• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.3
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• pp.97-103
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• 2023

Barrier films for transparent packaging materials with excellent moisture barrier properties are prepared, utilizing a nanoclay dispersion coating layer formed after a pretreatment process of plasma activation surface treatment process under vacuum at room temperature. Attention is paid on optimizing the coupling additive through the appropriate crosslinking process and optimal dispersion process of the coating process to enhance adhesion. Analysis of the functional coating thin film shows that the water vapor transmission rate is less than 10 g/m²/24 hrs (ASTM F-1249) and the oxygen transmission rate is less than 30 cc/m²/24 hrs (ASTM D3985). It is shown that water barrier properties of coating thin film prepared in this study are greater than conventional untreated films by 10 times or more. The thickness of the transparent gas barrier film is within 0.1 mm, and the transparent gas barrier complex is implemented in two layers. In the study of PET thin film interface characteristics, FT-IR experimental analysis shows the reaction activity was optimized at RDS 1.125 %.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.9-14
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• 2022

Silica aerogel is a porous material with a very low density and high specific surface area. Still, its application is limited due to its weak mechanical properties due to structural features. To solve this problem, a method of complexing it with various polymers has been proposed. We synthesized polyimide cross-linked silica aerogel by the sol-gel process to obtain high mechanical properties. Tetraethyl orthosilicate (TEOS) was used as a precursor to make silica aerogel, and 3- aminopropyltriethoxysilane (APTES) was used as a coupling agent for cross-linking polyimide. Polyimide was synthesized using pyromellitic dianhydride and 3,5-diaminobenzoic acid, and mechanical properties were improved by crosslinking polyimide with 10 repeating units in the polyimide chain using the reaction formula ${\frac{n_1}{n_2}}={\frac{n}{n+1}}$ To realize silica aerogel, polyimide having various weight ratios was added before gelation, resulting in a 19-fold or greater increase in maximum compressive strength compared to pure silica aerogel. From this study, an enhancement of silica aerogel could be enhanced through polymer cross-linking bonds.

• Composites Research
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• v.36 no.5
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• pp.297-302
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• 2023

There are several methods for shaping foams, but the most commonly used methods involve the use of resin mixed with a foaming agent, which is then foamed under high temperature and pressure in the case of compression foaming, or foamed under high temperature without applying pressure in the case of atmospheric foaming. The polymers used for foaming require design and analysis of optimal foaming conditions in order to achieve foaming under ambient pressure. Environmentally friendly bio-based polymers face challenges when it comes to foaming on their own, which has led to ongoing research in blending them with resins capable of traditional foam production. This study investigates changes in the characteristics of bio-based polymer-EVA blend foams based on variations in the content of bio-based polymers and explores the optimal foaming conditions according to crosslinking. The correlation between foaming characteristics and mechanical properties of the foams was examined. Through this research, we gained insights into how the content of bio-based polymers affects the properties of foams containing bio-based polymers and identified differences between ambient pressure and high-pressure foaming processes. Additionally, the feasibility of commercializing bio-based polymer-EVA composite foams was confirmed.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.3
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• pp.259-265
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• 2006

We polymerized material of AA(Acrylic acid) and BMA(butyl methacrylate) to make up for the weak points of hydrogel contact lens. The synthesis process of silicone synthesis is as follows. Acrylate-PDMS(Polydimethylsiloxane)-Urethane prepolymer was composed after Diisocynate reacted with HEMA(2-hydroxyethylmethacrylate) under the catalyst and it reacted again with bis(hydroxyalkyl) terminated poly(dimethylsiloxane) with high oxygen transmissibility characteristics. HEMA(2-hydroxyethylmethacrylate) was used to make prepolymer that can be polymerized and the urethane was used to improve elasticity and oxygen transmissibility, copolymerization was performed with conventional hydrogel contact lens materials to make silicone hydrogel contact lens with higher oxygen transmissibility. For manufacturing of contact lens, We added BMA(Butyl methacrylate) with better elasticity and flexibility, and AA(Acrylic acid) with higher moisturizing to used contact lens materials. AIBN (Azobis2-methylpropionitrile) as initiator and EGDMA(Ethylene Glycol Dimethacrylat) as crosslinking agent were used and the lens with higher oxygen transmissibility and better moisturizing were manufactured complying with basic contact lens properties, which have several combination trial of each monomer characteristics. Compounding SN which included SILICONE, HEMA, NVP and EGDMA etc was showed by swelling ratio of 9.38% and water content of 23.7%. SN was showed by swelling ratio of 9.38%, water content of 23.7% and a visible ray transmissibility of 89%. SB which added BMA in the SN was showed by swelling ratio of 12.50%, water content of 18.56% and a visible ray transmissibility of 88%. SAB which added both AA and BMA in the SN was showed by swelling ratio of 8.33%, water content of 12.93% and a visible ray transmissibility of 88%.

• Journal of the Korean Wood Science and Technology
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• v.40 no.3
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• pp.164-176
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• 2012

In the present study, rapeseed flour (RSF), which is a by-product from the production of edible oil and biodiesel extracted from rapeseed, was used to develop alternative adhesives for the production of plywood panels. To examine the effects of the enzyme on the adhesive properties and formaldehyde emission of the RSF-based adhesive resins, three enzymes, such as cellulase (CEL), pectinase (PEC) and protease (ALC), were used either separately or together. As a crosslinking agent, PF prepolymers, which were prepared with 1.5, 1.8 and 2.1 mole formaldehyde and 1 mol phenol (1.8-, 2.1- and 2.4-PF), were added into the RSF hydrolyzates. The adhesive resins formulated with CEL- or CEL-PEC-RSF hydrolyzates and 1.8-F/P PF prepolymers exhibited excellent adhesive strengths and formaldehyde emission. The tensile shear strength and formaldehyde emission of the plywood panels bonded with the formulate resins were satisfied with the minimum requirement of the KS standard for ordinary plywood panels (0.6 N/$mm^2$). In addition, formaldehyde emissions of the plywood panels approached to that of E0 specified in the KS standard (0.5 mg/${\ell}$), and even had much better than those of commercial UF glue mixes. Overall, the use of RSF-based adhesive resins for the production of plywood panels might provide durable adhesive properties and an environmentally friendly substitute for petroleum-based adhesive resins. However, further researches - the increase of solid content of RSF-based adhesives for reducing press time and the microscopic observation of plywood specimen for identifying the relationship between tensile shear strength and the penetration of adhesives into wood structure - are required to commercialize the RSF-based adhesives.

• Journal of Mushroom
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• v.13 no.1
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• pp.56-62
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• 2015

A lipase producing bacterium was isolated from button mushroom bed, which showing high clear zone on agar media containing Tributyrin as the substrate. The strain was identified as Burkholderia cepacia by analysis of 16S rDNA gene sequence. Crude lipase (CL) was partially purified from 70% ammonium sulfate precipitation using the culture filtrate of B. cepacia. Immobilized lipases were prepared by cross-linking method with CL from B. cepacia and Novozyme lipase (NL) onto silanized Silica-gel as support. Residual activitiy of the immobilized CL (ICL) and immobilized NL (INL) was maintained upto 61% and 72%, respectively. Biodiesel (Fatty acid methyl ester, FAME) was recovered by transesterification and methanolysis of Canola oil using NaOH, CL and ICL as the catalysts to compare the composition of fatty acids and the yield of FAME. Total FAME content was NaOH $781mg\;L^{-1}$, CL $681mg\;L^{-1}$ and ICL $596mg\;L^{-1}$, in which the highest levels of FAME was observed to 50% oleic acid (C18:1) and 22% stearic acid (C18:0). In addition, the unsaturated FAME (C18:1, C18:2) decreased, while saturated FAME (C16:0, C18:0) increased according to increasing the reaction times with both CL and ICL, supporting CL possess both transesterification and interesterification activity. When reusability of ICL and INL was estimated by using the continuous reaction of 4 cycles, the activity of ICL and INL was respectively maintained 66% and 79% until the fourth reaction.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.541-549
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• 2020

The Drug Delivery System (DDS) is defined as a technology for designing existing or new drug formulations and optimizing drug treatment. DDS is designed to efficiently deliver drugs for the care of diseases, minimize the side effects of drug, and maximize drug efficacy. In this study, the optimization of tripolyphosphate (TPP) concentration on the size of Chitosan nanoparticles (CNPs) produced by crosslinking with chitosan was measured. In addition, the characteristics of Fe₃O₄-CNPs according to the amount of iron oxide (Fe₃O₄) were measured, and it was confirmed that the higher the amount of Fe₃O₄, the better the characteristics as a magnetic drug carrier were displayed. Through the ninhydrin reaction, a calibration curve was obtained according to the concentration of γ-aminobutyric acid (GABA) of Y = 0.00373exp(179.729X)-0.0114 (R² = 0.989) in the low concentration (0.004 to 0.02 wt%) and Y = 21.680X-0.290 (R² = 0.999) in the high concentration (0.02 to 0.1 wt%). Absorption was constant at about 62.5% above 0.04 g of initial GABA. In addition, the amount of GABA released from GABA-Fe₃O₄-CNPs over time was measured to confirm that drug release was terminated after about 24 hr. Finally, GABA-Fe₃O₄-CNPs performed under the optimal conditions were spherical particles of about 150 nm, and it was confirmed that the properties of the particles appear well, indicating that GABA-Fe₃O₄-CNPs were suitable as drug carriers.

• Journal of the Korean Wood Science and Technology
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• v.38 no.4
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• pp.323-332
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• 2010

Petroleum-based adhesive resins have extensively been used for the production of wood panels. However, it is necessary to develop environmentally friendly adhesive resins due to the increase of manufacturing cost and the environmental issue, such as the emission of volatile organic compounds, of the pertroleum-based adhesive resins. This study was conducted to formulate environmentally friendly adhesive resins using by rapeseed flour (RSF), which is the by-product of bio-diesel produced from rapeseed, for replacing petroleum-based adhesives with them. To formulate RSF-based adhesive resins, RSF was hydrolyzed in de-ionized water, 1% and 3% sodium hydroxide solutions. As a crosslinking agent, PF prepolymers were prepared with 1.8, 2.1 and 2.4 mol formaldehyde and 1 mol phenol (1.8-, 2.1- and 2.4-PF), and then mixed with RSF hydrolyzates to complete the formulation of RSF-based adhesive resins. The RSF-based adhesive resins were applied to fabricate 3-ply plywood panels. The solid content of RSF-based adhesive resins were ranged from 26.08% to 36.12% depending on the hydrolysis condition of RSF and PF prepolymer type with a high viscosity. The tensile shear strength and wood failure of plywood fabricated with RSF-based adhesive resins exceeded a minimum requirement of KS standard for ordinary plywood regardless of the hydrolysis condition of RSF and PF prepolymer type. Formaldehyde emissions of the plywood panels fabricated with 1.8-PF and RSF hydrolyzates were lower than that of E0 specified in the KS standard. Based on the results, RSF might be used as a raw material of environmentally friendly adhesives for the production of plywood panels, but further researches - the increase of solid content of RSF-based adhesives for reducing press time and the microscopic observation of plywood specimen for identifying the relationship between tensile shear strength and the penetration of adhesives into wood structure - are required to commercialize the RSF-based adhesives.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.9
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• pp.1434-1442
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• 2005

The Present study was attempted to investigate the Possibility of modification of functional properties of the rice flour by crosslinking proteins using microbial transglutaminase (mTGase) derived from a variant of Streptoverticillium sp. MTGase was added at various levels (3,000, 5,000, 7,000 and 10,000 ppm) during making noodles mixed with the rice flour. Mixograph and farinograph showed that imported wheat flour (IWF) had strong dough stability, while the rice flour showed very weak dough strength. However addition of mTGase (3,000, 5,000 and 7,000 ppm) resulted in improvement of dough stability of the rice flour. Texture profile analysis (TPA) results indicated that most of texture parameters (gumminess, chewiness and hardness) of cooked noodles prepared from the rice flour were significantly lower than those of noodles prepared from IWF. However, by addition of mTGase (at the levels of 3,000, 5,000, 7,000 ppm) dough stability and all the TPA values and sensory score (at the level of 7,000 ppm mTGase) on chewiness and hardness of cooked noodles made with $30\%$ rice flour were improved significantly. These results suggest that dough stability and texture of rice noodles as well as sensory characteristics could be improved by addition of mTGase to the rice flour.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.9
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• pp.636-642
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• 2013

In order to overcome drawbacks (i.e., filtration and recovery) of conventional powder type photocatalysts, nano-ZnO/Laponite/PVA (ZLP) photocatalyzed adsorption balls were developed by using in situ mixing of nanoscale ZnO as a photocatalyst, and Laponite as both adsorbent and supporting media in deionized water, followed by the poly vinyl alcohol polymerization with boric acid. The optimum mixing ratio of nano-ZnO:Laponite:PVA:deionized water was found to be 3:1:1:16 (by weight), and the mesh and film produced by PVA polymerization with boric acid might inhibit both swelling of Laponite and detachment of nanoscale ZnO from ZLP balls. Drying ZLP balls with microwave (600 watt) was found to produce ZLP balls with stable structure in water, and various sizes (55~500 ${\mu}m$) of pore were found to be distributed based on SEM and TEM results. In the initial period of reaction (i. e., 40 min), adsorption through ionic interaction between methylene blue and Laponite was the main removal mechanism. After the saturation of methylene blue to available adsorption sites for Laponite, the photocatalytic degradation of methylene blue occurred. The effective removal of methylene blue was attributed to adsorption and photocatalytic degradation. Based on the results from this study, synthesized ZLP photocatalyzed adsorption balls were expected to remove recalcitrant organic compounds effectively through both adsorption and photocatalytic degradation, and the risks of environmental receptors caused by detachment of nanoscale photocatalysts can be reduced.