to theta-type plasmids, and RepA is homologous to a family of Rep proteins identified in several plasmids from Gram-positive bacteria. Here, we report molecular interactions between RepA and the replication origin of p703/5. DNase I footprinting using recombinant RepA together with electrophoretic mobility shift assays confirmed the binding of RepA to the replication origin of p703/5 via iterons and an inverted repeat. We also demonstrated the formation of RepA dimers and the different binding of RepA to the iteron and the inverted repeat using gel filtration chromatographic analysis, a chemical crosslinking assay, and electrophoretic mobility shift assays in the presence of guanidine hydrochloride. Our results suggest that RepA plays a regulatory role in the replication of the enterococcal plasmid p703/5 via mechanisms similar to those of typical iteroncarrying theta-type plasmids.

• Elastomers and Composites
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• v.36 no.4
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• pp.268-277
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• 2001

The MDI(4,4'-diphenyl methane diisocyanate) was mixed with PPG, PEG and trimethylolpropane(TMP) respectively to prepare polyurethane resin. The various physical properties were measured for the mixtures. The gel-time was shortened by adding of PEG and TMP The molecular weight made a greater influence on the gel-time than the number of functional groups. The NCO-OH reaction was more active and faster than the NCO-NCO reaction. The hardness was influenced by crosslinking-density and molecular structure. The NCO-OH reactions yielded the flexible films and the NCO-NCO reactions yielded the brittle films. The increase of crystallinity and shrinkage induced the low adhesion ratio but the adding of TMP induced the high adhesion ratio. The flame-retardancy was influenced by quantity and kinds of flame-retardant. IXOL B-251 was the most excellent among the flame-retardants employed in this study. TCCP was partially separated because of the lack of solubility.

• Fashion & Textile Research Journal
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• v.10 no.5
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• pp.748-755
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• 2008

The purpose of this study is to investigate the effect of chitosan treatment on the dyeing of cotton fabric using charcoal as colorants. Particle size of charcoal, dyeability(K/S), SEM morphology of dyed fabrics and color fastness were also investigated. In this study, cotton fabrics were treated with a crosslinking agent epichlorohydrin in the presence of chitosan to provide the cotton fabrics the dyeing properties of natural dye by the chemical linking of chitosan to the cellulose structure. The results obtained were as follows; Mean average diameter of charcoal was 1.44 ${\mu}m$. According to various conditions, the dyeing effects of 1% chitosan treatment on the dyeing of cotton fabrics using charcoal were the highest with 10%(owb) of charcoal at $90^{\circ}C$ for 120minutes and non-treatment of cotton fabrics were the highest with 15%(owb) of charcoal at $90^{\circ}C$ for 150minutes. Overall, K/S value of 1% chitosan treatment of cotton fabrics on the natural dyeing using charcoal was higher than non-treatment of cotton fabrics. It was observed the surfaces of cotton fabrics treated with chitosan were adsorbed with charcoal powders of particle size more than a non-treated chitosan fabric by SEM. The cotton fabrics were dyed with blackish gray color by charcoal gradually according to treating chitosan. The K/S value, that is indicative of dye affinity, became higher as the increase of treated chitosan concentration. The color fastness of charcoal, washing and light fastness was excellent as 4-5 grade.

• Fashion & Textile Research Journal
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• v.10 no.4
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• pp.552-559
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• 2008

Recent days, various inner wears, sheets and interior goods are manufactured using materials dyed with loess emphasizing its improved blood circulation, metabolism, anti-bacterial, deodorizing properties, and far-infrared ray emissions. The purpose of this study is to investigate the effect of chitosan treatment on the dyeing of cotton fabric using loess as colorants. Particle size of loess, the morphology and dyeability(K/S) of chitosan crosslinked cotton fabrics, and washing durability of loess dyed cotton fabric were investigated. In this study, cotton fabrics were treated with a crosslinking agent, epichlorohydrin, in the presence of chitosan to improve the dyeing properties of cotton fabrics with natural dye by the chemical linking of chitosan to the cellulose structure. This process was applied by means of the conventional mercerizing process. The results obtained were as follows; Mean average diameter of loess was $1.13{\mu}m$. According to various conditions, the optimum dyeing conditions for cotton fabrics pretreated by 1% chitosan treatment was where 10%(owb) of loess was applied at $90^{\circ}C$ for 120minutes, while for cotton fabrics without chitosan treatment was where 15%(owb) of loess was applied at $90^{\circ}C$ for 150minutes. Overall, K/S value of loess dyed cotton fabric pretreated with 1% chitosan was higher than that of cotton fabrics without chitosan treatment. The Color fastness, washing fastness and light fastness of loess were excellent as 4-5grade.

• Applied Chemistry for Engineering
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• v.7 no.1
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• pp.136-144
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• 1996

Polyacrylic super absorbent polymer(SAP) containing sorbitol was synthesized by inverse-suspension polymerization method. Sodium acrylate and acrylic acid were used as a monomer, ethylene glycol dimethacrylate(EGDMA) and glycerol polyglycidyl ether(GPGE) were used as a crosslinking agent, potassium persulfate(PPS) was used as an initiator, and cyclohexane was used as a solvent. Content of sorbitol was from 10mol% to 50mol% according to the mol ratio of acrylic acid monomer. The size distribution of the round shaped polymeric particle was $177{\sim}707{\mu}m$. Absorption amount of the polymer containing sorbitol was 785 to 1086 times of the polymer weight in distilled water, was 50 to 83 times in 0.9 % NaCl solution. Absorption and retention amount of the polymer were decreased with increasing the amount of sorbitol, but the polymer has an endothermic property which is +5 cal/g SAP.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.167-169
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• 2009

We have carried out quantitative structure and property analysis of the nanoporous structures of low dielectric constant (low-k) carbon-doped silicon oxide (SiCOH) films, which were deposited with plasma enhanced chemical vapor deposition (PECVD) using vinyltrimethylsilane (VTMS), divinyldimethylsilane (DVDMS), and tetravinylsilane (TVS) as precursor and oxygen as an oxidant gas. We found that the SiCOH film using VTMS only showed well defined spherical nanopores within the film after thermal annealing at $450^{\circ}C$ for 4 h. The average pore radius of the generated nanopores within VTMS SiCOH film was 1.21 nm with narrow size distribution of 0.2. It was noted that thermally labile $C_{x}H_{y}$ phase and Si-$CH_3$ was removed to make nanopore within the film by thermal annealing. Consequently, this induced that decrease of average electron density from 387 to $321\;nm^{-3}$ with increasing annealing temperature up to $450^{\circ}C$ and taking a longer annealing time up to 4 h. However, the other SiCOH films showed featureless scattering profiles irrespective of annealing conditions and the decreases of electron density were smaller than VTMS SiCOH film. Because, with more vinyl groups are introduced in original precursor molecule, films contain more organic phase with less volatile characteristic due to the crosslinking of vinyl groups. Collectively, the presenting findings show that the organosilane containing vinyl group was quite effective to deposit SiCOH/$C_{x}H_{y}$ dual phase films, and post annealing has an important role on generation of pores with the SiCOH film.

• YAKHAK HOEJI
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• v.55 no.1
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• pp.69-74
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• 2011

Hyaluronic acid (HA) is a natural polymer consisting of disaccharide units of D-glucuronic acid and N-acetyl-D-glucosamine. It has a great potential and success in cosmetic and biomedical applications. However, native HA is highly soluble and easily metabolized by enzymes such as hyaluronidase. Thus, various studies have been reported on modifying the physicochemical properties of HA, while maintaining its biocompatibility. For controlled drug delivery, many trials for fabricating HA microspheres were achieved under chemical reaction. The HA microspheres fabricated to improve the physical stability of HA using adipic acid dihydrazide (ADH) by cross-linking reaction has been reported earlier, however it lacks the desired physical stability and rapidly decomposes by swelling or enzymes. Therefore, we prepared double cross-linked HA microspheres (DC-HA microspheres) and alginate containing HA microspheres (AC-HA microspheres) to enhance its physicochemical properties. DC-HA microspheres were prepared using trisodium trimetaphosphate (STMP) under crosslinking reaction after ADH cross-linking reaction. AC-HA microspheres were prepared by adding alginate as a networking polymer. These microspheres were characterized by morphology, particle size, zeta potential, stability against hyaluronidase. Results showed that the DC-HA and AC-HA microspheres are more stable than that of HA microspheres.

• Polymer(Korea)
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• v.32 no.1
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• pp.56-62
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• 2008

Three types of network polyesters have been newly synthesized by a two-step condensation reaction by the various combination of several diols and diacids. When these polymer films were thermally treated at $240^{\circ}C$, they exhibited absorptions in a visible range despite the forbidden transition of carbonyl group. When excited at wavelengths above 330 nm, the polymers showed fluorescences in a wide visible range from blue to near yellow. These fluorescence phenomena are due to the formation of certain conjugated structures by the Knoevenagel type self-condensation under the high-temperature thermal treatment. These polymers showed significant difference in the thermal properties as a function of the degrees of chemical crosslinking. They also underwent photodegradation. Highly resolved, fluorescent image patterns were successfully obtained by the photodegradation of malonate group under a strong UV-light irradiation.

• Polymer(Korea)
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• v.39 no.2
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• pp.240-246
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• 2015

Formation of a strong 3-dimensional interfacial network structure via chemical reaction between hydroxyl group on silica surface and NR chain by the addition of bis(triethoxysilylpropyl)tetrasulfide (TESPT) into silica-filled NR compound was observed by using Py-GC/MS and SEM. Addition of TESPT into silica-filled NR compound decreased scorch time ($t_{10}$) due to increased sulfur content, and reduced cure rate index (CRI) via continuous reaction between sulfur atoms in TESPT, which acted as a sulfur donor, and activators and/or accelerators. Addition of TESPT in the compound improved processability and mechanical properties of the compound. Overall, we observed that the addition of TESPT into the silica-filled NR compound formed a silica-TESPT-NR network, and thus the degree of crosslinking was increased resulting in improved mechanical properties.