• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.30 no.1
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• pp.63-72
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• 2024

Poly (butylene adipate-co-terephthalate) (PBAT) is one of the representative biodegradable polymers with high ductility and processability to replace petroleum-based polymers. Many investigations have been conducted to broaden the applications of PBAT in a variety of industries, including the food packaging, agricultural mulching film, and logistics and distribution fields. Foaming process is widely known technique to generate the cell structure within the polymer matrix, offering the insulation and light weight properties. However, there was no commercially feasible foam product based on biodegradable polymers, especially PBAT, and maintaining a proper melt viscosity of the polymer would be a key parameter for the foaming process. In this study, chemical foaming agent and cross-linking agent were introduced to PBAT, and a compression molding process was applied to prepare a foam sheet. The correlation between cell morphological structures and mechanical and physical properties was evaluated. It was found that PBAT with foam structures effectively reduced the density and thermal conductivity, allowing them to be suitable for applications such as insulation and lightweight packaging or cushion materials.

• Journal of the Korean Ceramic Society
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• v.53 no.1
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• pp.116-121
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• 2016

The amount of carbon dioxide ($CO_2$) released while producing building materials is substantial and has been targeted as a leading contributor to global climate change. One of the most typical methods of reducing $CO_2$ in building materials is the addition of slag and fly ash, like pozzolan material another method is to reduce $CO_2$ production by developing carbon negative cement. MgO-based cement from the low-temperature calcination of magnesite required less energy and emitted less $CO_2$ than the manufacturing of Portland cements. It is also believed that adding reactive MgO to Portland-pozzolan cements can improve their performance and also increase their capacity to absorb atmospheric $CO_2$. In this study, basic research on magnesia cement using $MgCO_3$ and magnesium silicate ore (serpentine) as the main starting materials, as well as blast furnace slag for the mineral admixture, was carried out for industrial waste material recycling. In order to increase the overall hydration activity, $MgCl_2$ was also added. In the case of the addition of $MgCl_2$as accelerating admixture, there was a promoting effect on the compressive strength. This was found to be due to the production of needle-like dense Mg-Cl hydrates. Mgnesia cement has a high viscosity due to its high specific surface area therefore, when the PC-based dispersing agent was added at a level of more than 1.0%, it had the effect of improving fluidity. In particular, the addition of $MgCl_2$ in magnesia cement using $MgCO_3$and magnesium silicate ore (serpentine) as main starting materials led to a lower expansion ratio and an increase in the freeze-thaw resistance finally, the addition of $MgCl_2$ as accelerating admixture led to good overall durability.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.4
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• pp.345-353
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• 2014

This study was evaluated influence of fluidity properties according to basalt fiber and high volume fly ash in the mortar level, as part of a basic study for development of fiber reinforced concrete using basalt fiber and high volume fly ash. In the first step, it was evaluated that fluidity properties of mortar according to replacement ratio 6 level of fly ash(10, 20, 30, 40, 50 and 60mass%) and fluidity properties of mortar according to content 5 levels of SP(1.3, 1.5, 1.7, 1.9 and 2.1%) and content 5 levels of VA(0.2, 0.4, 0.6, 0.8 and 1.0%) for dispersion of the basalt fiber, in the second step, it was evaluated that fluidity properties of mortar using High-volume fly ash (50mass%) on 3 levels of basalt fiber length (6, 20 and 30mm). Results of assessment, if after a fiber mixed, it showed that viscosity agent is more effective to improve the fluidity and fiber dispersion than superplasticizer, high volume fly ash (50%) applying the mixing, due to three properties of fly ash, showed that the improved fiber dispersibility and flow improvement.

• Journal of the Korea Institute of Building Construction
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• v.18 no.4
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• pp.329-335
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• 2018

The objective of this study is to develop a mortar mixture with high workability and adhesive strength for section jacketing in seismic strengthening technology of existing concrete structures. To achieve targeted requirements of the mortars (initial flow exceeding 200 mm, compressive strength of 30MPa, and adhesive strength exceeding 1MPa), step-by-step tests were conducted under the variation of the following mixture parameters: water-to-binder ratio, sand-to-binder ratio, polymer-to-binder ratio, dosage of viscosity agent, and content of ultra-rapid-hardening cement. The adhesive strength of the mortars was also estimated with respect to the various surface treatment states of existing concrete. Based on the test results, the mortar mixture with the polymer-to-binder ratio of 10% and the content of ultra-rapid-hardening cement of 5% can be recommended for the section jacketing materials. The recommended mortar mixture satisfied the targeted requirements as follows: initial flow of 220 mm, high-early strength gain, 28-day compressive strength of 35MPa, and adhesive strength exceeding 1.2MPa.

• The Journal of Engineering Geology
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• v.28 no.1
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• pp.61-67
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• 2018

Grouting is reinforcement or cutoff method which uses the hardening agent which is typically represented by portland cement and injected into the ground or the structure. When mixing the cement in powder form with water, the particles tend to cohere each other. Once they cohered, the particle size tends to become larger while injection efficiency becomes lower. This study, in a bid to reduce the cohesion of cement, the screen was set inside the grout mixer so that the cement particles are separated while vibrating them. To validate the effect of vibration screen, comparison test was conducted by using ordinary portland cement, slag cement and micro cement. Viscosity test, bleeding test and grain-size analysis indicated that the characteristics varied significantly after passing through the vibration filter. It is expected that the vibration filter installed inside the grout mixer will reduce the cement cohesion when mixing with water.

• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.68-73
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• 2016

Silver nanoparticles were prepared by chemical reduction-protection method using 1-decanoic acid and tri-n-octylphosphine as surfactants, and using $NaBH_4$ as a reducing agent. The silver nanoparticles were also studied for their formation, structure, morphology and size using UV-Visible spectroscopy, XRD, TEM and SEM. Further the viscosity of the silver paste and the surface resistance of the silver metal film produced by screen coating onto a PET film were investigated. Well dispersed and quasispherical silver nanoparticles with the size of 10-200 nm were obtained under the optimal molar ratio of $NaBH_4/AgNO_3=1:5$. The surface resistance of silver metal film coated on the PET film made with the silver nanoparticles under the optimal molar ratio showed a minal value of $41{\mu}{\Omega}/cm^2$.

• Korean journal of food and cookery science
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• v.16 no.2
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• pp.128-134
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• 2000

Cysteine, a thiol group-containing reducing agent which is known to relax the strain and increase the viscosity of dough, was added to Korean and imported wheat flour noodles to investigate the effect on the properties of raw, dried, and cooked noodles and to determine the optimum cooking time and amount to improve the color of noodles. Addition of cysteine up to 1% of flour (8.25 mmole/100 g flour) was not effective in increasing the brightness of raw and dried noodles and in changing the water activity of dried noodle. However, cysteine improved the brightness of cooked noodle made of both Korean and imported wheat flours. Also, there were notable differences in cooking and sensory properties of cysteine-added cooked noodles such as less firm and stickier texture due to the extraction of organic compounds into broth. When the noodles were cooked for their optimum cooking time, no difference was noticed in the texture and overall preference regardless of the addition of cysteine. Overall, the addition of 1 % cysteine increased the brightness of cooked noodles and reduced the cooking time.

• The Korean Journal of Food And Nutrition
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• v.27 no.6
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• pp.1175-1181
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• 2014

This study was conducted to develop for the elderly food that is safe, well-shaped, and easy to chew and swallow, using gelification. Gelatin, which has low adhesiveness, thereby lowering the possibility of being swallowed wrongly into the respiratory track, was used as a viscosity agent for the gelification. Water and gelatin amounts were adjusted to facilitate breaking the food with the tongue. Various foods for the elderly with chewing and swallowing difficulties were used for sensory assessment. Sensory panel consisted of 10 dietitians (10 women) in nursing care facilities. The sensory optimal composite recipes were determined by central composite design (CCD). The sensory measurements were significantly different in appearance (p<0.05), saltiness (p<0.05), sweetness (p<0.01), and overall quality (p<0.05). The optimum formulation of the Korean barbecue beef calculated by numerical and graphical method was 3.71 g of sugar and 19.53 g of soy sauce. Moisture content, hardness and adhesiveness of the Korean barbecue beef were 78.85%, 2.40, -1.87, respectively. The result shows that food for the elderly, which is easy to chew and swallow, using gelification will have sufficient competitiveness in terms of safety, taste, and preference. The development of food for the elderly that take into account the difficulties in chewing and swallowing among the elderly, reflects their preference, and has sufficient nutrients, is important to enable the elderly to enjoy their meals. Also, as the Korean society is getting older, it remains one of the biggest social challenges.

• Korean Journal of Food Science and Technology
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• v.29 no.1
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• pp.101-106
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• 1997

This study was carried out to examine the possibility of using brown rice or paddy as raw materials for sikhe. Brown rice and paddy were soaked in water at $15^{\circ}C$ for 2 days and then germinated at $15,\;20,\;25,\;30^{\circ}C$ for upto 10 days. The higher the germination temperature, the higher the germination speed, the increase of ${\alpha}-amylase$ activity, and the increase of extract amount and its sugar content. The viscosity of extract rapidly decreased first and then slightly increased during germination. The activities of ${\alpha}-amylase$ of germinated brown rice and paddy were much smaller than those of germinated barley; however, the extract amount and its sugar content of germinated brown rice and paddy were similar to those of germinated barley. The germinated brown rice can be used for sikhe not as a saccharifying agent but as a substitute for white rice.

• Polymer(Korea)
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• v.38 no.3
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• pp.371-377
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• 2014

The effect of modification conditions on the physical properties of polydimethyl siloxane modified epoxy (PDMSME) was investigated. The number of ring opened epoxy attached to polydimethylsiloxane (PDMS) by silane coupling agent affected the physical properties of undercoating materials. The flexibility of thin coating was enhanced by PDMSME and the increase of ring opened epoxy attached to PDMS resulted in the increase of hardness by the crosslinking in the present with moisture. The higher molecular weight of PDMS caused the lowering of hardness while the surface contact angle increased due to the high silicone content in PDMS. The viscosity of silicone modified epoxy coating materials decreased with increasing of molecular weight of PDMS due to the lowering of entanglement of PDMSME molecules by acetone solvent and consequently, the smooth undercoated surface was obtained.